Anthropology.net

Ardipithecus ramidus

I want to be the first to break news to you that Science has published White’s contentious 4.4-million-year-old Ardipithecus ramidus! I caught news of the release on the internet. The link is not live yet, but when it is I’ll fill you in.

Owen Lovejoy is one of the authors of the paper, and he says that the fossil changes the notion that humans and chimps, our closest genetic cousins, both trace their lineage to a creature that was more like today’s chimp and we’ll have to be rewriting our text books soon. This is big folks. What this means is that our common ancestor was a bipedal forest forager and that chimps were an evolutionary offshoot.

White, the lead author, describes the fossil with flexible hands and a brain about a quarter the size of a human’s,

“We can’t say this species was a direct ancestor of modern humans, so we have to be careful. But it suggests that the direction of early hominids was away from the chimp.”

There are a lot of other implications that I won’t get into just yet, but keep checking us out from time to time as we get more!

Here are some of the press releases/news coverage that have come out since I’ve published this post:

• Kent State University Professor C. Owen Lovejoy helps unveil oldest hominid skeleton
• Fossil finds extend human story
• Before ‘Lucy,’ there was ‘Ardi’: First major analysis of early hominid published in Science
• Oldest hominid skeleton provides new evidence for human evolution
• Humanity Has a New 4.4 Million-Year-Old Baby Mama
• Ancient Skeleton May Rewrite Earliest Chapter of Human Evolution
• Fossil Skeleton From Africa Predates Lucy
• Ethiopian desert yields oldest hominid skeleton
• Ardi displaces Lucy as oldest hominid skeleton
• Fossil Primate Ardipithecus Ramidus Described (Finally)
• Oldest “Human” Skeleton Found–Disproves “Missing Link”
• ‘Ardi,’ Oldest Human Ancestor, Unveiled

That is what University of Liverpool’s Emma Nelson probably would have said if she were to meet our hominan ancestors in person. Known to hold true in anthropoids (humans, apes and monkeys), the index (second digit) to ring (fourth digit) fingers ratio or 2D:4D is an indication of how much an individual were exposed to androgen (such as testosterone) in the womb. The more androgen you are exposed to, the longer the ring fingers are (and the shorter the index fingers are compared to the index fingers).

Nelson et al. believe that a high ratio (longer index finger, shorter ring finger) suggests monogamy (or pair-bonded) while a low ratio (shorter index finger, longer ring finger) suggests polygamy (or non pair-bonded). Simply put, individuals with high androgen level is likely to be non pair-bonded and the telltale sign is in the index and ring fingers. Also, some controversial studies had suggested that both men and women who receive high levels of androgen in the womb are more likely to be stronger, faster, and more sexually competitive.

Nelson and her researchers recently looked at the fossils of two Neandertals and one Australopithecus afarensis with complete index and ring fingers to determine their 2D:4D. They found that Neandertals had long ring fingers, suggesting that they were polygamous just like modern day primates that live in groups. A. afarensis on the other hand, had long index fingers. Nelson is puzzled by this discovery. “These were small creatures that probably lived in groups and were being eaten by predators. How do you keep from mating with different members of the group?”, she said.

Indeed it does not make sense for A. afarensis to be monogamous if they live in groups. Notice that Nelson et al. only used one A. afarensis fossil to get the 2D:4D. Perhaps it is not their fault that only one A. afarensis specimen had complete index and ring fingers but such are the dilemma of using fossil specimens to generalize a whole species.The result might just be a statistical outlier. However, I can’t speculate the result or the implications but anyone that are familiar with statistical data knows that a small sample size leads to a higher sampling error. Also what would a 2D:4D = 1 (same index and ring finger length) be?

