Earliest human migrations

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One of my favorite paleoanthropological sites is Dmanisi, in the Republic of Georgia. It is the oldest securely dated hominid site outside Africa (just under 1.85 million years ago), and the hominids found there display a neat mix of primitive Homo habilis and derived H. erectus features. I consider myself lucky to have had the opportunity to excavate at Dmanisi last year, and to return to Georgia (lamazi Sakartvelo! [I hope I translated that correctly]) for more fieldwork next month.
Recently, Reid Ferring and others (2011) described the results of excavations of M5, a section of the site a bit aways from the area where the hominids were found. M5 is pretty cool because it presents a nice geological “layer cake,” as Ferring described it to us: each of the strata (different layers of deposition) are nicely and evenly stacked on one another. Check out the labeled layers on the right of the figure, from Ferring et al. 2011:
This is in stark contrast to the jumbled strata (like ‘spaghetti’) where the hominids were found. In geology and archaeology, there is a general “law of superposition,” which states that the lowest layers in a sequence would have been deposited earlier than the layers above them. The A sediments at Dmanisi, as seen in the figure above, are thus older than the Bs. Hominids have only been found in the B sediments. But work at M5 has shown that stone tools are found in the older A sediments, meaning that hominids arrived at the site and used it continually, beginning just after 1.85 million years ago.
Tools from the site differ between the older A and slightly later (still older than 1.75 million years!) B sediments in both material and manufacture. As they say in the paper (p. 2/5), a major difference in tool manufacture between the strata A and B occupations could be that during the earlier A times, “either cores were more intensively reduced or selected flakes were made elsewhere and carried to the site.” I’m not sure why this may be, but it is neat that within a fairly narrow time span, researchers can see habits change in our early ancestors.
The authors also note that the older tools from A sediments indicate “that Eurasia was probably occupied before Homo erectus appears in the East African fossil record” (from the paper’s abstract). If only hominids also came out of the A sediments! The News is touting this as meaning H. erectus evolved in Eurasia and then some members of the ‘new species’ moved back into Africa, but I don’t think this is necessarily the case. The Dmanisi hominids are described as H. erectus, but lack some key H. erectus apomorphies (most notably a large brain size) and really look pretty similar to contemporary hominids in Kenya (such as KNM-ER 3733) and Tanzania (such as OH 16). Plus, the E. African hominid fossil record around 1.9 million years ago leaves some tantalizing hints at hominids more erectus-like than habilis-like, such as the ER 2598 occipital fragment.
So while Dmanisi definitely demonstrates the presence of hominids outside Africa earlier than most well-accepted “Homo erectus” (or “ergaster”) fossils in E. Africa, I don’t think they necessarily indicate that the species arose in Eurasia. Rather, what the fossil record likely shows is the evolution of populations of early Homo, in Africa and Eurasia, toward the more ‘advanced’ H. erectus we know and love (due to gene flow w/in a widespread species, rather than parallel evolution of similar traits in different species).
ResearchBlogging.org


Reference
Ferring R, Oms O, Agustí J, Berna F, Nioradze M, Shelia T, Tappen M, Vekua A, Zhvania D, & Lordkipanidze D (2011). Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma. Proceedings of the National Academy of Sciences of the United States of America PMID: 21646521

