#FossilFriday: 2015 Retrospecticus

January 1, 2016January 1, 2016 / zcofran / Leave a comment

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

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:

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.

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

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.org What 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

November 15, 2015November 24, 2015 / zcofran / 2 Comments

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.

… 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). 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?”

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)

References
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

Osteology Everywhere: Bacon or first rib?

November 8, 2015November 9, 2015 / zcofran / 1 Comment

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.

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

What on earth is this?

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

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
Dmanisi 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

Bioanthro lab activity: What species is it?

October 30, 2015October 30, 2015 / zcofran / Leave a comment

We’re learning about the divergence between robust Australopithecus and early Homo 2.5-ish million years ago in my Human Evolution class this week. Because of this multiplicity of contemporaneous species, when scientists find new hominin fossils in Early Pleistocene sites, a preliminary question is, “What species is it?”

Scrutinizing the fossil record, asking the difficult questions. (Science credit)

To help my students learn how we know whether certain fossils belong to the same species, and to which group new fossils might belong, in this week’s lab we compared tooth sizes of Australopithecus boisei and early Homo. After seeing how tooth sizes differed between these groups, students then tested whether they could determine whether two “mystery” fossils (KNM-ER 60000 and 62000; Leakey et al. 2012) belonged either group.

Early Pleistocene hominin fossils from Kenya. Left to right: KNM-ER 406, ER 62000 and ER 1470. At the center is one f the lab’s “mystery jaws.”

Students downloaded 3D scans of hominin fossils from AfricanFossils.org, and measured buccolingual/labiolingual tooth crown diameters using MeshLab.

Early Pleistocene hominin mandibles. Left to right: KNM-ER 3230, ER 60000 (“mystery” jaw) and ER 1802.

The first purpose of this lab was to help familiarize students with skull and tooth anatomy of early Pleistocene humans. Although lectures and readings are full of images, a lab activity forces students to spend time visually examining fossils. Plus, they’re in 3D which is a whole D greater than 2D – the visual equivalent of going to eleven! The second goal of the lab was to help prepare students for their term projects, in which they must pose a research question about human evolution, generate predictions, and find and use data to test hypotheses.

If you’re interested in using or adapting this activity for your class, here are the handout and data sheet into which students enter their measurements. The data sheet specifies the fossils that can be downloaded from africanfossils.org. Some relevant fossils (i.e., KNM WT 15000 and ER 992) were not included because the 3D scans yield larger measurements than in reality.

Lab 3-Mystery Jaws (instructions and questions)

Lab 3-Mystery jaws data sheet

Reference
Leakey MG, Spoor F, Dean MC, Feibel CS, Antón SC, Kiarie C, & Leakey LN (2012). New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo. Nature, 488 (7410), 201-4 PMID: 22874966

Homo naledi in a lawn chair

September 14, 2015September 15, 2015 / zcofran / 1 Comment

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.

Berger 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

Osteology Everywhere: Ilium Nublar

June 30, 2015 / zcofran / 1 Comment

Jurassic Park is objectively the greatest film ever made, so I don’t need to explain why I recently watched it for the bajillionth time. Despite having seen this empirically excellent movie countless times, I finally noticed something I’d never seen before.

Hold on to your butts. What's that on the screen in front of Ray Arnold?

Hold on to your butts – what’s that on the screen in front of John Arnold? (image credit)

The film takes place on the fictitious island “Isla Nublar,” a map of which features prominently in the computer control room when s**t starts to go down. Here’s a clearer screenshot of one of Dennis Nedry‘s monitors:

Isla Nublar from the JP control room. Quiet, all of you! They’re approaching the tyrannosaur paddock…. (image credit)

It dawned on me that the inspiration for this island is none other than MLD 7, a juvenile Australopithecus africanus ilium from the Makapansgat site in South Africa:

Figure 1 from Dart, 1958. Left side is MLD 7 and right is MLD 25. Top row is the lateral view (from the side) and bottom row is the medial view (from the inside). These two hip bones are from the left side of the body (see the pelvis figure in this post). Note the prominent anterior inferior iliac spine on MLD 7, a quintessential feature of bipeds.

Isla Nublar is basically MLD 7 viewed at an angle so that appears relatively narrower from side to side:

MLD at a slightly oblique view (or stretched top to bottom) magically transforms into Isla Nublar.

MLD 7 at a slightly oblique view (or stretched top to bottom) magically transforms into Isla Nublar.

