Zhoukoudian

Yves Coppens and colleagues have found a frontal bone, and a bit more, in Mongolia. They do not report a date for the specimen beyond Late Pleistocene; it comes from a pit dug for gold mining. The site is north of Zhoukoudian and other northern Chinese sites by several hundred kilometers, and is approximately the same latitude (though further east) as Okladnikov Cave (discussed in my interview with Mica Glantz). The place is called Salkhit.

They describe the anatomy of the specimen: it has a complete supraorbital torus, thicker in the superciliary area than laterally; a slight frontal keel, and an overall sloping profile. In other words, it looks to be generally archaic in morphology. Their metrical comparisons put it generally with Middle Pleistocene crania like Zhoukoudian, Steinheim, and Petralona.

(via Paleoanthro)

References:

Coppens Y, Tseveendorj D, Demeter F, Turbat T, Giscard P-H. 2008. Discovery of an archaic Homo sapiens skullcap in Northeast Mongolia. Compte Rendus Palévol (in press) doi:10.1016/j.crpv.2007.12.004

John Kappelman was kind enough to send me a preprint of the report on the new Turkish Middle Pleistocene specimen. The specimen consists of frontal and parietal fragments from a single skull, and comes from a travertine quarry outside the town of Kacabaş, western Turkey. The skull was found in the course of quarrying activities, and may be the first hominid specimen to have been "reduced to a standard rough-cut tile thickness of about 35 mm."

The paper reports a date estimate of 490 ± 0.05 to 510 ± 0.05 kyr, based on thermoluminescence of travertine. The paper contains some pictures of the specimen, description of its anatomy, and evidence for the presence of tuberculosis.

I review these elements below.

Is it Homo erectus?

At 500,000 years old, the specimen is just the right age to be in the middle of a taxonomic mess. Many agree that the roughly contemporary Zhoukoudian sample should be referred to H. erectus. But there are other alternatives. Some people contribute a number of penecontemporary samples to "Homo heidelbergensis", or alternatively to "archaic Homo sapiens". Among these, the Bodo skull is earlier at 600,000 years old, and arguably so is the Sima de los Huesos sample (Bischoff et al. 2003, 2007). So in terms of time, this specimen might qualify for any number of names.

Kappelman and colleagues include this paragraph, which I think is an admirable discussion of the problem:

The most conservative approach is to provisionally attribute the Kocabaş specimen to H. erectus but the combination of features in the Kocabas hominin highlights the ongoing controversy about whether Pleistocene hominins attributed to the genus Homo represent a polytypic species with an Old World range (Asfaw et al., 2002) or instead provide evidence for multiple lineages with more limited temporal and geographical distributions (Schwartz, 2004). A single specimen clearly cannot answer this question, and it seems likely that the ongoing controversy will extend past the sample traditionally referred to H. erectus and on into that referred to H. heidelbergensis.

The problem of taxonomy is confounded with geography. Ultimately, whether this specimen looks like Homo erectus depends on whether it looks more like contemporary East Asians (e.g., Zhoukoudian, or possibly Sambungmachan), or whether instead it looks like contemporary Europeans or Africans (e.g., Bodo).

But this is to some extent complicated by variability within the western sample. Consider, the African Middle Pleistocene includes large skulls like Bodo and Kabwe but also small ones like Ndutu and Salé. Europe has Petralona, but also Steinheim. With this specimen, only the top of the skullcap is preserved, so the comparisons will be heavily dependent on size: browridge size, bone thickness and robusticity, and measured frontal breadth and length. The essential question is whether it is more like the contemporary Asian or African/European samples.

The frontal fragment includes the lateral two-thirds of the supraorbital torus, which is relatively uniform in thickness to its lateralmost extent. The browridge is very thick -- nearly as thick as Kabwe, and substantially thicker than any of the Zhoukoudian specimens. The frontal squama slopes posteriorly -- with less of a frontal boss than most of the Chinese specimens. This makes the supratoral sulcus relatively slight.

The minimum frontal breadth as reconstructed (by mirroring) is fairly narrow -- it is comparable to OH 9 or Sangiran 17. Kappelman and colleagues give a nice graph of this dimension compared to estimated cranial breadth and supraorbital torus thickness. With a vault thickness of 10 mm at bregma, the skull is relatively thick but inside the ranges of both contemporary Asian and African samples.

So, is the Kacabaş skull more like Asians or Africans? Metrically, Kappelman et al. show that the skull is a lot like the Zhoukoudian L3 skull, OH 9, and Sangiran 17. I could see more comparisons (and I am a bit curious about the way the orbital breadth compares to the other samples) but Kappelman et al. have done a nice job of presenting the skull and their description of the supraorbital region is quite detailed. The overall morphology of the specimen and its size are very comparable to Zhoukoudian, so it is fair to refer the skull to Homo erectus.

Compared to most of the Middle Pleistocene Africans and Europeans it is small -- but then, the sample did not include some very small crania like Ndutu or Salé.

On the other hand, there are those who would assign these small African crania to H. erectus. In other words, both taxonomy and geography are confounded by size!

