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In October 2004, excavation of fragmentary skeletal remains from the island of Flores in Indonesia yielded what was called "the most important find in human evolution for 100 years." Its discoverers dubbed the find Homo floresiensis, a name suggesting a previously unknown species of human. It has frequently referred to as the ‘Hobbit’ species due to its supposedly small stature.
Now detailed reanalysis by an international team of researchers including Robert B. Eckhardt, professor of developmental genetics and evolution at Penn State, Maciej Henneberg, professor of anatomy and pathology at the University of Adelaide, and Kenneth Hsü, a Chinese geologist and paleoclimatologist, suggests that the single specimen on which the new designation depends, known as LB1, does not represent a new species. Instead, it is the skeleton of a developmentally abnormal human and, according to the researchers, contains important features most consistent with a diagnosis of Down syndrome.
"The skeletal sample from Liang Bua cave contains fragmentary remains of several individuals," Eckhardt said. "LB1 has the only skull and thighbones in the entire sample."
No substantial new bone discoveries have been made in the cave since the finding of LB1.
The cave where the Flores bones were discovered. Image source: Wikipedia
Initial descriptions of Homo floresiensis focused on LB1's unusual anatomical characteristics: a cranial volume reported as only 380 milliliters (23.2 cubic inches), suggesting a brain less than one third the size of an average modern human's and short thighbones, which were used to reconstruct a hominid standing 1.06 meters (about 3.5 feet tall). Although LB1 lived only 15,000 years ago, comparisons were made to earlier hominins, including Homo erectus and Australopithecus. Other traits were characterized as unique and therefore indicative of a new species.
A thorough reexamination of the available evidence in the context of clinical studies, the researchers said, suggests a different explanation. The researchers report their findings in two papers published in the Proceedings of the National Academy of Sciences.
In the first place, they write, the original figures for cranial volume and stature are underestimates, "markedly lower than any later attempts to confirm them." Eckhardt, Henneberg, and other researchers have consistently found a cranial volume of about 430 milliliters, instead of 380.
"The difference is significant, and the revised figure falls in the range predicted for a modern human with Down syndrome from the same geographic region," Eckhardt said.
The original estimate of 3.5 feet for the hominid's height was based on extrapolation combining the short thighbone with a formula derived from an African pygmy population. But humans with Down syndrome also have diagnostically short thighbones, Eckhardt said.
Though these and other features are unusual, he acknowledged, "unusual does not equal unique. The originally reported traits are not so rare as to have required the invention of a new hominin species."
Instead, the researchers build the case for an alternative diagnosis: that of Down syndrome, one of the most commonly occurring developmental disorders in modern humans.
"When we first saw these bones, several of us immediately spotted a developmental disturbance," said Eckhardt, "but we did not assign a specific diagnosis because the bones were so fragmentary. Over the years, several lines of evidence have converged on Down syndrome."
The first indicator is craniofacial asymmetry, a left-right mismatch of the skull that is characteristic of this and other disorders. Eckhardt and colleagues noted this asymmetry in LB1 as early as 2006, but it had not been reported by the excavating team and was later dismissed as a result of the skull's being long buried, he said.
A previously unpublished measurement of LB1's occipital-frontal circumference -- the circumference of the skull taken roughly above the tops of the ears -- allowed the researchers to compare LB1 to clinical data routinely collected on patients with developmental disorders. Here too, the brain size they estimate is within the range expected for an Australomelanesian human with Down syndrome.
LB1's short thighbones not only match the height reduction seen in Down syndrome, Eckhardt said, but when corrected statistically for normal growth, they would yield a stature of about 1.26 meters, or just over four feet, a figure matched by some humans now living on Flores and in surrounding regions.
These and other Down-like characteristics, the researchers state, are present only in LB1, and not in the other Liang Bua skeletal remains, further evidence of LB1's abnormality.
"This work is not presented in the form of a fanciful story, but to test a hypothesis: Are the skeletons from Liang Bua cave sufficiently unusual to require invention of a new human species?" Eckhardt said.
"Our reanalysis shows that they are not. The less strained explanation is a developmental disorder. Here the signs point rather clearly to Down syndrome, which occurs in more than one per thousand human births around the world."
Featured image: A comparison of two skulls. Skulls of Homo sapiens (left) and Homo floresiensis. Photograph courtesy Yousuke Kaifu / National Geographic.
Source: The original source of the above article is: "Flores bones show features of Down syndrome, not a new 'Hobbit' human”, provided by Science Daily .
Liang Bua Homo floresiensis mandibles and mandibular teeth: a contribution to the comparative morphology of a new hominin species
In 2004, a new hominin species, Homo floresiensis, was described from Late Pleistocene cave deposits at Liang Bua, Flores. H. floresiensis was remarkable for its small body-size, endocranial volume in the chimpanzee range, limb proportions and skeletal robusticity similar to Pliocene Australopithecus, and a skeletal morphology with a distinctive combination of symplesiomorphic, derived, and unique traits. Critics of H. floresiensis as a novel species have argued that the Pleistocene skeletons from Liang Bua either fall within the range of living Australomelanesians, exhibit the attributes of growth disorders found in modern humans, or a combination of both. Here we describe the morphology of the LB1, LB2, and LB6 mandibles and mandibular teeth from Liang Bua. Morphological and metrical comparisons of the mandibles demonstrate that they share a distinctive suite of traits that place them outside both the H. sapiens and H. erectus ranges of variation. While having the derived molar size of later Homo, the symphyseal, corpus, ramus, and premolar morphologies share similarities with both Australopithecus and early Homo. When the mandibles are considered with the existing evidence for cranial and postcranial anatomy, limb proportions, and the functional anatomy of the wrist and shoulder, they are in many respects closer to African early Homo or Australopithecus than to later Homo. Taken together, this evidence suggests that the ancestors of H. floresiensis left Africa before the evolution of H. erectus, as defined by the Dmanisi and East African evidence.
Homo floresiensis: Two Years Out
Two years ago this month, I was taken aback by some explosive news. A team of Indonesian and Australian scientists reported that they had discovered fossils of what they claimed was a new species of hominid. It lived on the island of Flores in Indonesia, it stood three feet tall, and it had a brain about the size of a chimp’s. Making the report particularly remarkable was the fact that this hominid, which the scientists dubbed Homo floresiensis, lived as recently as 18,000 years ago. I wrote up a post on the paper, and took note of some strong skepticism from some quarters. And since then, I’ve found myself devoting a number of posts to the new papers from the discoverers of Homo floresiensis, and the emerging responses from the skeptics–so many that I gave them their own category. Recently there’s been so much stuff coming out pro and con that I have had to skip a couple opportunities to blog on Homo floresiensis–mainly because I’ve been frantically deep in the first draft of my current book on a very different topic: Escherichia coli. (I assume Homo floresiensis carried Escherichia coli in its gut, but the overlap stops there.)
Fortunately the first draft is now done, so I can let my mind drift back from the microbial world, to Homo floresiensis. And it just so happens that a big new paper has come out today which is a good topic on which to blog.
This paper, published in the Anatomical Record, actually builds on a much shorter one that appeared a few months ago in Science. To keep the strands of this story from tangling up with each other, let me lay out a timeline. (If you feel I’ve left something important out, remind me in the comments and I may insert it below…)
October 2004: Homo floresiensis makes its debut. The bones include only one brain-case, dubbed LB1. Along with the bones are lots of stone tools, raising the question of whether a small-brained hominid could have made or used them. Flores is also home to dwarf elephants, which illustrate the fact that many mammals evolve to smaller sizes on islands. Perhaps Homo floresiensis evolved from a bigger hominid. The best candidate, according to the authors, is Homo erectus, which spread from Africa about 1.8 million years ago and existed in southeast Asia perhaps as late as 50,000 years ago. Homo erectus was tall, could make simple tools, and had a brain about two-thirds the size our own. One line of evidence that may support this claim is the presence of stone tools on Flores dating back 840,000 years ago. They might have been left by Homo erectus migrants, whose descendants later evolved to tiny proportions.
November 2004: Things get weird. A prominent Indonesian paleoanthropologist named Teuku Jacob gets hold of the Flores bones and studies them for himself. He tells the press that Homo floresiensis is not a separate species, but a human pygmy, perhaps with a birth defect called microcephaly that causes small brains. (This is a line of argument taken by other skeptics.) The discoverers of the fossils cry foul, and three months later, when the bones are returned, they complain that some bones have been permanently damaged.
