Worst year in review

As we’re wrapping up what may be the worst year in recent global memory, especially geopolitically, let’s take a moment to review some more positive things that came up at Lawnchair in 2016.

Headed home

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Alternate subtitle: Go West
This was a quiet year on the blog, with only 18 posts compared with the roughly thirty per year in 2014-2015. The major reason for the silence was that I moved from Kazakhstan back to the US to join the Anthropology Department at Vassar College in New York. With all the movement there was  less time to blog. Much of the second half of 2016 was spent setting up the Biological Anthropology Lab at Vassar, which will focus on “virtual” anthropology, including 3D surface scanning…

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Cast of early Homo cranium KNM-ER 1470 and 3D surface scan made in the lab using an Artec Spider.

… and 3D printing.

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gibbon endocast, created from a CT scan using Avizo software and printed on a Zortrax M200.

This first semester stateside I reworked my ‘Intro to Bio Anthro’ and ‘Race’ courses, which I think went pretty well being presented to an American audience for the first time. The latter class examines human biological variation, situating empirical observations in modern and historical social contexts. This is an especially important class today as 2016 saw a rise in nationalist and racist movements across the globe. Just yesterday Sarah Zhang published an essay in The Atlantic titled, “Will the Alt-right peddle a new kind of racist genetics?” It’s a great read, and I’m pleased to say that in the Race class this semester, we addressed all of the various social and scientific issues that came up in that piece. Admittedly though, I’m dismayed that this scary question has to be raised at this point in time, but it’s important for scholars to address and publicize given our society’s tragically short and selective memory.

So the first semester went well, and next semester I’ll be teaching a seminar focused on Homo naledi and a mid-level course on the prehistory of Central Asia. The Homo naledi class will be lots of fun, as we’ll used 3D printouts of H. naledi and other hominin species to address questions in human evolution. The Central Asia class will be good prep for when I return to Kazakhstan next summer to continue the hunt for human fossils in the country.

Osteology is still everywhere

A recurring segment over the years has been “Osteology Everywhere,” in which I recount how something I’ve seen out and about reminds me of a certain bone or fossil. Five of the blog 18 posts this year were OAs, and four of these were fossiliferous: I saw …

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Anatomy terminology hidden in 3D block letters,

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Hominin canines in Kazakhstani baursaki cakes,

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The Ardipithecus ramidus ilium in Almaty,

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Homo naledi juvenile femur head in nutmeg,

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And a Homo erectus cranium on a Bangkok sidewalk. As I’m teaching a fossil-focused seminar next semester, OA will probably become increasingly about fossils, and I’ll probably get my students involved in the fun as well.

New discoveries and enduring questions

The most-read post on the blog this year was about the recovery of the oldest human Nuclear DNA, from the 450,000 year old Sima de los Huesos fossils. My 2013 prediction that nuclear DNA would conflict with mtDNA by showing these hominins to be closer to Neandertals than Denisovans was shown to be correct.

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These results are significant in part because they demonstrate one way that new insights can be gained from fossils that have been known for years. But more intriguingly, the ability of researchers to extract DNA from exceedingly old fossils suggests that this is only the tip of the iceberg.

The other major discoveries I covered this year were the capuchin monkeys who made stone tools and the possibility that living humans and extinct Neandertals share a common pattern of brain development.

Pride & Predator

An unrelated image from 2016 that makes me laugh.

The comparison between monkey-made and anthropogenic stone tools drives home the now dated fact that humans aren’t the only rock-modifiers. But the significance for the evolution of human tool use is less clear cut – what are the parallels (if any) in the motivation and modification of rocks between hominins and capuchins, who haven’t shared a common ancestor for tens of millions of years? I’m sure we’ll hear more on that in the coming years.

In the case of whether Neandertal brain development is like that of humans, I pointed out that new study’s results differ from previous research probably because of differences samples and methods. The only way to reconcile this issue is for the two teams of researchers, one based in Zurich and the other in Leipzig, to come together or for a third party to try their hand at the analysis. Maybe we’ll see this in 2017, maybe not.

