Early Homo Postcranial Fossils from Dmanisi

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.

Lordkipandize, et. al., 2007 - Figure 2: Dmanisi Postcranial ElementsThe 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.

D4166D4166 – 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

D2724 D4162 D4161

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

D2715 D2680 D4507

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

D2673 D2674 D2721 D2713 D2672

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

D4167

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

D3901

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.

7 thoughts on “Early Homo Postcranial Fossils from Dmanisi

  1. Kambiz. Your last comment,

    “Does this mean once the African H. erectus figured it out and moved out of Africa, that these primitive Homo were replaced?”

    To me it, along with the recent discovery of possible overlap of H. erectus and H. habilis in Africa, suggests African H. erectus evolved from something like this Dmanisi population who had moved back into Africa. This link from John Hawks’ Four Stone Hearth suggests this sort of movement has had a hand in human evolution over the last 10,000 years. Why not longer ago too?

  2. Terry,

    The oldest H. erectus fossils, to date, have come from Africa. Fossils like, KNM ER 3733, KNM ER 992, KNM ER 3883, and KNM WT 15000.

    The Dmanisi hominids show there are differences between populations of H. erectus in Africa, and the populations of Europe, Africa and Asia around 1.8-1.5 million years ago. But by 1 million years ago, fossils like Daka calvaria show that there are a lot of similarities in features that people were formerly using to separate early African erectus from late Asian ones. From the abstract,

    “Here we report that the ‘Daka’ calvaria’s metric and morphological attributes centre it firmly within H. erectus. Daka’s resemblance to Asian counterparts indicates that the early African and Eurasian fossil hominids represent demes of a widespread palaeospecies. Daka’s anatomical intermediacy between earlier and later African fossils provides evidence of evolutionary change. Its temporal and geographic position indicates that African H. erectus was the ancestor of Homo sapiens.”

    Here are the links to the two papers which show by 1 million years ago, erectus was pretty uniform. “Homo erectus, Homo ergaster, Homo “cepranensis,” and the Daka cranium,” and “Remains of Homo erectus from Bouri, Middle Awash, Ethiopia.”

    Kambiz

  3. Thanks Kambiz. The quote, “demes of a widespread palaeospecies” confirms pretty much what I suspected. We have a variable species, perhaps something between Homo habilis and H. erectus, that moves out of Africa. Over the next rather less than million years regional varieties move around its geographical distribution, much the same as modern humans have done. Introgression and selection eliminates the extreme variations and we finish up with a widespread species showing clinal variation, Homo erectus. The same process starts again. Still going on in fact.

  4. Kambiz,

    Extant apes (except small gibbons) have laryngeal air sacs, Selam and Lucy also had them (based on the hyoid bone). Humans don’t, though 2% of humans develop laryngocoels in the same position as air sacs (Fitsch).

    I believe one neandertal hyoid indicated no air sac. Has any other apith or early Homo fossils given indication of possessing air sacs?

    AFAICT, laryngeal air sacs developed in early apes as a result of natural selection for flotation in wetland (perhaps tidal) forests, with vocalization becoming more important with time. The vertical flotation resulting from inflated air sacs (during which the individual could exhale and inhale independently) eventually produced a more vertical posture and loss of the tail in hominoids.

    That the Dmanisi fossils were found near a river/lake and in the vicinity of flint quarries later used by Sumerians for trade is intriguing.
    Hope they find a hyoid or two!

Comments are closed.

A WordPress.com Website.

Up ↑

%d bloggers like this: