Last year, scientists reported discovering fossils of a three-foot-tall hominid that they named Homo floresiensis, and which I can’t keep myself from calling the Hobbit. Its bones turned up in a cave on the Indonesian island of Flores, dating from 97,000 to 12,000 years ago. The scientists argued that the Hobbit represented an ancient lineage of hominids, perhaps descending from Homo erectus, a human-sized species that existed in Asia 1.8 million years ago, or perhaps belonging to even an older lineage, known as australopithecines. Critics argued that the Hobbit was probably a fellow Homo sapiens. They generally focused their attention on Homo floresiensis’s skull. Only one skull has yet been found, from an adult female. It’s an odd skull at that, one that would have housed a strangely shaped brain a third the size of a normal adult human brain. As I wrote last week, the critics suggest that the Hobbit might have had a genetic disorder called microcephaly, which leads to very small heads. (The full repository of my Hobbit obsessions can be found here.)
With all the attention currently being lavished the Hobbit’s head, it’s easy to forget all the other things that have come out of the same cave. Scientists have found various chunks from its jaws, arms, and other bones, which have lots of weird features. These features suggest a separate species, the Hobbit team argues, not a deformed human. There’s a continuity that you can trace from the oldest bones to the youngest, a span of over 80,000 years. The critics haven’t had much to say on that point, although it’s only fair to point out that their output so far has been a few short papers. Longer rebuttals are in the works.
And then there are the tools.
Tools were actually what got the paleoanthropologists excited about Flores in the first place. In 1994 they found tools dating back roughly 800,000 years at another site on the island. The scientists speculated that the tools were made by Homo erectus that had gotten from Java across a wide expanse of open water to Flores. Whether they traveled by boat or tsunami-driven tree was an open question. The discovery spurred an intense search of the island for fossils of the toolmakers. The scientists found the much younger Hobbits instead.
But along with the fossils, the scientists also found more tools. In the initial reports on Homo floresiensis last year, the scientists reported that the tools spanned the oldest to youngest deposits where fossils had been found. Bones of dwarf elephants also found in the same layers suggested that the Hobbits were using the tools to hunt–perhaps even attaching the stone blades to sticks to make spears. As for the older tools, the scientists only said the identity of their creators would have to remain a matter of speculation.
Skeptics from the start wondered whether the Hobbits had actually made the tools. Paleoanthropologists Marta Mirazón Lahr and Robert Foley wrote a commentary for Nature on the initial papers last year in which they pointed out that
elsewhere such implements are associated with H. sapiens, and their contrast with tools found anywhere with H. erectus is very striking. One could speculate that modern humans, who were dispersing across southern Asia between 100,000 and 50,000 years ago, may have made the tools, and come across these creatures.
Others argued that a hominid with such a tiny brain could not have possible made or used such sophisticated tools.
In tomorrow’s issue of Nature, the Hobbit team takes on the skeptics yet again. They’ve analyzed all the old tools from Flores–the original 1994 cache and another trove that turned up not far away in 2004. (This picture shows the front, back, and side view of one of the 2004 finds.) New dating shows that some of these 507 tools date back at least 840,000 years ago. The scientists compared them to the 3626 younger tools found with the Hobbit bones.
The scientists found that the two sets of tools share many things in common. They were typically made from volcanic rocks found along rivers. The tool makers knocked off bits from these rocks in a similar fashion, creating a front and back face and sharpening the edges. In some cases they seem to have used anvils–setting their tools-in-the-making on other rocks before banging on them. Both sets of tools include distinctive kinds of tools, such as “perforators” with a long spike extending from a rounded base.
The simplest explanation for these similarities, the authors conclude, “is the stone artefacts from Mata Menge and Lui Bua [the old and new tool sites] represent a continuous technology made by the same hominin lineage.”
They argue that the notion that the new tools were produced by humans, as floated by Lahr and Foley, doesn’t fit the evidence. They point out that the oldest indisputable fossils of Homo sapiens on Flores are 10,500 year old. Along with those bones, tools have been found that don’t fit into the continuum from Mata Menge to Lui Bua. They include grinding stones and other tools never seen in older sites on Flores. And along with tools, humans arriving on Flores also made beads and formally buried their dead and left lots of other evidence of a very different mental make-up from Homo floresiensis. It makes more sense that humans showed up on Flores only after the Hobbits became extinct (perhaps during a volcanic eruption) and brought lots of new tools with them. As for the claim that small-brained Hobbits couldn’t possibly have made the tools found with them, the scientists argue that this is an assumption cloaked as a conclusion.
Inevitably, this study raises more questions than it can answer at the moment. I for one found myself thinking a lot about the size of the tools. Hobbits were small, and they had small hands. If Hobbits descend from Homo erectus, then they must have shrunk from a height of five to six feet to just three. On the other hand, if they descend from australopithecines or some other small lineage, then they might have arrived on the island already small. Would the size of the proto-Hobbits have been reflected in the size of their tools?
To visualize this matter, consider my Hobbit-sized daughter Veronica. She’s holding a rock that is about the size of an old Flores tool. I didn’t try to make a perforator for her, since I’m a lot clumsier than your typical Pleistocene hominid. Even if I had managed to make one, I doubt my wife Grace would have looked kindly on giving little girls sharp rocks. And it must be clearly stated that Homo floresiensis almost certainly never wore a Cinderella outfit. Snow White maybe, but never Cinderella.
The rock fits pretty well in her hand, I must say. Did this mean the old hominids of Flores were Veronica-sized? I sent an email to Adam Brumm of Australia National University, the lead author of the paper who did much of the analysis for his Ph.D. “The stone tools from Mata Menge and Liang Bua are basically the same size – all quite small,” he replied. It’s possible that the old hominids were already small, or that they were big but kept their tool kits light.
Brumm pointed out that Homo floresiensis may have carried rocks some distance from rivers before turning them into tools. Those rocks would have been much larger, but that doesn’t necessarily mean that the early inhabitants of Flores must have been big. After all, chimpanzees are short but extremely strong.
“There may well have been limitations on the maximum size of the stone artefacts H. flo could conveniently manipulate given their small hands but you would have to find a way to test this,” Brumm wrote. “H. flo might not be much bigger than your daughter, but if they were twice as strong or more than a full grown man imagine her flinging a sledge-hammer around the room and the constraints on tool handling become less apparent.”
When Veronica starts throwing Legos around, I’ll just try to remember that it could be worse. I could be dodging sledgehammers.
It’s been a little over a year and a half now since scientists announced the disocvery of the most controversial fossil in the field of human origins: Homo floresiensis a k a the Hobbit. Scientists found bones of a dimunitive hominid on the Indonesian island of Flores, and estimated that it lived there as recently as 12,000 years ago. It stood about as high as a normal three year old human child and had a brain the size of a chimpanzee’s. But its bones were also found with stone tools. The scientists declared the bones were not human. Instead, they belonged to a species of their own–one that branched off from much older hominids. Later, the scientists offered brain scans and more bones to bolster their case.
I’ve been chronicling the adventures of Homo floresiensis, trying to keep an eye out for new developments. My hobbit posts can be found here. In recent months the scientific reports have tapered off. That may be in part because of the ugly spat between rival paleoanthropologists over access to the bones and the site where they were found. Critics have been putting together attacks against the creation of a new species (most think the bones are from human pygmies, perhaps with birth defects). But those critical papers are slow in coming out.
Today we have the latest development in the hobbit wars, a critical paper from a team of American and British scientists and a response from the original team of scientists. They appear in the journal Science. I wish I could report some big surprising news, but these papers seem to be circling around two of the same questions that scientists have been asking for some time.
The new critical report comes from Robert Martin of the Field Museum in Chicago and his colleagues. The fact that Martin is not happy with the initial reports on Homo floresiensis is no secret. As I wrote last October, he was already working on his response back then, and Kate Wong at Scientific American offered some details in March. It’s still illuminating to look at his detailed comments in print.
There are two points to Martin’s complaint.
1. They picked the wrong human brain for their comparison. From the start, some critics argued that the hobbit was just a human with a case of microcephaly, a birth defect that produces a dramatically shrunken brain. Dean Falk of Florida State University led the effort to scan the brain case of Homo floresiensis, and for a point of comparison, she chose cast of a brain case of a microcephalic in the collection of the American Museum of Natural History. She concluded that the hobbit brain case looked less like that of a human microcephalic and more like the brain of Homo erectus, a six-foot tall hominid that appeared in Indonesia perhaps 1.8 million years ago.
Martin and his colleagues did a little detective work and discovered that the skull belonged to one Jakob Moegele, a German boy who died at age ten. Studying the original skull, they argued that it was a poor choice for a comparison. Moegele was a child, while the Hobbit was an adult. What’s more, his cranial capacity (272 cc) was very small for a microcephalic. Martin and his colleagues offered some sketches of a skull and two preserved brains of microcephalics that they claim are more similar to the Hobbit.
2. You can’t get a Hobbit by shrinking down Homo erectus. Lots of mammals have evolved from bigger to smaller–even elephants can become miniature. And by comparing related species of different sizes, scientists have gotten a rough idea of how their bodies change as they shrink. It turns out that bodies shrink faster than brains. As a result, small mammals have bigger brains relative to their bodies than big animals.
Martin and his colleagues used various formulas for brain and body dwarfing to predict what would happen if Homo erectus shrank down to Hobbit size. They found that its brain would have been far bigger than the actual size of Homo floresiensis’s fossil suggests. In fact, in order to get down to the Hobbit’s tiny brain, Homo erectus’s body would have to shrink down to a gram!
“We conclude,” Martin and his colleagues write, “that LB1 [the Hobbit fossil skull] was not an insular dwarf and may have been a microcephalic modern human.”
1. Our scans beat your sketches. Falk and company point out a lot of shortcoming in the sketches Martin offers. The brain drawings lack crucial details about their structure, and the skull drawings are not accompanied by any information about what they look like inside. “Without this evidence,” Falk and company write, “the assertions of Martin et al remain unsubstantiated and difficult to address in further detail.”
2. Who said anything about a dwarf Homo erectus? Falk and her colleagues point out that while the brain had a Homo erectus-structure, they wrote that it “is too small to be attributed to normal dwarfing on H. erectus and further showed that its relative brain size is consistent with those of apes/australopithecines.” Australopithecines were an early wave of hominid species that lived from about 4.5 million to 2.5 million years ago. They could walk upright, but they were short and had brains not much bigger than a chimpanzee’s. And there’s no clear evidence from the fossil record that they ever left Africa. Homo erectus is among the earliest hominids to be found out of Africa.