Culinary trends in an extinct hominid

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A few weeks ago I discussed a recent paper that analyzed the carbon and oxygen isotope ratios from Australopithecus boisei molars (Cerling et al. 2011). The major finding here was that an enlarged sample (n=24 more) corroborated earlier isotopic (van der Merwe et al. 2008) and tooth wear evidence (Ungar et al. 2008) that A. boisei probably did not subsist on as much hard foods as previously thought. Although this strange hominid probably ate mostly grass/aquatic tubers, some researchers think it may have looked something like this:
Left, A. boisei reconstructed skull, from McCollum (1999, Fig. 1). Right, artist’s reconstruction of what the individual on the left may have looked like during life.
But looking at the numbers I’m wondering if the carbon isotopes reveal anything more about this curious hominid. If we plot boisei‘s carbon 13 values against the fossils’ estimated ages, there’s a small hint of a temporal trend, of increasing carbon 13 levels over time (more C4 plant consumption). Fitting a line to these data does indicate an increasing C4 component over time, but the slope of the line is not significantly different from zero. The early, high value could be an outlier (not eating the same stuff as his/her peers?), although the lowest carbon 13 value of all that would support this trend is also much lower than the other values; it could be a more anomalous one. So while it’s tempting to hypothesize dietary change over time in A. boisei, at the moment it looks like you can’t reject the hypothesis that diet is consistent throughout the Pleistocene until the A. boisei’s demise.  Supporting dietary stasis, Ungar and colleagues (2008) reported similar molar tooth wear in specimens from 2.27-1.4 million years ago.
In addition, Cerling and colleagues sampled at least one of each of the cheek teeth. Because teeth form in the jaws in a sequence (not all at the exact same time), the isotopic signatures from given teeth represent the dietary intake of carbon at various different points in an individual’s childhood. In the figure below I lumped upper and lower teeth together; the un-numbered “M” indicates molars unassigned to a specific position.

The first molar crown starts to form right around birth, and note here that it’s carbon 13 values are slightly higher than the other molars. The premolars and second molar start to form around the same time, so it is curious that each of these teeth show distinctly different ranges of carbon 13 levels. The sole P3 is also the lowest value (eating fewer C4 plants) in the entire sample, but the P4 has less negative values (eating more C4 plants). Not sure what’s going on here, but maybe later analyses of more specimens will clarify the situation.

ResearchBlogging.org
Our australopithecine ancestors and cousins have proven to be a rag-tag bunch of funny bipeds, and A. boisei has proven to be one of the weirder ones, in my opinion. Of course descriptions of Ardipithecus ramidus and Australopithecus sediba skeletons have been recent reminders that we have lots left to learn about Pleistocene hominids. For my part, I’m interested in working out the deal with the group of “robust” Australopithecus.
References
Cerling, T., Mbua, E., Kirera, F., Manthi, F., Grine, F., Leakey, M., Sponheimer, M., & Uno, K. (2011). Diet of Paranthropus boisei in the early Pleistocene of East Africa Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1104627108
McCollum, M. (1999). The Robust Australopithecine Face: A Morphogenetic Perspective Science, 284 (5412), 301-305 DOI: 10.1126/science.284.5412.301
Ungar PS, Grine FE, & Teaford MF (2008). Dental microwear and diet of the Plio-Pleistocene hominin Paranthropus boisei. PloS one, 3 (4) PMID: 18446200
van der Merwe NJ, Masao FT and Bamford MK. 2008. Isotopic evidence for contrasting diets of early hominins Homo habilis and Australopithecus boisei of Tanzania. South African Journal of Science 104: 153-155

Good olde dentistrie

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I’m reading up on mandibular rotation, which is the change in orientation of the mandibular corpus relative to the rest of the skull during growth (the corpus is the horizontal part of your jaw that holds up your teeth; check out the shape changes in the mandibles in the blog header). So far as I can tell, the original classic paper on the topic is by Bjork (1955). Growth was studied by implanting metal pins into the jaws, then seeing how they move across ontogeny via X-rays (which were once called “roentgenograms,” neat-o!) Here’s a picture of the procedure, from Bjork (1955):
HOLY GOD WHAT DID THAT KID DO TO DESERVE THIS?! And although there must be a third person there, it sorta looks like there’s a three-handed dentist wielding a hammer, a nail, and a kid’s face. No wonder so many people are afraid of the dentist.
ResearchBlogging.org
Reference
BJORK A (1955). Facial growth in man, studied with the aid of metallic implants. Acta odontologica Scandinavica, 13 (1), 9-34 PMID: 14398173

Neandertal terminal biogeography

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How late did Neandertals persist in the Late Pleistocene? Two papers out this week discuss the dates of the latest Neandertals in western Asia.

