Sunday, November 27, 2011

The secret to running an amazing race: show up late

I don't usually stray far from the Sciences and into my personal life on this blog, because I wouldn't want anyone to get the impression that I have a life or actually do stuff. But not today. Today I wanna talk about one of my favorite things: running.

On Thanksgiving I ran the Detroit Turkey Trot 10k race with some friends (couldn't make it home to be with my awesome family this year, unfortunately). It was a cold and foggy morning, perfect for a race starting at 7:45 am. Knowing that over 20 thousand people would be in downtown Detroit just for the races (there was also a 5k and 1-miler), we peaced out of Ann Arbor at 6:00 to make sure we'd get to the starting line on time. But in a combined assault of incompetence, the City of Detroit and The Parade Co. made sure this would be impossible. After crawling from I-94 into downtown, we got the car parked with about 10 minutes to drain everyone's bladder (it's important to be properly hydrated for physical activity) and join the 7500 other runners doing the 10k. Race organizers had the foresight to make sure there were a whopping 10 Porta Potties near the starting line, perfectly adequate to serve the 20,000+ runners and onlookers; it was a long line.

My race bib, next to my sexy dinosaur poster and classy Kokoschka tiger-cat.
So much product placement.
So, we finally got to the starting line about 15 minutes after the race began. FORTUNATELY science and technology were on our side, and some benevolent genius thought to invent chips that go in one's race bib (right) so that one's official time does not begin until one crosses the start line.

Being young and brash, we were hoping to start with the faster "comet" or "Wave 1" group, which started earlier than the other waves. Having to start the race some 15 minutes later than scheduled, you'd think we'd've been off to a bad start - FALSE! Because our wave got a head start on us, we ended up running alongside the slower waves, meaning that we spent literally the entire race passing people. Unlike every other race I've done (where I started on time), no one passed me for all 6.2 miles, which was a real morale booster. This ended up being my fastest 10k (and really the fastest of the brief history of all my races)

Nothing makes you run faster than feeling like you're a fast runner. So if you want to have an amazing race (not the show), start late.

Saturday, November 26, 2011

Updated note on jaw growth in Australopithecus robustus

A few weeks ago I posted some early observations I've made about mandible growth in Australopithecus robustus compared with humans. My dissertation tests the null hypothesis that overall mandible growth is identical in the two species. This is complicated by the fact that there are many aspects of jaw growth (i.e. lots of variables) and not all fossils preserve the same parts. In these early preparatory stages I'm looking only at the height and width of the jaw at the second baby molar (in kids) and the second permanent premolar that replaces this baby tooth in older individuals, since this is something most of the fossils have. This work will get me ready for the hard comparisons, where the fossils aren't so kind.

One concern I had in the earlier post was that my human sample was (and still is) fairly small, making comparisons rather tentative. Since then, I have about doubled my human sample (but I still have lots of work to do), so it's timely to see if my earlier observations have held up. AND THEY DO!

To the right is a plot of jaw height at said tooth position across the growth period, humans being the black circles and A. robustus the thick red ones. Note that measures are standardized, taken relative to the smallest (not necessarily the youngest) individual in each sample. Before, I'd found that the two samples overlapped up to dental stage 4 (when the first permanent tooth comes in). After this point, the A. robustus jaw gets much larger through early adulthood, whereas in humans the height increase isn't so drastic. With a larger sample, there is a bit more overlap in relative jaw height (especially early on), but the overall result is the same as I found earlier. Neat!
To the left is a similar plot, this time looking at width of the jaw across the growth period (these are also size-standardized as above, colors are the same). What's remarkable is that the width of the human jaw is pretty much the same from infancy to adulthood. I remember thinking this when I first started looking at human jaws early last summer, but I'd never looked at how they compare with A. robustus, whose jaw continues to increase in absolute and relative width with age (and possibly even through adulthood; Lockwood et al. 2007). This plot is admittedly a bit confusing, as sizes are measured relative to the smallest and not youngest individuals, and the narrowest human jaw is in dental stage 4. The A. robustus sample also includes a very old adult (the highest point on the plot) while the human sample only goes to early adulthood. But the basic patterns are still pretty different: A. robustus jaws get wider up to dental stage 5 (you could think of it as pre- or early adolescence) then level out (not including our large older adult), but humans' average jaw width is fairly constant throughout ontogeny. Of course, this is at only one position along the jaw, and others will probably different.