That’s it. Frankly, I had a feeling of deja vu reading this material. Last October, I wrote about another attack in Science. Those critics had microcephalic brains
of their own to show, but Falk argued that they also failed to analyze the brains in a consistent way. I wondered then, and I wonder now, why the editors of Science don’t make sure that everyone agrees on the ground rules for comparing these brains before they publish? Otherwise both sides just squabble about methods and presentation, rather than about meatier matters.
The problem may be that in both cases Science has relegated this exchange to the “Technical Comment” section, where reports are much shorter than normal papers. The descriptions of methods used in the research are often scant, and the comments also tend to include cryptic interpretations that cry out for more explanation. Falk and her colleagues say that the Hobbit’s brain is consistent with apes or australopithecines, not Homo erectus. Now, I’d imagine that this might imply that the Hobbit descends not from Homo erectus, but from some Australopithecine that came out of Africa. That would be huge news if true. Yet the scientists just leave us hanging with a statement that is so cryptic as to be nearly useless.
I hope that the debate doesn’t keep circling this way until someone finds a new fossil on Flores or some other Indonesian island. We hobbit junkies need a better fix.
Well, here’s an idea I haven’t heard of before…
Last year scientists found the bones of what they recognized as a new species of hominid that lived as recently as 12,000 years ago. They named it Homo floresiensis, and its three foot stature earned it the nickname the Hobbit. All of the reconstructions I’ve seen until now have shown the Hobbit standing upright–which you might expect of a hominid that descended from upright ancestors (perhaps Homo erectus or even the more primitive Australopithecus).
But in the November issue of the Dutch science magazine Natuurwetenschap & Techniek, paleontologist and Hobbit team-member Gert van den Bergh offers a new vision: the Hobbit on all fours.
Van den Bergh makes his case based on the long, strangely shaped arm bones of Homo floresiensis, which were recently described in the journal Nature. “The humerus of Homo sapiens (modern man) and Homo erectus (our ancestor) has a significant twist in the connection to the shoulder,” van den Bergh said in a statement issued from the magazine. “In the Hobbit, however, the humerus is connected to the shoulder without twist. You don’t see this in the even more ancient Australopithecus, nor in erectus or sapiens, nor in apes, but you do see it in gibbons and macaques! As a consequence, the Hobbit’s shoulder is less mobile. Probably she could freely move her arms forward and backward, but had difficulty moving them sideways, like we can.”
Van den Bergh speculates the Homo floresiensis might have adapted to climbing steep mountain slopes as well as trees, like macaques do. “This could be an adaptation to the inhospitable and rugged island of Flores, where the largest coastal plain is just fifteen kilometers wide. The larger part of the island consists of very steep mountain sides.”
The article is all in Dutch, but I received an image of the reconstruction with a lot of captions in English. I’ve posted it here.
Normally I’d let such a reconstruction pass by, since I’m not a big fan of science-by-popular-magazine. But given Dr. van den Bergh’s experience, I thought I’d post it–at least to get people’s imaginations going. I wonder if other signatures of quadrupedalism can be found on the fossils. The hole at the bottom of the skull where the spinal cord exits, known as the foramen magnum, is one clue. I’m going to see if I can find out what other members of the Hobbit team think. If I get a response, I’ll post it here.
UPDATE 10/27 5 PM: Well, Peter Brown, the anthropologist on the hobbit team, is not impressed. In an email reply, he wrote:
Completely inconsistent with the anatomy of the LB1 skeleton, which is consistent with that of an obligate biped. Simply no way the limbs could have functioned like this. Anatomy of the cranial base, pelvis, legs, feet, hands… all those of an obligate biped.
UPDATE 10/27 6:40 PM Another guffaw from Dan Lieberman, a Harvard anthropologist who has been a careful observer of H. floresiensis research:
Very amusing and one of the silliest ideas yet I’ve seen regarding this odd skeleton. But I like the figure! Their idea its a monkey comes from the humeral torsion, but it really is clearly a biped in so many features that the idea is, well, silly.
Just goes to show that one can publish anything somewhere…
I suspect we’ve just reached the end of a very short, very weird side-story in the Hobbit’s saga.
UPDATE: Friday 10/28/05 12:40 pm: The Australian has picked up on the monkey business now. They even quote Lieberman here. While it’s nice to beat the papers (especially one that’s been on top of the Hobbit beat since the beginning), they seem to be ignoring the fact that the story was reported here first.
Dr van den Bergh’s claim is generating cyber ridicule. “Very amusing and one of the silliest ideas yet I’ve seen regarding this odd skeleton,” wrote Harvard University anthropologist Dan Lieberman on Corante.com.
Excuse me, that was reporting. Another sign, I suspect, that some newspapers don’t like being beaten by blogs.
Finally, more brains.
On Tuesday I wrote about how the second batch of Homo floresiensis bones had at last seen the scientific light of day. Today the critics who don’t think the Hobbit is a new species are making their way into scientific journals as well. They’re saying that the Hobbit brain looks an awful lot like a human brain.
Last year, as I described here, Dean Falk of Florida State University and her colleagues reported on a scan they had made of the braincase of Homo floresiensis. They compared it to the braincase of normal humans, of a human born with a congenital defect called microcephaly, and the braincases of other hominid species. Falk concluded that the brain did not belong to a human. While the Hobbit brain is small (about a third the size of a normal brain) it had several key differences in shape compared to the microcephalic brain.