Pinhasi and colleagues (2011) stress the importance of directly dating Late Pleistocene human-ish fossils. There are numerous techniques used to estimate the ages of the fun stuff we find underground. For fairly old fossils like australopithecines, perhaps the most reliable radiometric method is Argon-Argon, though this requires the fossils to be relatable to volcanic sediments whose argon levels can be measured. The point is that dates of burial are often not estimated from the fossil materials themselves, but rather the sediments and such surrounding the fossil of interest. But younger fossils (than say 50,000) preserve some of the bone’s original carbon -allowing age estimates of the fossils themselves by radiocarbon dating.

Pinhasi and colleagues note that while seven separate Neandertal specimens from across Europe and western Asia have been directly dated to be younger than 36 thousand years, these dates may be underestimates. In other words, Neandertals may not have lived after 40 thousand years. To this end, these researchers directly re-dated the infant Neandertal from Mezmaiskaya Cave in Russia, and estimate the poor lad to have died around 42-44 thousand years ago. The authors predict that future direct redating of other Neandertals will show Neandertals to have disappeared by 40 thousand years ago, and that they would have overlapped in time with more modern-looking humans either minimally or not at all. If only there were more information on the latest dates for Middle Paleolithic people!

Lucky me, in tomorrow’s Science, Ludovic Slimak and colleagues report on Mousterian tools dating to 32-34 thousand years ago, from the site of Byzovaya Cave “in the western foothills of the Polar Urals” (Slimak et al. 2011: 841). “POLAR!” The site is way further north than any site with Neandertal bones like Mezmaiskaya and Okladnikov, which is pretty impressive. But, there are no human remains associated with the tools, so we don’t know who made them. To what extent do these finds address Pinhasi’s and others’ contention of no Neandertals after 40 thousand years ago?

Slimak and colleagues carbon-dated animal bones that were butchered with the Mousterian tools, which were allegedly made only by Neandertals. There is a major problem with the wide-held assumption that Mousterian (Middle Paleolithic) tools were made only by Neandertals, whereas Upper Paleolithic industries beginning with the Aurignacian were made only by humans. This goes along with people’s wont to make a connection between stone tool ‘culture’ and biologically determined, phylogenetically significant behavioral capacities. But of course, we know biology doesn’t determine behavior, and so there’s no reason to assume [Mousterian:Neandertal::Aurignacian:’Modern’ Human]. Where Mousterian remains have been associated with diagnostic skeletal remains, they are Neandertal. But the Aurignacian, so far as I know, is not associated with diagnostic fossils – we can’t say for certain who made it. Plus we know Neandertals were doing something kooky, yet logical in some sort of cognitively complex way, with bird feathers in Italy 44 thousand years ago (Peresani et al. 2011). So the Byzovaya stone tools may demonstrate a late, northern holdout of Neandertals, but then they could simply mean that the new technology either hadn’t arrived or hadn’t been successful in the far reaches of sub-Artic Pleistocene humanity.

If the latter is the case and Pinhasi & team’s hypothesis that Neandertals didn’t coexist in time and space (or did only minimally) holds, then the old assumption of Mousterian = Neandertal becomes dubious for other sites with Mousterian tools but no diagnostic fossils. This would also beg the question of the role of modern humans in the Neandertal demise – did the Neandertals disappear and open a niche for other groups of people (‘moderns’)?

So how were Neandertal populations distributed through space and time in their latest days? I dunno! But for the moment I suppose I’d be surprised if no fossils with Neandertal morphology turn out to be younger than 40 thousand years as suggested by Pinhasi and co. But then I could be wrong.

