eFfing #FossilFriday: toolmakers without tools?

Matt Skinner and colleagues report in today’s Science an analysis of trabecular bone structure in the hand bones of humans, fossil hominins and living apes. Trabecular bone, the sponge-like network of bony lattices on the insides of many of your bones, adapts during life to better withstand the directions and amounts of force it experiences. This is a pretty great property of the skeleton: bone is organized in a way that helps withstand usual forces, and the spongy organization of trabeculae also keeps bones fairly lightweight. Win-win.

An X-ray of my foot. Note that most of the individual foot bones are filled with tiny 'spicules' (=trabeculae) of bone. Very often they have a very directed, or non-random, orientation, such as in the heel.

An X-ray of my foot. The individual foot bones are filled with narrow spicules (=trabeculae) of bone. Very often they have a directed, or non-random, orientation: in the calcaneus, for instance, they are oriented mostly from the heel to the ankle joint.

This adaptive nature of trabecular bone also means that we can learn a lot about how animals lived in the past when all they’ve left behind are scattered fossils. In the present case, Skinner and colleagues tested whether tool use leaves a ‘trabecular signature’ in hand bones, looking then for whether fossil hominins fit this signature. Their study design is beautifully simple but profoundly insightful: First, they compared humans and apes to see if the internal structure of their hand bones can be distinguished. Second, they tested whether these differences accord with theoretical predictions based on how these animals use their hands (humans manipulate objects, apes use hands for walking and climbing). Third, they determined whether fossil hand bones look more like either group.

Comparison of first metacarpals (the thumb bone in your palm) between a chimpanzee (left), three australopithecines, and a human (right). In each, the palm side is to the left and the wrist end of the bone (proximal) is down. Image by Tracy Kivell, and found here.

Looking at the image above, it’s difficult to spot trabecular differences between the specimens with the naked eye. But computer software can easily measure the density and distribution of trabecular bone from CT scans. With these tools, researchers found key differences between humans and apes consistent with the different ways they use their hands. Neandertals (humans in the past 100 thousand years or so) showed the human pattern, not unexpected since their bones look like ours and they used their hands to make tools and manipulate objects like we do.

What’s more interesting, though, is that the australopithecines, dating to between 1.8-3.0 million years ago, also show the human pattern. This is an important finding since the external anatomy of Australopithecus hand bones shows a mixture of human- and ape-like features, with unclear implications for how they used their hands. Their trabecular architecture, reflecting the forces their hands experienced in life, is consistent with tool use.

This is a very significant finding. Australopithecus africanus fossils from Sterkfontein aren’t associated with any stone tools; bone tools are known from Swartkrans, though it is unclear whether Australopithecus robustus or Early Homo from the site made/used these. In addition, in 2010 McPherron and colleagues reported on a possibly cut-marked animal bone from the 3.4 million year old site of Dikika in Ethiopia, where Australopithecus afarensis fossils but no tools are found. Skinner and colleagues’ results show that at the very least, South African Australopithecus species were using their hands like tool-makers and -users do.

This raises many fascinating questions – were australopithecines using stone tools, but we haven’t found them? Were they using tools made of other materials? What do the insides of Australopithecus afarensis metacarpals look like? What I like about this study is that it presents both compelling results, and raises further (testable) questions about both the nature of the earliest tools and our ability to detect their use from fossils.

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Kryptonians’ DNA in the Sts 71 fossil

I don’t love flying. In fact I’m writing this post in a traffic jam on the tarmac of Frankfurt International between a 9 hour and a 5 hour flight. On a related note, reclining your seatback all the way for most of a long flight does in fact make you the worst person on earth.

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Hey, guy, how’s that 10th X-Men movie? What kind of shampoo is that I smell? Why yes, I do work best when I can’t open my computer fully. What a joyous way for us to learn all about each other, new best friend!

A plus of all this airtime, though, is that I can get caught up on recent movies I’ve missed living under the proverbial rock of research and teaching. On the ~7500 mile trip from Kazakhstan to Kanada I got to watch Man of Steel, a new take on an ancient comic. It was tacky and entertaining and there are some interesting takes on biology, but it had a boss paleo surprise.

The best part of the movie is at the beginning when The Gladiator steals a mysterious “codex” as his planet Krypton plunges catastrophically into implosive oblivion. Amid the chaos, Russel Crowe swims through some chamber, and what does he encounter?

