The most complete Australopithecus skeleton

StW 573, a hominin skeleton more palatably nicknamed “Little Foot,” made its big debut last week:

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Ron Clarke showcases the lovingly-excavated skeleton (Photo credit: AP/Themba Hadebe)

The skeleton is remarkable in that it is the most complete australopithecine individual ever discovered, and is among the most complete in the entire hominin fossil record. Below I’ve compared it to the most complete Australopithecus afarensis (KSD-VP-1/1 and AL 288-1), A. africanus (StW 431 and Sts 14), and A. sediba (MH1-2); the Dikika infant would be a neat comparison, too, but I don’t know of any photos of its bones nicely laid out. The other skeletons are practically naked (or dismembered) compared to Little Foot.

Australopithecus skeletons.png

Little Foot (red) compared with other australopithecine skeletons. Images not to scale! (Photo credit: The Internet!)

Beyond it’s completeness, the other parts of story of Little Foot are equally fascinating – from its discovery based on already-known fragments to the possibility that it is older than “Lucy” (AL-288). Ron Clarke has painstakingly and I’d say very successfully removed the skeleton from the hard breccia in which the fossils were encased. Having spent the better part of the past two decades with the skeleton, he has argued that Little Foot represents a second hominin species at Sterkfontein, Australopithecus prometheus (Clarke 2013), the species to which hominin fossils at Makapansgat were originally attributed (Dart 1948). With the unveiling of the skeleton, I’d guess that in the coming years we’ll see renewed investigations into the number of species at Sterkfontein, and the general comparison between hominins from there and Makapansgat.

From pictures in the media releases, we can see a few things that weren’t known from previous publications. I’ll outline a few here, but emphasize that these are only  superficial observations and will need to be borne out by further research.

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At the top of the trunk, the cervical vertebra seems to have a fairly wide spinal canal, a human-like ‘bulging’ which Meyer and Hausler (2015) suggest might reflect innervation of highly manipulative hominin hands.

Stw 573 thorax

Close up of the skull and upper trunk of StW 573, highlighting the cervical vertebral canal (white arrow) and first rib (orange arrow). Original photo credit: AP//Themba Hadebe.

In addition, the first rib may be relatively long front-to-back (as opposed to wide side-to-side), possibly indicating a more barrel-like chest than in other early hominins; the angle of the photo and the clear break between the proximal and distal portions, however, makes this unclear.

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Hominin first ribs/bacon, with StW 573 on the far right. Not to scale! Modified from this post.

The distal forelimb (i.e., radius and ulna) are not as elongated as in apes, but the femur is not as elongated as in the genus Homo. From the pictures, the femur neck appears short like in humans, not as elongated as is characteristic for australopiths and early Homo.

Limb comparison Stw 573

Limb proportion comparison. Humerus (top row), radius & ulna (middle), and femur (bottom). Image modified from Asfaw et al. (1999). StW 573 scaled to same humerus length as the human. Note also that all bones are from the right except the StW 573 upper limb.

The apparently short femur neck, similar to humans, contrasts with the wide, flaring ilium of the pelvis. This appears fairly flat, short and wide (Australopithecus af) compared to modern humans’ more strongly curved ilium. But this inference is just from a picture and it’s likely that the fossil needs a bit of reconstruction to uncover the true anatomy.

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StW 573 pelvis (left) compared with Sts 14 (A. africanus, middle) and SH pelvis 1 (archaic Homo, right). Sts 14 modified from Berge & Goularis (2010) and SH pelvis 1 from Bonmati et al. (2010).

I’d like to emphasize that these are just first impressions based on press release photos, and actual analysis of the skeleton are necessary to tell if these impressions are correct. As could be expected, the skeleton as a whole looks typically australopithecine, although the short femur neck may be a bit different. As 2017 draws to a close, let’s hope 2018 sees the testing of these predictions.


Asfaw B. et al. 1999. Australopithecus garhi: a new species of early hominid from Ethiopia. Science 284: 629-635.

