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.

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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.

Osteology Everywhere: Bacon or first rib?

I went to a cafe today to eat breakfast and get some work done. Write, write, write. It’s important to be properly nourished to ensure maximal productivity.

The Ron Swanson diet.

The Ron Swanson diet.

But I was aghast to behold the food they placed before me:

More bacon, please.

What on earth is this?

First of all, this is not a sufficient amount of bacon.

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Secondably, this bacon is a spitting image of a first rib:

First ribs, from left to right: Human, chimpanzee, bacon. First two images from eSkeletons.org.

First ribs from the right side of the body, viewed from the top. From left to right: Human, chimpanzee, bacon. First two images from eSkeletons.org.

At the top of the ribcage, just beneath the clavicle and subclavian artery and vein, the first rib is much shorter and flatter than the rest of the ribs. As Jess Beck at Bone Broke points out, “The first and second rib give something of an awkward ‘slow song at a middle-school dance’ kind of a hug, while the lower ribs provide a more comfortable and self-assured embrace.” I mean, just lookit how sheepishly the bacon dances with the eggs in the first picture, it has ‘middle-school dance’ written all over it.

But the bacon is not totally identical to the human and chimpanzee counterparts. It’s missing their anteromedially sweeping arc, and the distal portion reaching out to the egg is fairly straight. This suggests we’re probably missing much of the original distal end. Posteriorly or dorsally (toward the bottom in the pic), it also appears to be missing much of the lateral portion including the vertebral facet. In this regard, this bacon rib looks a lot like the first rib of Homo naledi:

Full stack of ribs. From left to right: Human, bacon, Homo naledi, Dmanisi Homo erectus, Australopithecus sediba (x2), Australopithecus afarensis specimen "Lucy," Ardipithecus ramidus, and chimpanzee. Images not to scale except Lucy and Ardi.

Full stack of ribs. Left to right: Human, bacon, Homo naledi, Dmanisi Homo erectus, Australopithecus sediba (x2), Australopithecus afarensis specimen “Lucy,” Ardipithecus ramidus, and chimpanzee. Images not to scale except Lucy and Ardi. Image credits given below.

It is hard to make good homologous comparisons among these fossils and bacon, since so many are so incomplete. But it looks like the hominins are relatively longer (front to back, or dorsoventrally) compared to the chimpanzee. That is, oriented along the rib “neck,” the ventral/distal end projects far more medially beyond the proximal vertebral facet in the chimp, while in the hominins the two ends are more flush.  Ardi is really incomplete and so very hard to orient, but it may be more like the chimp (I think it needs to be rotated to the right more, to make the lateral edge more vertical like all the other specimens).

It will be interesting to see what my colleagues working on the Homo naledi thorax have to say about rib shapes and their functional importance, hopefully not too long from now.

Anyway, I really wish I had more bacon.

Fossil rib sources
ResearchBlogging.orgDmanisi Homo erectus: Lordkipanidze D, Jashashvili T, Vekua A, Ponce de León MS, Zollikofer CP, Rightmire GP, Pontzer H, Ferring R, Oms O, Tappen M, Bukhsianidze M, Agusti J, Kahlke R, Kiladze G, Martinez-Navarro B, Mouskhelishvili A, Nioradze M, & Rook L (2007). Postcranial evidence from early Homo from Dmanisi, Georgia. Nature, 449 (7160), 305-10 PMID: 17882214

Australopithecus sediba: Schmid P, Churchill SE, Nalla S, Weissen E, Carlson KJ, de Ruiter DJ, & Berger LR (2013). Mosaic morphology in the thorax of Australopithecus sediba. Science, 340 (6129) PMID: 23580537

Homo naledi: Morphosource.

Australopithecus afarensis and Ardipithecus ramidus: White TD, Asfaw B, Beyene Y, Haile-Selassie Y, Lovejoy CO, Suwa G, & WoldeGabriel G (2009). Ardipithecus ramidus and the paleobiology of early hominids. Science, 326 (5949), 75-86 PMID: 19810190

Osteology Everywhere: Why we number our premolars 3-4

Portishead* came on the radio the other day, making iTunes display the cover of their album, Third. My inner osteologist rejoiced to see it prominently features a tooth!

Third album cover by Porthishead (2008). Image from Wikipedia

Well not a picture, but rather the name, of a tooth. In each quadrant of your mouth (most likely) are two premolars, commonly referred to as “bicuspids.” In the biz, we usually call these pals,  “P3” and “P4.”