Interesting enough, John Hawks at John Hawk’s Weblog mentioned the correlation of 2D:4D with male homosexuality (Robinson and Manning, 2000). I would know about this. In fact, my 2D:4D is indeed low.  Robinson and Manning predicted right! Maybe …

I do find both Nelson et al. and Robinson and Manning (2000) research interesting but I would like to stress that the results are mere predictors and correlations. Take it with a grain of salt. Don’t go measuring 2D:4D of your future spouse, boyfriend or girlfriend and accuse them of not being monogamous or a homosexual.

Emma Nelson and her team presented their research at this year’s Society for Vertebrate Paleontology meeting held in Bristol, United Kingdom. Read more about Emma Nelson’s research.

References:

Reilly M. 2009. Human Ancestors Conflicted on Monogamy. Discovery News. Retrieved September 25, 2009, from http://dsc.discovery.com/news/2009/09/24/human-monogamy.html

Robinson SJ. Manning JT. 2000. The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior 21(5): 333-345. [doi:10.1016/S1090-5138(00)00052-0]

Originally posted on The Prancing Papio

Speaking of the Johansons and fossils …

Earlier this year, I’ve blogged about the 2009 Human Evolution Leakey Symposium at Stony Brook that I went to. For more about that blog post, click here.

The symposium, entitled “Hobbit in the Haystack: Homo floresiensis and Human Evolution” can now be streamed live through the Stony Brook website. The website also includes previous Human Evolution Leakey symposia. Click here to watch.

Thanks to Afarensis: Anthropology, Evolution and Science for the heads up!

Originally posted on The Prancing Papio

PLoS One completely surprised me today by releasing this paper, “Small-Bodied Humans from Palau, Micronesia.” The research comes from South African and American researchers, and the paper was edited by John Hawks, who apparently can really keep a secret it seems. I had no idea about this study and find it a really remarkable find since fossils of another small bodied human, Homo floresiensis, were found about 1,000 miles south of these new findings.

If I read this correctly, a minimum of 25 individuals have been found. Lots more will be found according the authors, which is always welcoming to me. The Palau fossils are of small people, similar in size to the Flores hominins. Preliminary analysis of more than a dozen individuals, including a male weighing about 43 kg and a female weighing about 29 kg, document that these were tiny. Analyzing some of the cranial and dental features like the distinct presence of a maxillary canine fossa, a clearly delimited mandibular mental trigone, moderate bossing of the frontal and parietal squama, a lateral prominence on the temporal mastoid process, reduced temporal juxtamastoid eminences and an en maison cranial vault profile with the greatest interparietal breadth high on the vault indicates that these individuals were simply small H. sapiens adapted for life on a small island.

So how were these bones found? Lead author, Lee Berger, writes to National Geographic News that he was kayaking around rocky islands about 370 miles east of the Philippines, when he found the bones in a pair of caves in 2006. Crazy story! I wish I would find something like that while vacationing. He reports that the,

“the [Ucheliungs and Omedokel] caves were littered with bones that had been dislodged by waves and piled like driftwood. Others had remained buried deep in the sandy floor, and more, including several skulls, were cemented to the cave walls.”

Radiocarbon dating was applied to pinpoint an age for the bones. The antiquity of the bones is between 1,410 and 2,890 years ago, which is remarkably much more recent than 18,000 year old antiquity of the Flores hominins. Along with the small size, the Palau fossils have similar features to H. floresiensis, such as their pronounced supraorbital tori, non-projecting chins, relative megadontia, expansion of the occlusal surface of the premolars, rotation of teeth within the maxilla and mandible, and dental agenesis.

But again, Berger and colleagues do not infer from these features any direct relationship between the peoples of Palau and Flores; however, they conservatively write that these similarities may be a common adaptation in humans of reduced stature. In their own words,

“Based on the evidence from Palau, we hypothesize that reduction in the size of the face and chin, large dental size and other features noted here may in some cases be correlates of extreme body size reduction in H. sapiens. These features when seen in Flores may be best explained as correlates of small body size in an island adaptation, regardless of taxonomic affinity. Under any circumstances the Palauan sample supports at least the possibility that the Flores hominins are simply an island adapted population of H. sapiens, perhaps with some individuals expressing congenital abnormalities.”

