Flores

In
an article about the controversy over the Liang Bua fossils, Rex Dalton of Nature inserts this non sequitur:

Somewhat scientifically isolated, the 75-year-old Jacob has continued to adhere to the theory that hominin species from multiple regions around the globe evolved into a single line that produced modern H. sapiens. In this theory, Neanderthals were direct ancestors of modern humans, but most studies have shown that they were not related to H. sapiens. The 'multi-regional' theory has virtually no support among the world's leading anthropologists (Dalton 2005:433).

Those knowledgable about the field will recognize that this comment is startingly false. One may dispute whether this scientist or that one is a "leading anthropologist" but there is a better way to address the question: simply do a citation survey. My own informal survey of citation rates indicates that the top two paleoanthropologists in terms of citations both are public supporters of a multiregional model. The next few have written mainly about australopithecines, with varying opinions about modern human origins. (UPDATE: A later post has provided a top ten list of citation rates. The top two are no longer the same as indicated here -- formerly they were Wolpoff and Trinkaus, who are now 3 and 10 on the list -- and I make no claims about the opinions of the current leaders about modern human origins).

Now suppose we extend the frame to encompass the top 100 or so paleoanthropologists. Does anyone seriously think that this does injury to the representation of the multiregional perspective?

OK, but suppose we consider only those that have their work published in Nature. After all, we can presume safely I think that Dalton reads his own journal. And it is true that scientists that have been asked to comment on new finds within the past five years have been supporters of a more speciose, bushy taxonomy for the hominids. But this is partly because of the recent finds themselves, like the Lomekwi hominids, that invite the splitter-vs.-lumper dialectic. Among research articles we find not only Tim White and colleagues' (2003) Herto paper arguing for a recent African origin, but also Alan Templeton's (2002) paper supporting multiregional evolution from a genetic perspective. In short, there is no single perspective that dominates the field today, and I think that is a very good thing. We do not need comments that appear to stifle honest disagreement or marginalize those who remain skeptics of even widely-held notions.

I have addressed elsewhere the idea that the Liang Bua skeleton somehow addresses the modern human origins problem. I concluded, and still believe, that it makes virtually no difference one way or another. Clearly if a small population of ancient humans became isolated 900,000 or more years ago and no longer exchanged genes with other human populations, its evolution can say nothing about the possibility of genetic exchanges across the continental areas of the Old World. Multiregional evolution simply has nothing to say about this particular problem

But it cannot be denied that people like Teuku Jacob, Alan Thorne, and Maciej Henneberg who have expressed skepticism over the original interpretation of the skeleton have elsewhere written in support of a multiregional model of human evolution. Some, like Dalton, have argued that this shows that the multiregional model is threatened by the possibility that Homo floresiensis was a real dwarf species of hominid.

I disagree. In my opinion, the reason is that some scientists treat variation more seriously than others. The real split in the field is not between lumpers and splitters or between multiregional evolution and a recent African origin. The real split is between populationists and typologists. Not all populationists are multiregionalists, but the hypothesis is more often accepted by those who consider variation within populations as an important product of evolution. A populationist is less likely to accept the idea that a singular fossil is representative of its population (or species), because no single individual can be representative of a range of variation. It is that perspective that leads to skepticism about the Liang Bua fossil.

The variability within species of hominoids is often underestimated. For apes, this is often because researchers have only examined a small number of specimens in detail. Most research studies that include extant apes as comparisons use fewer than 30 specimens. Moreover, even very extensive skeletal collections of apes, like that at the
Cleveland Museum of Natural History have biases that may underrepresent variability. Most of the specimens in that collection were wild-shot, and among the gorillas males are highly overrepresented. It is plausible, even likely, that there is a bias among these males for large, healthy specimens that would fetch a good price. Paleopathology is very different in an ape context than in a human context. Among apes, serious pathologies are generally fatal early in life, and we do not find them in skeletal collections. So from that perspective, apes make a poor comparative model for early humans.

For humans, there is not only the problem that collections are often small and geographically represent only a small area, but also that pathologies may have been specifically excluded. For example, the Hamann-Todd collection at the Cleveland Museum of Natural History consists of a large proportion of indigents whose bodies were assigned to the collection by the state. In various ways, these people were not representative of the Ohio population in health and other characteristics, but for our present purposes the most obvious problem is that microcephalics do not tend to die in circumstances that would get them into this collection. Pathological specimens do end up in medical pathology collections, but these are in many instances separated out from the normal variation within their populations.

