Tuesday, January 30, 2007

 

Anthropologist confirms 'Hobbit' a separate species (+ BBC Video)

Contents:

1) Anthropologist confirms 'Hobbit' indeed a separate species: News + Related Paper
2) The Mystery of the Human Hobbit: BBC Horizon Video (49 minutes)
3) Excerpts from "What is the Hobbit?"

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1) Anthropologist confirms 'Hobbit' indeed a separate species: News + Related Paper

After the skeletal remains of an 18,000-year-old, Hobbit-sized human were discovered on the Indonesian island of Flores in 2003, some scientists thought that the specimen must have been a pygmy or a microcephalic - a human with an abnormally small skull.

Not so, said Dean Falk, a world-renowned paleoneurologist and chair of Florida State University's anthropology department, who along with an international team of experts created detailed maps of imprints left on the ancient hominid's braincase and concluded that the so-called Hobbit was actually a new species closely related to Homo sapiens.

Now after further study, Falk is absolutely convinced that her team was right and that the species cataloged as LB1, Homo floresiensis, is definitely not a human born with microcephalia - a somewhat rare pathological condition that still occurs today. Usually the result of a double-recessive gene, the condition is characterized by a small head and accompanied by some mental retardation.

"We have answered the people who contend that the Hobbit is a microcephalic," Falk said of her team's study of both normal and microcephalic human brains published in the January 29 issue of the journal PNAS (Proceedings of the National Academy of Sciences of the United States) [1].

The debate stemmed from the fact that archaeologists had found sophisticated tools and evidence of a fire near the remains of the 3-foot-tall adult female with a brain roughly one-third the size of a contemporary human.

"People refused to believe that someone with that small of a brain could make the tools. How could it be a sophisticated new species?"

But that's exactly what it is, according to Falk, whose team had previously created a "virtual endocast" from a three-dimensional computer model of the Hobbit's braincase, which reproduces the surface of the brain including its shape, grooves, vessels and sinuses. The endocasts revealed large parts of the frontal lobe and other anatomical features consistent with higher cognitive processes.

"LB1 has a highly evolved brain," she said. "It didn't get bigger, it got rewired and reorganized, and that's very interesting."

In this latest study, the researchers compared 3-D, computer-generated reconstructions of nine microcephalic modern human brains and 10 normal modern human brains. They found that certain shape features completely separate the two groups and that Hobbit classifies with normal humans rather than microcephalic humans in these features. In other ways, however, Hobbit's brain is unique, which is consistent with its attribution to a new species.

Comparison of two areas in the frontal lobe, the temporal lobe and the back of the brain show the Hobbit brain is nothing like a microcephalic's and is advanced in a way that is different from living humans. In fact, the LB1 brain was the "antithesis" of the microcephalic brain, according to Falk, a finding the researchers hope puts this part of the Hobbit controversy to rest.

It's time to move on to other important questions, Falk said, namely the origin of this species that co-existed at the same time that Homo sapiens was presumed to be the Earth's sole human inhabitant.

"It's the 64,000 dollar question: Where did it come from?" she said. "Who did it descend from, who are its relatives, and what does it say about human evolution? That's the real excitement about this discovery."

Source: University of Florida/PhysOrg

[1] Falk, D.; Hildebolt, C.; Smith, K.; Morwood, M.J.; Sutikna, T.; Jatmiko; Saptomo W.E.; Imhof, H., Seidler, H. & F. Prior. Brain shape in human microcephalics and Homo floresiensis
Published online before print February 2, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0609185104

Abstract

Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm3, some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an {approx}3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.

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2) The Mystery of the Human Hobbit: BBC Horizon Video 2005

"Is the hobbit a new human species or nothing more than a modern human with a crippling deformity?"

From the BBC website:

On the far-flung island of Flores, in the Indonesian archipelago, a team of archaeologists happened upon a tiny 18,000-year old skeleton. It was no more than a metre tall. They assumed they have found the remains of a young girl. But other signs suggested she was in fact much older. They had discovered one of the smallest human adults ever found.

As the dig continued, the evidence unearthed got stranger. The diggers found elephants the size of cows, rats the size of dogs, lizards the size of crocodiles. It was like stepping with Alice into Wonderland. It was not just the humans that were peculiarly sized, everything large had shrunk and everything small had grown.

Further digging uncovered spear points scattered among the bones of the pygmy elephants that appear to have been roasted on fires. It seemed that their tiny human must have been a skilled and intelligent hunter. Yet when they looked more closely at her skeleton, they discovered her brain was smaller than any other known human and no bigger than a chimpanzee's...

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3) Excerpts from "What is the Hobbit?"

An open access/free PLoS Biology article by the science writer Tabitha M. Powledge.