March 2005: Homo floresiensis gets a brain scan. The fossil discoverers team up with Dean Falk, a hominid brain expert, to give the LB1 brain case a CT scan. They reconstruct its brain and compare it to the brain of a human microcephalic, from a skull kept at the American Museum of Natural History. They argue that the brain is significantly different from the microcephalic, and most resembles that of Homo erectus.
June 2005: The site where Homo floresiensis was found is sealed off from any further investigation, reportedly due to the conflicts among the rival scientists. (I have not heard if it has been opened since then.)
October 2005: More bones. The discoverers of Homo floresiensis publish descriptions of additional fossils. These bones, including material from the lower jaw, arms, and legs, show strong similarities to the original fossils. They lack a chin, they have long arms relative to their legs, their teeth have some odd double roots, and so on. What’s more, they come from several ages. The bones that the authors assign to Homo floresiensis now range from 97,000 to 12,000 years. If LB1’s small skull belonged to a human with a genetic disorder, then why would all of these other individuals show so many similarities? Robert Martin, a primatologist at the Field Museum in Chicago who has expressed skepticism about Homo floresiensis, says he’s writing up a critical paper.
October 2005: After more bones come more brains. A few days after the new fossil paper is published, a German team of scientists publishes a comparison of LB1 to skulls from a different sample of microcephalics. The scientists argue that the brains are quite similar. They point out that microcephalics are quite variable in the shape and size of their brains, and say it’s premature to rule out the possibility that LB1 was microcephalic too. Dean Falk and her colleagues come right back at the Germans, arguing that they tipped the brains at the wrong angle before comparing them. If all the brains are lined up at the same angle, they look less similar.
May 2006: More skeptics weigh in. After a long winter without more news to take in, Robert Martin publishes his first attack on Homo floresiensis, teaming up with experts in other relevant areas such as William Dobyns, an expert on microcephaly at the University of Chicago. They present evidence that the microcephalic Falk chose was a nineteenth-century child named Jakob Moegele. An adult would have been a better comparison. The scientists present a couple sketches which they claim are more similar to LB1. The scientists also argue that LB1 is too small to be the result of evolutionary dwarfing. If Homo floresiensis followed the same trend that other mammals have, it should have had a much bigger brain relative to its body. Falk and her colleagues responded by asking how they could judge sketches (as opposed to detailed scans). They also hinted that perhaps Homo floresiensis might have evolved from an older, smaller branch of hominids.
June 2006: The discoverers of Homo floresiensis now publish new details on the stone tools. They argue that the tools from 840,000 years ago and the more recent ones found alongside the fossils probably represent a continuous technology made by the same lineage of hominids. To say that a small-brained hominid could not make such impressive tools is an assumption cloaked as a conclusion.
June 2006: A new idea emerges: Homo floresiensis is a healthy human. Gary Richards of the University of California at Berkeley argues that humans could have settled on the island of Flores and rapidly evolved into pygmies with small brains. Many of the traits that seem to set Homo floresiensis apart are also found sprinkled among living humans–particularly among pygmies.
August 2006: Teuku Jacob and an international team of colleagues take on Homo floresiensis. Their criticisms come from many different directions. They complain, for example, that the discoverers compared the hominid to European individuals. The proper comparison is between Homo floresiensis to people from southeast Asia and the Pacific (Australomelanesians)–especially pygmy Australomelanesians. They would have discovered many traits from Homo floresiensis in modern humans that they claimed were not found in our species. Jacob’s team also presents evidence that LB1 had an asymmetrical face–which is sometimes seen in microcephaly. The original discoverers hit back, telling reporters that the asymmetry might have come after death, as the skull was squeezed under sediment.
October 2006: A second vote for Homo floresiensis. The Journal of Human Evolution publishes an analysis of the Flores bones from a different team of scientists from Australia. I was too busy to write this one up, so let me just quote from the abstract now:
“We explore the affinities of LB1 using cranial and postcranial metric and non-metric analyses. LB1 is compared to early Homo, two microcephalic humans, a ‘pygmoid’ excavated from another cave on Flores, H. sapiens (including African pygmies and Andaman Islanders), Australopithecus, and Paranthropus. Based on these comparisons, we conclude that it is unlikely that LB1 is a microcephalic human, and it cannot be attributed to any known species. Its attribution to a new species, Homo floresiensis, is supported.”
Today: The Anatomical Record publishes a 23-page report from Martin, Dobyns, and company (Anatomical Record (DOI: 10.1002/ar.a.20394). This is not a new paper, so much as the paper Martin et al probably wanted to publish in the first place, rather than the clipped “Technical Comment” that is all Science will allow for such matters. So it’s a mix of points raised before, more evidence marshalled in support of those points, and some new information as well. It’s a very detailed attack on Homo floresiensis, and I don’t know of anything coming down the pike that will be more substantial. So if the original discoverers decide to write a detailed rebuttal of all the recent papers that have come out, this is one I’d imagine they’d pay a lot of attention to.
One subject that is new is the matter of the tools. Martin et al argue that the tools from 18,000 years ago are not like any simple tool linked to Homo erectus. They are more sophisticated, and have only been associated before with Homo sapiens and Neanderthals. The preservation of the tools in the Liang Bua cave, where the fossils were found, suggests to the scientists modern humans coming back again and again to the cave after they arrived on Flores.
The paper also presents new information on microcephalics. The researchers scanned Jakob Moegele’s skull (the original, not the cast that Falk used) to generate an endocast of his brain. They then carried out some of the same statistical studies on the shape of the LB1 brain. They compared LB1 to Jakob, as well as to two microcephalics who lived to adulthood, and a range of hominids and apes. They conclude several important things from this study. One is that microcephalics cover a huge range of shapes. Jakob’s brain was very different from that of the adult microcephalics. But those adults had brains that in some ways resembled Homo floresiensis. “LB1 is not clearly distinct from all modern human microcephalics,” the authors write. (Martin et al cast doubt on the recent Journal of Human Evolution paper, pointing out that the two microcephalic skulls studied there were over two thousand years old. One probably died before adulthood.)
Martin et al also argue (like Richards) that the other odd traits of Homo floresiensis are not as odd as the original discoverers claimed. For example, the discoverers pointed out the massive teeth in LB1’s jaws. But teeth are like brains: they don’t follow quite the same path as a shrinking body. If you compare primate species, a primate with a smaller body has teeth that are not as proportionately small. And one of the microcephalics Martin et al studied turned out to have similarly big teeth as well.
As we come up on the second anniversary of the initial announcement of Homo floresiensis, we’re in a strange spot. Microcephaly turns out to be a very peculiar condition that makes it very hard to distinguish humans from a possible species of very small hominids. Many different genes can give rise to the same conditions, producing different shapes to the brain, as well as different changes to other parts of the body. Scientists actually have a lot to learn about microcephaly–for one thing, many studies rely on remains in museum collections, which almost never included anything below the skull. At this point it’s not even clear if discovering more tiny hominids on Flores would make the case for a separate species. Under some conditions, it might be possible that a small population of islanders had a high proportion of microcephaly-triggering genes floating about. But that may be moot if nobody’s actually digging in the Liang Bua cave.
Now, if Homo floresiensis is the result of evolutionary dwarfing, then perhaps the debate might be advanced a bit if someone could find hominid fossils on other islands around southeast Asia that have also followed the Homo floresiensis path. On the other hand, if Homo floresiensis descended from ancient small hominids, those hominids would have to have come to Flores from Africa, where the oldest hominids are found. That’s a long path, with plenty of opportunities for fossils to be formed along the way. Whether anyone finds them is another question. Finally, there have been rumors of DNA from Liang Bua, but no published reports. So there’s another avenue of hope. I have no idea when I will be writing the next Homo floresiensis post, but I can only hope it continues to be interesting.
Small skull, huge controversy: Saga of the Flores 'hobbit' continues
In October 2004, while working in his lab, Bob Eckhardtheard a report on National Public Radio: A team of archaeologists had unearthed bones of a three-foot-tall humanlike creature on the island of Flores in Indonesia. Based on the shape and size of the skull and other skeletal remains, the archaeologists, led by Michael J. Morwood of the University of New England in Armidale, Australia, claimed they had discovered a new species of human.
The diminutive biped had a cranium no larger than a chimpanzee's, yet its bones had been found along with abundant stone tools. Radiocarbon dating of charcoal in the same stratum, along with luminescence dating of surrounding sediments, implied that the skeleton was only 18,000 years old. Considering other earlier archaeological finds on Flores, Morwood and his colleagues concluded that a new human species had evolved from a preceding population of Homo erectus that had been isolated for over 840,000 years on Flores, in the archipelago between Asia and Australia.