ResearchBlogging.org
References
Hoffmann, A., Hublin, J., Hüls, M., & Terberger, T. (2011). The Homo aurignaciensis hauseri from Combe-Capelle – A Mesolithic burial Journal of Human Evolution DOI:10.1016/j.jhevol.2011.03.001

Peresani, M., Fiore, I., Gala, M., Romandini, M., & Tagliacozzo, A. (2011). Late Neandertals and the intentional removal of feathers as evidenced from bird bone taphonomy at Fumane Cave 44 ky B.P., Italy Proceedings of the National Academy of Sciences, 108 (10), 3888-3893 DOI:10.1073/pnas.1016212108

Pinhasi R, Higham TF, Golovanova LV, & Doronichev VB (2011). Revised age of late Neanderthal occupation and the end of the Middle Paleolithic in the northern Caucasus.Proceedings of the National Academy of Sciences of the United States of America PMID:21555570

Slimak, L., Svendsen, J., Mangerud, J., Plisson, H., Heggen, H., Brugere, A., & Pavlov, P. (2011). Late Mousterian Persistence near the Arctic Circle Science, 332 (6031), 841-845 DOI:10.1126/science.1203866

If imitation is the sincerest form of flattery

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Life as we know it has taken some strange courses. Of all the things an animal could do with its time, pretending to be an ant is apparently pretty popular. According to a review article in the latest Current Biology, there are probably over 2000 abhorrent species of myrmecomorphs (ant impersonators), including spiders, caterpillars, mites, beetles, and other types of arthropod biodiversity I’m not familiar with, that have come to resemble ants in some form or another.
It’s interesting how and why different life forms have come to p-ant-omime. For example, in the picture above, (Maderspacher & Stensmyr 2011, Fig. 3) on the left side is the crab spider (Aphantochilus rogersi) mimicking ant species in the genus Cephalotes – which the spider comes upon unawares and then feeds upon (getting pwned on the right side of the photo). If imitation is the sincerest form of flattery, then mimicry must be the most malevolent means of creepy.
Or here’s a treehopper (Cyphonia clavata, an insect and not a spider like above) that doesn’t just disguise itself as an ant, but rather has a whole ant-shaped appendage bursting from its back in a disgusting perversion of alien birth in the Alien series (Maderspacher & Stensmyr 2011, Fig. 1). It is quite remarkable that a surprisingly common yearning to be perceived as an ant has resulted in convergent evolution of an ant-ish figure in myriad of nature’s more disgusting creations, not to mention in ants themselves.
Reference
Florian Maderspacher & Marcus Stensmyr (2011). Myrmecomorphomania Current Biology, 21 (9) : R291-293. doi:10.1016/j.cub.2011.04.006
ResearchBlogging.org

What the hell was Australopithecus boisei doing?

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A little over 2 million years ago there a major divergence of hominins, leading on the one hand to our earliest ancestors in the genus Homo, and on the other hand to a group of ‘robust’ australopiths, the latter group a failed evolutionary experiment in being human. In our ancestors, parts of the skull associated with chewing began to get smaller and more delicate, while the robust australopiths increased the sizes of their crushin’-teeth and chewin’-muscle attachments.

Cartoon of a “robust” australopith face, Fig. 1 from McCollum (1999). Note the very tall face, flaring cheeks, and massive lower jaw which would have facilitated wicked-pissah chewing power.

Weirder, there is a South African form (Australopithecus robustus) and an East African form (A. boisei, the figure here looks like it’s based off this species) of robust. These two may have inherited their robust adaptations from a common ancestor, or they may be unrelated lineages that evolved these features in parallel. The East African A. boisei has been referred to as ‘hyper-robust,’ its face and teeth generally larger than those of A. robustus.

For a while it’s been supposed that these ‘robust’ chewing adaptations in our weird, extinct evolutionary cousins (every family has those, right?) reflected a diet of hard objects requiring powerful crushing and grinding – things like hard fruits, seeds, Italian bread, etc. But a few years ago Peter Ungar and others (2008) examined the microscopic wear patterns on the surfaces of molar teeth of A. boisei and noted that they lacked the characteristic pits of a hard-object feeder. A. robustus on the other hand does have wear patterns more like an animal that ate hard foods. Why such a difference? Why the hell wasn’t boisei behaving robustly?