In terms of this specimen, the morphology is more similar to Zhoukoudian, but it is not so very different from Kabwe or Bodo, other than its smaller size. If we approach the skull with the hypothesis that it is part of a West Asian population intermediate between Middle Pleistocene East Asians, Africans, and Europeans, I don't see anything to disprove that hypothesis.

Tuberculosis

I think the absolute coolest part of the paper is its demonstration of cranial lesions attributable to tuberculosis. They provide microscopic views of the lesions and detail why they are consistent with the disease. I'm no paleopathologist, but it looks like a solid case to me.

The discussion of the paper considers why the specimen might have faced an unusual risk of TB, focusing on the possibility of vitamin D deficiency. The authors suggest that a dark-skinned, presumably African population of H. erectus may have moved north into temperate latitudes, where lower UV radiation levels caused vitamin D deficiency. In theory, low vitamin D levels may have an immunosuppressive effect, possibly increasing the risk or severity of TB. The paper discusses the increased incidence of TB in dark-skinned immigrants to Europe as support for this hypothesis.

Personally, I think this section was unnecessary. The fact stands on its own: the individual suffered from TB, by no means an uncommon disease in historic human populations. There has been no shortage of light-skinned TB sufferers. While it is possible that dark-skinned people have an higher intrinsic risk, there are other factors such as access to health care that may contribute to this risk as well. Most important, there is really no reason to suppose that a 500,000-year-old Turkish hominid need have been dark-skinned. Indeed, the presence of at least one light pigmentation variant in Neandertals plainly shows that we can assume nothing about earlier hominids.

The idea that tuberculosis is a very old hominid disease has gained currency in the last few years. Older molecular analyses made this hypothesis seem unlikely -- most pathogenic strains of Mycobacterium tuberculosis stem from a common ancestor sometime during the last 20,000-35,000 years. This passage from Gutierrez et al. (2005) describes the history:

Members of the Mycobacterium tuberculosis complex (MTBC), the agents responsible for tuberculosis, are among the most successful human pathogens. The MTBC as defined here comprises the so-called M. tuberculosis, M. bovis, M. microti, M. africanum, M. pinnipedii, and M. caprae species. Although the members of the MTBC display different phenotypic characteristics and mammalian host ranges, they represent one of the most extreme examples of genetic homogeneity, with about 0.01%-0.03% synonymous nucleotide variation and no significant trace of genetic exchange among them. Therefore, it is believed that the members of the MTBC are the clonal progeny of a single successful ancestor, resulting from a recent evolutionary bottleneck that occurred 20,000 to 35,000 y ago.

However, Gutierrez and colleagues studied several strains of "smooth" bacilli from East Africans, finding that these were distant relatives of the MTBC strains, with a divergence around 3 million years ago. The usual hypothesis had been that TB was a zoonotic pathogen, possibly from cattle, which entered humans recently. But the presence of TB-related bacilli in humans suggests instead that TB is an old hominid pathogen, and that a particularly virulent strain may have spread recently through the human population, spreading from people into cattle and other domesticates. That may seem surprising (how exactly did it spread from humans into seals, one may ask?), but all of the identified animal forms are pathogenic in humans under some circumstances, and the majority of human cases come from three different bacterial species -- M. tuberculosis, M. bovis, and M. africanum.

The hypothesis of an old hominid-specific strain of TB has been challenged (Smith 2006), mainly because working out divergence times and relationships among reticulating bacterial strains is complicated. Gutierrez and colleagues defended their hypothesis in a reply, but this problem clearly is not yet settled. Actually finding the disease in such an ancient specimen pretty much brings closure to the initial question of whether TB is old, but doesn't yet tell us whether the particular phylogenetic scenario really happened.

I think tuberculosis is especially likely to be an old human pathogen, because it has a number of characteristics that would facilitate its survival in small-scale hunter-gatherer societies. Infections last a long time and they are symptomatic for a large proportion of that time. The primary mode of infection is respiratory, and the bacteria are easily spread. Present-day tuberculosis is predominantly a crowd disease -- spreading quickly in crowded cities. But if Gutierrez and colleagues are correct about the smooth bacilli being an ancestral form of the bacterium, this earlier form may not have been as dependent on population density for its spread.

Other pathogens with these characteristics are also candidates for old Pleistocene human diseases. My favorite at the moment is pertussis (whooping cough), which Diavatopoulos and colleagues (2005) showed may have diverged from an old, human-specific strain of Bordetella bronchiseptica. It has nothing to do with this specimen, but the common thread of diseases suitable for spread in Pleistocene humans may give us some things to look for in terms of ancient genetic adaptations to disease.