Eckhardt, a professor of developmental genetics and evolutionary morphology in Penn State's department of kinesiology, added it up. Three feet tall. A tiny brain. Complex stone tools. Evolved in complete isolation in 40,000 generations. He says: "It just didn't ring true."
Eckhardt read the scientific papers, published in the British journal Nature, setting forth the findings and conclusions of Morwood's group. "A lot of things didn't make sense," he says. "For instance, the overall height seemed to be off. I took the long-bone measurements from the paper and plugged them into standard regression formulas." Where Morwood and colleagues estimated an overall height of 1.06 meters for their specimen, Eckhardt came up with figures ranging from 1.15 to 1.33 meters, with an average of 1.25 meters—more than seven inches taller than Morwood's estimate. Eckhardt also wondered about the proximity of the small cranium to sophisticated stone tools, including points, perforators, blades, and microblades. Over a century of research by anthropologists has established a rough correlation between an increasing brain size and advances in stone-tool technology. The kinds of tools described in the Nature article matched those made elsewhere by Homo sapiens. Says Eckhardt, "It seemed very unlikely that a human with a chimp-sized brain would have invented such tools independently and in total isolation."
A "hobbit" is born
That the Morwood find represented a new species also seemed doubtful to Maciej Henneberg. Henneberg works at the University of Adelaide in Australia, where he is the Wood Jones Chair of Anthropological and Comparative Anatomy and heads the division of Anatomical Sciences. The day the Morwood papers appeared in Nature, Henneberg announced during a radio interview that the most complete skeleton recovered by the Morwood group likely came from a developmentally abnormal individual, a member of Homo sapiens whose tiny head exhibited microcephaly, a condition in which a person's braincase remains very small because the brain fails to attain a normal adult size.
A flurry of e-mails passed between Eckhardt and Henneberg. (The two have known each other for years and currently are co-investigators on a project funded by the Australian Research Council.) Says Eckhardt, "Maciej's hunch complemented my own conviction that the 'new species' scenario didn't make sense. And it dovetailed with my belief that the Morwood group had exaggerated the size of their specimen downward." Eckhardt notes that the apparent novelty of the Flores skeleton was enhanced by comparisons with populations from Europe and other major continents where the "normal" stature approaches six feet.
Peter Brown, also of the University of New England, had worked with Morwood in analyzing the Flores remains. They named the purported new species Homo floresiensis, since it had been found on Flores.
The nearly complete skeleton (the arms were missing, but they turned up in a later dig) was categorized as LB1, in reference to the expansive limestone cave, Liang Bua, where the bones had been unearthed about six meters below the cave floor. (Liang Bua means "cool cave" in the local language.) Less formally, members of Morwood's team dubbed the creature a "hobbit"—capitalizing, Eckhardt believes, on the popularity of the film adaptation of J. R. R. Tolkien's fictional trilogy The Lord of the
Rings, in which small humans known as hobbits do heroic things.
The press, both popular and science-oriented, latched onto the name. And they embraced the new-species notion enthusiastically.
In February 2005, Scientific American ran an article accompanied by a color illustration of a band of pint-sized, spear-toting hunters overwhelming a Stegodon, an extinct dwarf elephant. (Stegodon bones had also been found in Liang Bua, bearing marks made by bladed tools.) The article, by Kate Wong, was entitled "The Littlest Human" and included as a subhead: "A spectacular find in Indonesia reveals that a strikingly different hominid shared the earth with our kind in the not so distant past." It continued: "Conventional wisdom holds that Homo sapiens has been the sole human species on the earth for the past 25,000 years," but the remains found on Flores "have upended that view."
The cover of the May 2005 National Geographic presented a mockup portrait of the hobbit—dark-skinned, big-eyed, startled-looking. Morwood, in a feature article inside, wrote: "We had discovered a new kind of human . We had stumbled on a lost world: pygmy survivors from an earlier era, hanging on far from themain currents of human prehistory." Jared Diamond, a UCLA evolutionary biologist, stated in a Public Broadcasting System interview: "This is the most amazing discovery in any field of science in the last ten years." Others touted the find as the most important discovery in human evolution and paleoanthropology in half a century.
Alone on an island?
Those characterizations of the importance of the Flores skeletons only intensified Eckhardt's interest. In the kinesiology department he teaches a graduate course in Experimental Design and Methodology. "The course stresses a key principle articulated by Sir Peter Medawar, who shared a Nobel Prize for pioneering work in immunology," Eckhardt says. "Scientists, particularly those of us with decades of experience, are supposed to work on the most important problems that we have a reasonable chance of solving." To Eckhardt and his colleagues, the Flores find represented precisely such a problem. They would attack it, Medawar-style, not through armchair theorizing but by testing hypotheses.
Flores is one of the Lesser Sunda Islands, in the Malay archipelago.
Morwood and his colleagues speculated that a founding cohort of Homo erectus individuals had reached Flores from a nearby island, probably during a period of intense global glaciation, when huge volumes of
water would have been tied up in the polar icecaps, lowering sea level and exposing a greater amount of land. It was unclear how the hominids had gotten to Flores, whether by using primitive rafts or clinging to flotsam. Stegodons had also colonized Flores at about the same time. (Elephants are known to be
strong swimmers.) Once isolated on the island, both hominids and elephants shrank. The stegodons went from being slightly larger than modern African elephants to about the size of a water buffalo. The hominids supposedly dwindled as well from their more robust Homo erectus ancestors.
The so-called island rule is a widely accepted biological precept holding that mammals larger than approximately rabbit size tend to become smaller over millennia in an adaptive response to an island's limited food resources. Most paleoanthropologists, however, believe that our culture and behaviors buffer humans against some of the factors that cause other mammals to evolve rapidly where another species might develop a thick pelt to ward off the cold, we make clothes and harness fire. In his National Geographic article, Morwood said that the small human skeletons provided "powerful evidence" for hominid evolution in isolation on Flores.
But had the island really been isolated? In the 1950s and 1960s, evidence of an early human presence had been found on Flores. Theodor Verhoeven, a Dutch priest and amateur archaeologist, had excavated crude stone artifacts near the fossilized bones of stegodons thought to be around 750,000 years old.
On nearby Java, others had found 1.5-million-year old Homo erectus remains, which led Verhoeven to conclude that erectus had somehow made the crossing to Flores.
Morwood and his colleagues had unearthed a number of hominid bones in Liang Bua, although only the one complete cranium. They noted the sloping forehead, arched brow ridges, large jawbones, and receding chin on LB1, which, they said, mirrored Homo erectus traits. However, as Morwood wrote in National Geographic, "The tiny skull is most reminiscent not of the hefty Homo erectus from elsewhere in East
Asia but of older, smaller erectus fossils." The Morwood team stated in their Nature article that a CT scan demonstrated a congenital absence of a third molar, and they noted a unique positioning of other teeth. They also pointed to an unusual robustness of the leg bones and a low degree of humeral torsion, the twisting of the upper arm bone between the shoulder and the elbow. All of these characteristics were advanced as proof of a new species.
"Hobbit wars" heat up
Eckhardt knew that populations still living in parts of the world near Flores—on the Malay Peninsula, in the Philippines—were short-statured. He checked his impressions against a book he had read decades
before, The Origin of Races, by the anthropologist Carleton Coon, published in 1962. There Eckhardt found a footnote describing two small skeletons excavated in separate caves on Flores in the 1950s by
the amateur archaeologist Verhoeven. Deciding that he needed to see those previous finds, Eckhardt tracked down the skeletons at Naturalis, the Dutch national museum of natural history in Leiden. In January 2005, Eckhardt flew to the Netherlands to examine the skeletons. "The two measured 1.5 and
1.6 meters in length—quite small but somewhat larger than the height Morwood's group was proposing for LB1," Eckhardt says. He realized something else: The Verhoeven skeletons differed not only from
Morwood's Liang Bua specimen but also from each other. He says, "To me, those differences clearly suggested that Flores, far from being isolated, had been reached repeatedly by people from other regional populations."
At left, side view of Liang Momer E skull in Naturalis (Netherlands National Natural History Museum, Leiden). Right, side view of Liang TogÃ© skull in Naturalis.
By that time, Radien Soejono of the National Archaeological Research Center in Jakarta, listed as one of the coauthors of the Morwood Nature paper, had asked the Indonesian paleoanthropologist Teuku Jacob to restudy LB1. Jacob is with Gadjah Mada University in Yogyakarta his entire career has centered on the analysis of ancient human remains. Says Eckhardt, "Radien and Teuku are considered to be the two grand
old men of Indonesian archaeology. Radien works mainly with stones, Teuku with bones."