Thus, few biological anthropologists gain a full understanding of human variation including pathological variants. No one knows to what extent the proportion of congenital or developmental defects may have been in early human populations that differed from ours in environment. For that matter, no one knows how a pathology present in today's humans may necessarily have manifested in a Stone Age human lacking today's medical interventions, nutrition, and lifestyle. These are some of the reasons why paleopathology is such an interesting and problematic research field.

None of this proves that the Liang Bua specimen does not represent a new species of hominid. But they do give reason for cautious skepticism.

More on the Flores hominids

Home

References:

Dalton R. 2005. Looking for the ancestors. Nature 434:432-434. Nature online

OK, I was drawn in by the first few minutes, so I'm liveblogging the National Geographic show, "The Ultimate Survivor."

8:02 -- Lee Berger has fossil evidence of a giant race of ancient humans?

8:05 -- The basic theme is the bush vs. ladder theme. To illustrate the ladder, they have an australopithecine pick up a steel baton and pass it on to later hominids. Forty years of Hollywood technology since "2001" and we've got a bunch of plasticine freaks passing a steel baton. I want the monolith back!

8:10 -- The idea of a family tree is very easily illustrated--use a tree. So we have a tree with hominid pictures on it. But did you notice that this particular tree looks remarkably like Ernst Haeckel's primate phylogeny tree?

8:13 -- Establishing the bush theme: Kenyanthropus as a new species apart from A. afarensis. Louise Leakey is featured.

8:16 -- Obviously Kenyanthropus was a different genus. It has brown fur and Lucy has black fur!

8:22 -- The Homo erectus model is a little distracting. He looks like an airbrushed white guy. Are these the same actors the BBC used?

8:23 -- On to Dmanisi. Reid Ferring says there are many piles of round river stones that were probably collected for throwing. They show a couple of hominids throwing rocks at a sabertooth. OK, the skull suddenly fleshing to life in Lordkipanidze's hand is frightening. There's a Hollywood touch.

8:35 -- Gretchen is complaining about their made-up common names, "Nutcracker" for A. boisei, "Handyman" for Homo habilis. Is there any point to dumbing it down this way? Who do they think is watching?

8:38 -- Swartkrans burned bones. "If these burned bones aren't the result of a natural fire, then they are the first evidence of a controlled fire by humans." Well, yes, since those are the only two choices.

8:39 -- RICHARD WRANGHAM ALERT! He's talking about fire IN FRONT OF A SMOKING WEBER GRILL! NOW HE"S CHEWING RAW MEAT! Whoa, man, that grill is smoking up a storm....NOW HE'S BEATING MEAT ON A TREE!

8:42 -- This is a very clever illustration of the small gut, small tooth, small jaw muscle changes, with body parts computer morphing.

8:48 -- Lucinda Backwell is talking about A. robustus diet and termites. There is really too much narration here. I would much rather hear the scientists telling us about this stuff. It's not that complicated that it needs to be dumbed down.

8:55 -- "Lee Berger is on erectus's trail." He's excavating a fossil hyena den. He has a leg bone from an ancient human that he estimates was six feet tall. The amazing thing "is that we think it's a child or female." Berger and Steve Churchill build a reconstruction of the Kabwe specimen. OK, this is nothing new -- it was published in 1923, people! I guess this is just going along with the theme of giving everything a nonsensical name: "Goliath" is the name for Homo rhodesiensis. Nothing against Lee and Steve; I'm sure they think it is as hokey as I do. On the other hand, they did pose in front of a computer at a library workstation to have a mockup of a hominid computer-inserted in the film later....

9:06 -- Steve Chuchill is measuring the volume and surface area of his H. rhodesiensis mold. He ends up dangling a macabre skin with face painted on. Too cool!

9:07 -- The voiceover still hasn't called it anything but Goliath, but the hint that it may have went to Europe means that we may be talking about Homo heidelbergensis instead. Hey, I have a suggestion: if the taxonomic names are too complicated, maybe we could call them all Homo sapiens and just talk about the site names?

9:10 -- Another Flores snippet. The film is really jumping around a lot, but it is clear that the only new thing is Flores, and the rest is just a summary of results from paleoanthropology over the last five years.

9:15 -- The hobbit skeleton laid out includes a humerus and ulna. The computer-generated hobbits are walking around the Liang Bua excavation like Kevin Pollack and his buddy in "Willow."

