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."
In the same issue of Science, Falk and her colleagues responded to both points.
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.
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>> Those critics had microcephalic brains of their own to show
That's a little harsh, Carl
In your view, did the "science media" (e.g., National Geographic) jump the gun in publishing major stories on this find? I would think that after the feathered dinosaur debacle, they would be quite careful, but the level of actual hot scientist-on-scientist action here (as opposed to the unsexy creationist-on-scientist action) makes me wonder if more details should have been hammered out before the public was alerted of the discovery.
I am pleased that the controversy has avoided the stone tools that are presumably found in good asssociation with the fossil(s). There are several alternative hypothesis about how these arrived there then. Several of the hypothesis do not require hobbits actually making the tools, although some suppose they used them.
I, for one, am happy to have this out in the open, so to speak. It is interesting and helps non-scientists understand something of the actual practice of science.
Greg--In the case you mentioned (the fossil Archaeoraptor), the scientific description of the fossil was not published before the NG article came out. (For the full details, go here. In the case of Homo floresiensis, it underwent a very long period of peer review (I heard over a year) before being published in Nature. Only then did the media report on it, and the critics were interviewed in many articles. Archaeoraptor turned out to be two fossils fraudulently combined into one, but no one is crying fraud when it comes to the hobbit. And as all the good histories of paleoanthropology make clear, even the best fossils stir up fierce debates.
The question here is plausability. In the United States there are less than 500 microcephalics. We are talking about 300 million people. In the few 10,000 years covered by the sediments in the cave the total number of people reaching adult ages on the island must have been much smaller. Of course severe dietary problems and genetic disorders could make it more common, but the probability of a microcephalic reaching adulthood in a hunter gatherer society and being the owner of the only skull found is vanishingly small. With these odds, I don't understand how people can claim something based in subjective cranial readings.
This is the best picture I've seen yet for comprehending the remarkable scale of the hobbit skull.
Filipe has a great point and I wonder why it is not raised as an argument more often against the microcephalic explanation.
To expand on this point, there were post-cranial remains found in the site suggesting other individuals of the same size. Are all of these supposed to be microcephalic too or do microcephaly proponents suggest this was a population of undersized modern humans with a microcephalic among them that happen to own the only skull to fossilize? This is a little too convenient scenario.
I think it is acceptable to disagree with a theory but only if you can propose a better alternative.
Hey there Carl:
You write a good blog, and I thought your Soul Made Flesh was a solid, much needed work on Willis; I've come to expect from you thoughtful writing on matters of scientific interest for and from the lay person. I hope you won't feel the need, therefore, to make personal attacks ("Those critics had microcephalic brains of their own to show") or unseemly criticism ("Yet the scientists just leave us hanging with a statement that is so cryptic as to be nearly useless" - they are writing for a specialist scientific audience to whom I suspect their statements are not "useless" at all) a regular feature of your writing.
Regards
to expand further, contemporary hunter-gatherer cultures routinely kill infants born with severe disabilities - and even twins or babies born to single mothers, simply because the necesarily mobile group doesn´t have the resources to transport or maintain these people. Would a society thousands of years ago likely have done things differently. And anyway, where ARE the normal individuals?
Regards,
Mike
Unless I missed it, there's no mention of DNA in the story ?
Wouldn't that be the way to go instead of speculating about microcephaly ?
Samples from the bones were sent for DNA analysis months ago. The analysis would surely settle the arguments once and for all. What's happened to the results ?
( that's bearing in mind that the bones aren't really fossils - they're just old bones - much easier to sample than a true fossil )
I'm puzzled. Surely there *are* other Hobbit fossils?? I distinctly recall a TV documentary (a respectable one, either BBC Horizon or C4 Equinox series) about this controversy, which ended with the news that the researchers had now discovered remains of about 10 individuals, ranging over a long period of time, all similar in size to the original find.
I think these people concentrating on the braincase are missing the bigger picture (as Carl has mentioned before). Where are the microcephalics with double-rooted premolars and no chin? And why were the only two jaws found identical in this regard? How would microcephaly cause a rotation of the humerus? Some people need to open their eyes to all the evidence.
Zimmer make fun small brain critic. Why you make fun small brain critic Zimmer? Small brain critic cry. Small brain critic no like Zimmer.
http://milkriverarchive.blogspot.com/2005/10/env-more-little-jawbones.html
has this quote from:
By JOHN NOBLE WILFORD, The New York Times, October 12, 2005
"In Dr. Martin's view, in which he is joined by several prominent scientists, the more likely explanation for the small stature is, in part, a phenomenon known as island dwarfing."
If Martin did say "island dwarfing" then he has fallen between two stools. Perhaps he has resiled back to "micro-cephalic". However I saw a report of further small bones 3000 years younger. When does a race of microCephalics become a species?
Re "island dwarfing" having lived in the worlds largest Polynesian city (Auckland NZ) amongst Tongans,Samoans,Fijians & Cook Islanders, I can assure you those guys are BIG. If you are convinced of Island Dwarfing, try expounding that theory in public bar of the "Gluepot" hotel on Ponsonby Rd any evening, if you dare!
It looks like the spirit of Rudolf Virchow is once again haunting paleoanthropology.
Clearly, Carl writes a thoughtful and clear blog, to which I have linked in my Cryptomundo update of the media circus regarding this "technical paper," with some interesting comments from Peter Brown.
See:
http://www.cryptomundo.com/cryptozoo-news/browndsdebunk/
Allow me to point out a couple things here, in answer to the comments...
There is no DNA on LB1 because Teuku Jacob of the Gadjah Mada University in Yogyakarta, Java, not only allegedly destroyed some of the bone specimens, but he even glued one fractured bone together to mask the damage. Jacob reportedly also washed and dissolved the LB1 skull in acetone to make it impossible to extract any DNA for analysis.
Martin ignored the fact of the other 6 - 9 individuals that have been found of Homo floresiensis.
Some rather incredible things are being revealed in what is being overlooked by the microcelphaic camp in their rush to overturn this species.
Unfortunately, the media has been all too quick to accept Martin's "feelings" on what might be occurring as "facts."