References:

Bischoff JL, Shamp DD, Aramburu A, Arsuaga JL, Carbonell E, Bermudez de Castro JM. 2003. The Sima de los Huesos hominids date to beyond U/Th equilibrium (>350 kyr) and perhaps to 400-500 kyr: new radiometric dates. J Archaeol Sci 30:275-280. doi:10.1006/jasc.2002.0834

Bischoff JL, Williams RW, Rosenbauer RJ, Aramburu A, Arsuaga JL, Garcia N, Cuenca-Bescós G. 2007. High-resolution U-series dates from the Sima de los Huesos hominids yields 600 kyrs: implications for the evolution of the early Neanderthal lineage. J Archaeol Sci 34:763-770. doi:10.1016/j.jas.2006.08.003

Diavatopoulos DA, Cummings CA, Schouls LM, Brinig MM, Relman DA, Mooi FR. 2005. Bordetella pertussis, the Causative Agent of Whooping Cough, Evolved from a Distinct, Human-Associated Lineage of B. bronchiseptica. PLoS Pathog 1: e45. doi:10.1371/journal.ppat.0010045

Kappelman J, Alçiçek MC, Kazancı N, Schultz M, Özkul M, Şen Ş. 2007. First Homo erectus from Turkey and implications for migrations into temperate Eurasia. Am J Phys Anthropol (in press) doi:10.1002/ajpa.20739

Gutierrez MC, Brisse S, Brosch R, Fabre M, Omaïs B, Marmiesse M, Supply P, Vincent V. 2005. Ancient Origin and Gene Mosaicism of the Progenitor of Mycobacterium tuberculosis. PLoS Pathogens 1:e5. doi:10.1371/journal.ppat.0010005

Smith NH. 2006. A re-evaluation of M. prototuberculosis. PLoS Pathogens 2:e98. doi:10.1371/journal.ppat.0020098

Slate's Scott Solomon asked some people, and presents a nice, short explanation of why original fossils are important to paleoanthropology:

You can't rely on bone-length measurements taken from a cast, either, since the replicas tend to deteriorate or deform faster than original fossil material. Casts made from plaster or plastic -- such as most casts of Lucy -- often become misshapen in unpredictable ways, especially when they are repeatedly handled or moved. The problem becomes worse when new casts are made from old casts, since a copy of a copy is less likely to be accurate.

And then there's this:

The [Piltdown] forgery was not exposed until 1953, in part because many paleontologists were allowed to carefully examine only casts but not the original "fossils," which contained clues about the subterfuge.

The same goes for reconstructing fragmentary specimens: it is often not possible to tell which details of a cast may be determined entirely by reconstruction, and which are genuine features of the preserved anatomy.

UPDATE(2007/09/19): Wow, a lot of people didn't like this post! Don't read so much into it; the linked article is about why you don't want to lose original fossils. Casts do become misshapen in unpredictable ways. Later methods of analysis can reveal new facts about them. There are lost originals we'd like to have back; like those from Mladeč and Zhoukoudian, all lost or destroyed during World War II. I guess an even better example is Vindija 33.19, which shows that some fossils can be very unique in their preservation in ways that later become very, very important. I've posted some new thoughts related to the correspondence I've gotten.

I've read through the new paper by Martinón-Torres et al., on Eurasian continuity in the Middle Pleistocene. They've put out an interesting hypothesis, with some support from previous work, but ultimately I think their methods are too weak to test it.

The press coverage of the paper so far (e.g., this AP article) has been a little confusing, because it misses this point: this paper is not about modern human origins, it's about much earlier evolutionary relationships. National Geographic News resorts to the always-safe:

The finding suggests that the hominid family tree could be much more complex than previously thought.

Ah, so that's what it means! More complex than previously thought! Why isn't there ever a story that makes things simpler than previously thought? I mean, isn't it a sign of a failed science if you have to add complexity to your hypothesis every time you make a new observation? It's like Ptolemaic paleoanthropology!

Anyway, enough of that rant. Let's look at what the paper really says, which is much more interesting than the press! Here's the abstract:

A common assumption in the evolutionary scenario of the first Eurasian hominin populations is that they all had an African origin. This assumption also seems to apply for the Early and Middle Pleistocene populations, whose presence in Europe has been largely explained by a discontinuous flow of African emigrant waves. Only recently, some voices have speculated about the possibility of Asia being a center of speciation. However, no hard evidence has been presented to support this hypothesis. We present evidence from the most complete and up-to-date analysis of the hominin permanent dentition from Africa and Eurasia. The results show important morphological differences between the hominins found in both continents during the Pleistocene, suggesting that their evolutionary courses were relatively independent. We propose that the genetic impact of Asia in the colonization of Europe during the Early and Middle Pleistocene was stronger than that of Africa.

OK, so this is about the initial colonization of Europe and the subsequent evolutionary trends in Europe, Asia, and Africa. The observation is that European teeth show a continued similarity to Asians during the Middle Pleistocene, and there is no evidence that European teeth evolved in the direction of Africans during that time period.

Why is that interesting? Two reasons:

1. The hypothesis directly conflicts with the idea that Middle Pleistocene Europeans were linked to Africans. A large number of anthropologists have been pushing the European-African link, under the old hypothesis that these ancient people belonged to a species that was distinct from East Asians. The European-African clade in this hypothesis is often called Homo heidelbergensis; the Asian clade remains Homo erectus.

