On exposition in the Naturalis Museum of Leiden, Netherlands 29 november 2009 t/m 28 februari 2010: the Dmanisi Man of Georgia.

The D2700 skull from Dmanisi.

A special exposition of the original skull of the earliest humanoid ever found outside of Africa. The find of this skull in Georgia raises a lot of questions all over the world on the evolution of mankind. The high age of 1.8 million year as well as the small braincapacity and the location outside Africa don’t fit into the current theories on the migration of our forebears. For the first time the skull will leave the safe of the National Historic Museum in Tbilisi, Georgia, to be exposed to the public.

I had a quick visit to the Leiden exposition of Dmanisi Man. The information was really very basic since “the book” still has to be written. Who ever said that Dmanisi is old news? Let him send me the articles everybody agree upon. In short, three competing theories were mentioned. No evaluation, the visitors of the exposition are required to decide for themselves.

1. Out of Africa : according to this view Dmanisi Man should somehow fit within the framework of an African exodus of early humans that was theorized to have happened between 1.5 -1 million years ago. However, since Dmanisi Man was about 1.8 million years old he doesn’t fit in this scenario. So do others BTW (from the start this Out of Africa was a fairy tale).

2. Earlier Out of Africa : Human (? not proven) artefacts are known from 2.6 million years ago onward. This theory proposes that the earliest humans thus could have left Africa a lot earlier and reached Asia from 2.6 million years ago onwards. New human species developed in Asia that also reached Europe. Not a word about backmigrations (a weak point).

3. Back and Forth : At any time of history humanids or early humans left Africa, developed into more advanced species and then returned to Africa.

Obviously the third theory is more viable, but I could not find more information: what species left Africa? Were they necessarily human? Should this explain why Homo Erectus could coexist next to Homo Habils as a separate species for so long in Africa, while previously Homo Habilis was considered the ancestor of Homo Erectus? Does the same apply to Homo Habilis in relation to Australopithecus? Of course few can be said, since no African Homo were found between the first artefacts of 2.6 million years ago and the first unequivocal remains of Homo Habilis dated 1.8-1.6 million years ago. Maybe those artefacts were not human at all and rather belong to Australopithecus? There is no evidence, only conjecture.

About the skull: the last molars (wisdom teeth) did not develop yet, so Dmanisi was a teenager. This could explain some about the outrageous low brain capacity. Possibly this skull is the best evidence we can get to prove that the human adolescent growth spurt was already a feature of the very first Homo.
At least superficially it looks quite similar to Homo Habilis. It has a horizontal brow ridge and more protruding zygomatic facial bones in common with Asiatic samples of Homo Erectus, against the V-shaped brow ridge and weaker zygomatic facial bones among the African/European samples. Unfortunately, no dentals were preserved so nothing can be said of this sample about shoveling.

Extrapolating from the Back and Forth model, I can easily imagine Homo Habilis to be from the same stock as the inmediate ancestors of Dmanisi. However, though Asiatic Homo Erectus features are clear and documented, I think the age and intermediate characteristics of Dmanisi do not support a role of this specific human type in the backmigration of Homo Erectus. Maybe rather of Homo Ergaster?

We may even reconsider the human origin completely and remind Von Koenigswald, that located the origin of humans in India. He was already familiar to Homo Modjakertensis and postulated that our predecessors were apes like Dryopithecae, Rampithecae, Sivapithecae that all seem to have a predominantly northern non-African distribution. The question whether or not Australopithecus should be separated completely from the humanoid line would need another evaluation, as well as the position of Afarensis within the Australopithecus family that may be invalid. Maybe Australopithecae (excluding Lucy?) came together with the precursors of Chimpansees and Gorillas in a first migration wave from Asia, while Lucy and Homo Habilis were the result of subsequent migration waves from Asia?

The Out of Africa hypothesis was wrong and still it is the precursor of  the Recent Single Origin hypothesis. Its assumption that early hominids elsewhere don’t matter at all is basic and circular: all hominids originate in Africa, thus all observed characteristics of hominids elsewhere should be assumed to originate in Africa as well. Well, did they?