The fragmented jaws of the youngest A. robustus (i.e. SK 63 and SK 438) do not look too different from their human counterparts, but adults are very different. Here we can see part of the reason why. Bear in mind, though, that other aspects of mandible shape do differ between these species from birth. For example, humans have a bony chin from infancy, whereas A. robustus always lacks a true chin (SK 74 is an older, probably female adult A. robustus that does have a rather anomalous "chin" but it is not homologous to ours). Not all aspects of species-specific mandible shape arise during postnatal growth!
But there you go, an enlarged human sample produces a result consistent with my earlier observation. Note that these pictures do not represent statistical tests of my hypothesis! Yes, a visual inspection of the plotted numbers suggests the two species differ in how jaw height and width grows. But saying something statistical and "definitive" is difficult. In terms of height, growth does seem pretty much the same during childhood, but then divergent later on. Width growth in the two species seems totally different. To further complicate things, a "shape" ratio of jaw width divided by height (not shown) suggests parallel (but not identical) growth trajectories in the two species. What do these observed differences mean for the null hypothesis? Which and how many variables can differ before I can feel confident about whether to reject the hypothesis? Oy, I have my work cut out for me. Stay tuned!

That paper I referenced
Lockwood, C., Menter, C., Moggi-Cecchi, J., & Keyser, A. (2007). Extended Male Growth in a Fossil Hominin Species Science, 318 (5855), 1443-1446 DOI: 10.1126/science.1149211

Sunday, November 20, 2011

Look inside bones for free on the interwebs

I forget how I stumbled upon this badass resource, but Kyoto University's Primate Research Institute made a "Digital Morphology Museum: an awesome online database of CT scans of sundry primate skeletal parts. Ever wonder what an articulated siamang skeleton looks like? Or whether the flaring bony snout of a mandrill is hollow or filled with bone (below)? If you're a normal person, probably not. But either way, this website provides easy access to the internal views of all sorts of body parts.
Coronal slice through a male mandrill face.  You can see a bone-filled lower jaw,  internal views of some teeth, the nasal cavity. The pics above and on the right give an idea of where in the skull we are. Note the fat flanks above the nasal cavity are filled with bone (they hollow out as you move further into the face).
What's cool is you can view and manipulate 3D views of these things on the website, or you can register with KUPRI to download the raw CT data. Really a great resource.

A few weeks ago, a paper came out wherein researchers used CT scans to compare the the sides of the nasal opening in skulls of Australopithecus species (Villmoare and Kimbel 2011). They found that although the external nose of the South African Australopithecus africanus and A. robustus appear similar in looking like rounded "pillars," on the inside these pillars differed between the two species. A. africanus's (and the earlier, east African A. afarensis's) nasal pillar was hollow, while A. robustus's was filled with "spongy" bone, like the contemporaneous A. boisei in East Africa. So the early (and "gracile") australopiths had hollow pillars while the later (and "robust") ones had a bony pillar, hmm... It'd be neat to try to see how such bone-filled or hollow pillars develop (i.e. are they hollow in babies but then fill with trabecular bone during growth in the "robust" group? Does this difference arise for functional (e.g. chewing) reasons, or could it be a developmental 'byproduct' of the tall robust australopithecine face [cf. McCollum 1999]).

It's a neat study, and they include lots of great CT images of the hominid sample. But another question arises - what is the inside of the bony nose like in modern primates, and how much variation is there within a species? (NB Villmoare and Kimbel found pretty much no variation within each fossil species, save for two curious examples, but which were based on casts). If I had the time (i.e. weren't dissertation-ating) I'd love to peruse the KUPRI files to see what "pillar" variation is like in, say, chimps (paleoanthropologists' go-to referent species). Cursorily looking at just one (female chimpanzee, left), it looks like the sides of the nose are empty higher up, but then fill with bone to form the tooth socket surrounding the canine root. I'll leave it to someone else to see what the rest look like.