UW 101-1277 mandible, part of the Homo naledi holotype skull. Modified from the Wits media gallery.

UW 101-1277 mandible, part of the Homo naledi holotype skull. Each capital letter stands for the tooth type (incisor, canine, premolar, and molar). Modified from Wits’ image gallery.

You might be wondering why we call them P3 and P4, when there are only two premolars per quadrant — what happened to P1 and P2?  Homology to the rescue!

The ancestral mammalian condition was to have four premolars (and a 3rd incisor) in each side of the jaw. This is a “dental formula” of 3-1-4-3, indicating the numbers of each tooth type from front to back. Over time, different groups of animals have lost some of these teeth. Baleen whales have lost all of them.

P1 and an incisor were lost early in the evolution of Primates. Most Strepsirrhines and New World monkeys retain this primitive”2-1-3-3″ dental formula :

Ring tailed lemur (left) and woolly monkey (right) maxillae, showing the primitive primate dental formula including a P2. For scale, gridlines are 10 mm (left) and 20 mm (right).

Ring tailed lemur (left) and woolly monkey (right) maxillae, showing the primitive primate dental formula including a P2. For scale, gridlines are 10 mm (left) and 20 mm (right). Images from this boss database.

The last common ancestor of catarrhines (living humans, apes and Old World monkeys) lost the P2, and so we have only two premolars left in each side of the jaw. These are homologous with the third and fourth premolars of the earliest mammals. And that’s why we call them P3-4.

*The song was “The Rip.” It’s a very good song with an insanely creepy and trippy video:

Homo naledi in a lawn chair

It is a great relief that Homo naledi, a most curious critter, was announced to the world on Thursday. I’ve been working on these fossils since May 2014, and it was really hard to keep my trap shut about it for over a year.

Homo naledi on my mind, and phone, all year.

Homo naledi on my mind, and the lock screen on my phone, all year. CT rendering of cranium DH3, top is to the left and front is to the top.

I was in London for the ESHE conference last week when **it hit the fan, and so I got to attend a small press conference from the paper’s publisher, eLife, for the announcement.

eLife press conference last Thursday. From left to right: Will Harcourt-Smith, Matthew Skinner, Noel Cameron, Alia Gurtov and Tracy Kivell.

eLife press conference last Thursday. From left to right: friends and colleagues Will Harcourt-Smith, Matthew Skinner, Noel Cameron, Alia Gurtov and Tracy Kivell.

I had just flown in from Kazakhstan, and was presenting some recent work on the evolution of brain growth (I’ll write a post about it soon, promise), so it was a bit hard to appreciate the gravity of the announcement. Although the awesome spread in National Geographic did help it sink in a bit.

Really blurry photo of Markus Bastir holding up the heaviest copy of National Geographic ever.

I’m wending my way back to Kazakhstan now, but in the coming weeks I will try to post more about these fossils, the project, and specifically what I’m working on.

Until then, I’d like to point out how much information is freely and easily available to the entire world about these fossils. The paper, full-length and filled with excellent images of many of the specimens and reconstructions, is available for free online here. In addition, you can download 3D surface scans of over 80 of the original fossils on MorphoSource, also totally free. Everything about this scientific discovery and its dissemination is unprecedented – the sheer number of fossils and the ease of access with which literally everyone (well, with an internet connection) can access this information has never occurred before. This is the way paleoanthropology should be. Hats off to Lee Berger and the other senior scientists on the project for making such a monumental resource available to all.

ResearchBlogging.orgBerger LR, Hawks J, de Ruiter DJ, Churchill SE, Schmid P, Delezene LK, Kivell TL, Garvin HM, Williams SA, DeSilva JM, Skinner MM, Musiba CM, Cameron N, Holliday TW, Harcourt-Smith W, Ackermann RR, Bastir M, Bogin B, Bolter D, Brophy J, Cofran ZD, Congdon KA, Deane AS, Dembo M, Drapeau M, Elliott MC, Feuerriegel EM, Garcia-Martinez D, Green DJ, Gurtov A, Irish JD, Kruger A, Laird MF, Marchi D, Meyer MR, Nalla S, Negash EW, Orr CM, Radovcic D, Schroeder L, Scott JE, Throckmorton Z, Tocheri MW, VanSickle C, Walker CS, Wei P, & Zipfel B (2015). Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. eLife, 4 PMID: 26354291