A number of scientists had begun questioning the new-species designation through letters and comments in a range of scientific journals. The group that included Eckhardt and Henneberg was at the forefront of the critics, while other specialists had lined up behind Morwood and his team. What the press started
calling "the hobbit wars" had begun to heat up.
Following preliminary analysis of LB1, Jacob also concluded that the skeleton was not normal and did not represent a new species. Says Eckhardt, "Morwood's team reacted in an odd manner for scientists, who
are supposed to believe in the value of independent study of evidence and replication of results." Instead, through the popular scientific press, "They made numerous charges, including that Jacob was holding on to LB1 and would restrict access to the bones in the future."
Continues Eckhardt: "Just the opposite was the case. Teuku had repeatedly invited me to examine the bones myself. Then, early in February 2005, I got an e-mail from Teuku saying he was under intense pressure to return the remains. If I wanted to see them firsthand, it had better be now." Eckhardt rearranged his Penn State classes and flew to Yogjakarta in mid-February, where he joined a group that included Jacob Henneberg Etty Indriati, a University of Chicago-educated anthropologist specializing in dentition, and Jacob's colleague at Gadjah Mada University and Alan Thorne, a paleontologist with the Research School of Pacific and Asian Studies at the
Australian National University in Canberra.
Look at the bones
"There we were," recalls Eckhardt, "sitting around a four-by-four table covered with a batch of plastic trays holding the remains of several small, long-dead Indonesians. We were picking up the bones, examining them, putting them back down. Every once in a while, looks would be exchanged across the table, and then one of us would articulate something we had all probably noticed. For instance, Maciej held up one of the femurs and said, 'The Nature paper says this is a right femur. But it is a left femur.'"
Indriati handed the LB1 skull to Eckhardt. "She said, 'Look at the back of the maxilla.' She whisked off some bits of dirt. Where the third molar was supposed to be congenitally absent, instead we have a socket with a piece of tooth in it." Discussions were intense and wide-ranging as the scientists drew upon their collective knowledge of mammalian evolution, human variation, and regional conditions in Indonesia and Southeast Asia.
The international team came up with four key areas of evidence disproving the assertion that LB1 represented a new species: geographical factors a pronounced asymmetry of the skull and face of LB1 dental traits and abnormalities in bones other than the cranium. The Proceedings of the National Academy of Sciences (PNAS) published their findings on September 5, 2006.
Team including Eckhardt in Yogjakarta, discussing LB1 fossils before Indonesian media. Left to right: Eckhardt, Indriati, Henneberg, Thorne, Soejono.
Morwood and his colleagues had theorized that Homo erectus individuals traveled to Flores around 840,000 years ago and subsequently evolved in isolation to become Homo floresiensis. That claim assumed no additional influx of humans to the island until just before or just after the "hobbits" had died out around 15,000 years ago, perhaps following a volcanic eruption that also led to the extinction of the stegodons. Jacob's team pointed out that other studies showed that the dwarf elephants had been able to reach the island on at least two separate occasions. Fluctuating cycles of glaciation at the earth's poles would have repeatedly enlarged the land mass of Flores and adjacent islands, leaving water gaps
of only a few kilometers. (That conclusion was based on research by K. Hsu of the National Institute of Earth Sciences in Beijing, a specialist in Pleistocene geology and a coauthor of the PNAS paper.)
Says Eckhardt, "There could have been numerous arrivals of humans during glacial stages with low sea levels, before final higher sea levels around ten thousand years ago widened the water gap separating Flores from neighboring islands. But by then, watercraft made crossings easy."
According to Eckhardt and his colleagues, the 14,200-square-kilometer island would not have offered food resources sufficient "for sustaining in isolation an adequate effective population" of hominids that would have provided enough genetic diversity to allow for survival and adaptation over hundreds of thousands of years. Rather, sporadic immigration from other Homo sapiens groups was far more likely.
After the Jacobs team had noticed that the LB1 skull was highly asymmetrical, they brought in David Frayer, an anthropologist at the University of Kansas. Using a set of photographs of the skull taken by a professional photographer, Frayer worked up computerized composite images of the hobbit's face. The combining of two left and two right side images of the face allowed for a comparison that made the asymmetry in the actual specimen strikingly obvious. The researchers also compared seven data points of left and right side measurements on the skull to quantify the asymmetry.
Evidence for abnormality
Base of LB1 skull showing socket of alleged "congenitally missing" upper right third molar.
"It turns out there's a huge forgotten body of literature on facial asymmetry, including many papers published nearly a century ago, based on studies at England's prestigious Galton Laboratory," Eckhardt says. "Everybody's face is asymmetrical to some extent. But when asymmetry exceeds about 1 percent, you're over the line into abnormality." In studying LB1, Eckhardt and Adam Kuperavage, a graduate student in kinesiology at Penn State, found that six of seven measurements taken on the skull's right side were larger than corresponding measurements on the left side by as much as 40 percent, while the seventh was 6 percent larger on the left side.
"Craniofacial asymmetry that extreme demonstrates that LB1 did not develop normally," Eckhardt says. "When we pointed out the asymmetry—which the Morwood group said in their original paper wasn't present—they backpedaled and said, sure, there's a small amount of asymmetry, but it was probably caused by pressure from sediments." Eckhardt cites a rebuttal of this explanation by the University of Wisconsin paleoanthropologist John Hawks, who writes in his weblog: "Yes, it is true that any archaeological specimen is likely to be distorted to some extent by reconstruction or postdepositional deformation. That might be true of this skull also. But in this case, the asymmetry clearly extends to morphological characters that should be relatively unaffected by such distortion."
Anthropologists frequently cite a unique shape or placement of teeth when describing a new species. According to Morwood's team, a CT scan had demonstrated the absence of a third molar for LB1. Etty Indriati had found the existing socket and a tooth fragment where the "missing" molar should have been. But LB1's teeth displayed other peculiarities, including enlarged wear surfaces, long roots, and an unusual rotated position of premolars in the upper jaw. "Those traits were characterized as unique," says Eckhardt. "But it turns out that the rotated premolars are shared by about 20 percent of the people still living in Rampasasa, a village near Liang Bua." This particular Australomelanesian population is
short-statured enough to be known as the Rampasasa pygmies. Many individuals in the population show receding chins (another supposed species-distinguishing characteristic), leading Eckhardt and his colleagues to state in their PNAS paper: "Absence of a chin cannot be a valid taxonomic character for the Liang Bua mandibles." The Jacob team contends that Morwood and his research group should have compared LB1's teeth with those of other populations in the same region, such as the Rampasasa cohort, rather than with Homo sapiens from other geographic areas of the world, principally Europe and Africa.
LB1 humerus, showing torsion between shoulder and elbow that is low but within the range of living humans.
Morwood's group had cited an unusual robustness of the leg bones of LB1. Eckhardt's team had CT scans done on the bones. "We paid for the scans with a few thousand dollars in traveler's checks that I was
carrying," Eckhardt says. "Others in the group combined funds and paid the professional photographer. Our involvement in this project moved so rapidly that there wasn't time to apply for conventional grants."
The CT scans showed that the cortex, or outer solid bone, was actually quite thin: "Those femurs are not robust at all," says Eckhardt. On the bones, the location of attachment points for the muscles suggest at least some paralysis. The LB1 skeleton also showed a low degree of humeral torsion, the twisting of the upper arm bone between shoulder and elbow. Normal humeral torsion in Homo sapienscommonly is about 140 degrees LB1's arms show 110 degrees of torsion. "When a limb develops with serious muscle weakness, torsion is usually only about 110 degrees," Eckhardt says. "Many points of evidence combine to suggest that this individual probably had severe movement disabilities."
How did humans evolve?
Was LB1 microcephalic? According to Eckhardt, around two hundred medically distinctive disease conditions can produce microcephaly. The malady can be genetic in origin, and it can be caused by various diseases and by infection. Asymmetries in the face and other bones often accompany microcephaly. Microcephaly exists in skeletons from the Upper Pleistocene and the Holocene periods. The ratio of LB1's small cranial capacity and short stature are similar to ratios found over several generations of microcephalics studied by physicians in the twentieth century. Scientists have also traced the
condition through succeeding generations of humans.
Says Eckhardt, "The archaeologists who dug up LB1 made serious mistakes in characterizing what they found, and they drew conclusions that were not supported by the balance of evidence. Altogether, they have one complete skull, plus a second mandible, which is similarly small, and assorted other bones from perhaps eight individuals. You cannot designate a new species based largely on an abnormal individual.
Group photo in Yogjakarta. Left to right: Thorne, Indriati, Henneberg, Jacob, Soejono, Eckhardt.