But just lookit what other fun stuff you can see! At the top (anatomically toward the back) are the bone-filled mandibular condyles, beneath (anatomically a bit more toward the front) and between them are the pterygoid plates, and beneath them is a big gross maxillary sinus. Man, if only I had the time, I'd make an anatomy scavenger hunt on this site, and it'd be pretty epic.

Those papers I mentioned
McCollum, M. (1999). The Robust Australopithecine Face: A Morphogenetic Perspective Science, 284 (5412), 301-305 DOI: 10.1126/science.284.5412.301

Villmoare, B., & Kimbel, W. (2011). CT-based study of internal structure of the anterior pillar in extinct hominins and its implications for the phylogeny of robust Australopithecus Proceedings of the National Academy of Sciences, 108 (39), 16200-16205 DOI: 10.1073/pnas.1105844108

Saturday, November 12, 2011


I just made what what may be the most amazing discovery of the century at a local booze emporium. Dogfish Head brewing company makes a beer whose label is adorned with Jay Matternes's reconstruction of an upright Ardipithecus ramidus. Note that the left foot grasps the earth with it's ape-like big toe.

In a whimsical use of artistic license, whoever adopted this image added a curlicue pig's tail. In animals with a tail, a number of caudal vertebrae continue off the set of fused vertebrae called the sacrum. Humans and other apes don't have true tails but a coccyx, a small clump of tiny, fused vertebral segments. Our tail vestige may not help us hang onto trees like in Ateline monkeys, or sting our enemies like a scorpion, but the coccyx is still pretty important. In people this evolutionary memory of a tail anchors some muscles of the pelvic floor (including sphincter ani externus and levator ani), which are critical for the to control of our bowels.

Below is a close up of the Ardipithecus ramidus pelvis fossils (from White et al. 2009, fig. 3). No coccyx was discovered for Ardi, and little is said about the sacrum, other than that it's merely broken piece of the end of the bone (Lovejoy et al. 2009). Nevertheless, I'm sure this end of sacrum would lead one to reject this artist's hypothesis that Ardipithecus had a tail.

Had I been in charge of labeling at Dogfish Head, the beer would've been called "Party-pithecus" instead of "namaste," and this label would've been slapped on some exotic IPA or porter instead of a wheat beer. Still pretty awesome, though.

Learn about Ardi and its pelvis
Lovejoy, C., Suwa, G., Spurlock, L., Asfaw, B., & White, T. (2009). The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking Science, 326 (5949), 71-71 DOI: 10.1126/science.1175831

White, T., Asfaw, B., Beyene, Y., Haile-Selassie, Y., Lovejoy, C., Suwa, G., & WoldeGabriel, G. (2009). Ardipithecus ramidus and the Paleobiology of Early Hominids Science, 326 (5949), 64-64 DOI: 10.1126/science.1175802

Thursday, November 10, 2011

A poor depiction, indeed

As I've alluded to in some previous posts, in the Spring semester of 2012, I'll be teaching "Anthrbio 297: Human Evo-devo" at the University of Michigan. It should be a really fun and interesting class, examining the role of development in human evolution.
Ernst Haeckel's drawing of embryonic stages in some vertebrates. Taken from Richardson et al. 1997
My department recommends I create a flier that can be posted around campus. One of my first ideas was to adapt a Haeckel's classic illustration of embryos of different animals passing through similar stages in utero (which we know today isn't exactly correct; Richardson et al. 1997), but spin it to include primates and fossil humans. I started sketching it out (very crudely), but kept getting distracted with my pitiful attempts at multitasking. When I stopped zoning out, I was aghast to find my adaptation had taken a peculiar turn.
ResearchBlogging.orgI won't quit my day job.
More about vertebrate embryology
Richardson, M., Hanken, J., Gooneratne, M., Pieau, C., Raynaud, A., Selwood, L., & Wright, G. (1997). There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development Anatomy and Embryology, 196 (2), 91-106 DOI: 10.1007/s004290050082