9:20 -- "Goliath!" The reconstruction of Kabwe is 6 foot 4 inches. I especially like the veins popping out on the arms -- he's a pro wrestler! -- and that goes with the theme of him being hot all the time. He didn't have the surface area to get rid of heat in a hot, moist climate, so he had to stay where it was dry. Not sure what the problem is here, exactly; are there no large people living in Africa now?

9:26 -- Henshilwood at Blombos. Nice shots of the ocean, and reconstruction of the cave during occupation. Good emphasis on the incised ochre chunks. This is a nice part.

9:30 -- "Equipped with greater brain power, some of us headed to Europe." A suddenly Caucasian modern human comes face-to-face with a Neandertal! BZZZAP -- they're gone!

9:32 -- Back to Flores: "For thousands of years, modern human migrants likely shared this island with another species: hobbits." Hmmm...could it be that these modern humans made all those tools at Liang Bua? Nope, can't ask that question.

9:36 -- Commercial break. How is it that they can make "Hogzilla" seem intrinsically more interesting than human evolution?

9:37 -- Spencer Wells "has made a startling discovery about our struggle to survive: we almost didn't make it." Wells is selling us Toba! Voiceover:"There is no way to know how many of us died...only how many lived." Wells:"It may have taken a global catastrophe to actually kick-start the mind into high gear." OK, the concept du jour is "survivor genes," that were spread around Africa before Toba erupted (they haven't named the volcano for us yet) and allowed some people scattered around Africa (but nowhere else? except for Neandertals and hobbits?) to survive. I guess this is supposed to explain why our genes show geographic diversity dating to the Lower Pleistocene?

9:42 -- "You don't wear jewelry unless you care about what others think about you, and that is a uniquely modern human trait." Well, and Neandertals....

9:45 -- Lice genetics. "Body lice live under clothes, not just the rough animal hides worn by earlier humans." What?

9:51 -- FoxP2: it allowed us to ululate, and that sets us apart from other animals, "more than any other human talent, it is the ultimate power tool."

9:52 -- RICHARD WRANGHAM ALERT: The grill is still smoking. "Chimpanzees have bouts of violent aggression with each other about 100 to 1000 times more often within their communities." "We have a coalition of the timid." "That kind of killing [of violent people within groups] led to selection against the genes that cause aggression within groups." That, and BEATING MEAT AGAINST A TREE! OK, that's overkill. In any event, this is one of the most sensible parts of the show, and it's only two minutes long. This could be expanded into a half-hour section--how did cooperation arise in ancient humans?

9:55 -- "Consider the tuber." Lee Berger is mincing, grating, ricing, and macerating potatoes with 18 different kitchen tools. And yet, he isn't in Wrangham's backyard. Hmmm...better to stay out of the SMOKY MEAT WARFARE ZONE.

9:58 -- Steve Churchill gets the last word: "Wherever we encountered them, we outcompeted them. We made this come to pass."

News story on MSNBC

News story on BBC

Michael Balter story in Science

Update:

The original post is listed below. A reader has kindly forwarded the text of the Falk et al. (2005) article, so I add a few comments to the original. The paper is a very nice description of the endocast, with pretty much every detail covered whether in the affirmative or negative. If a similar paper could be published about each of the skeletal elements, they would constitute a very decent monograph. My comments focus on the pathology issue and the analyses of shape.

As Maciej Henneberg has pointed out online, the study includes a specimen with primary microcephaly as a comparison. Henneberg and others have suggested the specimen may have secondary microcephaly. According to Falk et al. (2005:1):

The only criterion for secondary microcephaly is an occipitofrontal circumference below -2 standard deviations for age and sex, but these data are unavailable for LB1's population. Unless a Homo erectus-like endocast shape is characteristic of an unrecognized form of secondary microcephaly, we reject the hypothesis that LB1 was a pathological microcephalic.

And in the Supplementary material:

Since LB1 lacks the diagnostic head shape associated with [primary microcephaly] and lacks the gyral morphology associated with [microcephaly with simplified gyral pattern], its interpretation as a microcephalic can only be made by claiming that it is a secondary microcephalic. This amounts to saying LB1 is small-headed (literally microcephalic) because it is small-headed, which does not lend itself to hypothesis testing.