"In summary, the normal traits of LB1 were not unique but rather are characteristic of human populations in the region. The degree of humeral torsion, the structure of the long bones, the facial asymmetry, and the unusually small braincase all point to developmental abnormalities of the sort that often accompany microcephaly."
Continues Eckhardt: "We may be dealing with a population of individuals who went through a period of food shortages that made them smaller than they might otherwise have been. LB1 was about 1.25 meters
tall, and abnormalities of the sort from which that individual suffered commonly reduce stature markedly. The Rampasasa pygmies living near Liang Bua average just under 1.5 meters. That's not a huge stature difference."
In an apparent reaction to the Jacob group's PNAS paper, "the proponents of Homo floresiensis have now switched to arguing that the small humans must have originated elsewhere," Eckhardt says. "It seems that whenever we test one hypothesis and disprove it, they reinterpret the hypothesis into a less
readily testable form."
Since 1971, when Eckhardt earned his Ph.D. in anthropology and human genetics from the University of Michigan, many bones have passed through his hands. He has studied skeletal material in many of the major museums in the world, and spent five summers working with samples at the Institute of Anthropology and Human Genetics at the University of Frankfurt in Germany. In 1992 he published a comprehensive study of
skeletal changes in native Peruvians, based on samples ranging in age from 10,000 years before present to living populations. He has studied variation in skeletons as it is affected by age at death sex pathologies and developmental abnormalities and evolutionary changes over time. He has also worked with the bones of other mammals, including chimpanzees, gorillas, orangutans, macaques, and baboons.
"Most people in the fields of anthropology and archaeology believe the process of human evolution has been one of intense splitting over time," he concedes. "My belief, based on studying thousands of specimens during my career, is the opposite. Variation within any given species seems to be consistently underestimated."
The study of human evolution has always been a notably contentious field, and the Flores skeletons remain the focus of an intense and not always collegial debate. Currently scientists from different disciplines are studying the volume and shape of LB1's cranium, and trying—unsuccessfully, so far—to recover mitochondrial DNA from the skeletal material. (If found, this DNA might be compared to samples taken from both Neanderthal fossils and modern humans.) Morwood's team continues digging on Flores. The
scientific press and mainstream media seem happy to keep the controversy alive.
Says Eckhardt, "My estimate is that 80 percent or so of paleoanthropologists want this new species to be real—so much so that they are willing to overlook glaring errors and inconsistencies in the studies
and conclusions of the archaeologists who found the bones. This is not surprising, since LB1 was proclaimed to be our generation's critical test case of paleoanthropological theory. By disproving the validity of this new species, we have called a central dogma into question.
"Core beliefs are incredibly resistant to change. But testing and rejecting cherished hypotheses is how science moves forward."
There just isn’t enough evidence yet, according to some anthropologists
Two of the most recent hominin species discoveries were based on far more fossil material than Homo luzonensis‘ unveiling was.
When scientists discoveredHomo floresiensis, nicknamed “the Hobbit” for its short stature, on the Indonesian island of Flores, they described a near-complete female skeleton, including a skull. Since the discovery in 2003, bones and teeth from some 12H. floresiensis individuals have been recovered at the Liang Bua cave.
The discovery of Homo naledi included at least 15 individuals, which allowed the anthropologists to study and assess several specimens of the same bone.
But when it comes to Homo luzonensis, scientists have found just 13 bones total, and for DeSilva and Harcourt-Smith, that just isn’t enough data to make the call on whether what Detroit and his colleagues found in the Phillippines is a new species.
“I’m going to consider myself a fence sitter on this one,” DeSilva said about whether or not he agreed with the designation.
Researchers claim Flores bones do not represent new species of 'Hobbit' human - History
The popular science press went bonkers last month with news that fossilized bones of a previously unknown hominid had been discovered in a cave system in South Africa. Dubbed Homo naledi by lead researcher and University of the Witwatersrand paleoanthropologist Lee Berger, these proto-humans appeared to have lived somewhere between 1 to 3 million years ago, used tools, walked upright, and may have buried their dead, a practice that has only been attributed to our own species, Homo sapiens, and Neanderthals.
So there was a lot of talk of a “missing link”—the biggest find in paleoanthropology since Lucy, the skeleton of a female Australopithecus, was excavated from a gully near Ethiopia’s Awash River in 1974. (Donald Johanson, the lead researcher in Lucy’s discovery team, founded the Institute of Human Origins, which later moved from Berkeley to Arizona State.)
Certainly, the discovery seemed destined to open a new chapter in the study of ancient hominids, kick the telegenic Berger into the firmament of paleoanthropological superstars, and likely pay off big time for the National Geographic Society, which funded Berger and made the diminutive H. naledi the cover story for the October issue of its magazine. Indeed, the find seems destined for the full Nat Geo multimedia treatment, including television specials.
Amid all the hoopla and confetti, however, a growing number of scientists are advising caution. They’re not denying the importance of the find the fossils, they say, are invaluable. But they contend that the bones may not represent a new species. The evidence these skeptics point to suggests that the finds may actually be bones from Homo erectus, the earliest known hominid to manifest the general proportions, stance and gait of modern humans. H. erectus had a long tenure on the planet, living from about 2 million to 70,000 years ago. The species was widely distributed (from Africa to East Asia and possibly southern Europe), used tools and fire, and may have constructed rafts to cross wide bodies of water.
By virtue of his scholarly bona fides, Berkeley paleoanthropologist Tim White seems the default, if somewhat reluctant, lead spokesman for the H. naledi contrarians. White worked with Richard Leakey in Kenya and Mary Leakey in Tanzania. In 1994, as a co-director of the Middle Awash Project in Ethiopia, White and his fellow researchers unearthed a fossilized partial female skeleton of Ardipithecus ramidus at 4.4 million years of age, “Ardi” is the oldest know human antecedent. Two years later, White and his fellow researchers discovered fossils from Australopithecus garhi, a 2.5-million-year-old hominid who was contemporaneous with the earliest known use of stone tools.
And to White’s eye, Berger’s findings are probably South African representatives of Homo erectus. The Homo naledi cranium is similar in conformation and size to the earliest and most primitive Homo erectus representatives, White said.
Berger maintains that 13 of the 83 characteristics he noted on H. naledi’s skull differ from characteristics on known H. erectus skulls. “But many of these 13 characteristics are also present in H. erectus, not absent [as Berger and his co-researchers] claim,” White said during a recent interview in his Berkeley lab. “I wrote a text on human osteology [the study of bones]. Also, I teach a class on [osteological] variation in humans. Many of the characteristics that [Berger and company] claim differentiate H. naledi from H. erectus vary within our own species.”
Further, said White, some of Berger’s conclusions about H. erectus’s cranial features are just plain wrong. Berger maintains that an external occipital protuberance—basically, a bump at the back of the skull—is present in H. naledi but absent in H. erectus. White disputed this assertion by opening a cabinet in his lab, picking up a replica of an H. erectus skull found in Kenya, and pointing to a blatant occipital protuberance.
“That feature was noted in H. erectus fossils found in both [the former Soviet republic] Georgia and Kenya,” said White. “So you look at that, and you realize these claims of a new species are a little sketchy.”
Berger brushed off the criticism at a press conference near the findings. “Could this be the body of Homo erectus? Absolutely not. It could not be erectus,” he said.
Since then, White has cited other elements of the H. naledi saga that he finds troubling. The fossils come not from a single specimen, but from as many as 15 different individuals it is therefore difficult to identify which bone came from which individual, and even whether they lived in the same period. Nor has Berger’s team been able to definitively establish the age of the bones. Photos taken of the find demonstrate to White that many of the fossils were not found in situ in rocky matrix, but had been “very disturbed, perhaps by earlier cavers, in the geologically recent past.”
“One tibia, for example, was white on one end, a clear indication it had been snapped off in the recent past,” said White. “This (region’s) complex is extensive and like Swiss cheese, and it’s a favorite with spelunkers. You find beer cans next to fossils that are 3.5 million years old. So it’s important not to jump to conclusions.”
Further, the excavation itself seems inadequate to justify Berger’s claims, White said. “It was about the size of a phone booth floor, roughly 80 x 80 cm and 20 cm deep,” White said. “That’s much smaller than you would expect for a discovery of this magnitude. Virtually all excavations related to important finds are much larger. With a typical excavation, you must establish a threshold that provides an understanding of the successive layers, that provides the means for comprehensive analysis and comparison with specimens from other sites.”