In today’s issue of Science, a neursurgeon and two anthropologists from Germany published a "Technical Comment" on last year’s scan. The researchers had access to a collection of microcephalic brains, and they analyzed 19 of them. One brain drew their attention in particular, shown here in the top picture. The human microcephalic is on the left, and the Hobbit is on the right. They certainly look similar, and the German team report that they are almost identical in size (415 cc for the human, 417 cc for the Hobbit) and they have similar proportions, such as breadth to length (85% versus 86%).
In last year’s report, Falk’s team pointed out an area on the front of the Hobbit brain that was remarkably enlarged. Known as Brodmann’s area 10, it is also enlarged in humans, and is associated with planning and taking iniative. Given that the Hobbit bones were found alongside stone tools, one could imagine that this sort of mental equipment allowed them to make the tools despite having chimp-sized brains. But the German team found seven brains in their collection that had enlarged Brodmann’s area 10. Their medical records show that one of these individuals couldn’t even speak a few words, which suggests that one shouldn’t read too much in this particular bulge.
On a more general note, the German team points out that human microcephalic brains come in a wide range of sizes and shapes. The 19 brains they studied varied in size from 280 to 591 cc, for example, a range in which the Hobbit’s 417 cc fits comfortably. And so even if no single brain from their collection matches all of the details of the Hobbit brain, their variability show that it could plausibly be produced by microcephaly. Since only a single Hobbit braincase has yet been found, the German scientists conclude, "it is premature to exclude LB1 [the technical name of the fossil] from any pathological anatomy. Analysis of other skulls from the Indonesian island of Flores wil help address the correct taxonomy of the small-brained hominid."
And now, for a word from Dean Falk and company…
The nice thing about Technical Comments is that they allow scientists to respond immediately to their critics. And the most powerful response Falk has is to publish a picture of her own, shown here.
Falk and her colleagues accuse the Germans of some basic mistakes–most significantly not measuring their brains in a conventional way, as Falk did. Falk tilted the human microcephalic braincase to the same orientation as the Hobbit brain. The second illustration here shows the human microcephalic braincase from Falk’s study to the left, the tilted microcephalic braincase in the middle column, and the Hobbit braincase to the right. Suddenly, the human braincase from the German report looks a lot more like Falk’s human than the Hobbit, particularly in the side view in the bottom row. As for Brodmann’s area 10, Falk’s team points out that it is smooth on the microcephalic brains shown in the German report and convoluted on the Hobbit’s.
Falk’s team make one particularly sharp accusation. They point out that one view of the human microcephalic braincase in the Germany report (the top middle braincase in Falk’s figure here) has a striking tip, but the side view doesn’t seem to show it (the bottom middle braincase). "We do not believe these images represent the same individual," they write.
"If this is the best evidence that can be produced froma sample of 19 microcephalics," they conclude, "we suggest that the authors reconsider their position on the microcephalic hypothesis regarding Homo floresiensis."
It’s nice to see the debate move beyond sound bites on cable TV, but I found it odd that Science’s editors didn’t get more involved in this exchange. These sorts of arguments can only be settled if everyone plays by the same rules. So why didn’t both teams settle on exactly how to orient the braincases? And why didn’t the German team satisfy Falk’s group that they hadn’t mixed pictures of two braincases together? That seems like pretty simple procedural stuff.
More significantly, it seems odd that the German team wasn’t required to consider all of the evidence assembled so far about Homo floresiensis–including the various jaws, limb bones, and other remains from several individuals scattered across 80,000 years. It’s not just LB1′s braincase that’s weird–the jaw has no chin, some of its teeth have strange double roots, the arms are long, and some of the limb bones have peculiar twists. What’s more, all the evidence at hand suggests that they were all about three feet high. So if LB1′s braincase does belong to a microcephalic human, as the Germans suggest, then what’s their explanation for all the other bones? Could they have all belonged to humans too? Biologists learned a long time ago that they had to consider the total evidence when it comes to figuring out how individuals are related to one another, because of the complexities of evolution. In one particularly famous screw-up, scientists thought they had isolated DNA from a dinosaur fossil. Only when they had considered all the evidence (in other words, all the potential sources of the DNA) did it turn out to be a bit of contamination from a human. I know this new Hobbit paper was written as a technical comment on Falk’s study in particular, but it leaves lots of unanswered questions.
Admittedly, the total evidence is pretty sparse when it comes to Homo floresiensis. Just a single additional braincase would help enormously, and a tiny fragment of DNA could close the case. Which makes the ban on digging in the cave where the Homo floresiensis bones were found all the more incomprehensible. Fortunately, this new article from BBC reports that the Hobbit team is expanding their search to other sites, even on other islands in Indonesia. Let’s hope the braincases come rolling out like bowling balls.
Update, 12 pm: John Hawks has some questions too.
Last October the world marveled at the announcement of the discovery of a new species of hominid, Homo floresiensis, in a cave called Liang Bua on the Indonesian island of Flores. One conclusion was more shocking than the next. First, this hominid stood only three feet high, earning it the nickname The Hobbit. Second, it lived as recently as 18,000 years ago, which was some 30,000 years after our own species had already been in southeast Asia for 30,000 years or more. The scientists argued that Homo floresiensis was a separate species that might have descended from Homo erectus of East Asia–which would mean that the last common ancestor of the Hobbits and us lived perhaps two million years ago.