The codex? No, it’s…

Sts 71_R lateral1

Sts seventy f*ing one

Sts 71 is my favorite fossil I’ve seen because it looks totally badass (not a scientific reason, but it’s the truth). It comes from Sterkfontein cave in South Africa, dates to probably around 2.5 million years ago, and is attributed to the species Australopithecus africanus.

I realize I’m behind the times here, but in case you haven’t seen the movie but are planning to, then read no further (SPOILER ALERT). In the film, this codex/fossil apparently contains the genetic code for the entire species of Kryptonians (whose resemblance to living humans is so remarkable it requires a statistically impossible amount of parallel evolution). Now, the oldest DNA recovered from a fossil is from a horse that lived about 700 thousand years ago (Orlando et al., 2013). Sts 71 is some 3-4 times older than that, and illusorily contains the genomes of a billion human-like aliens with super powers.

What a badass fossil.

Bloodsport in Australopithecus africanus?

ResearchBlogging.orgA few months ago in a post about the ilium and cannibals, I relayed a quote by Dr. Raymond Dart who was the first to recognize (and name) the hominid genus Australopithecus, back in 1925. I’d also mentioned that he was described [in a reference that escapes me] as “blood-thirsty.” This macabre descriptor came to mind again, as I’m reading his (1948) description of the MLD 2 mandible, of a juvenile A. africanus from Makapansgat cave in South Africa (figure is from the paper):

“[Individuals represented by MLD2 and another skull fragment] met their death by manually applied violence. The fractures exhibited by the mandible show that the violence, which probably occurred in fatal combat, was a localized crushing impact received by the face slightly to the left of the midline in the incisor region, and administered presumably by a bludgeon… this youth probably met his fate at the hands of a kinsman more expert than himself in the accurate application of directed implements” (p. 393-394)

This rather fanciful hypothesis may reflect Dart’s alleged bloodlust, and the condition of the fossil likely reflects damage that occurred after death during the sometimes abusive process of fossilization.


Reference
Dart, R. (1948). The adolescent mandible of Australopithecus prometheus American Journal of Physical Anthropology, 6 (4), 391-412 DOI: 10.1002/ajpa.1330060410

01/01/2011: Looking forward and backward, so fast you may barf

2010 was a big year for anthropology and lawn-chair-anthropologists. There was laughter and crying, and maybe also some yelling. And smiling. Let’s take a look back at some of the big events of the past year.

  1. Ancient DNA. What a great year for ancient human DNA! In April, Krause and colleagues (2010) announced the sequencing of mitochondrial DNA from a ~50,000 year old girl from Denisova in Siberia. This sequence was twice as divergent from humans as Neandertal mtDNA, which really shocked a lot of people. Then just a week or so ago Reich and colleagues (2010) announced nuclear DNA from the site. The big news was that these ancient humans contributed genes to modern day Melanesians, but not other modern humans sampled. In May, Green and the Pääbo lab announced a draft sequence of the Neandertal nuclear genome. Like with the Denisova story, Neandertal mtDNA is fairly distinct from that of modern humans, and the nuclear genome revealed contribution to some modern humans but not to others. Basically, ancient DNA came out supporting the multiregional model of modern human origins.
  2. Malapa hominids. Lee Berger and researchers announced a new fossil site, Malapa, in South Africa. This site yielded 2 partial skeletons (and others forthcoming), including a very well-preserved skull of a subadult. Superficially the thing looked to me like Australopithecus africanus, though the authors argue that it shows some features derived toward the condition of early Homo. But at an estimated 1.9-1.7 million years old, it’s a little too young to have anything to do with the origin of Homo – not to mention its small 400 cubic centimeter cranial capacity. I really don’t know what to do with Malapa yet.
  3. Woranso-Mille Australopithecus afarensis. This site dates to around 3.6 million years ago, so it’s roughly contemporaneous with Laetoli afarensis, or intermediate in age between Laetoli and later afarensis sites like Maka and Hadar. Haile-Selassie and colleagues described a partial skeleton from the site. This male includes part of the pelvis, which didn’t get much coverage. But it has a 1st rib, scapula and clavicle, indicating a fairly human-like (rather than ape-like) torso shape. So even for how well we know A. afarensis, we’re always learning more about our ancestor.
  4. Saadanius hijazensis and catarrhines. I didn’t blog about this one at the time as I was getting ready to hit the field. But this was exciting because Iyad Zalmout and friends here at UM discovered and analyzed it. Saadanius was found in ~29 million year old deposits in Saudi Arabia, right around the estimated time of origins of apes. The fossil looks like an Aegyptopithecus to my untrained eye, but apparently may be similar to the last common ancestor of apes and old world monkeys.
  5. Field work. I had my first (of hopefully more!) field season at Dmanisi in Georgia. Paleoanthropology would be nothing without fossils, so an important aspect of the job I’d like to do more of is increasing the fossil record. Dmanisi is an amazing place for this, being among the oldest human sites outside Africa, and the interesting ‘intermediacy’ of the Dmanisi hominids between early Homo and more classic H. erectus. We found some great stuff last year, and I anticipate the site will produce more great fossils in the future. Who knows, maybe more fossiliferous deposits will be found in nearby regions?
So it was a helluva year, 2010. What excitement will 2011 bring? Here are some things I’d like to, or expect to, see this year:
  1. More ancient DNA – the surprise that many researchers got from Denisova and Neandertal ancient DNA clearly warrants more work on other ancient DNA. What does that of other fossil humans look like? Will the picture of human origins become further complicated (that is, different from paradigmatic out-of-Africa replacement)? In this regard we need to analyze DNA from more late Pleistocene fossils regarded as ‘anatomically modern.’
  2. a) More about Malapa. I want to say I heard somewhere that there were more hominids than just the 2 presented in the Science paper. These additional specimens will provide further evidence, including what variation within the site was like, and how it fits with other South African specimens. From the appearance of things, these fossils may be late-persisting A. africanus, somehow contemporaneous (roughly sympatric?) with A. robustus and possibly early Homo. Perhaps more work on the geology and taphonomy of Malapa will show it to be older, contemporaneous with the nearby site of Sterkfontein known for abundant A. africanus fossils? Probably not.

    b) More hominid sites and fossils in South Africa. One thing that was neat about Malapa was that it was from slightly outside the rest of the South African ‘cradle’ sites like Sterkfontein, Kromdraai, Drimolen, and Swartkrans. When I was in the area in 2008 I went with some researchers on survey of the Sterkfontein valley, new sites are definitely being sought. Perhaps 2011 will see the discovery of more Malapa-like sites?
  3. Human fossils from East Asia. Maybe even ancient DNA recovery from the region. East Asia has long been thought to be a potential ‘center’ of human origins. Earlier in the year, fossils coming from Zhirendong suggest some of the earliest evidence of chin, arguably a ‘modern human’ feature. Recent fossil and genetic discoveries ought to usher a renewed vigor in examining human evolution in Asia.

That’s all I feel like doing for now. Happy New Year, all!

ResearchBlogging.org
References
Berger, L., de Ruiter, D., Churchill, S., Schmid, P., Carlson, K., Dirks, P., & Kibii, J. (2010). Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa Science, 328 (5975), 195-204 DOI: 10.1126/science.1184944
Cann, R., Stoneking, M., & Wilson, A. (1987). Mitochondrial DNA and human evolution Nature, 325 (6099), 31-36 DOI: 10.1038/325031a0
Green, R., Krause, J., Briggs, A., Maricic, T., Stenzel, U., Kircher, M., Patterson, N., Li, H., Zhai, W., Fritz, M., Hansen, N., Durand, E., Malaspinas, A., Jensen, J., Marques-Bonet, T., Alkan, C., Prufer, K., Meyer, M., Burbano, H., Good, J., Schultz, R., Aximu-Petri, A., Butthof, A., Hober, B., Hoffner, B., Siegemund, M., Weihmann, A., Nusbaum, C., Lander, E., Russ, C., Novod, N., Affourtit, J., Egholm, M., Verna, C., Rudan, P., Brajkovic, D., Kucan, Z., Gusic, I., Doronichev, V., Golovanova, L., Lalueza-Fox, C., de la Rasilla, M., Fortea, J., Rosas, A., Schmitz, R., Johnson, P., Eichler, E., Falush, D., Birney, E., Mullikin, J., Slatkin, M., Nielsen, R., Kelso, J., Lachmann, M., Reich, D., & Paabo, S. (2010). A Draft Sequence of the Neandertal Genome Science, 328 (5979), 710-722 DOI: 10.1126/science.1188021
Haile-Selassie, Y., Latimer, B., Alene, M., Deino, A., Gibert, L., Melillo, S., Saylor, B., Scott, G., & Lovejoy, C. (2010). An early Australopithecus afarensis postcranium from Woranso-Mille, Ethiopia Proceedings of the National Academy of Sciences, 107 (27), 12121-12126 DOI: 10.1073/pnas.1004527107
Krause, J., Fu, Q., Good, J., Viola, B., Shunkov, M., Derevianko, A., & Pääbo, S. (2010). The complete mitochondrial DNA genome of an unknown hominin from southern Siberia Nature, 464 (7290), 894-897 DOI: 10.1038/nature08976
Liu W, Jin CZ, Zhang YQ, Cai YJ, Xing S, Wu XJ, Cheng H, Edwards RL, Pan WS, Qin DG, An ZS, Trinkaus E, & Wu XZ (2010). Human remains from Zhirendong, South China, and modern human emergence in East Asia. Proceedings of the National Academy of Sciences of the United States of America, 107 (45), 19201-6 PMID: 20974952
Reich D, Green RE, Kircher M, Krause J, Patterson N, Durand EY, Viola B, Briggs AW, Stenzel U, Johnson PL, Maricic T, Good JM, Marques-Bonet T, Alkan C, Fu Q, Mallick S, Li H, Meyer M, Eichler EE, Stoneking M, Richards M, Talamo S, Shunkov MV, Derevianko AP, Hublin JJ, Kelso J, Slatkin M, & Pääbo S (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature, 468 (7327), 1053-60 PMID: 21179161
Zalmout IS, Sanders WJ, Maclatchy LM, Gunnell GF, Al-Mufarreh YA, Ali MA, Nasser AA, Al-Masari AM, Al-Sobhi SA, Nadhra AO, Matari AH, Wilson JA, & Gingerich PD (2010). New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys. Nature, 466 (7304), 360-4 PMID: 20631798

Holy Effing Crap II: Australopithecus from Malapa

Lee Berger and colleagues report in Science today on 2 incredibly well preserved skeletons – including perhaps the best-preserved hominid skull in South Africa, in some ways as good as or better than Sts 5 (Australopithecus africanus). The specimens come from a site called Malapa in South Africa, dating to around 1.9 – 1.7 million years ago. The authors argue that it is so unique in its features that it warrants a new species – Australopithecus sediba – linking the earlier A. africanus with later Homo habilis. Is it really a new species? In my personal opinion, there’s not much distinguishing it from A. africanus.
The amazingly preserved skull is of a subadult, maybe 11 years old. The highly angled root of the zygomatic, positioned just above the M1 alveolus is classic A. africanus. It really reminds me of Sts 17, or possibly Sts 52 in the lower face. The prognathism is modest and lacks the anterior nasal pillars which tend to be fairly pronounced in A. africanus; in this regard it is quite comparable to specimens like TM 1512. Like Sts 52, it has multiple infraorbital foramina. The cranial capacity is estimated at 420 cubic centimeters (cc), which is pretty small, but within the estimated A. africanus range of variation. The authors say that the relatively low position of the temporal lines, spaced far apart from the sagittal suture, and the fact that the zygomatic arches do not flare to the sides, are features more like Homo than like A. africanus. But the specimen is only 11 years old; while the brain is finished growing, the face and chewing muscles probably aren’t. So if this were a fully adult specimen, I’m sure both of these features would come to look more like A. africanus.
The upper and lower first and second molars increase in size posteriorly, and have a distinct protostylid (enamel shelf along the side of one of the cusps) which has a very high frequency in A. africanus. The upper molars, while not totally complete, preserve something that I’ve noticed and I’m sure is in the literature, that the M1 is fairly small and squared compared to the generally larger and not-quite-as-square M2. In a few words, then, the skull seems to fit comfortably in the range of A. africanus variation.
Perhaps the least A. africanus-like aspect of the skull is the supraorbital torus. The supraorbital, or brow, is generally a modestly expressed in most africanus specimens that preserve it. The Malapa specimen is much more similar, to my eye, to later Homo in its projection and arching over the eyes. What could this mean? Moss and Young’s (1960) functional matrix model of looking at the cranium views the supraorbital as a function of the relative position of the brain to the orbits. Perhaps the spatial relationship between the vault and the face which becomes characteristic of later homo becomes established in earlier in the lineage. Other than the supraorbital, this specimen seems purely A. africanus to me. In all, the contour of the vault may not be too different from younger Dmanisi specimens like D2700 or 2280; that Malapa lacks the occiput gives an artificially short front-to-back look to the specimen. The face, however, is totally A. africanus.
Perhaps one of the most striking images is the lateral view. This photo looks strikingly similar to a subadult chimpanzee, albeit with a taller face and less prognathic snout. Maybe I’ve just seen a subadult ape before that this thing reminds me of.
So, this is an immensely exciting set of fossils. Is there a new species of Australopithecus? I wouldn’t bet my life on it. If you go with the widely held idea, that A. africanus or something like it was ancestral to later A. robustus on the one hand, and our Homo ancestors on the other, this thing would fall on the Homo side of that split. So in this case, since we’re not seeing anagenetic evolution – evolutionary change within a lineage – but rather branching, how do you name this thing? It might be slightly more derived toward a Homo than either its “pure” africanus ancestors and A. robustus evolutionary cousins, does this make it Homo? The issue is that adaptively its morphology doesn’t seem to be different from A. africanus, which would argue against the generic distinction. But if its later ancestors become H. habilis and nothing else, then I suppose this would make it a “chronospecies” of H. habilis. So maybe we should call this thing H. habilis? I think most people would argue with this simply on the brain size issue. And the brain is way smaller than any proclaimed Homo specimen.
Taxonomically, this will be a tough call.
References
Berger L, de Ruiter DJ, Churchill SE, Schmid P, Carlson KJ, Dirks PHGM, and Kibii JM. 2010. Australopithecus sediba: A New Species of Homo-like Australopith from South Africa. Science 328: 195 – 204
Moss ML and Young R. 1960. A functional approach to craniology. American Journal of Physical Anthropology 18: 281 – 292

Australopithecus africanus (?) foot bone, and a small rant

Be forewarned, this summary of a recent article on an A. africanus fifth metatarsal also features a short rant. So feel free to stop reading after I start to sound preachy or crazy.



Friend and colleague Jerry DeSilva is part of a recent study of the fossil Stw 114/115, the earliest and most complete hominin fifth metatarsal (the bone forming the side “wall” of your foot just before your little toe). Probably it can be attributed to Australopithecus africanus. Lead author is Bernhard Zipfel of the University of the Witswatersrand. On an aside, Bernhard is the curator of the fossil collections at Wits, so if you’re interested in researching their collection, he’s the one to contact. I met him a few weeks ago, and he is very nice and friendly.

Back to the paper, the authors present a thorough description of the fossil foot bone, a thorough comparison of it to human and great ape homologues, and an exploratory multivariate analysis. The conclusion is that the fossil is decidedly human-like, indicating that the individual who possessed this foot (presumably A. africanus) had a lateral foot functionally identical to modern humans (read “obligate biped”). The authors infer from its overall form that feet of A. africanus (or, again, whatever species this fossil belonged to) had both a longitudinal and a transverse arch, just like humans (non-human primate feet only have the transverse arch).

I have to say, this is an excellent paper, especially compared to lots of studies I’ve read over the past few years. The qualitative description and comparison of the fossil points to many differences between human and ape fifth metatarsals, and similarities between the fossil and humans. Observations made with the eye are then corroborated and elaborated with a quantitative analysis. In contrast, many (but of course not all) studies today largely omit qualitative descriptions and comparisons, delving straight into quantitative analyses. I think this is in attempt to be “scientific” and objective. This zeal for being ‘scientific’ with regard to quantitative methods stands in curious opposition to a general lack of actual hypothesis testing in much of the literature. Of course, this is not a jab at exploratory and descriptive studies, which by their nature usually don’t have hypotheses to test.

I think it’s important to remember that not all questions can (or have to) be addressed by strictly quantitative studies (i.e. by numbers). For example, human metatarsals have a groove separating the head from the shaft—this feature relates to our increased ability to “dorsiflex” our toes when we walk (think of how your toes are oriented relative to the rest of your foot when on tip-toes). This groove is absent in apes. How can a quantitative analysis of human vs. ape metatarsals account for this? I suppose it could be scored as ‘present’ or ‘absent,’ or scored by the relative expression of the groove (i.e.0=absent, 1=weak, 2=deep, etc.). But, the former, dichotomizing scoring system fails to account for variation, while the latter can become quite subjective. On the other hand, I suppose a very complex geometric morphometric analysis could use an immense amount of landmarks to describe the shape of the metatarsal, including the groove (or lack thereof) behind the head. But then you get into the issue of comparing biologically non-homologous structures (although Bookstein and others have done a good—or rather ingenious—job developing methods for making ‘geometrically homologous’ semi-landmarks, and Klingenberg has recently described a way to compare features that are variably present or absent). The main point here is that by focusing/relying solely on ‘the numbers’ (or ‘the science’), researchers stand to miss some important anatomical information.