Finally, White observed, claims that the hominids might have buried their dead (because so many bones were found in the same chamber) were hyped heavily in publicity materials but the scientific paper that Berger and his fellow researchers produced on the fossils is much more circumspect about such possibilities. “There is no evidence of burial rituals,” the Berkeley professor said. “The only evidence seems to be ‘We can’t think of anything else.’ This is not evidence.”
When California queried Berger on White’s comments on the discovery, he emailed the following response:
“I would really rather debate Tim’s ideas in a scientific journal where they belong rather than him attempting to debate this in the media. We have had almost 60 scientists working for two years on these refereed papers—Tim is shooting from the hip using characters that appear to largely concentrate on the head rather than the whole organism and well, the one thing I can assure you is the debate on Homo naledi being a ‘primitive Homo erectus,’ whatever that is, will not be settled in the media, either traditional or social. [Reporter’s note: The query was meant to imply an early representative of H. erectus, not a biologically ‘primitive’ form.] Tim continuing to use the media to argue whatever unsupported case he has for such assertions while protesting we are using media to ‘hype’ our fossils (although our ideas are in fact published in a well respected scientific journal) appears to be a way of just getting his name in the media rather than any form of scientific discourse. I would rather confine such discourse to where it belongs, a scientific paper published by Tim White in whatever journal he might be able to get such an argument in based on real numbers, real fossils and not just his opinion.”
The Academy can be a hothouse of discord and dissent, and some fields—paleoanthropology among them—seem particularly fertile ground for contention. But White is not alone in his uneasiness over H. naledi. Reviewers at top scientific journals also found the evidence for the new hominid species to be suspect. Berger and his team originally submitted multiple papers on H. naledi to the prestigious journal Nature, which rejected them.
“Tim continuing to use the media to argue whatever unsupported case he has for such assertions while protesting we are using media to ‘hype’ our fossils (although our ideas are in fact published in a well respected scientific journal) appears to be a way of just getting his name in the media rather than any form of scientific dis-course.”
Berger and his co-authors ultimately published their findings in eLife, an open-access, peer-reviewed, online journal edited by Cal biology professor and Nobel laureate Randy Schekman, the former editor-in-chief of the Proceedings of the National Academies of Science. Schekman assumed the editorship of eLife after declaring that he would no longer publish in closed-access journals such as Cell, Nature, and Science because the editors were more concerned with burnishing the reputations of their journals than publishing cutting-edge research. Like other open-access journals, eLife usually has a quicker peer-review process than long-established journals, and a much higher acceptance rate: around 25 percent, compared to the 7 percent acceptance rate of Science.
White said he agrees with Schekman that the peer-review process at the established journals is often flawed, but maintains that open-access journals such as eLife and PLOS One are not necessarily a panacea, in that research can be rushed to publication before being properly vetted by gimlet-eyed peers. “That’s clearly the case here [with H. naledi],” he said, noting the timeline between the discovery of the fossil site and the publication of the findings in the peer-reviewed and general press was only two years.
Indeed, the H. naledi announcement essentially was made simultaneously in the academic and popular media. During the press conference heralding the publication of Berger’s findings in eLife, a mock-up of National Geographic’s October magazine cover featuring the find was presented, and a television special sponsored by National Geographic and Pithecus was announced. By contrast, White and his colleagues took 15 years to publish their findings on “Ardi.” It took three years just to remove the fossils from the field. Years were spent carefully teasing the fossils from the matrix in the lab, obtaining moulds, photographs, and micro CT scans, compiling and analyzing the data, and comparing the fossils with all other known fossils and relevant living species.
Ultimately, findings on “Ardi” were published in both the journal Science and in National Geographic but White made sure the material appeared first in the peer-reviewed publication.
“We held the popular press off for 10 years,” says White, “for the simple reason that you can’t do good science when those guys are in the room. So when you actually invite them into the room—as Berger did, when they’re in the (tent) filming while excavation is going on, that has a very high impact on the work.”
Also, said White, Berger’s team was negligent in the handling and care of their find. He produced a photo of a member of Berger’s team scraping some of the bones a small pile of shavings is clearly visible. “Those are bone scrapings, and that’s a terrible thing to see. You lose valuable information when you remove bone like that, information you’ll never be able to recover.”
“This find is remarkable enough for what it is—a huge injection of new data important for understanding early hominid evolution. There was no need to turn it into something more than that.”
Both Berger and National Geographic have run into hominid-associated controversy before. In 2008, Berger was the lead author of a paper in PLOS One on the discovery of the remains of dwarfish, Hobbit-like hominids in the Palau archipelago. They were reported to be similar to bones found earlier on the Indonesian island of Flores 2,000 kilometers to the south. The Flores find was tentatively identified as a new species, H. floresiensis, a designation that has since become highly controversial. Berger suggested that the Palau discovery indicated the Flores hominids may not constitute a separate species, but are rather a manifestation of the dwarfism that sometimes occurs among mammals isolated on islands.
But Berger’s hypothesis for a troupe of island-bound dwarves was quickly disparaged by many of his academic peers, who maintain the bones were more likely those of juvenile normal-sized humans. Michael Pietrusewsky, a University of Hawaii at Manoa anthropologist widely considered the preeminent authority on ancient South Pacific human remains, stated: “The more I read the paper, the more I am convinced it is complete nonsense and cannot be accepted as serious science.”
In a Nature piece on the Palauan discovery, reporter Rex Dalton described the controversy and Berger’s claims as a “crossfire between entertainment and science,” with entertainment winning. Dalton noted that Berger appears often on television, and that he and the National Geographic Society collaborated with a London production company, Parthenon Entertainment, to make a film of the Palauan finds.
Though National Geographic provides seed grants to scientists in an array of fields, many of whom produce valuable research, Dalton writes that “National Geographic is also a nonprofit media empire…. Its editors work to get featured discoveries by its funded researchers into both its flagship magazine and peer-reviewed journals at the same time. This arrangement can sometimes backfire, as it did in 2000 when the magazine featured a report of a flying dinosaur fossil that later turned out to be a cleverly faked composite. Berger’s project in Palau provides a behind-the-scenes view of when entertainment and science meet….” (Last month, National Geographic magazine’s nonprofit parent organization effectively sold it to a for-profit operation whose chief shareholder is one of Rupert Murdoch’s global media companies.)
Berger, for his part, remains largely undaunted by the controversy his work has engendered. In response to misgivings over his Palau project, he emailed Nature’s editors: “Might it be that such critics have not read our manuscript as carefully as is required of a sophisticated debate on human variation before commenting?”
H. naledi—or whatever it is—certainly isn’t a modern-day Piltdown Man. White emphasizes that the discovery constitutes a major event in paleoanthropology. To illustrate his point during his recent interview with California, he produced another photo of one of Berger’s fossils. Even to an untrained eye, it was clear that it included digit bones.
“That’s a complete hand,” White said, calling these the first fossils ever found of a probable Homo erectus hand. “This find is remarkable enough for what it is—a huge injection of new data important for understanding early hominid evolution. There was no need to turn it into something more than that. Speculations about mortuary ritual or the need for a new metaphor to describe evolutionary process are both unnecessary and unwarranted.”
Researchers claim Flores bones do not represent new species of 'Hobbit' human - History
Recent developments in research regarding the so-called "hobbits" of Flores, Indonesia, may lend support to the multilineal or "branching" view of human evolution. The weight of evidence being accumulated increasingly tends to validate Homo floresiensis, the taxonomic designation given to these specimens by their discoverers, as a distinct species of hominin rather than as deformed modern humans.* A summary of these new developments has been presented in a recent Nova program on PBS. However, not all researchers in the field of paleoanthropology have accepted this view. Alternate interpretations continue to be proposed.
The controversy over the taxonomic and evolutionary status of the Flores hobbits provides a good example of the dialectical process whereby advances in scientific knowledge are achieved. Both major camps in this controversy (i.e., those who view the hobbits as a new species and those who think they are deformed modern humans) base themselves on modern evolutionary theory. The debate is not over whether other hominin species have existed, but how these particular specimens should be interpreted within the framework of human evolution.