It’s rather remarkable that some of the most complete pelvic remains we have for australopithecines are two juveniles of similar developmental ages and sizes from the same site. In both, the iliac crest is not fused, and joints of the acetabulum (hip socket) hadn’t fused together yet. The immaturity of these two fossils matches what is seen prior to puberty in humans and chimpanzees. Berge (1998) also noted that MLD 7, serving as an archetype for juvenile Australopithecus, is similar in shape to juvenile humans, whereas adult Australopithecus (represented by Sts 14 and AL 288) are much flatter and wider side to side. Berge took this pattern of ontogenetic variation to match an ape-like pattern of ilium shape growth. This suggests a role of heterochrony in the evolution of human pelvic shape, or as Berge (1998: 451) put it, “Parallel change in pelvic shape between human ontogeny and hominid phylogeny.” In layman’s terms, ‘similar changes in both pelvic growth and pelvis evolution.’

eFfing #FossilFriday: Rekindling an old friend’s hip

June 12, 2015January 1, 2016 / zcofran / 2 Comments

Sorry for the crappy pun. Carol Ward and colleagues recently reported an associated hip joint, KNM-ER 5881, attributable to the genus Homo (1.9 million years old). Fossils coming from the same skeleton are pretty rare, but what’s more remarkable is that portions of this bone were discovered 29 years apart: a femur fragment was first found in 1980, and more of the femur and part of the ilium were found at the same location when scientists returned in 2009:

Figure 3 from Ward et al. 2015. A little distal to the hip, yes, but the pun still works. Views are, going clockwise starting at the top the top left, from above, from below, from the back, from the side, and from the front.

There’s also a partial ilium associated with the femur – that makes a pretty complete hip!

Figure 5 from Ward et al. shows the fossil. Jump for joy that it’s complete enough for us to tell it comes from the left side!

Despite how fragmentary the femur and ilium are, the researchers were able to estimate the diameter of the femur head and hip socket reliably. The hip joints are smaller than all Early Pleistocene Homo except for the Gona pelvis. Comparing ER 5881 the large contemporaneous KNM-ER 3228 hip bone, the authors found these two specimens to be more different in size than is usually seen between sexes of many primate species. The size difference best matches male-female differences in highly dimorphic species like gorillas.

Ward et al. find that the specimen generally looks like early Homo but that the inferred shape of the pelvic inlet is a little different from all other Early and Middle Pleistocene human fossils. The authors take this discrepancy to suggest that there was more than one “morphotype” (‘kind of shape’), and therefore possibly species, of Homo around 1.9 million years ago. While I wouldn’t just yet go so far as to say this anatomy is due to species differences, I do agree that KNM ER 5881 helps our understanding and appreciation of anatomical variation in our early ancestors. Like all great fossil discoveries, the more we find, the more we learn that we don’t know. Here’s to more Homo hips in the near future!

Quick thought on the Australopithecus deyiremeda maxilla

May 28, 2015May 28, 2015 / zcofran / 1 Comment

It will be lots of work to prep my Human Evolution course for the Fall. This past year has seen many major fossil discoveries, and adding to the list is the newly described species Australopithecus deyiremeda (Haile-Selassie et al., 2015). The fossils come from newly announced sites in Ethiopia (here it is on a map!), dating to around 3.4 million years ago. These new fossils are contemporaneous with Australopithecus afarensis, fossils attributed to Kenyanthropus platyops, and whatever the hell the Burtele foot belongs to.

The main specimens are a fairly complete half of a maxilla (upper jaw) and two decent mandibles (lower jaw bones). These fossils do not belong to the same individual (despite all the media pictures of the upper and lower jaws together). One of the most distinctive features of these fossils is how thick, both in absolute and relative terms, the mandibles are, especially given how short they are. What sticks out to me though, is that the upper jaw looks like it might have still had some growing to do. Why on earth would I think so? (The following is based off pictures from the publications, so I could be wrong!)

Extended Figure 1a from the paper. The type specimnen BRT-VP-3/1 maxilla. Front is to the left.

Extended Figure 1a from the paper, the type specimnen BRT-VP-3/1 maxilla viewed from the left side. I’ve added the M2 label for your reading pleasure.

The holotype maxilla (BRT-VP-3/1) is described as coming from a “young adult” in the Supplementary Information. However, it looks like the second molar tooth (M2) is not quite fully erupted and in occlusion, although this could be due to the natural arc of the tooth row. There is no visible wear on the tooth in the pictures, and indeed the Supplementary Information says the tooth is unworn. This means that the tooth is only recently emerged, and may not have passed the gum line, and therefore hasn’t seen much/any use yet. Authors note in the Supplementary Information that there is no M3 (a.k.a. “wisdom tooth”) wear facet on the back of M2 , meaning the last tooth hadn’t yet emerged yet either. So, this all points to a non-adult age by tooth eruption standards.

Extended Figure 1d from the paper. Same fossil, but from the bottom, like a dentist peering into its mouth. Back is to the bottom.

Extended Figure 1d from the paper. Same fossil, but from the bottom; pretend you’re a dentist peering into its mouth. Back is to the bottom.

In addition, the M2 roots don’t look fully formed. This is especially apparent in Extended Figure 1h, a CT section through the teeth:

Left side: Extended Figure 1h from the paper. From left to right, the teeth are P3, P4, M1, and M2. For comparison, to the right are Demirjian tooth development stages, modified from Table 2 of Kuykendall, 1996. Also compare the M2 roots with completed roots of the M1.