2. The hypothesis also seems to conflict with genetic data, which suggest that the relationship of European and African hominids is more recent than the early Middle Pleistocene. In particular, the genetic divergence time between human and Neandertal genomes appears to date to more recently than 700,000 years ago (Green et al. 2006, Noonan et al. 2006), which means that the population divergence must be still more recent. Also, Alan Templeton's papers (e.g., 2002, 2006) claim evidence for migrations from Africa into Europe and Asia during the Middle Pleistocene. Those claims are consistent with the Neandertal genome data, as far as we know it, and they suggest gene flow from Africa into Eurasia.

So, the authors ought to deal with these issues. They do so in their discussion, which in this short paper is one long paragraph. I'm quoting it here in full to comment on the details:

If the population of the Eurasian continent during the Early and
Middle Pleistocene was mainly the result of several out-of-Africa incursions, we should have found African influences in the morphology of the Eurasian populations. However, the continuity of the "Eurasian dental pattern" from the Early Pleistocene until the appearance of the Upper Pleistocene Neanderthals suggests that the evolutionary courses of the Eurasian and the African continents were relatively independent for a long period and that the impact of Asia in the colonization of Europe was stronger than that of Africa.

That is the conclusion of the analysis, in brief. The strength of the conclusion depends on the power of the analytical methods to detect gene flow based on morphological similarities. More on that below.

This finding does not necessarily imply that there was not genetic flow between continents, but emphasizes that this interchange could have been both ways (25, 26).

This seems a little misleading. They have no particular evidence of gene flow from Eurasia to Africa (that would be the "both ways"). Nor do they have evidence in their analysis of gene flow from Africa to Eurasia, after the initial colonization. So they don't have any evidence for gene flow at all. So the finding doesn't emphasize anything about gene flow, other than that the teeth don't show obvious evidence for it.

Around 1 Ma, hominins appear to have dispersed into temperate latitudes as far north as 40 - 45° N (27-29), not only from Africa, but also within Eurasia (29 - 31). These populations were probably descendants of an ancient out-of-Africa exodus, rather than a later one at the end of the Early Pleistocene (30).

This is an important assertion. Other workers have emphasized the similarities of some African fossils to East Asian fossils (mainly from Java, plus Gongwangling in China) in the late Early Pleistocene. That has always been the case with OH 9, and it influenced the description of the Daka and Buia crania as well. The question is how early Asian populations became morphologically distinctive. Here, the authors argue that it was very early, without substantial signs for later interaction, which in the context of the cranial comparisons is now an extreme claim.

In addition, a recent study on the European Lower Pleistocene hominin populations has revealed a possible Eurasian origin for these groups (32).

This refers to the description of the ATD6-96 mandible, which contains an earlier assertion about Asian-European connections. I return to this below.

Furthermore, it has been pointed out that during the Middle Pleistocene there was hardly any faunal exchange bet ween East Africa and the Levant (33) and that the desert between the Sahara and Arabia was an important barrier at that time (26), therefore contributing to the isolation of both continents.

This is an important argument in support of their hypothesis. If movement between Africa and Eurasia was difficult during this time span, that reinforces their claim, and makes it less plausible that there were large-scale dispersals out of Africa during the Middle Pleistocene. That leaves us with a mention of a major exception to their proposed pattern: the evolution of humans in the Late Pleistocene:

With the exception of the SAP [i.e., H. sapiens] out-of Africa dispersion based mainly on genetic data (2), the history of human populations in Eurasia may not have been the result of a few high-impact replacement waves of dispersals from Africa, but a much more complex puzzle of dispersals and contacts among populations within and outside continents. In the light of these results, we propose that Asia has played an important role in the colonization of Europe, and that future studies on this issue are obliged to pay serious attention to the "unknown" continent (Martinón-Torres et al. 2007:3).

The citation of the ATD6-96 mandible leads us to a passage from that earlier paper (Carbonell et al. 2005), which also describes the hypothesis that the founding population of Europe was Asian. Remember that this research group calls the Gran Dolina sample, Homo antecessor, and they initially had written that this species probably colonized Europe from Africa in the late Lower Pleistocene. Here's the relevant paragraph from the cited paper (Carbonell et al. 2005):