While individual researchers' viewpoints may be motivated by a variety of factors, one important component in the division between the two camps is their differing underlying assumptions regarding whether hominin evolution has tended toward a unilineal or multilineal pattern. The significance of the hobbit controversy is that if these individuals were indeed members of a previously unknown species, it would imply that hominin evolution has followed the multilineal pattern to an even greater degree than has generally been thought by its proponents. Resolution of the "hobbit question" is likely to significantly influence how the majority of researchers in the field conceptualize human evolution and, therefore, impact the direction of investigations for decades to come.LB1 "Hobbit" skull compared to a modern human skull
The new data
If the recent research results are correct, it may be that H. floresiensis represents a very ancient split among hominins, possibly dating back more than a million years, substantially earlier than the separation between the lineage that ultimately gave rise to modern humans and that which developed into Neanderthals. Perhaps even more interesting are indications that the apparent ability of H. floresiensis to produce relatively sophisticated stone tools was based on the evolution of their brains independently and in a manner different from the main Homo lineage (i.e., the one that led to Homo erectus, Neanderthals, and modern humans). And yet they were capable of supporting a technology at least equivalent to that of H. erectus. If so, this would provide powerful support for the view that not only is intelligence subject to evolutionary processes just as much as other aspects of biology but also that there are multiple ways in which intelligence can evolve.
Following the announcement of the discovery of the small (about 3.5 feet or just over 1 meter tall), human-like skeletal remains on Flores (an island in Indonesia) back in 2003, reaction in the scientific community essentially fell into two camps. One included those who accepted the discoverers' interpretation that this was a new species of hominin that had coexisted with modern humans on the island until at least as recently as about 12,000 years ago. The other camp consisted of those who expressed varying degrees of skepticism regarding this claim. The major competing interpretation was that the bones (note: they are not lithified [i.e., turned to stone] and are, therefore, not technically fossils) were the remains of an individual (initially only one, largely complete individual was identified, plus one tooth of a second) who had suffered some sort of disease or deformity, such as microcephaly (a genetic disorder which results in a substantial underdevelopment of the brain as well as general stunting).
The basis for the microcephaly hypothesis was that the Flores hobbit (named LB1, because it was the first specimen found in the Liang Bua cave) not only had a very small body compared to modern humans, but a highly reduced brain size. The body size range of normal (i.e., healthy) modern humans varies widely. The best known of those at the small end of the body size spectrum are those people popularly known as "pygmies" who inhabit certain tropical forest areas of Africa. Other populations of "small" people exist in similar environmental settings in Asia and Melanesia. Small size in humans is thought to be, at least in part, an evolutionary adaptation for thermo-regulation (i.e., control of body temperature) in forests with hot, humid climates where heat dissipation by sweating is not effective. However, "pygmies" have brain sizes within the normal range for modern humans, though at the low end, and are in all respects Homo sapiens. The brain sizes of pygmy populations are, in fact, relatively larger in proportion to their body sizes than the brain to body size ratios of larger modern humans, indicating that an adaptive reduction in body size has not resulted in a commensurate brain-size reduction).
By contrast, the Flores "hobbit" has a brain size approximately equal to that of chimpanzees and australopithecines. Modern humans' cranial capacity (space inside the skull) is approximately 1,150-1,750 cubic centimeters (mean 1,325 cc) and that of chimps 285-500 cc (mean 395 cc). The cranial capacity of the single known Flores hobbit skull is approximately 417 cc, just slightly larger than the mean for chimps. The hobbit's brain size is at the low end of known sizes of australopithecines (410-530 cc), such as the famous Lucy fossil (Australopithecus afarensis), which has a cranial capacity of 438 cc and dates to 3.2 million years ago. These early hominins became extinct more than a million years ago. The essential observation is that all healthy modern humans, regardless of their body size, have brains that fall within a specific size range. The Flores skull is definitely outside of that range.
Over the course of hominin evolution there has been a general, though not necessarily steady increase in brain size. This trend toward encephalization is most especially pronounced in modern humans. Partly, this has been due to increases in body size. However, the growth in brain size has been proportionally greater than that of body size. The difference is thought to represent the increase in capacity needed to support higher intelligence. It is also important to note that not only has there been a disproportionate increase in brain size, but there have also been changes in brain architecture (i.e., some parts of the brain have grown more than others). Again, this is most probably associated with increases in mental capacity.
The abnormally small brain size of the Flores hobbit, if it were simply a downsized modern human, would imply a greatly diminished mental capacity. The hypothesis of microcephaly is at least plausible if the first known hobbit specimen represents a single, diseased individual which belonged to a population of otherwise normal modern humans, even if small in stature. However, evidence has been developed to counter the microcephaly hypothesis.
One of these lines of evidence consists of detailed studies of brain morphology, comparing the gross structure (i.e., the relative sizes and shapes of various parts of the brain) of the hobbit brain with that of normal modern humans, modern humans afflicted with microcephaly, various apes, and a series of fossil hominins going all the way back to australopithecines. Although brains normally do not fossilize, if at least a good portion of the skull is recovered it is possible to create an endocast by filling the inside of the skull with plastic. The plastic conforms to the skull's interior and, since the external configuration of the brain closely matches the inside surface of the skull, a detailed cast of the brain can be created. Since the hobbit remains are not fossilized, and are therefore rather fragile, a "virtual" endocast was created by use of CT scans of the skull.
A major result of the study of the hobbit brain endocast is to indicate significant differences between it and the morphology of the brains of modern humans with microcephaly. If true, the hobbit is unlikely to have been a modern human suffering from that disease. This research further found that, although it bears some similarities with the brain of Homo erectus, there are differences as well, indicating that LB1 is not simply a downsized member of that species. This interpretation, if upheld by examination of additional hobbit skulls yet to be found, will force researchers to try to find a new place for the Flores hobbits somewhere in the pattern of hominin evolution. However, there remains fierce debate in the scientific community regarding the nature of the hobbit brain and body.
Other genetic deformities have now been proposed as explanations for the small brain as well as other skeletal characteristics. Some have claimed that the hobbits represent a combination of endemic genetic deformities in a pygmy-like population caused by the phenomenon of island dwarfism.
Island dwarfism is a phenomenon that has been observed in a number of species, including the dwarf elephants (Stegadon, now extinct) on Flores. Such dwarfism is thought to result from a variety of factors, including restricted nutrient availability on small islands (smaller individuals need less to eat) and lack of predators (larger size is a defense against predators). These factors, and the previously cited thermodynamic advantage of small bodies in tropical rainforest environments, may all have contributed to further reducing the body size of the ancestors of the hobbits who, if they were indeed very early members of the genus Homo, such as the early Homo erectus specimens from Dmanisi, Georgia, dating to 1.7 million years ago, or even a form of australopithecine, would have been small to begin with.
Stone tools have been found on Flores in contexts dating to 840,000 years ago. However, no hominin skeletal remains of any kind have yet been found on Flores dating back to that time. The earliest hobbit remains recovered so far date to 95,000 years ago. Therefore, there is currently no direct paleontological data to indicate the sort of hominin the hobbits may have descended from.
The apparent association of fairly sophisticated stone tools with the hobbits, along with butchered animal bone and evidence of the use of fire would seem to argue against the microcephaly argument, since individuals suffering such a disability are unlikely to have been able to make and use stone tools. Therefore, the unique characteristics of hobbit brain morphology mean either that they had evolved sufficient mental capacity for such technological accomplishments in a manner different from that of the main line of human evolution or that the tools were made by another, as yet undiscovered hominin that coexisted with the hobbits on Flores.
Remains of small hominins have recently been found on the Palau islands of Micronesia. In contrast to the Flores specimens, however, initial reports indicate that although those on Palau exhibit some "primitive" anatomical characteristics, the preponderance of data supports the interpretation that these are dwarfed modern humans, but smaller than contemporary pygmies. If true, this would support the interpretation that the Flores individuals' small size may have been at least in part due to the size-reducing factors cited above, regardless of whether they were ancient or modern humans. The claim that the Palau specimens are dwarfed has been disputed, however.
One very important line of evidence that could help to sort out the controversy over the evolutionary status of the Flores hobbits would be the comparison of their DNA with that of fossil and modern humans, as is being done with Neanderthals and modern humans. Unfortunately, given the warm and wet conditions of Flores, which are not conducive to the preservation of DNA, no samples have yet been recovered. Therefore, for the time being at least, researchers must look to anatomy and archaeology for the necessary data.
Proponents of hobbits as a new species have marshaled a number of additional lines of evidence. One is that the characteristics of hobbit carpals (wrist bones) resemble those of the great apes and australopithecines rather than those of more recent hominins—Neanderthals and modern humans. Based on this finding, the ancestors of the Flores hobbits would have had to split from the line leading to the latter groups before the evolution of this new configuration of wrist bones, probably more than 1 million years ago. This difference would likely have implications regarding the hobbits' dexterity of manipulation, particularly with respect to the human "precision grip," perhaps indicating that they were more limited than Homo erectus and later hominins with regard to delicate manual work. The researchers believe that the hobbit wrist morphology could not be the result of genetic deformity or disease.