It seems to me this passage pointedly glosses over the troublesome parts of the pathology hypothesis. As defined here, secondary microcephaly does not result in the gross abnormalities in brain shape that can result from primary microcephaly. Instead, it is defined by brain size. Clearly the brain size of LB1 would qualify as microcephalic under this definition -- even if it were a member of a Homo erectus-like population.

So what response is there to this? Firstly, we don't know what brain size the rest of the LB1 population had. If they were all small like LB1, then clearly that specimen can't be microcephalic. And secondly, LB1's endocast is abnormally-shaped; it is shaped just like a Homo erectus endocast. If secondary microcephaly doesn't result in abnormal brain shape, then it certainly can't produce a Homo erectus-shaped brain.

I don't know about anyone else, but that argument doesn't satisfy me. Basically, what I wrote below still holds, and I would suggest a working relationship between a pathologist specializing in brain disorders and a paleopathologist who can give some context on the ways that Stone Age lifestyles can alter the characteristic symptoms of developmental abnormalities.

Endocast shape

Falk et al. (2005) provide a series of metric comparisons to give an idea of the similarities in endocast shape between LB1 and other fossil hominids and extant hominoids. The major method of comparison is by principal components analysis, performed upon endocast ratios and/or measurements. In a first analysis, the gross measurements of size (length, breadth, height, and frontal breadth) were tabulated into six bivariate ratios, to which principal components analysis was applied. The second principal components analysis was performed on six measurements of the endocast base.

The reason for doing a PC analysis of ratios escapes me entirely, since there is no information in the four ratios that is not already in the measurements. One possible justification is to discard information, with the notion that ratios will be scale-free. But several of these ratios appear to be quite strongly correlated with cranial size. And there are only three important PCs for a four variable analysis. At any rate, the second PC in this analysis is almost entirely determined by the microcephalic, so the inclusion of that specimen really dominates the overall variation in the samples. Meanwhile, within-population variability is essentially assumed away by the use of population means for humans and chimpanzees instead of real data. In the end, the analysis appears to show that LB1 is most similar to ... the Black Skull! And next most similar to ... chimpanzees! In my opinion, this analysis isn't telling us about anything other than cranial size -- WT 17000 comes out as similar because it is the most similar in size (410 cc).

The second analysis is the one that places LB1 near humans. Again, this is a PC plot based on ratios, in this case including some values that express the difference between two linear measurements as a ratio with a third linear measurement. LB1 is similar to Homo because of the third PC, which is loaded heavily on the distance to the olfactory bulb from the rostral end of the endocast, and the distance between the rostral and caudal ends of the olfactory bulbs. The reason for this similarity is not obvious to me, but it may be important. In any event, it would help to have ellipses of real data instead of just species means, so the variability in the values could be evaluated.

Cognitive capabilities

The lede of the story is the idea that the convolutions on the endocast of LB 1 show that its brain may have had relatively advanced cognitive abilities. In particular, the temporal lobes are relatively large, and the frontal lobe is fairly strongly convoluted. Dean Falk says that the greatest convolutions correspond to Brodmann's area 10, "which is expanded in modern humans and is involved in undertaking initiatives and planning future actions -- key components of higher cognition" (Balter 2005:1386).

According to the story:

This enlarged area suggests that the little Flores people may well have been capable of creating the stone tools that were found near them, which are more typical of those made by prehistoric modern humans than earlier hominids including Homo erectus. "The real take-home message here is that advanced behaviors, like making sophisticated stone tools, do not necessarily require a large, modern, humanlike brain," says [Fred] Spoor. "It can be done by reorganizing a small brain, with convolutions and rewiring, and this goes to the heart of our understanding of human evolution." (Balter 2005:1386)

The idea that there are huge frontal convolutions here that are absent in H. erectus certainly is not evidence of cognitive function. That is to say, if they are new in this putative species compared to its ancestor, then they cannot be said to be homologous with modern human frontal convolutions, which means we can conclude nothing about their function. If, and that's a big if, the brain actually shrank from a larger brain in an ancestor species, then to maintain the same function it might well have increased in convolutions, thereby retaining a more similar surface area (and thereby neurons) with respect to volume. These convolutions would not attest to advanced cognitive skills, except in the sense that they might be beyond those expected for a 380 mL brain.

For me, the key facts here are the ones that are missing. There is no suggestion that Broca's area was evident. Considering that KNM-ER 1470 has a pronounced Broca's area, this is potentially important. Endocasts have little to say about brain function in the first place, but this endocast in particular has little to set it apart from any early hominid.