There were other cool things in 2016 that I just didn’t get around to writing about, such as the publication of new Laetoli footprints with accompanying free 3D scans, new papers on Homo naledi that are in press in the Journal of Human Evolution, and new analysis of old Lucy (Australopithecus afarensis) fossils suggesting that she spent a lifetime climbing trees but may have sucked at it. But here’s hoping that 2017 tops 2016, on the blog, in the fossil record, and basically on Earth in general.

Osteology Everywhere: Skull in the Stone #FossilFriday edition

It’s that time of year again.

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It’s the end of the year and I’ve got Homo erectus on the brain somethin fierce. Our precedent-erect first popped up in Africa around 1.9 million years ago, quickly spread throughout much of the Old World, and persisted until perhaps as late as ~ 100,000 years ago in Java, Indonesia. This was a very successful species by all accounts, and as a result of its great range and duration, you can imagine it was also pretty variable.

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Hominin brain sizes. Boxes and whiskers represent sample tendencies and points are individual specimens. 1 = Australopithecus, 2 = Early Homo (cf. habilisrudolfensis), 3 = Dmanisi H. erectus, 4 = Early African H. erectus, 5 = Early Indonesian H. erectus, 6 = Chinese H. erectus, 7 = Later Indonesian H. erectus, 8 = modern humans.

Despite this great variation, H. erectus skulls generally share a common visage: long and low cranial vault, low forehead, protruding brow ridges, fun tuberosities and tori in the back. You’d recognize them anywhere. Including the sidewalk!

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Homo erectus in front of Ploenchit Tower, Bangkok (lateral view, front is to the right).

The relief in this sidewalk slat superficially looks like a trace fossil of partial H. erectus cranium, the face either missing (from the lower right) or taphonomically displaced toward the left side of the tile (see here for actual H. erectus trace fossils). This looks really similar to H. erectus from Indonesia, not surprising given its discovery in Thailand. Why, it could have come straight out of Figure 6 from a 2006 paper by Yousuke Kaifu and colleagues:

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Left lateral views of Javanese H. erectus crania, modestly modified from Kaifu et al. (2006: Fig. 6). Front is to the left this time.

Using my insane photo editing skills, I’ve inserted the Ploenchit Tower trace fossil (reversed) within the horde of heads presented by Kaifu et al., above. Like many of the real fossils, the Ploenchit specimen is missing the face (due to taphonomy), the supraorbital torus or brow ridge juts out from a low-rising forehead, and the occipital bone also projects out about from the otherwise rounded contour of the cranium. Note that there is a good deal of variation in each of these features among the real fossils.

What a happy holiday accident to find a Homo erectus cranium on the street!

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ResearchBlogging.org Reference
Kaifu Y, Aziz F, Indriati E, Jacob T, Kurniawan I, & Baba H (2008). Cranial morphology of Javanese Homo erectus: new evidence for continuous evolution, specialization, and terminal extinction. Journal of human evolution, 55 (4), 551-80 PMID: 18635247

Osteology Everywhere: Skeletal Spice

The American winter holiday season is steeped in special spices, such as nutmeg, cloves, cinnamon, and whatever the hell pumpkin spice is. I guess as part of the never-ending War on Christmas, each year this sensory and commercial immersion begins earlier and earlier. Since these have become old news, I’d pretty much forgotten about the seasonal spicecapade until just the other day. In prep for minor holiday gluttony, I was grinding fresh nutmeg when I made a startling discovery. Nutmeg is not just the fragrant fruit of the Myristica fragrans tree. No, there’s something far more sinister in this holiday staple.

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Merely nutmeg?

The ground section looks superficially like an unfused epiphyseal surface, whereas the rounded outer surface is more spherical. It turns out, in the most nefarious of all holiday conspiracies since the War on Christmas, nutmeg halves are nothing more than unfused femur heads! Compare with the epiphyseal surface of this Homo naledi femur head:

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Nutmeg (left) and H. naledi specimen UW 101-1098 (right).

This immature H. naledi specimen was recently published (Marchi et al., in press), and the associated 3D surface scan has been available for free download on Morphosource.org for a while now. It fits onto a proximal femur fragment, UW 101-1000, also free to download from Morphosource.

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Modified Fig. 11 from Marchi et al. It’s weird that only H. naledi bones were found in the Dinaledi chamber, but even weirder is the underreported presence of nutmeg.

Like most  bones in the skeleton, the femur is comprised of many separate pieces that appear and fuse together at different, fairly predictable ages. The shaft of the femur appears and turns to bone before birth, and the femur head, which forms the ball in the hip joint, usually appears within the first year of life and fuses to the femur neck in adolescence (Scheuer and Black, 2000). So we know this H. naledi individual was somewhere between 1–15ish years by human standards, probably in the latter half of this large range.

So there you have it. Osteology is everywhere – the holidays are practically a pit of bones if you keep your eyes open.

ResearchBlogging.orgREFERENCES

Marchi D, Walker CS, Wei P, Holliday TW, Churchill SE, Berger LR, & DeSilva JM (2016). The thigh and leg of Homo naledi. Journal of Human Evolution PMID: 27855981.

Scheuer L and Black S. 2000. Developmental Juvenile Osteology. New York: Elsevier Academic Press.

The strange days of yore

Today is not like the good ol’ days. In many ways things have changed for the better. For instance, in the good ol’ days, many paleontologists would find fossils but let nary a soul examine them; today, you can download high quality 3D models of many important fossils from both East and South Africa, completely for free!

Robert Broom’s (1938) account of the discovery of the first Paranthropus (or Australopithecus) robustus is also a reminder of the strangeness of the bygone days of yore:

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Wait for it …

In June of this year a most important discovery was made. A schoolboy, Gert Terblanche, found in an outcrop of bone breccia near the top of a hill, a couple of miles from the Sterkfontein caves, much of the skull and lower jaw of a new type of anthropoid. Not realizing the value of the find, he damaged the specimen considerably in hammering it out of the rock. The palate with one molar tooth he gave to Mr. Barlow at Sterkfontein, from whom I obtained it. Recognizing that some of the teeth had recently been broken off, and that there must be other parts of the skull where the palate was found, I had to hunt up the schoolboy. I went to his home two miles off and found that he was at the school another two miles away, and his mother told me that he had four beautiful teeth with him. I naturally went to the school, and found the boy with four of what are perhaps the most valuable teeth in the world in his trouser pocket. He told me that there were more bits of the skull on the hillside. After school he took me to the place and I gathered every scrap I could find; and when these were later examined and cleaned and joined up, I found I had not only the nearly perfect palate with most of the teeth, but also practically the whole of the left side of the lower half of the skull and the nearly complete right lower jaw.

What a wild time – Broom hunts down poor Gert, barges into the school, then makes the kid show him where he hacked the skull out of the rock. Poor, poor Gertie.

Maybe it was a different Gertie, but surely the reaction was the same.

Maybe it was a different Gertie, but surely the reaction was the same.

Of course, there was a lot at stake. I mean, brazen Gert harbored not just “beautiful teeth,” but “the most valuable teeth in the world.” IN HIS TROUSERS! And of course Gert was also the soul possessor of priceless intel – the source of the fossils. So maybe Broom was justified in this zealous abduction. And O! such prose in a Nature paper! WAS IT WORTH IT, DR. BROOM?

At Sterkfontein, a bronzed Broom considers the weight of his actions.

At Sterkfontein, a bronzed Broom considers the weight of his actions.

Of course, Gert wasn’t the last kid to discover an important human fossil. The game-changing Australopithecus sediba  was discovered when Matthew Berger, son of famed Lee Berger and only 9 years old at the time, saw a piece of a clavicle sticking out of a block of breccia. Both Gert and Matthew show that you don’t have to be a doctor to make amazing discoveries. What future fossil discoveries will be made by kids, and making my adult accomplishments pale in comparison?!