Beyond the specifics of the debate over whether the Flores hobbit remains represent evidence of a new, previously unknown form of hominin or of a deformed modern human, this controversy illustrates the process by which scientific knowledge is advanced.
Both the unilineal and multilineal models of human evolution have been constructed within the overall paradigm of modern evolutionary theory. However, the two place different emphases on the degree to which culture (i.e., non-biological adaptation) modified the selective pressures of the natural environment on hominin populations and, therefore, on the course of evolutionary development. The conflict between these two interpretations, and there are certainly variations within each camp, acts to continually test the "fit" between predictions made on the basis of each model and the results of discovery and experimentation. The adherents of one camp are ever ready to attempt to poke holes in the interpretations of the other. This drives research to examine specific questions in ever-greater detail, questions that might otherwise not have been considered worthy of investigation or even have been formulated at all.
For example, the back-and-forth dialogue over whether hobbit morphology could be explained as due to microcephaly has prompted detailed research into the brain morphology of a variety of fossil hominins as well as modern individuals with this affliction. New data is being sought concerning the actual range of variation in particular morphological structures of the brain between various populations and what those variations may mean regarding the behaviors controlled by those structures. Furthermore, previously unanticipated complications are being identified regarding how the existence of genetic abnormalities, such as microcephaly, among small, isolated populations may have combined with the effects of island dwarfism to create unexpected biological manifestations that could mimic certain characteristics of early hominins. Researchers are forced to identify and demonstrate the validity of experimental criteria that differentiate between the predicted outcomes of various interpretations.
Pursuit of such topics can lead to unexpected results that may either enrich the understanding of current formulations or identify significant flaws, bringing into question higher-level theoretical constructs. It is this constant dialectic involving the individual researchers, schools of thought, and experimental results that drives progress in scientific research. None of these opposites exists by themselves. Each to some degree both determines and is determined by the others. However, ultimately, it is the reality of the material world, the "ground truth" that determines the shape of scientific knowledge.
At some point, the majority of researchers in human evolution will reach a consensus regarding the status of the Flores hobbits, probably supported by the discovery and analysis of additional specimens. One interpretation will be seen to be more effective in explaining the available data and to have successfully weathered a sufficient number of attacks by proponents of other viewpoints so that it is adopted as the correct resolution of the controversy. This will then be seen as "settled science" and its implications for the larger model of human evolution will have to be worked out.
One of these implications may be that differences between fossil specimens that were previously considered to represent the normal range of variation within a species may have to be reexamined to evaluate the possibility that this variation is in fact evidence of the existence of distinct species. Another consequence could be that the focus of field investigations may shift or grow to encompass locations not previously thought of as likely to yield relevant data.
The discovery of the Flores hominins has already brought to a higher level a simmering debate regarding the "out of Africa" paradigm, which views Africa as the center of evolution and dispersal of successive waves of human ancestors.
The relatively neat and tidy formulation, which had become the consensus view among at least a substantial proportion of paleoanthropologists in recent decades, received its first significant blow with the discovery of the hominin fossils at Dmanisi, Georgia. These specimens were substantially older, 1.7 million years, and more primitive than the existing formulation had predicted for the earliest ventures out of Africa. The Flores discoveries may support the new interpretation that the earliest hominin dispersal from Africa took place significantly earlier, both chronologically and in terms of evolutionary development, than had previously been thought. Furthermore, these discoveries raise the possibility that important developments in human evolution may have taken place in Asia as well as in Africa.
The discoveries on the island of Flores were not expected within the frameworks of either the unilineal or multilineal models of human evolution. The survival of australopithecine or very early Homo descendants down to nearly the present challenges the existing view, held to varying degrees by supporters of both models, that through time more-progressive forms successively replaced older, less-advanced ones, whether by genetic flow or extinction. Nevertheless, the new discovery is more easily encompassed by the multilineal model. It merely means that the multilineality of human evolution has been even more extreme than had been thought and that there have been many evolutionary experiments in how to be an intelligent, technologically based species.
In science, the validity of a theory rests on its ability to more accurately and comprehensively explain and predict patterns observed in the material world than can its competitors. In this sense, the Flores discoveries tend to support the superiority of the multilineal model. This, in turn, reinforces our understanding of the active and complex dialectic between culture and nature that has shaped human evolution for millions of years.
* The term hominin reflects a recent change in taxonomic nomenclature. Essentially, it is equivalent to the previous term "hominid," including modern humans and all their predecessors and collateral lines back to the split with chimpanzees, at least 6-7 million years ago. A more detailed explanation can be found here.
Researchers claim Flores bones do not represent new species of 'Hobbit' human - HistoryHomo floresiensis (nicknamed "the hobbit") is the name given to a hominin species whose remains were discovered in 2004 on the island of Flores, Indonesia. But do the bones represent a new species at all, or were they, mundanely, anatomically modern humans with some pathological disorder that caused them to have smaller brains (
400 cc) and be shorter (106 cm) than humans (
1130 cc and 147 cm, average for women and Indonesian women, respectively)?
I have previously made clear where I stand in that debate, and for what reasons, but at the same time I do have some reservations with a paper in the Journal of Human Evolution that applies cladistic analysis (also known as phylogenetics) to determine where in hominin evolution H. floresiensis fits in.
The authors, Argue et al., examined multiple morphological features of bones of H. floresiensis , H. ergaster , H. erectus , H. habilis , H. rudolfensis , A. africanus , A. afarensis , H. rhodesiensis , H. georgicus , and H. sapiens in order to compare them and construct cladograms (evolutionary or phylogenetic trees showing ancestral relationships). Because some scientists suggest that the smaller brain case could have been caused by microencephaly, they excluded cranial capacity from the comparisons.
The result is that two trees are the most parsimonious, meaning that they are the shortest of all the trees they examined. In other words, under the assumption that the fewer morphological changes between the species is the better model for the evolutionary relationship, these two trees are the most likely of all.
The two most parsimonious cladograms, with H. floresiensis branching off just after and just before H. habilis , respectively. Dmanisi is also known as Homo georgicus .
So the conclusion the authors make seems fair enough: H. floresiensis branched off either just after or just before H. habilis .
Skipping over the problems I have with the assumption of parsimony, does anyone else notice something really fishy so far?
The fishy part is that in order to construct cladograms like the ones above, the authors assumed that H. floresiensis and H. sapiens are different species. Once that is done, no other conclusion can be reached. It is perhaps interesting by itself to see what the evolutionary relationship is between them, assuming that they have one, but it can't address the question of whether they are different species or not. However, Argue et al. state clearly in their introduction that this is their goal:
Again, I do not see how using cladistic analysis can be used to resolve this question of whether H. floresiensis was a human with a pathological condition or a separate species. In fact, the same issue exists between H. georgicus (Dmanisi) and H. erectus . H. georgicus is now thought to represent an early stage before H. erectus , rather than being a separate species. Yet, here they are assumed to be different species.
In their earlier paper (Argue et al., 2006) the morphological data were used to support this conclusion, but, again, the results in the present paper does not "sustain H. floresiensis as a new species (. ) and favor the hypothesis that H. floresiensis descended from an early species of Homo," when it is assumed that they are separate species.
Argue D, Morwood M, Sutikna T, Jatmiko, & Saptomo W (2009). Homo floresiensis: A cladistic analysis. Journal of human evolution PMID:19628252
Update inserted 5 October 2006
Not surprisingly, perhaps, a Journal of Human Evolution article has now come out with an alternative analysis to that cited here, claiming that the hobbit deserves to be classified as a different species, after all&mdashHomo floresiensis. See Homo floresiensis: Microcephalic, pygmoid, Australopithecus, or Homo?, D. Argue et al. J. Hum. Evol. 51, 360&ndash374 2006.
The analysis was done at the Australian National University (ANU), site of a longstanding feud between two paleoanthropologists. One of them is Dr Colin Groves, who has long favoured the &lsquoout of Africa&rsquo or evolutionary school of thought (associated with the notion of &lsquomitochondrial Eve&rsquo and the &lsquoreplacement hypothesis&rsquo, the idea that as modern humans swept out of Africa in the last few kya, they totally replaced, even wiped out, more &lsquoarchaic&rsquo populations). The other is Dr Alan Thorne, now retired from the ANU, but one who favours the competing hypothesis of &lsquomultiregionalism&rsquo (like Dr Milford Wolpoff, of the University of Michigan).
It looks like the feud is set to continue in &lsquohobbit territory&rsquo. Thorne is one of the authors of the study cited in the main article here, that concluded that the hobbit was a deformed pygmy Groves was one of the authors of the study cited here that said the opposite. Stay tuned!