The differences in dimensions and robustness between the TD6 mandibles and the East and North African mandibles cast doubt on the African origin of H. antecessor. In contrast, our comparative analysis suggests looking toward the Asian continent. In this respect, it is relevant to mention some data that remained unpublished in 1997, when the new species was named (10), and that are relevant to this discussion. The partial cranium Nanjing I, recovered in 1993-1994 from the Hulu Cave (Tangshan Hill, eastern central China), shows clear modern midfacial traits similar to those observed in the specimen ATD6-69 (19). Wang and Tobias (20) also found similarities between Nanjing I and the Zhoukoudian hominins. Geochronological dates, combined with ecological and paleoclimatic evidence, indicate that the Nanjing skull is ~600 thousand years old (21). Furthermore, the Locality 1 levels at Zhoukoudian, which yielded most hominin specimens, are now considered at least 800 thousand years old (22). Thus, these Chinese hominins may be contemporaneous with or slightly younger than the TD6 hominins. If the Gran Dolina and Chinese populations are phylogenetically related, they should share a common ancestor that also had a modern midfacial pattern and a gracile mandible. In the cranium, this hypothetical common ancestor would have had a low and flat temporal squama, and an unfused styloid process. These traits would have been retained in the Asian hominins but lost in the TD6 hominins, who exhibit a fused styloid process, a convex temporal squama, and probably a significant increase in cranial capacity (19). The Ceprano calvaria (Italy), which has been tentatively assigned to H. antecessor (23), exhibits a convex temporal squama and a cranial capacity of about 1,057 ml (24). Interestingly, TD6 and Zhoukoudian are the only hominins that have a zygomaxillary tubercle before the Upper Pleistocene (19).

So that provides cranial and mandibular evidence of an Asia-Europe connection, supporting the dental evidence provided in the current paper. Still, that evidence is from the initial founding of Europe in the Early Pleistocene and doesn't necessarily apply to the trends during the Middle Pleistocene.

After working through the data supplements for the paper, I think that the analysis is much weaker in statistical power than it could be. In their analysis, they disregard much of the variation within these ancient samples and focus on the differences between samples according to their scoring methods. This may reveal the broad relationships among samples -- if we disregard the possibility of selected parallelisms -- but it does not say anything about the possibility of gene flow among the samples.

Indeed, the result of their analysis (a dendrogram, or branching tree) is quite incapable of showing genetic exchanges at all. It can only show branching events, which means that the result will show either an exclusive relationship between Europeans and Asians, or an exclusive relationship between Europeans and Africans, but never a mixed relationship.

The only result in the paper that indicates a European-Asian relationship is from their cladistic analysis of a subset of the data. And it isn't especially strong evidence, since the Middle Pleistocene Africans are limited to the relatively early sites of Rabat and Tighenif (Ternifine). Granted, the later sample is also small in number, but this isn't really a test of relationships; it's more of a suggestion.

The phenogram inexplicably omits Middle and Lower Pleistocene Africans entirely, and considers only australopithecines and habilines as the African sample.

So, at the moment I consider this to be a very interesting hypothesis in search of a good test. There is no test of gene flow here, just an assertion. Yet, the cranial comparisons give the assertion some plausibility -- and remember, another idea out there is the hypothesis that early Homo originated in Asia and migrated to Africa later.

I think that these topics together constitute the important problem in early human relationships right now, so I'll be writing some more about them. There are many additional interesting facts to consider...

References:

Martinón-Torres M, Bermúdez de Castro JM, Gómez-Robles A, Arsuaga JL, Carbonell E, Lordkipanidze D, Manzi, G, Margvelashvili A. 2007. Dental evidence on the hominin dispersals during the Pleistocene. Proc Nat Acad Sci USA (early) doi:10.1073/pnas.0706152104

Stringer C. 2002. Modern human origins: progress and prospects. Phil Trans Roy Soc Lond B 357:563-579. doi:10.1098/rstb.2001.1057

Rightmire GP. 1998. Human evolution in the Middle Pleistocene: the role of Homo heidelbergensis. Evol Anthropol 6:218-227. doi:10.1002/(SICI)1520-6505(1998)6:6<218::AID-EVAN4>3.0.CO;2-6

Carbonell E and 19 others. 2005. An Early Pleistocene hominin mandible from Atapuerca-TD6, Spain. Proc Nat Acad Sci USA 102:5674-5678. doi:10.1073/pnas.0501841102

Bruner E, Manzi G. 2005. CT-based description and phyletic evaluation of the archaic human calvarium from Ceprano, Italy. Anat Rec A 285A:643-657. doi:10.1002/ar.a.20205

OK, NEWS FLASH: "Out of Africa dispersal was not as simple as once thought."

That's the lede in the press release about the Tianyuan skeleton.

That's very nice and all, but as someone who never thought things were very simple, I have a bit more latitude to talk about why this specimen is interesting.

I have an early edition of the paper by Hong Shang and colleagues. Here is the abstract:

Thirty-four elements of an early modern human (EMH) were found in Tianyuan Cave, Zhoukoudian, China in 2003. Dated to 35,500 -33,500 radiocarbon years before present by using direct accelerator mass spectrometry radiocarbon, the Tianyuan 1 skeleton is the among the oldest directly dated EMHs in eastern Eurasia. Morphological comparison shows Tianyuan 1 to have a series of derived modern human characteristics, including a projecting tuber symphyseos, a high anterior symphyseal angle, a broad scapular glenoid fossa, a reduced hamulus, a gluteal buttress, and a pilaster on the femora. Other features of Tianyuan 1 that are more common among EMHs are its modest humeral pectoralis major tuberosities, anteriorly rotated radial tuberosity, reduced radial curvature, and small talar trochlea. It also lacks several mandibular features common among western Eurasian late archaic humans, including mandibular foramen bridging, mandibular notch asymmetry, and a large superior medial pterygoid tubercle. However, Tianyuan 1 exhibits several late archaic human features, such as its anterior to posterior dental proportions, a large hamulus length, and a broad and rounded distal phalangeal tuberosity. This morphological pattern implies that a simple spread of modern humans from Africa is unlikely.