Berge C and Goularis D. 2010. A new reconstruction of Sts 14 pelvis (Australopithecus africanus) from computed tomography and three-dimensional modeling techniques. Journal of Human Evolution 58: 262-272.

Bonmati A. et al. 2010.Middle Pleistocene lower back and pelvis from an aged human individual from the Sima de los Huesos site, Spain. Proceedings of the National Academy of Sciences 107: 18386-18391.

Clarke RJ. 2013. Australopithecus from Sterkfontein Caves, South Africa. In The Paleobiology of Australopithecus, Reed et al., eds. Dordrecht: Springer Science+Business.

Dart R. 1948. The Makapansgat proto-human Australopithecus prometheusAmerican Journal of Physical Anthropology 6: 259-284.

Meyer M. and Hausler M. 2015. Spinal cord evolution in early Homo. Journal of Human Evolution 88: 43-53.


Osteology Everywhere: Aerial Ossicles

Last month I was flying down to New Orleans for the AAPA conference. I was excited to try authentic beignets & sazeracs, present new research, and catch up with colleagues. Midway through the flight I glanced out the window, not expecting to see much. But lo!


Thankfully there wasn’t something on the wing. But there was something strange out there in the sparkle of sprawling city lights:


What’s that I spy outside the city center?

A bit outside of the main jumble of street lamps appears to be a concentration of light superficially similar to an incus, one of the three auditory ossicles of the middle ear:


Left: An osteologist’s nightmare at 20,000 feet. Right: Ear ossicles from White et al. (2012).

As a good mammal, there are three small bones inside your middle ear. These are fully formed at birth, and help transfer and amplify sound vibrations from your eardrum to your inner ear. It’s nuts. What’s even more nuts is that paleontologists and anatomists have figured out that the tiny, internal incus and malleus of mammals evolved from larger, external pieces of the jaws of our pre-mammalian ancestors. INSANITY!


Cross section of a right ear, viewed from the front. Image credit.

Being so tiny, it’s not surprising that auditory ossicles are not often recovered from skeletal remains, and are pretty rare in the human fossil record. Nevertheless, some are known and their comparison with humans’ ossicles is pretty interesting. The oldest inci I know of are from SK 848 and SKW 18Australopithecus robustus fossils from Swartkrans in South Africa (Rak and Clarke, 1979; Quam et al., 2013). SK 848 is on the left in the set of images below:


Incus bones in three different views of SK 848, human chimpanzee, gorilla, sock puppet (left to right). Modified from Rak and Clarke, 1979.

SK 848 to differs from humans and African apes in looking more like a screaming sock puppet with a horn on the back of its head. Additional ossicles are known from South African australopithecines, including the older A. africanus from Sterkfontein (Quam et al., 2013). Interestingly, malleus of these hominins is very similar to that of humans, and Quam et al. (2013) think this ossicle may be one of the first bones in the entire skeleton to take on a human-like configuration during hominin evolution. Functionally, this may mean that the frequency range to which human ears are adapted may have appeared pretty early in our lineage as well (Quam et al., 2015).

Who’d’ve thunk we’d learn so much just from looking out an airplane window?

ResearchBlogging.orgRead more!

Quam, R., de Ruiter, D., Masali, M., Arsuaga, J., Martinez, I., & Moggi-Cecchi, J. (2013). Early hominin auditory ossicles from South Africa Proceedings of the National Academy of Sciences, 110 (22), 8847-8851 DOI: 10.1073/pnas.1303375110

Quam, R., Martinez, I., Rosa, M., Bonmati, A., Lorenzo, C., de Ruiter, D., Moggi-Cecchi, J., Conde Valverde, M., Jarabo, P., Menter, C., Thackeray, J., & Arsuaga, J. (2015). Early hominin auditory capacities Science Advances, 1 (8) DOI: 10.1126/sciadv.1500355

Rak Y, & Clarke RJ (1979). Ear ossicle of australopithecus robustus. Nature, 279 (5708), 62-3 PMID: 377094

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.