Homo erectus fossils have been found on Flores, dating back 800,000 years. The oldest H. floresiensis bones dated back 90,000 years. The researchers suggested that during the intervening period Homo erectus on the island might have dwindled from about six feet tall to three. And despite the Hobbit’s distant relation to our own species, not to mention its small brain (a third the size of a human’s, and about the same as a chimp’s), the scientists argued that it was a clever hominid. They pointed to the stone tools in the cave and the evidence they had found of fires. Just writing about this stuff nearly a year later makes me shake my head in shock.
As I have detailed in a series of posts here, things soon went from controversial to ugly. Several scientists went on the record with skeptical reactions. They pointed out that the bones came mostly from a single individual. They proposed that this individual was a pygmy (like the ones that live today on Flores), or was born with a congenitally small head, or both. One source of friction in the debate was the fact that some researchers see in the fossil record of hominids a lot of diversity while others see little. The fossils then wound up in the possession of a rival scientist who made casts of them, apparently damaging them in the process.
For the most part, Hobbit junkies like myself have had to content ourselves with reading gossipy articles in newspapers. The Hobbit’s discoverers published a brain scan of the fossil skull in April, but otherwise nothing appeared in scientific journals either from the discoverers or their critics. Until now.
In this week’s issue of Nature, the scientists describe bones from nine individuals from the Liang Bua cave. Some of the bones–parts of the right arm and jaw–belong to an individual. Other leg bones, shoulder bones, and various bits of fingers and toes come from other levels in the cave. They were laid down in the cave over thousands of years, the youngest being just 12,000 years old–around the time when our ancestors were inventing agriculture.
The key conclusion of the paper is that these fossils look a lot like the original Hobbit bones reported last year. The new jaw, for example, has the same peculiar roots on its teeth as the old one, and both also lack a chin. If the original Hobbit was just a pathological human, the authors argue, then all of these new individuals would have to be pathological too. And the fact that these fossils span 80,000 years makes it even harder to hold the pathology argument. According to Harvard’s Daniel Lieberman this pattern refutes the aberrant dwarf argument, which now "strains credulity," as he writes in an accompany commentary.
This is not the final chapter, by any means. Robert Martin of the Field Museum in Chicago has confirmed that he is putting together a paper that will dispute the claim that the Hobbit is something other than human, and others may well be up to the same. "Regardless of one’s stand on this issue," Dr. Martin wrote to me in an email, "it is about time that the message got out that there are serious grounds for doubt about current interpretation of the Flores remains."
This a vital part of the scientific process, but the high stakes in paleoanthropology always slow it down. And the bitterness caused by the tussle over Homo floresiensis’s fossils will probably make it even harder for these precious few fossils to be shared. Still, I’m curious to see how Martin and others expand their attack from the original individual to the expanded collection of Hobbits. (I’ll update this post when I come across any interesting responses from skeptics.)
If the Hobbits hold up under this scrutiny, there are still a lot of deep questions that will have to be answered. Were Homo erectus really their ancestors, for example? Tim White, a prominent paleoanthropologist at Berkeley, has suggested that they might be descended from our own species, having undergone a radical evolutionary change into a separate species of small-brained dwarves in just tens of thousands of years. The peculiar traits of Homo floresiensis such as its teeth might make that unlikely. The Nature author meanwhile offer some evidence that might suggest they belong to an even older branch of hominid evolution that Homo erectus. Earlier hominids, dating back before Homo erectus moved out of Africa, had the same overal body proportions as Homo floresiensis, as well as a small brain. Lieberman’s skeptical on this possibility, because there are so many traits that Homo erectus and Homo floresiensis share. Still, the exodus of hominids from Africa 2 million years ago still poses a lot of puzzles; maybe different pioneers leaving Africa around the same time gave rise to the two different species. And what about all the other islands of Indonesia? Are more little bones waiting to be found on them as well?
Unfortunately, on Flores at least, these questions may be left hanging. The dispute has led to the absurd situation that the team who found the Hobbits can’t get a permit to go back to Liang Bua. You have to wonder just how wise we are as a species.
Update: 2:30 pm Greetings, visitors from the National Review. I’m not sure how the Hobbit fits in with The Corner’s political discussions, but I’m happy you’re here.
Update Friday 10/14: See my latest: a human with a Hobbit brain?
In October 2004 Australian and Indonesian announced they had discovered a three-foot tall species of hominid, Homo floresiensis, that was still alive no earlier than18,000 years ago. As I’ve detailed in previous posts, this claim has inspired a lot of debate, much which revolves around whether the fossils, found on the Indonesian island of Flores do in fact represent a new species, or whether they were human pygmies. This week a new study was published in the journal Biology Letters (link to come) that puts this debate in the proper evolutionary frame. The paper is not about hominids, however, but about bats.
Before I get to the bats, let me dwell a little longer on these Pleistocene hobbits. A great deal of the controversy has focused on the one Homo floresiensis skull found so far, which held a brain less than a third the size of a human’s and about the size of a chimpanzee’s. If Homo floresiensis really does represent a separate species, then its ancestors may have undergone a drastic evolution, which not only shrank their bodies but also their brains. One hypothesis for the origin of Homo floresiensis holds that it off from another species of hominid, Homo erectus, which arrived in southeast Asia 1.8 million years ago and may have been present there as recently as 30,000 years ago. Homo erectus was already about as tall as our own species is today, and had brains that were about three-quarters the size of ours.
Skeptics find this possibility implausible, arguing that it’s more likely this individual was just a pygmy human with some genetic defect. As far as I can tell, this skepticism about shrinking hominid brains flows from two sources.
One is the fact that digs on Flores have yielded some sophisticated stone tools and other clues that the hominids of Flores—human or otherwise—were able to hunt. Some people wonder whether it would be possible for a hominid with a chimp-size brain to use such tools, since the rise of tool use in hominids roughly coincides with the rise in brain size. It’s a fair question, since chimpanzees today can’t make the sorts of stone tools found on Flores. But it’s not any sort of slam-dunk refutation of the claim that Homo floresiensis were a separate species. First, consider the fact that the first signs of hominid tool use, 2.6 million years ago, came at a time when hominids still had brains barely bigger than a chimp’s. Second, size isn’t everything. Tool use may also depend on how a brain is wired, not just how much data-processing power it has. It doesn’t seem absurd to argue that as Homo floresiensis evolved a smaller brain, it retained the circuitry that made tool use possible. At least it’s a hypothesis worth testing.
The other source of skepticism, which I mentioned in my last post, is a vague sense that when it comes to hominid brains, evolution cannot run in reverse. It’s certainly true that if you draw a graph of hominid brain size over time, it has climbed to spectacular heights. Scientists prefer to chart brain evolution not simply by its raw increase in weight, but in how large the brain becomes in proportion to the rest of the body. For a mammal our size, we humans have a brain about seven times you’d predict. A great deal of research has gone into charting how brains get bigger over the course of evolution—not just in our immediate hominid ancestors, but over the past 200 million years of mammal evolution. The ability of our species to thrive so spectacularly seems to mainly depend on our extraordinary brains. Given that their size is one thing that makes them so extraordinary—and given that they’ve been increasing for so long—the notion of a shrinking hominid brain can seem absurd.
The discoverers of Homo floresiensis have pointed out reversals do happen. They point to how many species become dwarfs when they arrive on isolated islands. Elephants, deer, buffalo, and other species have shrunk over the course of just a few thousand years. It’s not entirely clear why this happens, but scientists suspect that being small is an advantage on an island with limited resources, and when animals arrive on an island without a lot of predators, there’s no longer a defensive advantage to being big. In some cases, these island dwarfs have evolved a simpler nervous system. So, the argument goes, Homo floresiensis is simply a hominid that happened to get washed up on a remote island and proceeded to evolve according to the rule of islands.
This argument may give you the impression that the evolution of smaller brains is just a digression from the main story of progress. Sure, a few hominids wind up on desert islands and evolve small brains, but back on the mainland, the hominid brain marches on towards our own spectacular size. In fact, it now appears that shrinking brains are a much more general feature of mammal evolution. And this is where we get to the bats.
Bats evolved about 50 million years ago. The first bats could fly and listen to the echoes of their shrieks to find prey, a radar-like technique called echolocation. These two adaptations allowed them to become efficient nocturnal airborne predators, taking advantage of a niche that may have been empty at that time. (Owls seem to have diversified at around the same point in history.) The result was a staggering evolutionary success, with bats now making up 20% of all mammal species on Earth. Bats obviously depend on their brains. They need to be able to process the complex information that they get from echolocation, and they need to be able to control their membranous wings. So you might think that bat evolution has been dominated by a steady expansion of their brains.
But as much as we may value the brain, it is just another organ. If the brain becomes bigger, an animal has to dedicate more energy to it and has less to supply to other parts of the body. This evolutionary trade-off has produced a lot of the diversity of life we see today—including even the size of beetle horns, a subject I blogged on a few days ago. And brains are particularly costly, requiring twelve times more calories ounce for ounce than muscle. It’s not easy to gauge the effect of this trade-off in our own lineage, because only 20 or so hominid species are known from the past six million years. But with so many bat species alive today, it is possible to see major trends in brain evolution by comparing them.
Kamran Safi, a biologist at Zurich University, and his colleagues compared 104 species of bats, noting their brain size, the shape of their body, and the ways in which they hunted. (Some bats specialize in hunting in open spaces, for example, while others can weave their way through forest foliage.) They then extrapolated back along the bat family tree to calculate how big the brain of the common ancestor of living bats was. And from their, they then moved forward through evolution, seeing whether there was a directional trend towards bigger brains.
They didn’t. It turns out that the first bats probably had brains that would be considered average for a living bat. Some bats have bigger brains, and some have smaller ones. Safi and his colleagues looked for other factors that had changed along with brain size in different lineages. They found that bats that had specialized for hunting in tight spaces evolved broad, large wings that provided them with agile maneuverability but also use up a lot of energy. They also tended to evolve bigger brains. By contrast, the bats that adapted to open spaces evolved narrow, small wings that didn’t demand much energy but also didn’t provide much maneuverability. These bats evolved smaller brains. This trend was especially strong in bats that hunt insects, as opposed to ones that have shifted to eating fruit or flowers. When bats evolved in ecological niches that demand a lot of brain power to control their wings, they evolved bigger brains. But when they could afford to slim their brains, they did—thus saving themselves the cost of fueling this hungry organ. These bats with shrunken brainsn were not defective, nor were they even rare flukes sequestered on some tiny island. They could still fly and hunt with perfectly respectable skill. They simply adapted to their surroundings.