Also in 2008 Nikolaas van der Merwe and colleagues analyzed the carbon isotopes preserved in the teeth of A. boisei and some other fossils. Briefly, plants utilize two isotopes of carbon (C12 and C13), but ‘prefer’ the lighter-weight C12. Some groups of plants like grasses have thrived because they’re less picky and can get by just as well with C13. Different kinds of plants, then, incorporate different amounts of these two carbon isotopes into their tissues, then when animals eat it, these isotopes get incorporated into the animal’s developing tissues, including tooth enamel. So by looking at the relative amounts of these two carbon isotopes in teeth, researchers can get a rough idea of whether an animal was eating more of the C13-loving or C13-loathing plants (or the animals eating the plants). van der Merwe and others found A. boisei to have a way higher percentage of the plants that don’t discriminate against C13 as much, possibly things like grass, sedges or terrestrial flowering plants. GRASS?!

Last week, Thure Cerling and colleagues expanded on the earlier study led by van der Merwe, including a larger set of boisei teeth spanning 500 thousand years of the species’ existence. Lo and behold, they got similar results: the isotopic signature in A boisei is similar to grass-feeding pigs and horses in its habitat — was the badass “hyper robust” A boisei just a hominin version of a horse? Now, the silica in grass make it extremely wearing on tooth enamel, and while A. boisei had crazy thick molar enamel, I would be a little surprised if the boisei dentition could withstand a lifetime of a grassy diet. Nevertheless, boisei‘s diet clearly differed from robustus, based on both dental wear and carbon isotopes.

This raises interesting questions about the evolution of the robust group. Does their shared ‘robust’ morphology reflect common ancestry, with the subtle differences the result of their divergent diets? Or do the subtle differences indicate that they evolved separately but their diets for whatever reasons resulted in similar mechanical loading on their jaws and faces? It should also be noted that while the dates for South African cave sites are always a bit uncertain, it is possible that A. robustus persisted alongside genus Homo until around 1 million years ago, whereas the fossil record for A. boisei craps out around 1.4 million years ago – was A. boisei too specialized on crappy grass, resulting in its evolutionary demise?

A horse-ish human-ish hominin, Australopithecus boisei, rest in peace. 2.1 – 1.4 mya

References
Cerling TE, Mbua E, Kirera FM, Manthi FK, Grine FE, Leakey MG, Sponheimer M, & Uno KT (2011). Diet of Paranthropus boisei in the early Pleistocene of East Africa. Proceedings of the National Academy of Sciences of the United States of America PMID: 21536914
McCollum, M. (1999). The Robust Australopithecine Face: A Morphogenetic Perspective Science, 284 (5412), 301-305 DOI: 10.1126/science.284.5412.301
Ungar PS, Grine FE, & Teaford MF (2008). Dental microwear and diet of the Plio-Pleistocene hominin Paranthropus boisei. PloS one, 3 (4) PMID: 18446200
van der Merwe NJ, Masao FT, & Bamford MK (2008). Isotopic evidence for contrasting diets of early hominins Homo habilis and Australopithecus boisei of Tanzania. South African Journal of Science 104: 153-155 (link)

Is eugenics really dead?

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My advisor passed along a USA Today story about the eugenics origins of the journal Annals of Human Genetics. Eugenics was a popular movement in the early 20th century, in which people thought it wise to take the onus of natural selection upon themselves, to encourage smart wealthy people to breed and ‘dullard’ poor folk to be sterilized. The movement was based on a misunderstanding of evolution, heredity and the genetic basis for complex traits like ‘intelligence’ (whatever the hell that term really means). Not to mention a sense of intellectual and moral superiority among moneyed white people. Eugenic thinking is what underlay the reprehensibly regrettable misgivings of the Holocaust.