Sorry about the rant. Anyway, the paper doesn’t really miss anything. It’s a great example of the union of qualitative and quantitative analyses. My only comment is on their human reference sample of “Victorian British” people. I don’t know the sample, but they probably wore shoes. A more apt comparison might have been with humans that didn’t wear shoes, since shoes really affect our foot anatomy. Of course if this sample was habitually unshod, then this doesn’t really matter. And regardless, the Sts 114/115 Australopithecus africanus (?) fifth metatarsal shows great similarity to those of humans, and probably functioned like those of humans.



Reference

Zipfel B, DeSilva J and Kidd R. Earliest complete hominin fifth metatarsal—Implications for the evolution of the lateral column of the foot. American Journal of Physical Anthropology, in press. DOI 10.1002/ajpa.21103

Australopithecus africanus–a highly strained face?

A cool paper came out today [1] in which researchers used finite element analysis to test hypotheses about the biomechanics of chewing in Australopithecus africanus, a South African hominin that lived probably 3-2 million years ago. Finite element analysis is a technique adapted from engineering in which one creates a virtual model of a structure (here, CT data to make a composite cranium of two fossils, Sts 5 and Sts 52), gives the structure mechanical properties (here, the properties of bone), apply various forces of various direction and magnitude, and then can see how the structure is affected by these loads. It’s an interesting technique that has only recently become popular in physical anthropology, probably as the technology becomes better and cheaper, even though Chris Ruff recommended the technique twenty years ago [2].

The authors used this technique to see if the bony facial structure of A. africanus was adapted specially withstand special bite-loads, specifically at the premolars. For example, A. africanus‘s ‘anterior nasal pillars’—bony struts on either side of the nasal aperture—have long been thought to be buttresses against bite forces, but this had yet to be demonstrated. The authors tried different loading patterns—molars only, premolars only, and molars + premolars–to see how strains were distributed across the cranium.

Regardless of the loading regime, the strains through most of the face were the same. However, when just the premolars were loaded, strains increased noticeably on the nasal margins, compared to the other loading patterns. Thus, the results were consistent with the hypothesis that the face of A. africanus, specifically its anterior nasal pillars, are special adaptations for high-strain bite forces concentrated on the premolars. The results also indicate that the A. africanus cranium was adapted to such a high-force diet, rather than a high-volume (i.e. chewing lots of food) diet, because overall strains were the same regardless of whether the only the molars or all the posterior teth were loaded.

This last result leaves me perplexed as to the significance of a major trend in hominin evolution (except with the inception of Homo): postcanine megadontia. On the whole, through hominin evolution the molars and premolars get bigger and bigger (again, not really in Homo)—this is extreme in A. boisei, one of the latest surviving, “robust” australopiths. Presumably, this tendency toward megadonty increased the amount of food that could be ingested at a given time. But, the paper suggests that premolar loading was, if nothing else, an important selective factor in A. africanus, and presumably later hominins–this explains molarization of premolars (again, most noticeably in A. boisei). But it does not explain why molars should also enlarge, unless molar and premolar size are integrated, that is, under the same genetic and developmental control(s). Hey, that’s a cool hypothesis.… Also, I suppose the results don’t refute the possibility that molar size increased in order to accommodate higher volume of food, but rather they simply indicate that the face was not specially adapted to withstand such a diet.

It would also have been interesting to see how the cranium performed under more loading regimes, expecially of the anterior teeth. What really distinguishes A. africanus from its offshoot A. robustus (and especially A. boisei, to whom I don’t think africanus is ancestral) is its retention of large canines and incisors. How do the crania of these taxa differ in their ability to withstand different dental loading patterns? The DNH 7 skull [3], of a very small female from the S. African site of Drimolen, is probably complete enough to be subject to a similar study.

Anyway, it’s a cool paper that really shows off the promise of ‘virtual anthropology.’

Suggested Reading
1 David S. Strait, Gerhard W. Weber, Simon Neubauer et al., Proceedings of the National Academy of Sciences, USA (2009).
2 C. B. Ruff, Folia Primatologica 53 (1-4), 142 (1989).
3 A. W. Keyser, S. Afr. J. Sci. 96 (4), 189 (2000).