Safi and his colleagues conclude that mammal brains may shrink thanks to many evolutionary forces, including a species’s diet, social system, or the length of its pregnancy. “A reduction in brain size should be a general property of evolution,” they write, adding that “The assumption that larger brains are derived [a new development in a lineage] is probably associated with the quest to explain why humans have large brains.”
The question of whether Homo floresiensis really did evolve a shrunken brain remains an open one. But if it does prove to be the case, we shouldn’t consider it a bizarre fluke. The bats are beginning to fly here in Connecticut, and when I see them flit across a twilight sky this summer, I’ll think of them as flying hobbits.
So let’s recap: It’s been almost eight months now since scientists announced the discovery of Homo floresiensis, the diminutive people that some claim belong to a new branch of hominid evolution and skeptics claim were just small humans. We seem to have entered a lull in the flow of new scientific information about Homo floresiensis. The last thing we heard from its discoverers came in March, when they published scans of the Homo floresiensis braincase, which bolstered their case that the skull they found didn’t happen to belong to someone with a birth defect. The skeptics have made various noises about evidence that the fossils are indeed pathological, and thus can’t be the basis for recognizing a new species. They have told reporters about their visits to pygmies who live near the fossil site on the Indonesian island of Flores. But they have yet to publish any of this in a scientific journal, where their claims could be put to some serious scrutiny. For example, you can’t refute the claim that the fossils are a separate hominid species by showing that living pygmies on Flores are very short. You also have to deal with the odd body proportions of Homo floresiensis, such as its long arms. Perhaps these are pathological too, but no one has gone on the scientific record yet.
For now Homo floresiensis junkies like myself have to content ourselves with scraps: the various details of the nasty battles between the discoverers of the fossils and their foe, Teuku Jacob, grand old man of Indonesian anthrolopology and lead skeptic. An article in today’s Los Angeles Times, offers the latest overview of the squabbles. If you are new these misadventures, it’s pretty good way to catch up. For those who keep up on this stuff, I see a couple interesting new tidbits.
1. A lot of Teuku Jacob’s arguments against this being a new species seem wacky to me, at least as they’ve been presented in the press. In the LA Times, he “argues that evolution cannot ‘go backward’ and produce a human with a smaller brain.” Perhaps Jacob will eventually make this case at length in a scientific paper, but for now I’d just say that there’s no Law of the Perpetually Increasing Brain that I’m familiar with. In fact, the mammal brain is surprisingly malleable over the course of evolution. This afternoon I will try to write up a post on a new study that makes this clear. UPDATE 6/16: Read it here.
2. Teuku Jacob took possession over the bones for a few months, and when he returned them, their discoverers claimed the delicate fossils were damaged. The damages included what appeared to be an attempt to reconstruct the jaw.
In the LA Times piece, one of the co-authors of the original Homo floresiensis report accused Jacob of trying to make the skull look more like a member of our own species (the other hominid species that lived in Indonesia, Homo erectus, had a weaker jaw).
For the first time that I’m aware of, Jacob admits that he was trying to “improve” the skull. “We tried to improve some of the things,” he acknowledged. “We didn’t damage any bones. Actually, we improved some.” Improve, or match your preconceptions?
3. As if this wasn’t bad enough, the controversy has now resulted in a complete halt to digging in the cave where the original fossils were found. Apparently the team that discovered the fossils didn’t get the proper permits from the Indonesian Institute of Science, although they believed they had. Now the Institute has decided that digging should stop, so that the dispute won’t get worse. While I can only judge this decision from a brief summary in a news article, the logic behind it baffles me. I doubt that forcing scientists to cool their heels while clues to what could be one of the most important discoveries in human evolution wait to be found on Flores will put them in a more pleasant mood. What’s more, digging in the cave could yield evidence that can settle this dispute once and for all—such as DNA, the odds of finding may have gone up thanks to the invention of new methods for culling it from the environment.
It’s frustrating to know that we could be enjoying a scientific feast, when all that’s on the menu for the foreseeable future are scraps like these.
The feud over Homo floresiensis, the little people of Indonesia, centers on whether they were an extinct diminutive species that evolved from some ancient hominid, such as Homo erectus, or whether they were just pygmy humans, perhaps suffering from some disease. The leading skeptic, paleoanthropologist Teuku Jacob, has claimed that there are pygmies living not far from where the fossils were found, on the island of Flores. I came across a short item at Japan Today about a scientific expedition to study the pygmies, which was based on an article in Kompas, an Indonesian publication. The original article is here, and my intrepid brother Ben, expert on Indonesian anthropology (cultural, not paleo-), did an on-the-fly translation for me, which I’ll run below. The team got back from Flores on April 25. While there, they went to a village called Rampasasa, made up of 77 families. About 80% of the people were pygmies. They measured 10 people who were a bit taller, with a height of 155 cm and 2 measuring 160 cm. Homo floresiensis was 130 cm. The researchers claim that these tall villagers got some extra height from having married non-pygmies from surrounding villages.
I imagine that we’ll be hearing something more official about the grandly-named Rampasasa Pygmy Somatology Expedition in a couple months. I wonder if they’ll have something more than height measurements to offer–just because living pygmies are close to H. floresiensis doesn’t seem terribly compelling, since it’s my impression that height changes can evolve relatively quickly in humans. (I can’t find a paper to back up this recollection at the moment, I confess.)