Osteology Everywhere: Cakes or canines?

I’ve been looking at so many teeth lately, I’m starting to feel like a sadist but with newer magazines.

Between putting together a talk about dental development in Homo naledi and teaching teeth in my human evo-devo class last week . . .

After these drawings, my students were fully trained and ready to tackle the odontological world.

After these drawings, my students are now fully trained and ready to tackle the odontological world.

. . . I’ve got dentition on the brain. WHICH IS NOT THEIR ANATOMICAL POSITION.

So last weekend some friends and I hit a local pub,  a life jacket for my dental inundation. Surely, a pint and a snack will expunge enamel, dissolve dentine, exhume zuby from my brain! We ordered some beer and baursaki, delicious fried bread made out here in Kazakhstan, the perfect snack to go with beer and chechil. Tearing into the pastry, I started to feel at peace, but then was horrified to look down and find myself hoist with my own petard:

Baursak or bite?

Baursak with a bite taken out? Our a hominin canine?

Seeing the snack, I saw the very thing I’d been fleeing – a hominin canine tooth. Inadvertently, I’d almost exactly replicated Sts 50, a lower left canine crown and broken root from the South African site of Sterkfontein.

Left: Sts 50, lower left canine. Right: bitten fried bread. Images not to scale.

Left: Sts 50, lower left canine. Right: bitten fried bread. Images not to scale. ANTIMERES?

They’re nearly identical but from opposite sides (the fancy word for which is “antimeres”). Note the tall-shouldered, sharp apex of the crown, and the little distal tubercle, the little ‘bump’ at the far left in the left picture above. The mesial, or front, crown shoulder is notably taller than the distal tubercle. At probably around 3 million years ago, Sts 50 likely belongs to Australopithecus africanus, and retains an ape-like asymmetrical crown shape compared to the more incisor-shaped canines we humans have today.

Left to right: Homo baursaki, three South African canines, and a modern human (from White et al. 2012). Images not to scale.

Hominin canines and definitely no cakes. Left to right: Homo baursaki, three canines from early Pleistocene South Africa, and a modern human (from White et al. 2011). Images not to scale. Note how much less asymmetrical the modern human canine crown (far right) is compared to the fossil hominins. Teeth 1, 2, 4, and 5 are from the right side while the center, Sts 50, is from the left.

 

Apparently all you need to go back in time is some beer and baursaki.

#FossilFriday: 2015 Retrospecticus

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Holy crap 2015 was a big year for fossils. And how fortuitous that 2016 begins on a Fossil Friday – let’s recap some of last year’s major discoveries.

Homo naledi

Homo naledi mandibles in order from least to most worn teeth.

Some Homo naledi mandibles in order from least to most worn teeth.

The Homo naledi sample is a paleoanthropologist’s dream – a new member of the genus Homo with a unique combination of traits, countless remains belonging to at least a dozen individuals from infant to old adult, representation of pretty much the entire skeleton, and a remarkable geological context indicative of intentional disposal of the dead (but certainly not homicide, grumble grumble grumble…).  The end of 2015 saw the announcement and uproar (often quite sexist) over this amazing sample. You can expect to see more, positive things about this amazing animal in 2016.

We’ll be presenting a bunch about Homo naledi at this year’s AAPA meeting in Hotlanta. I for one will be discussing dental development at Dinaledi- here’s a teaser:

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As long as we’re talking about the AAPA meetings, my colleague David Pappano and I are organizing a workshop, “Using the R Programming Language for Biological Anthropology.” Details to come!

Lemur graveyard

Homo naledi wasn’t the only miraculously copious primate sample announced in 2015. Early last year scientists also reported the discovery of an “Enormous underwater fossil graveyard,” containing fairly complete remains of probably hundreds of extinct lemurs and other animals. As with Homo naledi, such a large sample will reveal lots of critical information about the biology of these extinct species.