UPDATE: Falk et al. (2005:2) say this about Broca's area:

[W]e decline to identify rami that border the human pars triangularis (part of Broca's area) on the left, although the general morphology in this region would be consistent with their existence.

No smoking gun, in other words.

Of course the key evidence that the Flores hominids had advanced behavior is the archaeological record of that behavior. But there really is no reason to think the archaeology at Liang Bua was made by the hominids in the cave (even if they all represent the same population). The tools really are more typical of those made by modern humans. And there is every reason to think that by 18,000 years ago (and quite probably by 70,000 years ago or earlier) there were modern humans on Flores. There were modern humans in Australia by 50,000 years ago, and modern humans in island Melanesia by 30,000 years ago -- both places reached by oceangoing boats. In this context, it is extraordinary to suggest that the modern humans weren't responsible for the modern human-looking tools. So the archaeology is far from evidence of cognition for the LB 1 individual or its putative population.

Microcephaly

The paper provides a graphic comparison of the LB 1 endocast with the virtual endocast of a modern human microcephalic. They are not the same shape, but they are approximately the same size. The paper argues that this shows that the skull did not have microcephaly.

Personally, I think this interpretation is premature. Pathologies may affect modern humans in roughly consistent ways, but there is no reason to think they would affect an ancient human skull in exactly the same way. There are just too many potential variables when we turn to humans who did not live a modern lifestyle. We find this with every other kind of paleopathology, and I would expect microcephaly to be no different. Every case may be sufficiently ideosyncratic to defy generalization.

But we don't even have data about the distribution of brain shapes in modern microcephalics. Microcephaly is not only a disorder of the brain; it affects many aspects of cranial shape. If these are developmentally different to any substantial extent, the brain shape may be radically different. The same is true when we consider artificial cranial deformation -- the gross shape of the brain says little about what most of the genes would have it look like, and a few mechanical factors can greatly alter it. Again, the external shape of the brain just doesn't say that much about its wiring, and we really know too little to say anything with confidence about its development in this case.

The Balter article quotes Fred Spoor as saying, "Colleagues advocating that [the Flores hominid] is a modern human microcephalic should start publishing hard evidence in peer-reviewed journals to underpin their claims" (1387). I can see this point -- the "put up or shut up" priniciple -- but I just don't think we are there yet. Has anyone involved any experts in human brain pathologies in studying the skull yet? Is there even a single expert on microcephaly who has said anything about the skull? I know enough not to pretend that I can say this is or isn't pathological. I suspect that any qualified clinician would say the same; there is just no telling how microcephaly would manifest in a Stone Age specimen.

Australopithecines again

It's my hypothesis, and it won't go away. Here's what Balter writes (1388):

But the new paper urges consideration of an alternative hypothesis, that a small-brained, pre-erectus hominid managed to get to Flores in the distant past, and then, in a case of parallel evolution with modern humans, evolved a relatively advanced brain on its own. "Some of [the hominid's] traits indicate that the ancestral population may predate Homo erectus," says Morwood.

I find little to criticise here, except the idea that these hominids were necessarily cognitively advanced. That comes from the assumption that they made the tools, which I cannot justify.

The main problem with the australopithecine hypothesis is the small teeth, which did have to evolve in parallel with modern humans. But then, they also had to evolve in parallel with modern humans in the case that LB 1 descended from H. erectus, since LB 1 has smaller teeth than any other archaic hominid. Otherwise, it's a good australopithecine -- complete with a broad pelvis, long arms, and small brain and body sizes.

Now, if somebody would just give me credit for it. I really did publish it first, on this site.

More on the Flores hominids

More on the evolving story of the hobbit remains in
this story (smh.com.au). Like most custody battles, the fight over these little guys is burning a lot of people. I don't really have a comment, it's just interesting the way the wind is blowing.

Notice at the bottom that a sample has been sent to the
Max Planck Institute for DNA recovery.