The paper is largely descriptive (which is certainly appropriate for an initial publication), but there aren't many pictures. I imagine they are holding pictures for a more extensive publication on the skeleton. There are also few comparisons presented. These are all fine; it's not a monograph, it's a short descriptive paper. But the brevity means that there might be interesting comparisons beyond those presented, so this is possibly an abbreviated list.

How does the skeleton affect the "Out of Africa" story? It dates to 34,430 +/- 510 radiocarbon years, which is approximately the same age as the earliest "modern" European remains, from Pestera cu Oase, Romania. That makes it important, regardless -- but it is also by far the most complete skeleton in China from this early time period. The other remains that may represent the early modern Chinese population generally have some uncertainty about their dates (such as Liujiang) or more fragmentary (and also insecurely dated, like the Salawusu remains). The Upper Cave specimens from Zhoukoudian are substantially later, less than 25,000 and possibly as young as 12,000 years old. So the skeleton's date makes it very important

What about its features? In terms of morphology, it shares much with early modern humans in Europe. I got a chance to discuss the paper very briefly with Dave Frayer and Milford Wolpoff, who know this morphology better than me -- although any errors here are my own. The skeleton is relatively robust, but fits within the range of robusticity of post-Neandertal Upper Paleolithic Europeans. The paper discusses a number of pathological details of the skeleton, mostly age-related.

The abstract says that the anterior-to-posterior dental proportions of the mandible are similar to late archaic humans. Here is what the text says about this feature on page 4:

The buccolingual diameters of the I2 to M3 are similar to those of most Late Pleistocene humans, samples of which differ principally in their anterior dental dimensions (35; Table 4). However, an index of summed anterior (I2, C1) to posterior (M1, M2) crown breadths (Table 5) differentiates the Neandertals from most modern humans. The Tianyuan 1 index of 73.4 is matched among the EMHs only by the Upper Paleolithic Arene Candide 1, Dolni Vestonice 13, and Mladec 54 (11.5% of the EMHs), whereas it is exceeded by 81.3% of the Neandertals, the lowest of which is still 72.9. It is above all of the Middle Paleolithic modern human (MPMH) plus Nazlet Khater 2 values. Tianyuan 1 is even closer to the Neandertal pattern if the premolar breadths are added to the molar breadths; its value of 41.6 is exceeded only by the same three European EMHs and 60.0% of the Neandertals. The Tianyuan 1 dental proportions therefore fall in the overlap zone of late archaic and Upper Paleolithic EMHs and separate from the MPMH.

In other words, this specimen has a big lateral incisor and canine relative to its molars. This particular feature is interesting, but maybe not not all that informative relative to the comparative samples. The data make clear that both the lateral incisor and molars of the specimen are smaller than the average size of the Skhul-Qafzeh hominids; it's just that the molars have reduced more (and the canine is a bit larger, but easily in the range of variation).

About those hand bone features, here is what the paper says on page 5:

The hamulus has the reduced palmar projection of the EMHs (Table 8), but its relative proximodistal length aligns it with the Neandertals (Fig. 3). The one distal manual phalanx, probably from the second ray based on articular and osteoarthritic matching with the left second more proximal phalanges, has a moderately large distal tuberosity that is circular and lacks proximal ungual spines (Fig. 3). The relative breadth of the tuberosity falls between the Neandertals and modern humans (including the MPMH) (Table 8). The form of the tuberosity is the archaic Homo (and Neandertal) pattern, although it is occasionally seen in EMHs.

This is probably more interesting from a biobehavioral perspective than a phylogenetic one. In other words, these help us to infer the behavior of early Upper Paleolithic people, which for the hands appears to match that of the Neandertals in many respects. The strong robusticity of the femur, tibia, and humerus of the skeleton confirm that behavioral interpretation. These may still be informative in a phylogenetic sense -- that is, they may show the retention of genes from earlier Eurasian hominids. But more importantly, they show that the adaptive context of modern humans changed across the time span from 35,000 to 15,000 years ago or so, and modern human anatomy evolved as a consequence.

Probably the most interesting observation along biobehavioral lines is that shoe wear may have influenced the individual's foot development. This is from the BBC article:

The single toe bone which was unearthed seems to suggest the individual wore shoes, pushing back the earliest known evidence for footwear by about 10,000 years.

An earlier study by Professor Trinkaus shows that human small toes became weaker during the stage of prehistory known as the Upper Palaeolithic, and that this can probably be attributed to the adoption of sturdy shoes.

The invention of rugged shoes reduced humans' reliance on strong, flexile toes to grip and balance.

Or, as the paper puts it:

The second proximal pedal phalanx, however, is gracile, similar to MUP humans and distinct from the MPMH and Neandertals (Table 6). Given the apparent tibial robusticity, this suggests, as with MUP humans (43), the reduction of anterior pedal bending stress through the habitual use of footwear.