Tuesday, November 8, 2011

We should not try to clone Neandertals

Interesting that right after I posted about fossils, genotypes and phenotypes, the Leakey Foundation (via Twitter) posts a link to a discussion about cloning Neandertals in order to learn about the genetic bases of human uniqueness. It begins innocently enough, stating that the genotype-phenotype comparisons between humans and the Neandertal Frankenstein could lead us to insights about our genetic predispositions to certain pathogens. Sure, why not. But then this happens (emphases mine): 
"Yet, further discussion with [Harvard geneticist Dr. George Church] revealed an even more interesting benefit. Dr. Church thinks the cloning of a Neanderthal would encourage us to have a greater appreciation for and sensitivity to what he terms "neural diversity." He believes that by listening to the thoughts of a cloned Neanderthal, who might seem foreign and unusual to us, greater anti-discrimination and de-stigmatization efforts on behalf of those people whose actions are usually considered outside the range of "normal" human behavior might result. These would include individuals diagnosed with dyslexia, narcolepsy, autism, and bipolar disorders."
Dr. Church belies his own statements of concern for ethics and people's rights. "Neandertal" has historically been synonymous with ideas of what is ugly, stupid and an anthropological Other (i.e. unlike and less than human), and Church seems to follow this. However, decades of archaeology show us that Neandertals were probably just as capable of complex thinking as recent humans Neandertals buried their dead. Italian Neandertals over 40 thousand years ago appear to have made symbolic use of feathers (Peresani et al. 2011). We also know that the hearing range of the Sima de los Huesos hominids was probably tuned to frequencies used in human speech (Martinez et al. 2004). In addition, the presence of the human-derived FOXP2 gene in Neandertals (Krause et al. 2007) suggests (but of course does not prove) that they could, and probably did, speak to one another with language.

Neandertals were not dumb, so there's no a priori reason to think that reanimating Neandertal consciousness would provide us with novel insights into a 'neural other.' Worse, by equating people who have forms of cognitive/neural impairment with Neandertals, Church (probably inadvertently) otherizes the people he hopes we stop otherizing. Why the hell would a Neandertal clone - a being whose existence is solely an experiment to show us what makes us human based on what's not like the clone - make us treat differently-abled people better? Worse, what to do if Neandertal shows no cognitive impairments whatsoever? Have Eegah and Encino Man taught us nothing?!

And then there's the icing on the cake:
"Chicago-Kent College Law Professor Lori Andrews has stated unequivocally that Neanderthals should be accorded all forms of human rights."
Good, I was very worried about that. Luckily, I don't think any normal review board (or the FDA) would approve Neandertal cloning in the first place.

UPDATE: Obviously, "Prehistoric Ice Man" (1999), the last episode of the 2nd season of Southpark, provides further reasons not to bring cave-persons of the past into the present day.

Krause, J., Lalueza-Fox, C., Orlando, L., Enard, W., Green, R., Burbano, H., Hublin, J., Hänni, C., Fortea, J., de la Rasilla, M., Bertranpetit, J., Rosas, A., & Pääbo, S. (2007). The Derived FOXP2 Variant of Modern Humans Was Shared with Neandertals Current Biology, 17 (21), 1908-1912 DOI: 10.1016/j.cub.2007.10.008

Martinez, I. (2004). Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in Spain Proceedings of the National Academy of Sciences, 101 (27), 9976-9981 DOI: 10.1073/pnas.0403595101

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

Sterling, J. "Concerns over the cloning of a Neanderthal." GEN News. 02 November 2011.

Leopard horse: Fossils, phenotypes and genotypes

I wish I were talking about some beastly horse-big-cat hybrid, or at least a carnivorous horse. Instead... a ton of anthropology-related papers came out today in PNAS, and possibly the coolest one is a study that compares the DNA of Pleistocene fossil and modern horses with different coat colors/patterns, and then ties this in with Paleolithic cave art. A crazy confluence of four-field anthropology right there.

Modern horses and their depictions in Late Pleistocene French caves (Pruvost et al. 2011)
Melanie Pruvost and colleagues (in press) noted that the depiction of spotted horses at the site of Pech-Merle (they give 24 kya) could mean one of two things: (1) either the early human painters were depicting horses they actually saw on the landscape at the time, or (2) they were just being fanciful and frivolous, creative and carefree with their cavern canvas. Now, some modern horse breeds have a similar spotted, "leopard" phenotype, and a genetic basis for this is understood. So Pruvost and pals examined DNA from fossil horse bones from European sites dating to 20 - 2 kya to see if these mottled mares roamed the lands of the cave-painters. Sure enough, several samples show evidence for the mutation causing leopard spots.