Australopithecus deyiremeda

Extended Figure 1h from the paper, with a Demirjian developmental stages, modifed from Table 2 from Kuykendall et al., 1996. Compare the M2 roots with completed roots of the M1 (to the left).

Extended Figure 1h from Haile-Selassie et al. (2015), compared with Demirjian developmental stages 6-8 . While the M1 roots look like stage 8 (complete), M2 looks like stage 7 (incomplete).

We also got a new species of australopithecus last year. Australopithecus deyiremeda had fat mandibles, a relatively short face (possibly…), and smaller teeth than in contemporaneous A. afarensis. One tantalizing thing about this discovery is that we may finally be able to put a face to the mysterious foot from Burtele, since these fossils come from nearby sites of about the same geological age. Also intriguing is the possible evidence, based on published CT images (above), that A. deyiremeda had relatively advanced canine and delayed molar development, a pattern generally attributed to Homo and not other australopithecines (if this turns out to be the case, you heard it here first!).

Lomekwian stone tool industry

3D scan and geographical location of Lomekwian tools. From africanfossils.org

3D scan and geographical location of Lomekwian tools. From africanfossils.org.

Roughly contemporaneous with A. deyiremeda, Harmand et al. (2015) report the earliest known stone tools from the 3.3 million year old site of Lomekwi 3 in Kenya. These tools are a bit cruder and much older than the erstwhile oldest tools, the Oldowan from 2.6 million years ago. These Lomekwian tools, and possible evidence for animal butchery at the 3.4 million year old Dikika site in Ethiopia (McPherron et al. 2010;  Thompson et al. 2015), point to an earlier origin of lithic technology. Fossils attributed to Kenyanthropus platyops are also found at other sites at Lomekwi. With hints at hominin diversity but no direct associations between fossils and tools at this time, a lingering question is who exactly was making and using the first stone tools.

Earliest Homo

The reconstructed Ledi Geraru mandible (top left), compared with Homo naledi (top right), Australopithecus deyiremeda (bottom left), and the Uraha early Homo mandible from Malawi (bottom right).

The reconstructed Ledi Geraru mandible (top left), compared with Homo naledi (top right), A. deyiremeda (bottom left), and the Uraha early Homo mandible from Malawi (bottom right). Jaws are scaled to roughly the same length from the front to back teeth; the Uraha mandible does not have an erupted third molar whereas the others do and are fully adult.

Just as Sonia Harmand and colleagues pushed back the origins of technology, Brian Villmoare et al. pushed back the origins of the genus Homo, with a 2.7 million year old mandible from Ledi Geraru in Ethiopia. This fossil is only a few hundred thousand years younger than Australopithecus afarensis fossils from the nearby site of Hadar. But the overall anatomy of the Ledi Geraru jaw is quite distinct from A. afarensis, and is much more similar to later Homo fossils (see image above).  Hopefully 2016 will reveal other parts of the skeleton of whatever species this jaw belongs to, which will be critical in helping explain how and why our ancestors diverged from the australopithecines. (note that we don’t yet have a date for Homo naledi – maybe these will turn out to be older?)

Early and later Homo

Modified figures X from Maddux et al. (2015) and 13 from Ward et al. (2015).

Left: modified figures 2-3 from Maddux et al. (2015). Right: modified figures 7 & 13 from Ward et al. (2015). Note that in the right plot, ER 5881 femur head diameter is smaller than all other Homo except BSN 49/P27.

The earlier hominin fossil record wasn’t the only part to be shaken up. A small molar (KNM-ER 51261) and a set of associated hip bones (KNM-ER 5881) extended the lower range of size variation in Middle and Early (respectively) Pleistocene Homo. It remains to be seen whether this is due to intraspecific variation, for example sex differences, or taxonomic diversity; my money would be on the former.