OK, so what have we learned? The skeleton is certainly important, but some more comparative work will help to place it in a broader context. As it stands, it may be the most important single specimen for interpreting the Late Pleistocene population history of China, but it lacks many of the anatomical areas that would inform us more clearly of its relationships -- in particular, no face, upper teeth, or vault. Some of the most informative observations are relevant to interpreting its behavior. But it would help if we knew for sure whether it was male or female!

For more information on other Chinese Late Pleistocene sites, I can recommend Dennis Etler's excellent table of Chinese fossil hominids.

References:

Shang H, Tong H, Zhang S, Chen F, Trinkaus E. 2007. An early modern human from Tianyuan Cave, Zhoukoudian, China. Proc Nat Acad Sci USA (online early) doi:10.1073/pnas.0702169104

Afarensis has a post on Brazilian evidence relating to the origins of Native Americans (via Gene Expression). It's a good summary of recent work by Neves and colleagues, including the background to this:

In essence, Neves et al, is saying that Paleoindians were part of the expansion of H. sapiens out of Africa, whereas Native Americans represent a later expansion of specialized populations. I find this suggestion intriguing. There are skeptics, as you can see from the above quote from The National Geographic article. Powell is arguing that because America was populated by small populations, genetic drift would kick in and you would see a lot of variation between populations and that the Lagoa Santo populations fit within the pattern af variation seen in Native American populations. If that is the case, I would expect one or two populations to display morphology similar to Australians and Melanesians. Instead, what we have is a series running from southern Chile to Florida - and now Kennewick in Washington (which was not included in either study)- all of which display morphology similar to Australians, Melanesians and Polynesians.

The idea of a "generalized" form for early modern humans has been around for awhile now, applied not only to Paleoindians, but also the Upper Cave crania from Zhoukoudian, and -- by some -- early modern Europeans.

AFP is reporting possible progress in the hunt for the missing Zhoukoudian bones (via Palanthsci):

Several interesting clues have come to light in recent months, according to members of a recently established committee charged with looking for the Peking Man's bones and other missing relics, the China Daily reported.

If the clues lead anywhere, it could potentially mark a breakthrough in a search that has lasted since the early 1940s.

Five skull fragments belonging to Peking Man were lost under mysterious circumstances during World War II and have never been recovered.

Just in the last two months, the committee has received 63 tip-offs on the whereabouts of the elusive relics, said Liu Yajun, deputy head of the commission.

People's Daily Online has a more detailed account:

FOUR KEY CLUES AMONG 63 PIECES OF INFORMATION

The committee has received 63 pieces of information from areas like Beijing, Jilin Province, Fujian Province and Taiwan Province in the past two months. Experts with the committee screened the information and found four might be important:

A citizen surnamed Wu in Beijing claimed a professor surnamed Gu in Gansu Province once was invited to write autobiography for Jia Lanpo, one of the finders of the Peking Man skulls and also a guru on Peking Man studies. Gu once "recorded an American major's testimony at the Far East Military Court when researching at a Japanese archive, and the testimony mentioned the skulls."

A citizen surnamed Ren in Beijing claimed he knew one person whose father was a doctor in Peking Union Medical College Hospital, where the skulls were kept, and the doctor "took one skull home and the skull now is buried in a house."

A citizen surnamed Liu said he could help contact a wartime revolutionist who "has a Peking Man scull [sic] at hand."

A citizen surnamed Wu from Jiangxi Province said a 121-year-old man in Jiangxi once served as a high-ranking official under Dr. Sun Yat-sen, the forerunner of China's democratic revolution. The old man claimed that "the skulls are still in China" and he knows the whereabouts.

This quote seems like the significant one behind the committee's motivations:

"Mankind can give up many things, but there is one thing that we can never abandon -- that is our ancestors," said Gao Xing, an expert of ancient vertebrates, with the Chinese Academy of Sciences (CAS).

I think it's pretty safe to say that the bones don't have any hidden power to open a fifth dimension or anything. Not exactly the stuff of a Lara Croft movie.

Then again...CourtTV of all places has a long account of the Zhoukoudian discoveries, including the loss of the fossils. That article, by Rachael Bell covers some of the theories (in the crackpot notions sense, not the well-supported scientific ideas sense).

Anyway, don't hold your breath.

The History Channel is showing its new human evolution program, "Ape to Man" this Sunday, August 7, at 9:00 EDT / 8:00 CDT. The show has a website, which gives the list of interviewees (Leslie Aiello, Joe Cain (history of science), Chris Stringer, and Colin Menter (fossil sites of South Africa). There is also a quick synopsis:

Highlights of APE TO MAN include:

Reenactments of the work of Eugene DuBois, an Amsterdam physician who left his practice in 1890 in search of the Missing Link and found what would be called Homo erectus, a 500,000-year old ape-like skeleton, in Sumatra. DuBois' assertion that he has found the Missing Link results in his rejection by the scientific community. Only later did people realize the impact of the discovery.