This is pretty cool for evolutionary biology and paleontology. A major question in biology is how an individual's genes (genotype) relate to overall appearance/behavior (phenotype). To a certain extent, physical variation between organisms arises from genetic variation, so when we see things evolve through the fossil record, this ought to correspond with some genetic changes as well. But linking genes to appearances isn't so easy (especially for extinct animals). Pruvost and colleagues' study is a step in this direction, though. Plus, the recent sequencing of the fossil Neandertal (Green et al. 2010) and Denisovan (Reich et al. 2010) genomes makes it possible to try to figure out if/how humans' unique physical traits reflect our genes. In fact, even before these genomes were fully sequenced, Carles Lalueza-Fox and team (2007) identified a mutation on Neandertals' MC1R gene, strongly suggesting the Neandertals sampled had light skin and red hair.

But the genetic basis for skeletal phenotypes is harder to discern. For example, Green et al. (2010) identified the unique human version of the RUNX2 gene as having come under strong natural selection since the disappearance of Neandertals. The authors noted that because mutations of RUNX2 in humans are associated with a cleidocranial dysplasia affecting the form of the skull and shoulders, and because humans and Neandertals differ in some aspects of their skulls and shoulders, then RUNX2 variation between humans and Neandertals is likely related to visible differences in their skeletons. But that's about as much as could be said at the moment - RUNX2 is involved in bony development of the entire skeleton, interacting with other various genes in various places during ontogeny. So while it's tempting, it's still a little early to link RUNX2, or pretty much any other development-related gene, with physical differences between humans and our fossil relatives. But one day!
A Neandertal's ruddy locks have never preserved in the fossil record, but its bones are very well known. In an ironic twist, we may have a better understanding of the genetic basis of variation in a soft-tissue (for which there are no fossils), than we do for the skeleton (for which we have lots of fossils).

And maybe one day I'll get that leopard horse I was hoping for.

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

Pruvost, M., Bellone, R., Benecke, N., Sandoval-Castellanos, E., Cieslak, M., Kuznetsova, T., Morales-Muniz, A., O'Connor, T., Reissmann, M., Hofreiter, M., & Ludwig, A. (2011). Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1108982108

Reich, D., Green, R., Kircher, M., Krause, J., Patterson, N., Durand, E., Viola, B., Briggs, A., Stenzel, U., Johnson, P., Maricic, T., Good, J., Marques-Bonet, T., Alkan, C., Fu, Q., Mallick, S., Li, H., Meyer, M., Eichler, E., Stoneking, M., Richards, M., Talamo, S., Shunkov, M., Derevianko, A., Hublin, J., Kelso, J., Slatkin, M., & Pääbo, S. (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia Nature, 468 (7327), 1053-1060 DOI: 10.1038/nature09710

Sunday, November 6, 2011

Inanimate fossils getting older still

Two reports came out last week in the journal Nature, re-dating some European human fossils to before 40 thousand years ago (kya), a few thousand years older than previous evidence for modern-looking people in the region. The media have been reporting these studies as revealing "the first Europeans," but of course we all know that the first Europeans were the badass hominids, my favorites, from the 1.8 million year old site of Dmanisi.

KC4 maxilla (Higham et al. 2011)
From Kent's Cavern (United Kingdom) is a partial maxilla, now dated to 44 - 41 kya* (Higham et al. 2011; but see below). The jaw fragment with highly worn teeth was found just above some Aurignacian-like (Upper Paleolithic) blades in 1927. [NB below these 2 blades were 2 other blades of a tool "complex...tentatively associated with Neandertals] The laughable amount of bone makes it rather impossible to say whether the fossil represents a Neandertal or more modern-looking human. The authors examined what little of the morphology was left and concluded that the fossil shared the most similarities with recent humans but only a few with Neandertals. A more rigorous analysis of what this mix of traits means would have been nice (i.e. why would an individual have derived traits of both 'modern' humans and Neandertals?). The researchers tried to extract DNA for analysis, but apparently organic remains were too poorly preserved for a good analysis. Bummer.