Again the paper is published in PLoS One, which is an open access journal. That means you can download the original report and read it for yourself for free. I really recommend you do, this seems like one of the more significant paleoanthropological finds for 2008. Here’s the citation:

Berger, L.R., Churchill, S.E., De Klerk, B., Quinn, R.L., Hawks, J. (2008). Small-Bodied Humans from Palau, Micronesia. PLoS ONE, 3(3), e1780. DOI: 10.1371/journal.pone.0001780

Whoever manages the PNAS web servers should thank Afarensis because he found that paper prior to the March 4th date I threatened to bring down their site on. He’s written up an educational overview of the findings, so has Jason of Hominin Dental Anthropology. I eluted to the significance of this study earlier, but I’ll reiterate it once more. This paper is important because it gives a more reliable antiquity for Sahelanthropus tchadensis. The press release didn’t indicate that date for Australopithecus bahrelghazali was also calculated, so I’m super happy that we got a meal deal out of this paper.

Before I get into the details of the dating technique, let’s answer just the basics on what Sahelanthropus tchadensis and Australopithecus bahrelghazali are and how they integrate into our understandings of early human evolution. The formal description of S. tchadensis was made off of TM-266 fossil which is also known as Toumaï. Toumaï is at the very minimum a highly fragmented ape cranium. According to the original authors, Toumaï has some hominin derived dental traits. Some researchers, such as Milford Wolpoff and John Hawks reanalyzed the data of the dental morphology of Toumaï and concluded that the dentition of Toumaï is like that of earlier Miocene apes. This reanalysis was published in the 2006 paper, “An Ape or the Ape: Is the Toumaï Cranium TM 266 a Hominid?” Other, such as Yohannes Haile-Selassie, Tim White, and Gen Suwa adopted S. tchandensis as possibly a representative of variation with in a single genus of hominins from the late Miocene. Others that could be within the variation spectrum are fossils represented in the genera Orrorin and Ardipithecus. These three putative hominin genera all come from the late Miocene.

I’ve implied that S. tchadensis is old, Miocene old. But the original publication didn’t come with a really definitive dating technique. Instead the age of the Toumaï was based off of the presence of other taxa that was also recovered from the same horizon. The specific presence of the species Libycosaurus petrochii, an even toed ungulate, that was known to exist around 6 to 7 million years ago indicated the horizon was about that old. This sort of dating is called biochronology, where the relative age fossil bearing units is based on known dates of existence of species represented in the unit. A 2005 paper refined the date to 6.5 to 7.4 million years ago, and folded in more S. tchandensis specimens into the record.

Australopithecus bahrelghazali was also found by Michel Brunet. The paper which announces this find is, “The first australopithecine 2,500 kilometres west of the Rift Valley.” The significance of this finding is clearly stated in the title but because the Brunet et al. have locked the fossils away from others to investigate, criticism has ostracized this finding. Additionally, all the defining features of the teeth and a partial jaw associated with A. bahrelghazali fall within normal variation of A. afarensis. The only thing that definitively is derived, is the mandibular symphysis, which is is more modern in appearance than that of A afarensis. For these reasons, paleoanthropology doesn’t really acknowledge A. bahrelghazali as a new species of australopithecine. One last thing, in some sort of sad historical record of Brunet’s lack of attention to detail, the A. bahrelghazali fossil also did not have a definitive dating technique associated with it. Rather, biochronological dating gave us an estimate that A. bahrelghazali is about 3.5 to 3.0 million years ago.

With this basic overview of S. tchadensis A. bahrelghazali, I think you can get the idea that more accurate dating techniques are mandatory to at least fill in the temporal gaps. At around 7 or 6 million years ago, three genera of hominins paint a much different picture from two genera. Potentially, one of the three genera coulda gave rise to the australopithecine lineage. Or as Yohannes Haile-Selassie suggested, Sahelanthropus, Orrorin, and Ardipithecus coulda all been one representation of a widespread genus of hominin. At 3.5 million years, another diversity similar problem exists. If A. bahrelghazali does really represent a new species of australopithecine it is crucial to pinpoint an accurate time to this fossil because it’s so damn far away from all the other Australopithecus fossils.