I think it’s great that the Annals of Human Genetics is public about the journal’s off-color origins. Anthropology itself was borne of Western countries going off to figure out why the lands they were colonizing and exploiting contained humans that differed from themselves (as well as how to deal with ‘inferior races’). It’s important to know of your field’s past mistakes, lest history repeat itself.
Is it repeating itself? Nowadays, people can get ‘genetic counseling’ if they’re contemplating pregnancy, to learn their purportedly genetically predisposed risks for having a child with certain conditions like Down Syndrome. With such knowledge, people can elect not to have kids together. Is this a blessing from medical genetics, or are we seeing a resurgence of biological determinism and old school eugenics?

Evolution: What it is and why humans aren’t immune to it

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An alternate title for this post could be “BigThink Too Big For Own Britches.”

Physicist Michio Kaku (via John Hawks via Pharyngula) has re-brought my attention to the fact that a great deal of people (smart people like Kaku included) misunderstand the mechanics of biological evolution. Quite simply, evolution is change in a gene pool over time. This pool could be an entire species or a small population within that species.

There are a number of ways evolution can happen. A mutation is a new genetic variant that arises in an individual, which can then be spread to later generations when that individual reproduces. A single strand of human DNA is like a string of some 3 billion letters. When a person replicates their DNA for it to be passed on to their offspring (meiosis), having to reproduce such a long strand ensures that a mistake is made at least once in a while. Hence mutations increase variation in a gene pool.
But the frequencies of genes in a population can change, that is they may become more or less common within the gene pool. This could happen by genetic drift, which is the random loss of genes. If a gene is neither adaptive nor harmful, it could simply be lost over time due to sheer chance. In contrast to mutation, drift reduces genetic variation.
If genes are adaptive or harmful, their frequency in a gene pool becomes subject to natural selection. If a gene (or set of genes) is adaptive, that means the possessor of those genes will be more likely to survive and reproduce than others, i.e., the individual will be more likely to pass on these genes. Over time, the adaptive genes will increase in frequency in a population. Conversely, genes that lower the likelihood of surviving and reproducing will become less frequent in subsequent generations. Either of these scenarios means selection is reducing genetic variation. But sometimes different forms of a gene can be adaptive in different situations or combinations, so selection will act to maintain both of these in the gene pool. So in contrast to mutation and drift, selection can reduce or maintain genetic variation.
Finally, gene flow refers to genes being introduced into a gene pool from another source. This could occur when someone from one population reproduces with an individual from another population, and so new genes may enter one of the groups. Like mutation, this will increase genetic variation in a gene pool.
Common misconceptions
It may seem counterintuitive, but evolution does not equate with progress. This is a common misconception, probably due to the social ideologies under which evolutionary theory developed. Because of selection, evolution often means that a population becomes better-suited to its environment over time, which seems like progress. But as we’ve seen above, not all evolution is selection; mutation and drift are fairly random processes of evolution that don’t necessarily bear on adaptation. In addition, environments and circumstances change, so that even if something evolved in a place where it was adaptive, it may be harmful in a new context. For example, as the earliest humans lost their body hair, they probably evolved to have darker skin: adaptive in the tropics where humans originated. But later, when early humans moved into more northerly latitudes with less ultraviolet exposure from the sun, the dark skin that was adaptive for a hairless human in a tropical environment came to hinder the body’s vitamin D synthesis: maladaptive!
Also contra popular opinion, individuals do not evolve, populations do. Trojan brand condoms recently had an ad campaign in which they encouraged men to “evolve” by using Trojan condoms when having promiscuous sex. This is in line with the incorrect idea above that ‘evolving’ means ‘becoming better’ or ‘more sophisticated.’ Of course, condoms may actually help a population to evolve: those who use condoms to prevent pregnancy are ensuring they do not pass on their genes. And if there’s any genetic predisposition to make one more likely to use condoms (and there’s not), these genes would certainly become less common in future generations. [I am NOT encouraging people not to use protection, by the way]
So this brings us to a final point: the main misconception expressed in Dr. Kaku’s video is that humans are not evolving. Technology and urbanization, he tells us, have circumvented natural selection on human features (well, the “gross” or visible ones). This is very wrong and shortsighted. In fact, this is one of the bases of the eugenics movement of the early 20th century. Eugenicists thought, ‘Nature is no longer ensuring some people don’t pass on their genes, so we ought to do it ourselves for the good of humankind.’ This first thought, about the insufficiency of Nature, is echoed by Dr. Kaku (though surely he does not think the second).
Simply put, HUMANS ARE STILL EVOLVING. Remember, not all evolution = natural selection. The genetic composition of humankind is still subject to the random forces of mutation and drift. In fact, because the human population size has increased exponentially of late, the fact that there are way more people than ever means that there are more mutations entering the population, and at a faster rate, than ever! But selection is still at work, too. There are still diseases that kill people before they can pass on their genes. There are still environmental situations – even in ‘civilized’ places! – that prevent people from passing on their genes.
We humans are still evolving because we are still subject to the forces of evolution, and we always will be. Now what physicist could’ve told you that?!