In light of recent comments about DNA contamination, I'm now doubtful this will achieve a meaningful result. Consider the possibilities:

1. The hobbits have only modern human sequences. If this result could be authentically shown to come from endogenous DNA, then this would show that the Brown hypothesis about island dwarfism was wrong, and this indeed was a pathological, but otherwise unremarkable, human. But this result would almost certainly not be accepted, because the modern human sequences would be argued to be contamination. This is a much bigger problem than was usually acknowledged a few years ago, when people maintained that there was some way to authenticate whether sequences were endogenous. Now it is clear that all specimens have substantial modern contamination, and that the vast majority of sequence are of modern origin, even in specimens that actually do preserve ancient sequences. If only modern DNA is found in the hobbits, this will probably be interpreted as contamination whether it is endogenous or not. The only exception to this would be if it could be shown that the hobbit had a sequence that was closely related to some sample found in living Indonesians, but that there was a unique mutation that set it apart, and has never been found. But I am skeptical that even that would be enough; it is very difficult to respond to the argument that a rare sequence might have been present in one of the discoverers, researchers, or others who handled the sample.
2. The hobbits have racemization and collagen profiles that indicate that DNA should not be preserved. This is probably the most likely result, because Flores seems likely to be a climatic regime that would not facilitate DNA preservation over tens of thousands of years.
3. The hobbits preserve some sequence slightly divergent from all living people. By slightly divergent, here, I mean around as divergent as Neandertal mtDNA sequences from recent humans. This might seem to be a clear result, but is actually problematic. For example, the Mungo 3 specimen (Adcock et al. 2001b) appears to lie on a clade that is an outgroup to later people, along with a nuclear mtDNA insertion (called a numt) on chromosome 11. But this kind of interpretation faces a lot of potential problems. For example, Cooper and colleagues (2001) argued that the Mungo 3 sequence may actually lie on the human clade, and is associated with the chromosome 11 numt by homoplasy (Adcock and colleagues (2001a) reply to this argument, but it isn't settled). The same criticism has been made of the Neandertal sequences by Gutierrez and colleagues (2002): namely that these actually lie inside the human clade. It would appear that the degree of parallelism among mtDNA control region sequences is so high that most ancient human specimens will suffer from this problem. This is above and beyond the possibility that an ancient sequence may look unique purely because of imperfect preservation and resulting spurious genetic changes (Caldararo and Gabow 2000). And no close genetic difference can escape the criticism that recent human mtDNA has been subject to recent positive selection. If this were true, then a wide variety of genetic sequences may have been common within the human population before the selective sweep, including the Neandertal sequence, the Mungo 3 sequence, the chromosome 11 numt, and any putative Liang Bua sequence. In short, a closely related sequence to humans would not settle the issue of Homo floresiensis, even if it were basal to the clade including all living humans.
4. The hobbits preserve some sequence radically divergent from those of all living people. I view this as a relatively unlikely result, but would be expected if indeed these hominids descended from some very early human or australopithecine lineage. In this event, the divergence between Liang Bua and humans would be greater than (and perhaps substantially greater than) the difference between humans and Neandertals. The date of such a divergence is very likely to be between 1 million and 2.3 million years ago, considering that human presence on Flores began by around 900,000 years ago (Morwood et al. 1998), and any extra-African excursions by early Homo or late Australopithecus probably occurred after the origins of stone tool manufacture. The date might therefore be substantially informative about the relationships of early humans and australopithecines, depending on what it turns out to be. But again, I regard this result as by far the least likely, and I think it is much more likely that the DNA survey will be entirely uninformative about the relationships of the sampled specimen.

References:

Adcock GJ, Dennis ES, Easteal S, Huttley GA, Jermiin LS, Peacock WJ, Thorne A. 2001a. Human origins and ancient human DNA. Science 292:1655-1666.
Science

Adcock GJ, Dennis ES, Easteal S, Huttley GA, Jermlin LS, Peacock WJ, Thorne A. 2001b. Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins. Proc Natl Acad Sci U S A 98:537-542.

Brown P, Sutikna T, Morwood MJ, Soejono RP, Jatmiko, Saptomo EW, Due RA. 2004. A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia. Nature 431:1055-1061.

Caldararo N, Gabow S. 2000. Mitochondrial DNA analysis and the place of Neandertals in Homo. Ancient Biomol 3:135-158.

Cooper A, Rambaut A, Macaulay V, Willerslev E, Hansen AJ, Stringer C. 2001. Human origins and ancient human DNA. Science 292:1655-1666.
Science

Gutiérrez G, Sánchez D, Marín A. 2002. A reanalysis of the ancient mitochondrial DNA sequences recovered from Neandertal bones. Mol Biol Evol 19:1359-1366.

Morwood MJ, O'Sullivan PB, Aziz F, Raza A. 1998. Fission-track ages of stone tools and fossils on the east Indonesian island of flores. Nature 392:173-176.
Nature