In many human populations, this stage of M2 development is reached (on average) between 11-13 years (Liversidge et al., 2006). In the wild Taï Forest chimpanzee sample, two individuals with M2 root completely formed (Stage H) are 10 and 11 years old (Smith et al., 2010). These apes would not be fully mature and their facial dimensions would likely have increased had they reached adulthood (Zihlman et al., 2007).

So what this suggests to me is that this maxilla may not accurately represent adult anatomy in this newly described species. In humans, the face continues to grow downwards from adolescence into adulthood, and in apes the face continues growing both forward and downward. In the differential diagnosis of A. deyiremeda, Haile-Selassie and team state, in layman’s terms, that the cheeks are positioned more toward the front than in A. afarensis, and that the front of the face doesn’t stick out as much as in A. garhi. If this specimen was not fully grown, it is likely that the true adult anatomy would have had a face that sticks out more and has less forward-positioned cheeks than in this specimen.

But, this is all speculative, and I’d like to reiterate that these observations of dental development are based only on the published pictures. Just a thought!

Virtual paleontology activity

April 19, 2015April 19, 2015 / zcofran / Leave a comment

Last week Nazarbayev University hosted an Instructional Technology Showcase, in which professors demonstrated some of the ways we use technology in the classroom. This was the perfect venue to show off the sweet skeletal stuff we study in Biological Anthropology, through the use of pretty “virtual” fossils. In the past year I’ve started using CT and laser scans of skeletal remains to make lab activities in a few classes (I’ve posted two here and here). Such virtual specimens are especially useful since it is hard to get skeletal materials and casts of fossils here in the middle of the Steppe. These scans are pretty accurate, and what’s more, 3D printing technology has advanced such that physical copies of surface scans can be created from these virtual models. So for the Showcase, I had a table where passersby could try their hand at measuring fossils both in hand and in silico.

Lower jaw of an infant Australopithecus boisei (KNM ER 1477). Left is the plastic cast printed from the laser scan on the right.

The Robotics Department over in the School of Science and Technology was kind enough to print out two fossils: KNM ER 1477, an infant Australopithecus boisei mandible, and KNM KP 271 a distal humerus of Australopithecus anamensis. They used a UP Plus 2 printer, a small desktop printer that basically stacks layers of melted plastic to create 3D models; they said it took about 9 hours to print the pair. Before the Showcase, I measured the computer and printed models on my own for comparison with published measurements taken on the original fossils (KP 271 from Patterson and Howells, 1967; ER 1477 from Wood, 1991). The virtual fossils were measured using the free program Meshlab, while basic sliding calipers were used to measure the printed casts.

I was pleasantly surprised at how similar my measurements were to the published values (usually within 0.1 mm), since it means that the free fossil scans provided by the National Museums of Kenya are useful not only for teaching, but potentially also for research.

The Virtual Paleontology Lab. The Kanapoi distal humerus is held in the foreground while the A. bosei jaw rests on the table. Yes, those are real palm trees.

Knowing that these models are pretty true to life (well, true to death, since they’re fossils), I was curious how students, faculty and staff would do. I picked two fairly simple measurements for each fossil. None of the people that came by to participate had any experience with bones or fossils, or measuring these in person or on a computer. Here are their results:

Boxplots showing participants’ data, for two measurements on each of the fossils. The blue stars mark the published values. The red rugs on either side indicate measurements taken on the scans (left side) or printed casts (right).

For the most part, the inexperienced participants’ measurements are not too far off from the published values. There’s not really an apparent tendency for either cast or computer measurements to be more accurate, although measurements of the Kanapoi humerus are closer than the computer measurements (third and fourth boxes above). In my personal opinion, nothing beats handling fossils (or casts of them) directly, but this little activity suggests students can still make reliable observations using 3D scans on a computer.

Sweet free stuff:
Meshlab software
3D scans of fossils from the National Museums of Kenya

Australopithecus boisei bites

March 12, 2015 / zcofran / Leave a comment

I always wondered what our extinct relative, Australopithecus boisei tasted like, until I moved to Kazakhstan.

Mini calotte, or manti?

Here, dumplings with various fillings are called “manti” and usually have a distinct crimping running across the top. Along with their broad flaring bases and dome-like shapes, this gives manti the appearance of miniature A. boisei brain cases replete with sagittal crests:

They all look so delicious! Fillings from left to right: lamb, pumpkin+lamb, mushrooms ewwwww.

In case you had trouble discerning braincase from блюдо, calotte from закуски in the pic, check out africanfossils.org and see if their handy, free 3D scans of fossils OH 5 and ER 406 help you figure it out.

Lawn Chair Anthropology

Biological anthropology, paleontology, evolution, and development, by Dr. Zachary Cofran

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