Gracile & robust Australopithecus

Last week, I introduced my Human Evolution students to the “robust” australopithecines. It was a very delicate time, when we had to have a grown up, mature conversation about adult things. I reminded the students that they’re only human, but they must resist urges that seem only natural. No matter how much they want to, even if their friends are doing it, they must not act on the deep, dark desire to say that “robust” vs. “gracile” Australopithecus differ in their body build.

Don't do it, Homo naledi. Don't talk about body size when you mean to talk about jaw and tooth size. Illustration by Flos Vingerhoets.

Don’t do it, Homo naledi. Don’t talk about body size when you mean to talk about jaw and tooth size. Illustration by Flos Vingerhoets.

Every semester, students (who don’t read and/or pay attention to lecture) think that the difference between these two groups has to do with the species’ body sizes. This is a misconception that has reached the highest echelons of reference:

At least one person is not citing their source here. F-.

Apple and Google, at least one person here is not citing their source: F-. Also, is no one else surprised that this term is allegedly specific to anthropology?

No. In the case of australopiths, “gracile” and “robust” refer to the relative size of the jaws, teeth and chewing muscles (all contributing to the “masticatory apparatus”). Traditionally,  graciles include the ≥2 million year old Australopithecus afarensis and africanus, and robusts include the later A. boisei and robustus. The discovery of an A. aethiopicus cranium (Walker et al. 1986) somewhat blurred the lines between the two groups but it is usually included with the robusts (who are often collectively called Paranthropus). John Fleagle’s classic textbook (1999) illustrates the gracile-robust dichotomy very nicely:

Comparison of gracile (left) and robust (right) craniodental traits. From Fleagle, 1999.

So to recap: Jaws and teeth, people! To the best of my knowledge, there’s little or no evidence that the various australopithecines differed appreciably in body size (McHenry and Coffing, 2000), stoutness, or muscularity. Although the OH 80 partial skeleton, attributed to Australopithecus boisei  based on tooth size and proportions, includes a humerus with very thick cortical bone and a radius with a crazy big insertion for the biceps muscle – it was a very large and muscular A. boisei (Domínguez-Rodrigo et al., 2013). Nevertheless, gracile and robust australopithecine species differ most notably in their jaws and teeth, not bodies. Maybe this is why Liz Lemon was so confused about the term “robust”?

Today, these are somewhat antiquated terms. Back when the only hominins known to science were the species listed above, it was easy to make a distinction. However, as the fossil record has expanded of late, the gracile-robust dichotomy becomes blurry. Australopithecus garhi (Asfaw et al., 1999) has overall tooth proportions comparable to graciles, but absolute tooth sizes and sagittal cresting like robusts. The recently described Australopithecus deyiremeda has tooth sizes and proportions like graciles but lower jaws that are very thick, like those of robust australopithecines (Haile-Selassie et al., 2015).

So in light of all the confusion and blurring distinctions, maybe it’s time to scrap “gracile” vs. “robust”?

Further reading:  The “robust” australopiths (Constantino, 2013).

Asfaw B, White T, Lovejoy O, Latimer B, Simpson S, & Suwa G (1999). Australopithecus garhi: a new species of early hominid from Ethiopia. Science (New York, N.Y.), 284 (5414), 629-35 PMID: 10213683

Domínguez-Rodrigo, M., Pickering, T., Baquedano, E., Mabulla, A., Mark, D., Musiba, C., Bunn, H., Uribelarrea, D., Smith, V., Diez-Martin, F., Pérez-González, A., Sánchez, P., Santonja, M., Barboni, D., Gidna, A., Ashley, G., Yravedra, J., Heaton, J., & Arriaza, M. (2013). First Partial Skeleton of a 1.34-Million-Year-Old Paranthropus boisei from Bed II, Olduvai Gorge, Tanzania PLoS ONE, 8 (12) DOI: 10.1371/journal.pone.0080347

Haile-Selassie Y, Gibert L, Melillo SM, Ryan TM, Alene M, Deino A, Levin NE, Scott G, & Saylor BZ (2015). New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature, 521 (7553), 483-8 PMID: 26017448

Walker, A., Leakey, R., Harris, J., & Brown, F. (1986). 2.5-Myr Australopithecus boisei from west of Lake Turkana, Kenya Nature, 322 (6079), 517-522 DOI: 10.1038/322517a0

Blood spattered Easter eggs from Raymond Dart

Some of the more colorful ideas and text in the anthropological literature are courtesy of Raymond Dart.