About 7 years after Brunet found S. tchadensis and 15 years after he found A. bahrelghazali, it seems like he has finally gotten around to using radiochronology to date the sediments associated with either fossil. PNAS is hosting this paper, open access… which I really recommend since it gives anyone interested free and easy access to download the original research and investigate the results for themselves. If there ever was a complaint that Brunet wasn’t transparent with sharing the A. bahrelghazali fossils, it seems like he’s tried to make up for it by agreeing to release this paper open access. So go downloaded it now before PNAS closes down access, here’s the title and link, “Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad.”

The actual technique deployed is like any other isotope analysis, but there’s a twist. Since the fossiliferous sediments did have a volcanic tuff around, uranium, argon, nor potassium dating could be used. Instead, beryllium isotopes were analyzed. Based upon expontential decay and the observed ¹⁰Be/⁹Be ratio, the authors calculated Sahelanthropus tchadensis to be 7.04±0.18 million years old. If you want a more in depth review of science behind the beryllium isotope, please check out Jason’s blog post. He’s done an excellent job. Oh yeah, how could I forget? The date for Australopithecus bahrelghazali comes out at 3.58±0.27 million years old.

This means Sahelanthropus tchadensis is really that old and that (if A. bahrelghazali is really a novel species) it existed at the same time A. afarensis did. Jason and Afarensis have both expressed that last paragraph of this paper raises concern. The authors attempt to say a lot of things, such as their opinion that the last human-ape lineage diverged around 8 million years ago and how the “plesiomorphic and apomorphic characters Sahelanthropus tchadensis” indicate some early hominin and ape hybridization was occurring. If that’s the case, then to ask again, just how human was Sahelanthropus tchadensis?

Lebatard, A., Bourles, D.L., Duringer, P., Jolivet, M., Braucher, R., Carcaillet, J., Schuster, M., Arnaud, N., Monie, P., Lihoreau, F., Likius, A., Mackaye, H.T., Vignaud, P., Brunet, M. (2008). Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0708015105

Brunet, M., Guy, F., Pilbeam, D., Mackaye, H.T., Likius, A., Ahounta, D., Beauvilain, A., Blondel, C., Bocherens, H., Boisserie, J., De Bonis, L., Coppens, Y., Dejax, J., Denys, C., Duringer, P., Eisenmann, V., Fanone, G., Fronty, P., Geraads, D., Lehmann, T., Lihoreau, F., Louchart, A., Mahamat, A., Merceron, G., Mouchelin, G., Otero, O., Campomanes, P.P., De Leon, M.P., Rage, J., Sapanet, M., Schuster, M., Sudre, J., Tassy, P., Valentin, X., Vignaud, P., Viriot, L., Zazzo, A., Zollikofer, C. (2002). A new hominid from the Upper Miocene of Chad, Central Africa. Nature, 418(6894), 145-151. DOI: 10.1038/nature00879

Haile-Selassie, Y. (2004). Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution. Science, 303(5663), 1503-1505. DOI: 10.1126/science.1092978

Brunet , M., Beauvilain, A., Coppens, Y., Heintz, E., Moutaye, A.H., Pilbeam, D. (1995). The first australopithecine 2,500 kilometres west of the Rift Valley (Chad). Nature, 378(6554), 273-275. DOI: 10.1038/378273a0

Brunet, M., Guy, F., Pilbeam, D., Lieberman, D.E., Likius, A., Mackaye, H.T., Ponce de León, M.S., Zollikofer, C.P., Vignaud, P. (2005). New material of the earliest hominid from the Upper Miocene of Chad. Nature, 434(7034), 752-755. DOI: 10.1038/nature03392

I remember reading the announcement of Sahelanthropus tchadensis (a.k.a. Toumaï) in 2002. It was an exciting time. A cranium is hard to find and is a quite noteworthy for any early hominid. So, it wasn’t surprising that Nature published the findings, “A new hominid from the Upper Miocene of Chad, Central Africa.” But they did so without a firm antiquity for the fossil! See, the primary publication set an estimation of 6 to 7 million years old based upon associated fauna found in the same horizon. No other dating technique was published.