Neoteny in literature

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I’m trying something new: recreational reading, non-academic literature to get my mind of work at the end of the day. My Platonic soulmate recommended, almost a decade ago now, Still Life With Woodpecker by Tom Robbins. I was very surprised, then, to run into this passage:

“Neoteny” is “remaining young,” and it may be ironic that it is so little known, because human evolution has been dominated by it. Humans have evolved to their relatively high state by retaining the immature characteristics of their ancestors. Humans are the most advanced of mammals – although a case could be made for the dolphins – because they seldom grow up. Behavioral traits such as curiosity about the world, flexibility of response, and playfulness are common to practically all young mammals but are usually rapidly lost with the onset of maturity in all but humans. Humanity has advanced, when it has advanced, not because it has been sober, responsible, and cautious, but because it has been playful, rebellious, and immature.

Why Lucy, what sweet kicks you had

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For decades people have debated whether Australopithecus afarensis was an obligate biped like us, or whether our ancestor was a little less lithe in life on land. They asked, sort of, “Would Lucy have rocked some sweet Air Jordans, or would she have put some flat-foot orthotics in her new kicks?”

Carol Ward and colleagues report on a new fourth metatarsal of Australopithecus afarensis from Hadar in Ethiopia, over 3.2 million years old. The foot bone shows that A. afarensis had the two foot arches that we humans enjoy today.
Metatarsals are the longbones comprising much of the foot right before your silly-looking toes. One exceptional thing about our metatarsals compared to our ape cousins is that they contribute to two arches, one running front-to-back and another side-to-side. The arches provide critical support to our foot for bipedal stance, and a little Fred-Astaire-springiness as our foot hits the ground and then lifts off again when walking and running and sashaying.
The new A. afarensis metatarsal (AL 333-160, right) shows that by 3.2 million years ago, our ancestors had these arches, too. The twisting and angulation of the shaft relative to the base show these arches are similar to humans and our later fossil ancestors, whereas apes’ MT4s tend to be less twisted and angled. Such morphology was hinted at by the famous Laetoli footprints from Tanzania, around 3.7 million years ago, also attributed to A. afarensis. Other evidence from the skeleton suggested Lucy was a biped and nothing else, and so this new find from Hadar further solidifies the idea that some of our skeletal adaptations to bipedalism are ancient indeed.
UPDATE: Thinking about this finding in the shower this morning, I recalled that buddies Jerry DeSilva and Zach Throckmorton recently published a study where they concluded, based on the morphology of the end of the tibia, that A. afarensis probably had at least a rear-foot arch. Interestingly, though, they found some hominid specimens probably had “asymptomatic flatfoot.” Lucy (AL 288) was among these, so maybe she’d be sporting orthoticized Jordans after all.
ResearchBlogging.org
The Papers
DeSilva JM, & Throckmorton ZJ (2010). Lucy’s flat feet: the relationship between the ankle and rearfoot arching in early hominins. PloS one, 5 (12) PMID: 21203433

Ward, C., Kimbel, W., & Johanson, D. (2011). Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis Science, 331 (6018), 750-753 DOI: 10.1126/science.1201463