Cavallo B and C (Benazzi et al. 2011)
A similar older-than-we-thought story is reported by Stefano Benazzi and buddies, who reanalyzed teeth from the Italian site of Grotta del Cavallo (left). After the site was excavated in 1967, the teeth were attributed to Neandertals and the lithics classified as "Uluzzian." I would be a dirty liar if I said knew anything about the "Uluzzian" industry (try this other site which may be more informative), but apparently it's seen as transitional between the Neandertal-associated Mousterian and 'more advanced' Upper Paleolithic toolkits. So this assemblage could be used to argue that Neandertals were smart enough to upgrade to a sexier stone tool industry shortly before their anatomy (but not their genes!) disappeared. BUT! also like in Kent's Cavern paper, Benazzi and colleagues examined what little morphology is preserved in the fossil teeth, and (re)assigned them to modern-looking humans. The authors provided nice qualitative and quantitative arguments for the human status of the teeth, though again I have to raise caution that these are only teeth and we have no idea what the rest of the skeleton would have looked like. Researchers also analyzed shells associated with the now-human teeth and dated the site to around 44 kya, making them the oldest probably-human remains in Europe.

Now, according to conventional wisdom, the Neandertals were dullards who made and used the Mousterian stone tool industry. The Mousterian was nice and all, but not nearly as wicked-pisser as the smart and sassy modern-looking humans' Aurignacian toolkit. The thing is, though, there really hasn't been really a lot of evidence unequivocally linking modern-looking fossils with Aurignacian artifacts. So both of the recent studies in Nature lend support to the idea that maybe modern humans were the sole makers (and users) of an advanced stone tool industry. But it's important to remember [1] that the blades 'associated' with the Kent's Cavern jaw can't really be definitively attributed to a stone tool industry; [2] the blades were deeper in the cave than the jaw, and so may actually be appreciably older than the jaw; and [3] while the teeth from Kent's Cavern and Cavallo do look most comparable to those belonging to 'anatomically' modern humans, we don't know what the skulls or skeletons containing the teeth looked like. All that said, it's neat to see the possible appearance of certain anatomy and technology in Europe thousands of years earlier than previously thought. It also re-raises the issue of the degree to which modern-looking humans and Neandertals overlapped in space and time, and what these interactions would have been like (I'd guess terrifying, hilarious and/or sexy).

KC4 originally
(Higham et al. 2011)
A fun lesson also comes from the Kent's Cavern study. Higham and colleagues report that the KC4 human maxilla was excavated in 1927 and analyzed by Sir Arthur Keith, a well-trained anatomist and paleoanthropologist famous in his day. Keith described the fossil as containing a canine, second premolar and first molar (right, compare with above). Higham and colleagues, however, noticed that what Keith described as a second premolar was in fact a first premolar. The teeth are so worn they mostly lack information about their form and features, so this mistake probably didn't really mislead anatomists in any way. Still, it goes to show that even experts like Keith can make mistakes or overlook the things they know best, and this is not the first time I've seen this happen with fossils. So always (politely) question those giants whose shoulders you're standing upon.

*Update (07 Nov): John Hawks points out that the KC4 maxilla itself was not used to obtain the older radiocarbon age estimate. In 1989 the maxilla was directly dated to around 30 kya, over 10 ky younger than the new estimates. Higham and friends thought this date was too young, based on methodological grounds. An attempt to redate the KC4 maxilla based on one of the teeth yielded too little collagen (organic material) to produce a date. Bummer again! The new estimate is instead based on radiocarbon dates obtained from animal bones that were excavated from above and below the human jaw. So this 'redating' of the Kent's Cavern maxilla is very interesting, but should be taken with a grain of salt.
See for yourself
Benazzi, S., Douka, K., Fornai, C., Bauer, C., Kullmer, O., Svoboda, J., Pap, I., Mallegni, F., Bayle, P., Coquerelle, M., Condemi, S., Ronchitelli, A., Harvati, K., & Weber, G. (2011). Early dispersal of modern humans in Europe and implications for Neanderthal behaviour Nature DOI: 10.1038/nature10617

Higham, T., Compton, T., Stringer, C., Jacobi, R., Shapiro, B., Trinkaus, E., Chandler, B., Gröning, F., Collins, C., Hillson, S., O’Higgins, P., FitzGerald, C., & Fagan, M. (2011). The earliest evidence for anatomically modern humans in northwestern Europe Nature DOI: 10.1038/nature10484