With the possibility of 7 million old date, this fossil threw a big spoke in our understanding of early hominid evolution. Critics weren’t shy to voice their protest. They said the cranium was too squashed to confirm it was a hominid. A virtual reconstruction of the cranium did little to convince anyone. Paleonathropology was still reserved and not willing to fully accept Toumaï as a hominid. If Toumaï was really a hominid, then that would mean when we considered the human-chimpanzee divergence occured to be wrong. All our molecular clocks would be wrong too.

Well, according to this AP release, our anticipation for a real tangible date for the Toumaï should be resolved in next week’s issue of PNAS,

“French fossil hunters have pinned down the age of Toumai, which they contend is the remains of the earliest human ever found, at between 6.8 and 7.2 million years old…

‘The radiochronological data concerning Sahelanthropus tchadensis … is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock,’ Brunet wrote in a study which will appear in the March 4 edition of the Proceedings of the National Academy of Sciences.

‘Thus, Sahelanthropus tchadensis testifies that the last divergence between chimps and humans is certainly not much more recent than 8 Ma (million years ago.)’”

Wow, I can’t wait. You can be sure to expect me hitting the refresh page and hammering PNAS servers to download a copy of the paper when it comes out. In the mean time, all we have to pine over is the press release, “Oldest hominid discovered is 7 million years old: study.”

EurekAlert is running a very interesting press release on the discovery of a 500,000 year old Homo erectus fossil recovered from Turkey. Apparently the fossil, a fragment of skull bone, shows lesions that the individual had tuberculosis.

Tuberculosis is a deadly infectious disease caused by multiple strains of mycobacteria. Because the mycobacteria have lost numerous coding and non-coding regions in its genome, it is hard to retrace the genetic differences that would tell us of the origins, relationships, and movement of the disease causing pathogen. But through analyzing relatively modern human skeletal remains (I’m talking thousands of years modern) from Egypt and Peru, we know that tuberculosis was taking a big toll on humans relatively recently in our evolutionary history.

If this Homo erectus really did have tuberculosis, then that means he probably, and other hominids, got sick because his body produced less vitamin D due to darker skin and had a less vigilant immune system, hundreds of thousands of years ago. From what’s reported in the press release, I don’t buy it. And neither does John Hawks. I think it is over analyzed and sensationalized science to make big headlines.

I really don’t understand why a Homo erectus from Turkey isn’t enough of a killer headline. To my knowledge this is the first hominid found in Turkey and it fills a big spatial gap in understanding human evolution. Of course, I really don’t know enough about the tuberculosis evidence in this individual to make a solid judgment… we’ll have to wait until we get the paper…

Speaking of which, paper should be out anytime soon in the American Journal of Physical Anthropology, so the entire details of the fossil aren’t known to us until the AJPA decides to give the green light and publish the paper. I have, however, discussed this press release with several colleagues and they are all skeptical.

The first thing they are curious about is the date. We speculate that dating was established using faunal evidence. The problem with that is the faunal composition of Turkey during the Pleistocene isn’t well known. Sure, the late Miocene is, and that’s cause there are a lot of Miocene sites… but at 500,000 years ago it is hard to correlate a date to what organisms were around at the time.