Left: Penghu hemi-mandible (Chang et al. 2015: Fig. 3), viewed from the outside (top) and inside (bottom). Right: Manot 1 partial cranium (Hershkovitz et al. 2015: Fig. 2), viewed from the left (top) and back (bottom).

Left: Penghu 1 hemi-mandible (Chang et al. 2015: Fig. 3), viewed from the outside (top) and inside (bottom). Right: Manot 1 partial cranium (Hershkovitz et al. 2015: Fig. 2), viewed from the left (top) and back (bottom).

At the later end of the fossil human spectrum, researchers also announced an archaic looking mandible dredged up from the Taiwan Straits, and a more modern-looking brain case from Israel. The Penghu 1 mandible is likely under 200,000 years old, and suggests a late survival of archaic-looking humans in East Asia. Maybe this is a fossil Denisovan, who knows? What other human fossils are waiting to be discovered from murky depths?

The Manot 1 calvaria looks very similar to Upper Paleolithic European remains, but is about 20,000 years older. At the ESHE meetings, Israel Hershkovitz actually said the brain case compares well with the Shanidar Neandertals. So wait, is it modern or archaic? As is usually the case, with more fossils come more questions.

Crazy dinosaurs

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Yi qi was bringing Skeksi back, and its upper limb had a wing-like shape not seen in any other dinosaur, bird or pterosaur. There were a number of other interesting non-human fossil announcements in 2015 (see here and here), proving yet again that evolution is far more creative than your favorite monster movie makers.

ResearchBlogging.orgWhat a year – new species, new tool industries, new ranges of variation! 2015 was a great year to be a paleoanthropologist, and I’ll bet 2016 has just as much excitement in store.

References (in order of appearance)

Haile-Selassie, Y., Gibert, L., Melillo, S., Ryan, T., Alene, M., Deino, A., Levin, N., Scott, G., & Saylor, B. (2015). New species from Ethiopia further expands Middle Pliocene hominin diversity Nature, 521 (7553), 483-488 DOI: 10.1038/nature14448

Harmand, S., Lewis, J., Feibel, C., Lepre, C., Prat, S., Lenoble, A., Boës, X., Quinn, R., Brenet, M., Arroyo, A., Taylor, N., Clément, S., Daver, G., Brugal, J., Leakey, L., Mortlock, R., Wright, J., Lokorodi, S., Kirwa, C., Kent, D., & Roche, H. (2015). 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya. Nature, 521 (7552), 310-315. DOI: 10.1038/nature14464

McPherron, S., Alemseged, Z., Marean, C., Wynn, J., Reed, D., Geraads, D., Bobe, R., & Béarat, H. (2010). Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia. Nature, 466 (7308), 857-860. DOI: 10.1038/nature09248

Thompson, J., McPherron, S., Bobe, R., Reed, D., Barr, W., Wynn, J., Marean, C., Geraads, D., & Alemseged, Z. (2015). Taphonomy of fossils from the hominin-bearing deposits at Dikika, Ethiopia Journal of Human Evolution, 86, 112-135 DOI: 10.1016/j.jhevol.2015.06.013

Villmoare, B., Kimbel, W., Seyoum, C., Campisano, C., DiMaggio, E., Rowan, J., Braun, D., Arrowsmith, J., & Reed, K. (2015). Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia Science, 347 (6228), 1352-1355 DOI: 10.1126/science.aaa1343

Maddux, S., Ward, C., Brown, F., Plavcan, J., & Manthi, F. (2015). A 750,000 year old hominin molar from the site of Nadung’a, West Turkana, Kenya Journal of Human Evolution, 80, 179-183 DOI: 10.1016/j.jhevol.2014.11.004

Ward, C., Feibel, C., Hammond, A., Leakey, L., Moffett, E., Plavcan, J., Skinner, M., Spoor, F., & Leakey, M. (2015). Associated ilium and femur from Koobi Fora, Kenya, and postcranial diversity in early Homo Journal of Human Evolution, 81, 48-67 DOI: 10.1016/j.jhevol.2015.01.005