Such an important assumption should be verified with available evidence. Where is the proof that Homo Erectus of the Far East derives from Homo Habilis? Homo Modjakertensis as intermediate form does not attest a straightforward evolution at all. The Dmanisi find has characteristics in common with Homo Habilis, Australopithecus and Homo Erectus of eastern asia. We should expect Homo Habilis to have evolved to Dmanisi and to Homo Modjakertenis and subsequently to Homo Erectus. In Africa we miss these kind of intermediate forms, the change or development from Homo Habilis to Homo Erectus is thus not assumed straightforward and “treelike”, but “bushlike”. However, the set of Homo Habilis characteristics is even contrary to the assumption of being ancestral: together with Homo Modjakertensis they share the intermediate position between Australopitecus and Homo Erectus having a semicircular ear canal morphology, though they fail to show the “simian gap” what would suggest an advanced development in relation to the earliest Homo Erectus that is not supported by their age.

The controversal features of the Homo Modjakertensis catalogued as “Sangiran 4″ – projecting canines and precanine diastemata – are recently confirmed:

This analysis shows that the Sangiran 4 palate is not unique, and shares several of these putative pongid traits with other Javan hominid fossils as well as recently described hominid specimens from Dmanisi, Georgia. These results suggest that the evolution of the earliest Asians was more complex than has previously been appreciated. — The enigma of the Sangiran 4 palate revisited, Arthur C. Durband (2008).

However, the set of characteristic of homo habilis against Dmanisi and/or Homo Modjakertensis also includes some that are not transitional to all modern humans. The most notorious being the shovel-shaped teeth of 80% of mongoloid people. Like Homo Erectus, these can’t be derived unequivocally from Africa and it is hard to imagine that Asiatic food required shovel-shaped teeth already for millions of years and thus to assume parallel evolution. If this comes out this would be a bad day for Asiatic restaurants all over the world and good news for orthodontists.

The African origin of shovel-shaped teeth is precarious to say the least. The two Homo Habilis mentioned by Tobias for having shovel teeth are suspect finds: the position of OH6 is contested and OH16 was found completely shattered. Hardly convincing for universal currency among all early hominids. Homo Habilis and Homo Erectus coexisted for hundreds of thousand years in Africa, so maybe some evidence became mixed up, or maybe they just mixed. And what happened next?
Trinkhaus 2007: African Middle Paleolithic Modern Humans (MPMH) have chisel teeth. Archaic humans and Neanderthal, that grossly comprise all the rest in this period, have shovel-shaped teeth. Maxillary incisor shoveling remains in the Gravettian among Early European Modern Humans. The wave of chisel teeth thus only took effect much later in Europe.
Moreover it never reached Asia! The disproportionate presence of shovel teeth in asiatic populations and the preservation of this characteristic among native americans within a European civilization is a strong argument for a genetic component above “domestication”.
A relevant African Origin question: Were the “modern” chisel teeth a new evolutionary adaptation that spread from a single source in Africa, or is the chisel shape reminiscent of Homo Habilis and indicative for a minor influence of the mainstream evolutionary line that rather pertains to Homo Erectus? Could we  presume continuity? Or if Homo Habilis can now be discarted as an ancestor, and Homo Erectus was an immigrant in Africa: where and how did the shovel teeth of Homo Erectus originate?

For the record, Dmanisi Man should not have come as a surprise. We already knew of 2 million year old tools in Pakistan and Homo Modjakertensis was already dated in the same range half a century ago. So why Out of Africa was ever proposed at all to explain Homo Erectus? The facts show the hypothesis isn’t even overdue: it was all made up from the start.

Evidence ignored for so much time is bound to make sensation today, or tomorrow for that sake. Maybe a disproportionate importance of Anglosaxon scientists and public is the cause of the undue acceptance of Out of Africa? Just imagine that Indonesia would have been a British colony, and some kind of Leakey would have discovered Homo Modjokertensis. And just think what evidence would have been forgotten by the international scientific communitity if Kenia would have been a Dutch colony instead and Von Konigswald the anthropologists that found a few bones in Kenia that after all were just a shadow of the contemporary finds in Indonesia. The Dmanisi would have been the confirmation of what we already knew for a century.

Referenced:

• Erik Trinkaus – European early modern humans and the fate of the Neandertals, 2007, link
• Arthur C. Durband – The enigma of the Sangiran 4 palate revisited, 2008, link (paysite)
• G.H.R. von Koenigswald – De eerste aapmensen in Azië, 1981, ISBN 90 70157 20 9 (Dutch)
• M. Martinón-Torres et al. -Dental evidence on the hominin dispersals, 2007, link
• Christian R. Nichol et al. – Variation in the convexity of the human maxillary incisor labial surface , 1982, link (paysite)

Naturalis: exposition link.