Citation: Powledge TM (2006) What Is the Hobbit? PLoS Biol 4(12): e440 DOI: 10.1371/journal.pbio.0040440

Who - or what - is Homo floresiensis? The tiny hominid bones, which a joint Australian-Indonesian team unearthed in 2003 on the Indonesian island of Flores, have quickly become as celebrated (and derided) as any find in the tempestuous history of human paleontology. The mystery that shrouds these ancient skeletons, nicknamed hobbits after the diminutive characters in J. R. R. Tolkien's novels, seems to deepen with every study published. Two main camps have emerged, each certain they can settle the question. But many other paleoanthropologists confess they still have no idea.

H. floresiensis Discovered

The discovery team declared their find a new human species, H. floresiensis, based primarily on a single near-complete skeleton of one very small individual with a very small brain, known as LB1. Compared to H. sapiens, LB1, whose age was estimated from tooth wear at about 30 years, was only one meter tall - about the size of a 4-year-old H. sapiens child - with a brain the size of a newborn's. Although there are also fragments of eight other small individuals, they provide no information about brain size, nor is much skeleton preserved. Nonetheless, they possess a combination of features never before seen in human fossils, which makes it credible that a previously unknown population of people smaller than today's pygmies lived on Flores between 90,000 and 12,000 years ago.

Stone tools found at the site raise the possibility that hobbits had culture, even though LB1's brain size would make a chimpanzee sneer. H. floresiensis, the discovery team claimed, could be the first human example of island dwarfing. This phenomenon, thought to be evolution's response to limited resources, is known for other mammals, including dwarf elephants from Flores itself. But this is not the only possible conclusion. A long-awaited paper [2], which appeared online in Proceedings of the National Academy of Sciences of the United States of America (PNAS) on August 23, 2006, offers a radically different interpretation of these skeletal remains.

...The Hobbit's Brain

A March 2005 paper in the journal Science, whose authors include a subset of the discovery team, reported that a virtual endocast of LB1's cranium, which has brain features imprinted on it, suggested that hobbits were not simply miniature versions of sapiens or erectus, but still may have had human-like thinking abilities because the prefrontal cortex and temporal lobes seemed expanded. The region, known as Brodmann area 10, is thought to be the seat of higher cognitive processes like memory, communication, and planning.

By contrast, Holloway, who has also studied an LB1 endocast, says the brain's small size and some other features hint at pathology. Parts of area 10 called the gyri recti seem too thin, he reports, and he has never seen a human endocast so flattened out before, which also suggests abnormality. Like several other researchers, Holloway has tried (and failed) to find direct correspondences between LB1's cranium and those of people with microcephaly. Microcephaly, meaning simply small head, is an umbrella term for a miscellany of conditions with scores of different genetic and environmental causes and myriad manifestations. The most recent study, published online in Anatomical Record on October 9, 2006, concludes that "it is not possible to match any of these syndromes exactly with the LB1 fossil," although the authors argue that some microcephalic syndromes share features with LB1, including stature, head size, and anomalies of jaw and teeth. As all the studies point out, nothing so far unearthed in the clinical literature or the fossil record matches LB1's peculiar head. Those negatives, of course, don't rule out deformity, especially deformity unique to the hobbits; isolated populations routinely develop distinctive abnormalities.

Debbie Argue of Australian National University (Canberra, Australia) and co-authors of an October 2006 paper in the Journal of Human Evolution say LB1 is probably not microcephalic, and they endorse the designation of a new species. They also say the hobbits are not pygmy-like. They suggest instead (as have others) that, whereas LB1's cranium is not like anything else in the hominid fossil record, some other hobbit bones resemble much older early human (but non-Homo) fossils known only from Africa - the Australopithcines.

[2] Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities
T. Jacob et al.
Published online before print August 23, 2006, 10.1073/pnas.0605563103
OPEN ACCESS ARTICLE

Liang Bua 1 (LB1) exhibits marked craniofacial and postcranial asymmetries and other indicators of abnormal growth and development. Anomalies aside, 140 cranial features place LB1 within modern human ranges of variation, resembling Australomelanesian populations. Mandibular and dental features of LB1 and LB6/1 either show no substantial deviation from modern Homo sapiens or share features (receding chins and rotated premolars) with Rampasasa pygmies now living near Liang Bua Cave. We propose that LB1 is drawn from an earlier pygmy H. sapiens population but individually shows signs of a developmental abnormality, including microcephaly. Additional mandibular and postcranial remains from the site share small body size but not microcephaly.

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Related posts include:

"Komodo Dragons: News, Video, Further Reading"

"Bad News For Tolkien Fans - Flores 'Hobbit' Is Just A Miniman"

"Compelling evidence demonstrates that 'Hobbit' fossil does not represent a new species of hominid"

"Flores' Hobbits Update: New hominid species may be early version of Homo sapiens"

"Homo floresiensis - 'No Hobbits in this Shire'"

"The hullabaloo about hobbits"

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