I also got word that John Kappelman, and his team damaged the fossil. I don’t know if it was during excavation, transportation, or curation/research, but having rumors run around that your team damaged the first ever Turkish hominid isn’t something the bolsters ones reputation in the field. But again, take this with a grain of salt… it is a rumor. There aren’t any official reports that his team actually broke the fossil, and if Kappelman’s not really liked, I can see how people will start up these things. Physical anthropologists are a catty bunch. But to be really honest, I can’t help but think the tuberculosis is a smokescreen to distract attention from this broken specimen.

Anyways, just reporting on this new paleoanthropology paper… be sure to keep checking the AJPA for the paper, and check out Razib’s post as well.

I’m really behind on the anthropology news. There is just too much news floating around, and I feel like I don’t have enough time to catch up with it all. From studies on tool wielding chimps, chocolate brewing, a 4,000 year old temple in Peru, to how prehistoric Vinca women dressed in Europe, and yes… more discussion on race, genetics, and human populations…. I’m overwhelmed! I’m gonna do my best to share that all with you but I really want to point out the new African Miocene ape finding.

As you know, earlier this year we heard of Chororapithecus abyssinicus, a new Miocene ape found in Ethiopia. Kenyan and Japanese anthropologists have just published their report on a similarly aged Miocene ape which is dubbed, Nakalipithecus nakayamai. It resembles Ouranopithecus macedoniensis a lot, which reminds me you may wanna read about a new species of Ouranopithecus from the late Miocene of Turkey, a publication that my friend Ferhat co-wrote. The paper is freely accessible.

Fossils like Nakalipithecus nakayamai and Chororapithecus abyssinicus are crucial, because not only is the Miocene ape record very spotty but also because they help us in figuring out the what was happening to African apes before the human lineage diverged. I’m gonna blog over at Primatology.net about Nakalipithecus nakayamai in the near future so keep an eye out.

KNM-WT 15000 was found by Kamoya Kimeu in 1984 at the Nariokotome site near Lake Turkana in Kenya. It the most complete specimen of Homo erectus to date. All that’s missing from this 12 year old boy are the hands, feet, and left humerus. Its completeness and its 1.6 million years old age undoubtedly makes it an important specimen to anthropology and the study of human evolution

So to read from Ann Gibbons of Science that Turkana boy has been shipped to The Field Museum in Chicago, Illinois to be exhibited rings all sorts of alarm bells that rang when I read about Lucy’s trip to the west.

What if he gets damaged? Why doesn’t a really well done cast suffice?

I doubt that he will get damaged, it is a possibility, but people are really careful when packaging and handling priceless fossils like this. And about the cast, I must confess that I would personally be awestruck to see one of the most complete specimens of early Homo in person… especially because Turkana boy packs a lot of human like traits at 5′ 3″ tall. But what’s going on here? Why all of a sudden have two important hominid fossils been sent off to the US?

Any ideas?

Read the rest of this entry »

In preparation for today’s Nature paper on Dmanisi, yesterday I went over some of the hot Homo fossils that have come from Dmanisi. But I focused only on remains of the head. And of those remains, what I went over was a whole range of features, proportions, and sizes, that showed a lot of variation in early Homo cranium from Dmanisi. Size-wise, the fossils have been more in the range of H. habilis than erectus, but feature by feature each one seemed to have bits and pieces of what we acknowledge as H. erectus.

The paper that I’ve been waiting for, “Postcranial evidence from early Homo from Dmanisi, Georgia,” reminds me that there are other fossils than ones from the head, to analyze. Especially from such a rich site.

In this new paper, David Lordkipanidze and all the other authors, describe new fossils of the postcranial, of a teenager that is associated with D2700 cranium and 2735 mandible as well as three adults who are also associated with other fossils. The elements analyzed are pictured to the right. This last section of the abstract is the most important,

“This material shows that the postcranial anatomy of the Dmanisi hominins has a surprising mosaic of primitive and derived features. The primitive features include a small body size, a low encephalization quotient and absence of humeral torsion; the derived features include modern-human-like body proportions and lower limb morphology indicative of the capability for long-distance travel. Thus, the earliest known hominins to have lived outside of Africa in the temperate zones of Eurasia did not yet display the full set of derived skeletal features.”