How often have you heard the phrases “settled science” or “scientific fact”? They come up a lot in reference to issues like climate change, evolution, and abortion. Always the intention is to show that the currently prevailing scientific theory is correct beyond any doubt, and that anyone who suggests a contrary idea must be a crackpot.

This is contrary to the very nature of science. The success of science as a way of explaining the world around us is precisely due to science’s ability to revise theories in accordance with new evidence. Just as Einstein’s relativity replaced Newtonian physics, new discoveries continue to challenge our existing theories about life, the universe, and everything. Those who arrogantly insist on the infallibility of any scientific theory such as global warming or evolution are doomed to ultimate embarrassment when they turn out to be wrong.

A wonderful example of this comes to us from the science page of the Independent. Hominid skulls found in the Georgian village of Dmanisi are the oldest ever found outside of Africa, and they are challenging the long-held view that humans must have arisen in Africa and spread from there to Eurasia and other continents. This theory was, until recently, virtually universally accepted as fact. To suggest that one of the stages of human development (Homo erectus) evolved in Eurasia, as these fossils seem to suggest, would have been regarded as batty: 

“The question is whether Homo erectus originated in Africa or Eurasia, and if in Eurasia, did we have vice-versa migration? This idea looked very stupid a few years ago, but today it seems not so stupid.”

Ultimately, it may or may not be shown that human ancestors went “back to Africa”. It has little impact for the average person today either way. The point though, is that the out-of-Africa theory is far older, more venerable, and had more evidence behind it than the theory of global warming does. If the former can be called into question by new evidence, the latter certainly can. So the next time that someone tells you global warming is “settled science”, feel free to treat the comment with the disdain it deserves.

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.

Tommorrow, Nature will be publishing a new study of the Dmanisi fossil specimens. In preparation, I’m gonna introduce you to the importance of the Dmanisi site, overview the human fossils that have come out of it, and the related debates.

Firstly, Dmanisi is a rich paleoanthropological and archaeological site in Georgia. Multiple lines of evidence date the human occupation at Dmanisi as early as 1.85 million years ago, putting it in the Pleistocene. You ask, “What sort of data?” Layers of ash and sandy sediment, which contain remains along with numerous crude stone tools and flakes, have been dated radiometrically at 1.7 to 1.85 million years old.

Other dating techniques, such as isotopic potassium-argon (K-Ar) and argon-argon (⁴⁰Ar/³⁹Ar) dating give an age of 1.8 million years ago. Paleomagnetic analysis of the units around the fossil layer, hold a record of change in magnetic polarity about 1.77 million year ago, which correlates to other dated sites, most notably Olduvai Gorge in Tanzania. All of these dating techniques help place Dmanisi as one of the most ancient human habitation sites in Eurasia. Dmanisi is approximately equivalent in age to the oldest H. erectus localities in eastern Africa. The remains found from Dmanisi have become crucial, and at the same time very controversial, to the study of human evolution.

The remains I want to segue into have consistently brought up a heated debate. And since we’re talking early Pleistocene, i.e. 1.8 mya, we are in the Homo lineage. For anyone not in the know, the fossils record for early Homo is spotty. Trying to make sense of the spottiness, many anthropologists have been butting heads about what has been happening to Homo erectus and Homo habilis during a 2 to 1 million year ago time frame. John Hawks reviewed Brown’s revised chronology in 2006. And the most recent debate, the Ilert hominids, have complicated our understandings of what was going with these two taxa in Africa. So to say that H. erectus has a problematical heritage is to grossly simplify matters.

The best Dmanisi fossils from this time frame haven’t, as of yet, clarified the conundrum outside of Africa for us. The first hominid fossil from Dmanisi was a mandible, was found on the last day of the 1991 field season, by Antje Justus. This mandible was assigned as D211.