Dart, hammering away to remove a fossil from some breccia. I hope. Image credit.

Dart, hammering away at some breccia to remove a fossil. I hope. Image credit.

In 1925, Dart identified the Taung fossil as a close relative of humans, and coined the scientific name, Australopithecus africanus. This was a pretty good idea, as Taung was the first in what is now a large collection of fossils attributed to this species.

Taung was such an important discovery, you can now walk across it as you enter the fossil collections at Wits University.

Taung was such an important discovery, you can now walk across it not once, not twice, but thrice! as you enter the fossil collections at the Evolutionary Studies Institute at Wits University.

Some of Dart’s ideas that made it into print, though, were a bit more fanciful. Aside from his description of Taung, he is probably most famous for hypothesizing the “osteodontokeratic” culture, the idea that the myriad broken animal bones in Makapansgat cave were in fact tools used by australopiths for hunting and murder. MURDER! It was a neat idea at the time, but his vision of bloodthirsty, bone-dagger-wielding australopithecines is not accepted today (nor back when he was writing).

Dart was trained as an anatomist, and much of his work was devoted to writing up australopithecine fossils discovered at site of Makapansgat in South Africa. These are probably the best descriptive papers I’ve found in all the literature, as Dart’s whimsical visions of violence and bloodshed occasionally made their way into otherwise dry scientific prose.

In 1948 he very casually put it out there, that the front teeth of the MLD 2 mandible were lost in “fatal combat . . . presumably by a bludgeon” (emphasis added). Of course, the teeth were probably lost long after the poor kid died, rather than being knocked out “at the hands of a kinsman more expert than himself in the accurate application of directed implements” (Dart, 1948: 393-394). But Dart’s version is certainly more interesting than the more likely taphonomic explanation.


The MLD 2 mandible, poor kid, as illustrated in Dart (1948). Note that the incisor tooth sockets are empty, likely the result of taphonomy rather than bloodsport.

Dart (1958) later described the MLD 7 ilium, which he’d presumed to be a female, from the same site as MLD 2. Dart recounted the violent demise of MLD 2, raising the possibility of a similar death for the MLD 7 individual: “The adolescent boy [MLD 2] … was killed by a bone-smashing blow on the chin from a club or fist. Did brother and sister share here in death the same cannibalistic fate?” (emphasis added) Bloodshed, cannibalism, Australopithecus according to Dart had it all. Although these are unlikely characterizations of australopithecines, there is evidence of cannibalism in later fossil humans.

These gruesome Easter Eggs come to mind as I’m reading his 1956 paper about brain evolution. Here, Dart (1956: 28) says that hominins began walking on two legs after a dietary shift: “The forest-loving vegetarian anthropoids clung to their four-handed climbing and fruit while the terrestrial predaceous australopithecines, depending on their speed of foot and deftness of hand, lusted after flesh!” (emphasis added) Today, this idea would simply be written as, monkeys and apes live in trees and eat fruits while australopithecines lived on the ground and ate meat. But Raymond Dart wouldn’t stand for this. Oh no.

My grad school advisor, Milford Wolpoff, used to lament that students today don’t want to read anything older than the past 5-10 years. But Dart is a shining example of some of the rewarding Easter Eggs that await those who dig deeper into the literature. [I’m reminded also of Don Cousins describing “the colossal poundage of the lowland gorilla ‘Phil,’ who lived in the St. Louis Zoo from 1941-1958″ (1972: 269, emphasis added].
Some good, older stuff

Cousins D (1972). Body measurements and weights of wild and captive gorillas, Gorilla gorillaZoologische Garten NF Leipzig 41, 261-277.

Dart, RA (1925). Australopithecus africanus: The Man-Ape of South Africa Nature, 115 (2884), 195-199 DOI: 10.1038/115195a0

Dart, RA (1948). The adolescent mandible of Australopithecus prometheus American Journal of Physical Anthropology, 6 (4), 391-412 DOI: 10.1002/ajpa.1330060410

Dart RA (1956). The relationships of brain size and brain pattern to human status. The South African Journal of Medical Sciences, 21 (1-2), 23-45 PMID: 13380551

Dart, RA (1958). A further adolescent australopithecine ilium from Makapansgat American Journal of Physical Anthropology, 16 (4), 473-479 DOI: 10.1002/ajpa.1330160407

Osteology Everywhere: Vertebeer Fest

This past weekend was witness to the Summer Beer Festival, the annual showcase of Michigan’s brewing splendor. Dozens of breweries brought out batches of beer, from classics we know and love, to inspired innovations meriting a MacArthur Fellowship. There was an embeerrassment of boozes. Dark Horse Brewing Company, from Marshall, MI, put on quite the show:

Dark  Horse Brewing Co. pumping out the brews and blasting t-shirts into the crowd.

Dark Horse Brewing Co. pumping out the brews and blasting t-shirts into the crowd.

Besides towering over the bacchanal hordes, the Dark Horse beer fort also offered IPAs infused with pretty much anything that might pair well with hops. They even steeped habañero peppers in one, and it was maximally boss.

Beer still my heart.

Beer still my heart.

Having sampled only a small part of rich the smorgasbord on tap, a rest by the river was in order. The Festival was on the banks of the mighty Huron River, an excellent place to sit and sip Arcadia‘s scotch ale, taking in the evening under cloud-peppered, cerulean skies. Such a calm and relaxing setting would surely offer respite for a brain besieged by bones. Right?

Every year for the Festival they replace the river water with beer.

Every year for the Festival they replace the river water with beer.

Wrong! Peering through beer goggles over the shimmer of the river, seeking signs of Bigfoots lurking on the opposite shore, I locked eyes with a large, wooden vertebral body.

No ordinary tree stump

An eyeless frown marks the ventral surface of this centrum.

The human spine is composed of anywhere from 31-34 vertebrae (not counting the coccyx or tail bone). The body or “centrum” is the large, blocky portion of the bone, which is separated from other such bodies by intervertebral discs; it is literally a pile of bodies, stacked one on top of the other. And the intervertebral discs are remnants of the notochord, the embryonic structure that unites you and me and all other humans with all other animals known as chordates. Anyway, kiss my grits if this old tree stump across the mighty Huron River here doesn’t look like a lower thoracic or upper lumbar vertebral body, the metaphoric shark fin of a giant trunkless human waiting to pounce from the placid waters.

a) Our mystery vertebra. b) a lumbar vertebra from White et al. (2012). c) views of the right and front side of the Australopithecus africanus fossil StW H41, from Sanders (1998, Fig. 1).

a) Our mystery river vertebra. b) a lumbar vertebra from White et al. (2012). c) views of the right and front side of the Australopithecus africanus fossil StW H8/H41, modified from Fig. 1 of Sanders (1998).

Thinking on it, our mystery river vertebra doesn’t just look like any old human centrum, it is a ringer for the second lumbar vertebra of StW H8/H41, a series of the 11th thoracic to 4th lumbar vertebrae of Australopithecus africanus from Sterkfontein (see the red arrow in c, above). Sanders (1998) notes that this short segment of an early hominin spine shows clear adaptation to walking upright like we humans do today, although the size of the vertebral bodies is both absolutely and relatively small compared to ours, just as is seen in other Australopithecus fossils.

And what better way to celebrate this monumental discovery than returning to the Beer Festival – hooray beer!

Osteology Everywhere: Ilium Nublar

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).

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.’