Chang, C., Kaifu, Y., Takai, M., Kono, R., Grün, R., Matsu’ura, S., Kinsley, L., & Lin, L. (2015). The first archaic Homo from Taiwan Nature Communications, 6 DOI: 10.1038/ncomms7037

Hershkovitz, I., Marder, O., Ayalon, A., Bar-Matthews, M., Yasur, G., Boaretto, E., Caracuta, V., Alex, B., Frumkin, A., Goder-Goldberger, M., Gunz, P., Holloway, R., Latimer, B., Lavi, R., Matthews, A., Slon, V., Mayer, D., Berna, F., Bar-Oz, G., Yeshurun, R., May, H., Hans, M., Weber, G., & Barzilai, O. (2015). Levantine cranium from Manot Cave (Israel) foreshadows the first European modern humans Nature, 520 (7546), 216-219 DOI: 10.1038/nature14134

Bioanthro lab activity: Hominin brain size

Last week in my Human Evolution class we looked at whether we could estimate hominin brain sizes, or endocranial volumes (ECV), based on just the length and width of the bony brain case. Students took these measurements on 3D surface scans…

Maximum cranial length in Australopithecus boisei specimen KNM-ER 406.

Maximum cranial length in Australopithecus boisei specimen KNM-ER 406.

… and then plugged their data into equations relating these measurements to brain size in chimpanzees (Neubauer et al., 2012) and humans (Coqueugniot and Hublin, 2012).

The relationship between cranial length (x axis) and ECV (y axis).

The relationship between cranial length (x axis) and ECV (y axis). Left shows the chimpanzee regression (modified from Fig. 2 in Neubauer et al., 2012), while the right plot is humans (from the Supplementary Materials of Coqueugniot and Hublin, 2012).

So in addition to spending time with fossils, students also learned about osteometric landmarks with fun names like “glabella” and “opisthocranion.” More importantly, students compared their estimates with published endocranial volumes for these specimens, based on endocast measurements:

Human and chimpanzee regression equations don't do great at estimating hominin brain sizes.

Human and chimpanzee regression equations don’t do great at predicting hominin brain sizes. Each point is a hominin fossil, the x value depicting its directly-measured endocranial volume and the y value its estimated volume based on different regression equations. Black and red points are estimates based on chimpanzee cranial width and length, respectively, while green and blue points are based on human width and length, respectively. The dashed line shows y=x, or a correct estimate.

This comparison highlights the point that regression equations might not be appropriate outside of the samples on which they are developed. Here, estimates based on the relationship between cranial dimensions and brain size in chimpanzees tend to underestimate fossils’ actual values (black and red in the plot above), while the human regressions tend to overestimate hominins’ brain sizes. Students must think about why these equations perform poorly on fossil hominins.

Most of the fossil scans come from AfricanFossils.org, but a few are from Artec’s sample gallery. One of the cool, fairly recent humans at African Fossils (KNM ER 5306) will give students something else to think about:

"Why doesn't this look like the rest of the human crania we've seen this semester?"

“Why doesn’t this look like the rest of the human crania we’ve seen this semester?”

Here are the lab materials so you can use and adapt this for your own class:

Lab 4-Brain size (Instructions & questions)

Lab 4 data table (with equations)

ResearchBlogging.orgReferences
Coqueugniot, H., & Hublin, J. (2012). Age-related changes of digital endocranial volume during human ontogeny: Results from an osteological reference collection American Journal of Physical Anthropology, 147 (2), 312-318 DOI: 10.1002/ajpa.21655

Neubauer, S., Gunz, P., Schwarz, U., Hublin, J., & Boesch, C. (2012). Brief communication: Endocranial volumes in an ontogenetic sample of chimpanzees from the taï forest national park, ivory coast American Journal of Physical Anthropology, 147 (2), 319-325 DOI: 10.1002/ajpa.21641