Update at 3:50 PM: Apologies for the various typos, dead links, and missing facts in the first version of this post. I blame it on my Mac upgrade to Tiger today.
So here’s the article…
The "Pygmy" Community of Flores
The existence of a community of pygmy people in the Manggarai Regency of Flores, East Nusatenggara, is quite interesting but also quite mysterious. In the context of the archaeological discovery of the prehistoric human skeleton from Liang Bua in Flores — which has been published widely as belonging to the species named Homo floresiensis — the existence of the pygmy community in the village of Rampasasa, Waemulu region, Waeriri subdistrict, could possibly shatter all previous arguments.
"The existence of the pygmy community there is quite interesting and also quite surprising. For many years, experts from various corners of the world have only had the chance to see their footprints, but it turns out we can now find them living in a society. This means that for hundreds or maybe even thousands of years, this pygmy community has remained settled in that place without ever moving around," said Prof Teuku Jacob, emeritus professor at Gadjah Mada University.
Jacob, who also leads the Bio- and Paleo-Anthropology Laboratory at Gadjah Mada, further explained, "Pygmy people have indeed been reported as existing in the Andaman Islands and New Guinea, but only a few remain and it is difficult to find them because they live in dispersed conditions. Now we can find them living together in one village."
Since the 1920s, the East Nusatenggara region has been an object of interest for anthropologists, especially those from Holland, after seeing evidence that the residents there have rather short body height. The results of the 1929 Biljmer study indicate that more than 50 percent of the residents of the region have body height of about 155 to 163 cm. Besides that, in Flores there have long circulated folk tales about short people with darkly colored skin (Negritos) who live in the hills, hiding in caves.
Dr. Theodore Verhoeven, pastor at the Ledalero Maumere Seminary, conjectured in 1958 that these short people were a Proto-Negrito community. This term refers to the Schebesta study in the Andamans, remote areas of Borneo (Kalimantan), and also the southern Philippines.
According to Teuku Jacob, if the height of the Negritos is roughly between 155 and 163 cm, they would be called pygmoid. But if the Rampasasa people are true pygmies their height would have to be less than 145 cm for adult males and 135 cm for adult females. The maximum weight would be 40 kg for males and 30 kg for females.
Pygmies are indeed different from dwarfs. This is because the term dwarf indicates a small body with proportions that are out of order. Pygmies, meanwhile, have small bodies that are proportional.
Since last year, the team working under the leadership of Prof. RP Soejono and Dr. MJ Morwood conducting an excavation in Liang Bua, Flores, has found human skeletons with an approximate height of 130 cm and with brains about a third of the size of modern humans. This discovery was later claimed to be a new species of humans called Homo floresiensis (Flores Man).
Worwood, an expert in cave paintings from Australia, in fact called the results of the discovery "hobbits" in a popular fashion, a group of pygmy people like those in the film Lord of the Rings. The picture of miniature Flores Man then appeared as a major report in the April 2005 edition of National Geographic.
The above claim about the discovery of a new species was rejected by a number of experts. Etty Indriati, a PhD from Gadjah Mada, called it a baseless tale. How could there be a new species from the discovery of just one skeleton which in fact was misidentified? They said it was a female while from the dental structure it was clear that it was a male, and also a modern one.
"What is more unreasonable, it is not possible that a brain that has already developed as Homo sapiens could then become small and develop into a new species, left behind as prehistoric remains," she explained.
Indeed, for mammals trapped in remote islands for hundreds of years — and with insufficient food to eat — bodies will become smaller as an adaptation to the environment. "But, for humans, their menu is not just one type of food. Despite being isolated, they will try to find other types of food, so their bodies do not become small," she added.
Teuku Jacob explained, "The pygmy people of Flores are not a prehistoric race. Our team has successfully found a community of pygmies living in the modern world." What is even more ironic, the community of pygmies mentioned by Jacob is only about 1 kilometer from Liang Bua, the dwelling place of the species given the name Homo floresiensis by Worwood.
Koeshardjono, an expert in biology who was the first to announce the existence of a pygmy community in Flores, stated, "This expedition was named the Rampasasa Pygmy Somatology Expedition. This is because the pygmy community of about 77 families resides entirely in the village of Rampasasa, Waemulu region, Waeriri subdistrict, Manggarai regency, south Flores."
The results of the team of physical anthropologists led by Teuku Jacob recorded that 80 percent of the residents of Rampasasa are classified as pygmy. The provisional findings indicate that there are 10 people with a height of 155 cm and two people with a height of 160 cm. It turns out that their body size is relatively tall because of marriage with residents outside of the village. The team of researchers from Gadjah Mada has been in Rampasasa since April 18 and returns to Yogya Sunday night (April 25).
I’ve been catching up on my online reading, and a couple days ago John Hawks offered this tantalizing hint that Homo floresiensis a k a the Hobbit may be a pathological specimen. Such claims have been made before based on the small skull of the hominid, but they’ve been pretty powerfully rebutted. But Hawks is claiming that the rest of the skeleton is sickly. He seems to be basing this contention on having seen the bones, and on research by others that will be coming out soon. Now, normally I wouldn’t put much stock in this sort of off-hand remark, but Hawks has been so good on his blog that I have to say I’m intrigued. Adding to my interest is the fact that he now retracts his suggestion that the Hobbit represented a very early migration out of Africa by australopithecines.