While the H. erectus versus H. ergaster debate is largely settled in favor of calling everything that was once ergaster synonymous with erectus, at the time, D211 opened a Pandora’s box of sorts because it differs from known H. erectus specimens. D211 has certain similarities to ER992 (pictured) and ER730, both assigned as H. ergaster from Africa. D211 shares the following similarities:

• General form and robustness of the jaw
• Anterior position of the ascending ramus, including the edge of the retromolar space
• The absence of a trigonum mentale

D211 differs from ER992 and ER730 because it has smaller molars and premolars as well as a less receding anterior surface of symphysis. Despite these differences in size, and Brauer and Schulz’s contention that D211 is a representative of H. erectus, D211 was placed closer to H. ergaster group.

Even though the debate over classifying D211 was between calling it H. ergaster and H. erectus, and not H. habilis vs. H. erectus, it did set the tone for agreeing about future hominid finds from Dmanisi.

Fast forward to 1999, when D2280 and D2282 surfaced from the same stratigraphic level as D221. D2280 is an almost complete calvaria. It includes most of the left mandibular fossa of the temporal, a partial cranial base with a damaged occipital, and parts of the greater wing of the sphenoid. It is pictured in the photographs to your right.

You can see it is rounded, and doesn’t have such an angular posterior side, traits seen in H. habilis. The endocranial volume for D2280 is about 775 cm³, making it small… closer to the size of H. habilis than H. erectus. But because D2280 included a supraorbital torus, and shared some proportional similarities to H. ergaster (like WT15000 and ER3733), it was assigned as such.

D2282 is a much more complete specimen. As you can see, it is a cranium with many of the bones of the face and cranial vault. The major problem with D2282 is that it has been kinda deformed throughout the ages, the occipital and temporal ares are crushed on the left side, as are the zygomatic bones making a lot of the measurements and proportions convoluted.

To complicate it, much of the median upper facial skeleton is missing including the supraorbital torus at glabella, nasal bones, and frontal processes of the maxillae. Which makes it even harder to compare feature to feature to D2280.

However, all hope was not lost with our friend D2280. With a well persevered maxillae that still holds the right P⁴-M² and the left M¹ and M², as well as the alveoli of all other adult teeth including those of M³, a more thorough comparison was done. The comparison of the teeth lead to the conclusion that D2282 represents H. erectus. One example, the presence of singler roots in the upper premolar teeth is a H. erectus trait that.

D2282 is still small; the smaller of the two crania; 650 cm³ small; small like habilis.

Right above the tuff that locked away D211, D2280, and D2282, came another set of findings in 2001 and 2005, the D2700 cranium and the D2735 mandible, and the D3444 cranium and D3900 mandible.

The cool thing about D3444 cranium is that he was an old guy, completely toothless. His toothlessness was not something new, he had been toothless for several years before death, judging by the complete resorption of the tooth sockets. The implications of how he was cared for in his old age, were outstanding.

And about the D2700 cranium. It is even smaller than D2282, at 600 cm³. D2700 has many characteristics which resemble H. ergaster but also a handful that resembles the ER1813 H. habilis skull. Vekua et al., write in their 2002 paper that,

“In overall shape, D2700 is similar to D2280 and D2282, and D2735 resembles D211. Despite certain differences among these Dmanisi individuals, we do not see sufficient grounds for assigning them to more than one hominid taxon. We view the new specimen as a member of the same population as the other fossils, and we here assign the new skull provisionally to Homo erectus.”

So, other than showing you how bountiful Dmanisi has been in yielding Homo fossils, what else is going on here? We have a lot of small habilis-like skulls coming out from Dmanisi which have erectus-like features.

Do we go with size or do we go with morphology? As of right now, we’ve gone with morphology, but that’s problematic, especially dealing with heavily fragmented remains. Better yet, do the Dmanisi fossils represent a transitional species, one were humans were similar in size to habilis but similar in shape and form to erectus?

I think that will be answered in tomorrow’s Nature.

I don’t know really, but I’d like that to be answered because I’m pretty sure all you see right now is the great flaw in understanding evolutionary relationships and ancestors from fossil remains; when determining taxonomies with many traits, measurements, and damages to consider, it seems to be nothing more than a big pissing match between respective paleoanthropological groups.

References:

• Taxonomy of the Dmanisi Crania
• The morphological affinities of the Plio-Pleistocene mandible from Dmanisi, Georgia
• Earliest Pleistocene Hominid Cranial Remains from Dmanisi, Republic of Georgia: Taxonomy, Geological Setting, and Age
• Anthropology: The earliest toothless hominin skull