So we’re looking at at least four people in this collection of bones. As I mentioned, the authors think they have the teenager’s skull and mandible. The other parts, such as a left clavicle, some ribs, a set of cervical and thoracic vertebrae with one lumbar vertebrae, both humeri but one is broken, a left femur, and several bones of the hands and feet, of this youngin’ are the seen in “a”, all the bones in the left half of the above image.

So how do they know that these are the bones from the same individual? Well, I’m pretty sure they don’t know for sure because they did say a minimum of four people… But because the bones were found in the same stratigraphic layer, in close proximity to one another…. And that the cranial and postcranial bones both show similar developmental stages, such as fusion patterns in the sutures of the skull and fusion patterns of the epiphysis (ends) of long bones to the shaft, or diaphysis, they can make this claim with some confidence.

The other three individuals, two small folk and one larger person, weren’t anywhere close to the teenager. The large adult is represented by a big right femur, whole tibia, and a patella… which all articulate snuggly. That’s how they figured out this was one individual. The other two small ones are represented by metatarsals and bones of the feet from different stratigraphic layers.

This is an impressive collection of bones. Having more than one individual from the same place and time helps paint a much better picture of what was going on with early Homo than would a single skeleton. In the following paragraphs, I’m gonna summarize the analysis of each element.

D4166 – The Adult Right Scapula
This element has a short and wide coracoid process and a narrow glenocoracoid angle, which are primitive, great-ape like traits. But the position of the glenoid to the spine as well as the breadth of the spine fall right at the bottom of modern human variation and resemble Turkana Boy.

D2724, D4161 & D4162 – The Clavicles

These clavicles represent the right and left sides. As you can see, both D4161 and D4162 are missing the sternal and acromial ends. D2724 is a bit better and is similar to modern day teenagers in shaft length. Since all of these clavicles have a middle portion, the cross sectional shape was analyzed. That feature resembles H. habilis.

D2680, D2715, D4507 – The Humeri

The Dmanisi have straight humeri but a lot of torsion and lateral epicondyles that are higher than the lateral condyles which are all seen in most great apes, and other ancient hominin humeri. Modern humans do not have as much torsion.

D2673, D2674, D26721, D2713, D2672 – The Vertebrae

These vertebrae, such as the slope of the articular processes, represent primitive australopithecine-like or even great-ape like form. But since the spinal process is short, narrow, and the canal shapes of all the vertebrae are wider side to side, these bones represent more modern traits.

D4167 – The Femur

This is the most complete femur of an early Homo individual. It has a defined linea aspera, a ridge on the femur that serves as an attachment for the adductors and the intermuscular septa. It is very robust, straight. The neck of the femur, where the leg is attached to the hip, is similar to the autralopithecines and the bicondylar angle, a measurement of how the femur rests on the tibia, is similar to australopithecines too.

D3901 – The Tibia

This is the first complete fossil hominin tibia, pretty cool. It too is robust, and the joint surfaces on the top and bottom are large. The mid-shaft, though, is less robust and the degree of torsion is similar to modern humans…. something not seen that much in other great apes.

There are other bones, such as the the patella, the talus, and metatarsals which I’m not gonna review for several reasons, one of which is that this post has gotten long enough already. The second reason is that I think you can see that Lordkipanidze et al., have been really thorough in documenting how these specimens are a hodgepodge of archaic and modern traits. Very indicative of some sort of transition going on.

In their conclusion, the authors say, the most definitive, ancestral trait is the torsion seen in the humerus. And since the Dmanisi postcranial remains and endocranial volumes are awfully close in size to H. habilis that suggests the first hominis out of Africa weren’t completely like the H. erectus originating in Africa. What does that mean really? That means a wave of more primitive Homo fled Africa, all the while African hominins were doing their own thing. Does this mean once the African H. erectus figured it out and moved out of Africa, that these primitive Homo were replaced? This study certainly suggests that.