Examination of the key elements that marked the evolution from ape to man, including the ability to walk upright, the use of tools, the harnessing of fire, the ability to form communities, and the ability to reason and plan.

The story of Piltdown Man, a skeleton discovered in England in 1912 which was, for a time, considered by many to be the definitive Missing Link, but later discovered to be one of the greatest hoaxes in the history of science.

Raymond Dart's 1924 discovery of Taung Child, a fossilized brain in Africa, nearly two million years old. It was the oldest finding to date, but was completely ignored by the scientific community because people still believed in the erroneous story of Piltdown Man.

The two key shifts in thinking that led to our understanding today: the shift to Africa as the birthplace of the human species and the shift from the thinking that brain size was the driving force of evolution, to the understanding that the use of tools was really the key step.

The online preview shows a Dalmatian running in front of a Land Rover, so I assume they'll have reenactments of the Leakeys also.

I found the online game to be strangely entertaining, since you have to navigate a little Indiana Jones-looking archaeologist around his campsite to find fossils, while avoiding spiders, bees, and quicksand, and returning to the water bucket every couple of minutes for a drink. Of course, when you do it the third time around, and "Zhoukoudian" looks exactly like "Olduvai Gorge" except with more spiders and bees, well, you get the picture. The "quiz" I found less entertaining since several of the questions give out slightly wrong information, and one is really wrong (Dubois' Trinil discovery is around a million years old, not 50,000, in case you're wondering).

But at the end of the game, there is a cool newspaper, with the headline, "MISSING LINK FOUND!", a photo of the Bone Clones version of Toumaï, and the story:

One of the greatest riddles in human history has been solved after leading anthropologist Dr. John Hawks found The Missing Link in human evolution. The discovery came after a grueling quest that spanned three continents, and tested the very limits of human endurance.

Almost enough to get me to watch!

This is Richard Roberts in an Australian radio interview (the interview is formatted in one-sentence paragraphs, this is a single contiguous excerpt):

Let's take a point of argument that this particular individual with a small brain is a microcephalic individual, is such an individual.

They have other features that indicate they're not suffering from microcephaly, they have unusual tooth structures - three roots to the teeth.

You find those in three-million-year-old people like Lucy in Africa, that only exist in very early Homo erectus.

You don't find those with modern humans.

We don't suddenly develop three roots to the teeth.

Nor do you suddenly develop long arms if you have microcephaly.

And that's what the hobbit has, they have slightly longer arming compared to ourselves.

The pelvis is wider than in modern humans.

They have very thick eyebrow ridges.

None of these are features of microcephaly.

When you look at a complete set of features of the skeleton, one or two of them might be credible as being microcephalic problems, but the rest of them can't be explained by microcephaly.

If you pick some of the ones like Professor Jacob has done I can understand how he reached that conclusion.

But not on the basis of all available features.

In my book, this fits the "quacks like a duck" definition of australopithecines. Nothing really new here (except a confirmation of the second jaw earlier in the interview). It's not clear to what extent these comments really reflect the biologists'; for example, LB1 has no preserved arms, and the radius from the site is not all that long.

Trawling through the original Nature article, we find these descriptions of australopithecine-like similarities.

There is a strong posterior angulation of the symphyseal axis, and the overall morphology of the symphysis is very similar to LH4 A. afarensis and unlike Zhoukoudian and Sangiran H. erectus. (Brown et al. 2004:1058)

The femur shaft does not have a pilaster, is circular in cross-section, and has cross-sectional areas of 370 mm2 at the midshaft and 359 mm2 at the midneck. It is therefore slightly more robust than the best-preserved small-bodied hominin femur of similar length (AL288-1). Distally there is a relatively high bicondylar angle of 148, which overlaps with that found in Australopithecus (1059)

I would add to these the prominence of the anterior superior iliac spine, and I would quadruple the weight of the brain size in the decision--I just can't see a Homo-like brain size reducing to the smallest known for any hominid as a consequence of dwarfism.

Against these, we have a number of Homo-like features.

Although LB1 has the small endocranial volume and stature evident in early australopithecines, it does not have the great postcanine tooth size, deep and prognathic facial skeleton, and masticatory adaptations common to members of this genus. (1060)

But all of these specifically Homo-like similarities are problematic, because they all are correlated with a single feature: dental reduction. And several of these features are not shared with the members of early Homo to which the specimen is proposed to be related.

The tooth sizes of the LB 1 specimen are generally shared with humans. This means, significantly, that they are not synapomorphies of early Homo--it would take nearly as much change to generate this pattern from an early Homo dentition as from an australopithecine or habiline.

I haven't made up my mind entirely, and much of my consideration runs with the brain size. Again, I would say that pathology must be rejected for the brain size before turning to other hypotheses. But the recovery of additional similar specimens would make pathology seem infinitesimally unlikely as an explanation for all of them. We aren't there yet, but we must be on the cusp of it. A divergence date from mtDNA would help a lot.

More on the Flores hominids