Genetic Data Suggests That Early Modern Humans Migrated From South to East Africa

Science Daily is running a story that supports the idea that modern humans migrated from South to East Africa before exiting the continent.  Up until recently, all of the evidence seemed to suggest that South Africa, while having evidence of modern humans at Klasies Rivers Mouth, Border Cave and other sites, did not contribute to the migration out of Africa.  That has changed.

The Huddersfield-Minho team of geneticists, led by Professor Martin Richards at Huddersfield and Dr Pedro Soares in Braga, along with the eminent Cambridge archaeologist Professor Sir Paul Mellars, have studied the maternally-inherited mitochondrial DNA from Africans in unprecedented detail, and have identified a clear signal of a small-scale migration from South Africa to East Africa that took place at just that time, around 65,000 years ago. The signal is only evident today in the mitochondrial DNA. In the rest of the genome, it seems to have been eroded away to nothing by recombination -- the reshuffling of chromosomal genes between parents every generation, which doesn't affect the mitochondrial DNA -- in the intervening millennia.

Before going further, it is worth noting that purveyors of the mtDNA evidence have been burned before by incorrectly using the programs to input the information. Originally, those results supported a hard-line Out-of-africa model of modern human origins (Stringer and Andrews 1988), a model we now know is incorrect. Onward.The paper is available through Scientific Reports, which is open-access.  What is missing from this hypothesis is good human fossil material from South Africa which is between 160 and 200 ky.  The most current remains we have are around 120k.  More work needs to be done on this.

The Brain of Little Foot

Science Daily had a story just a bit back about research done on the new information surrounding the Little Foot australopithecine remains from South Africa.  They write:

MicroCT scans of the Australopithecus fossil known as Little Foot shows that the brain of this ancient human relative was small and shows features that are similar to our own brain and others that are closer to our ancestor shared with living chimpanzees.

While the brain features structures similar to modern humans -- such as an asymmetrical structure and pattern of middle meningeal vessels -- some of its critical areas such as an expanded visual cortex and reduced parietal association cortex points to a condition that is distinct from us.

One of the things that comes out in the paper is how much reorganization of the cranium we share with the higher primates, suggesting that quite a bit of brain evolution occurred prior to the Last common ancestor. The paper is currently free (at least I had no trouble accessing it) at http://dx.doi.org/10.1016/j.jhevol.2018.11.009. If not, the abstract is.

Here's Irony For Ya...

A study has found that residents of South Africa, historically the hotbed of human evolutionary studies, have a poorer understanding of human evolution than their neighbors.  Jacaranda FM reports:

The study, published in the South African Journal of Science this month, used responses from visitors to the Cradle of Human Kind World Heritage Site near Johannesburg. “South Africans were less likely to accept human evolution than their international counterparts,” the article said. “The survey I did was mainly of adults who would never have learned of evolution at school,” said author of the study, Professor Anthony Lelliott from Wits University in Johannesburg. The study surveyed more than 800 visitors and assessed their understanding of human evolution and the concept of “cradle”. The article explained that 60 percent of the people who rejected evolution used a religious foundation as the reason.

I guess that in a rural setting, most of the people living in South Africa would not encounter this information or understand its true significance. Still, the entire region has been at the forefront of this research for decades, and yet most people still reject it. The hold of creationism is strong, it seems, no matter where you go.

Early Homo in South Africa

The New York Times is reporting on a new find out of South Africa, by Lee Berger and his team, that indicates the presence of early Homo there.  John Noble Wilford writes:

The new hominin species was announced on Thursday by an international team of more than 60 scientists led by Lee R. Berger, an American paleoanthropologist who is a professor of human evolution studies at the University of the Witwatersrand in Johannesburg. The species name, H. naledi, refers to the cave where the bones lay undisturbed for so long; “naledi” means “star” in the local Sesotho language.

In two papers published this week in the open-access journal eLife, the researchers said that the more than 1,550 fossil elements documenting the discovery constituted the largest sample for any hominin species in a single African site, and one of the largest anywhere in the world. Further, the scientists said, that sample is probably a small fraction of the fossils yet to be recovered from the chamber. So far the team has recovered parts of at least 15 individuals.

“With almost every bone in the body represented multiple times, Homo naledi is already practically the best-known fossil member of our lineage,” Dr. Berger said.

Here is the link to the first paper, Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa, and here is the link to the taphonomic paper, Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa. Here is the picture from the main paper, as well as the abstract:

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

What does this mean?  Well, the principle problem is that we still have no date for these remains, so it is difficult to place them chronologically.  Berger is standing by his contention that early Homo arose from something like Au sediba, despite evidence to the contrary recently uncovered in Northeast Africa.  If the date is late, somewhere on the order of one million years, then a migration model might explain the appearance of such an advanced hominin in this area.  If it turns out to be much older, then other models might have to be entertained.  More thoughts on this find later.

Phillip Tobias Has Died

Phillip Tobias, a preeminent anthropologist who worked tirelessly to raise the standard for palaeoanthropology in South Africa, has died. From the Scotsman:

But for Tobias’ endeavours, the honours would probably have gone to East Africa, the territory of the more famous Leakey team, Louis and Mary. The Leakeys were great self-publicists and they made sure that East African discoveries – especially those they made in the Olduvai Gorge in Kenya’s Rift Valley – featured prominently in international media at a time when South Africa was mostly renowned for its apartheid policies.

However, Tobias, who was an anti-apartheid activist as well as a distinguished scientist, lived long enough to see the tide turn and South Africa take centre stage in the great debate on humanity’s origins. The huge shift in perceptions was largely Tobias’ doing. It was no mean feat to keep the torch alight for evolutionary studies in a land governed by white right-wing Christian fundamentalists who passionately dismissed the idea of evolution.

Tobias was partly responsible for the changes in attitudes in South Africa that led to the downfall of apartheid and, along with many biological anthropologists of the time, championed the idea that race, as a biological concept, is meaningless. He will be missed.

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Hominid Discoveries: Google Earth Helps Out

Apparently, subsequent to the recent discovery of Australopithecus sediba, Lee Berger used Google Earth to help map undiscovered caves in the vicinity of the find. As detailed on Mashable, here is a Google Video detailing the collaboration.



Cool.


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Australopithecus sediba Articles in Science

The Science Magazine articles on A. sediba are out. They are free for the time being. You just have to register at the site. The two articles cover the morphology of the finds as well as the geology of the Malapa Cave, in which they were found.
There is an extensive list of traits listed of both the cranium and face tabulated along with the other australopithecine species and early Homo. According to Berger and his team, it tells us the following:

The closest morphological comparison for Au. sediba is Au. africanus, as these taxa share numerous similarities in the cranial vault, facial skeleton, mandible, and teeth (Table 1). Nevertheless, Au. sediba can be readily differentiated from Au. africanus on both craniodental and postcranial evidence.

The face has the scooped appearance of australopithecines, with nice anterior pillars and the cranium is small, with a size of about 420 cubic centimeters. For reference, our heads are around 1400 cubic centimeters in size. On the Homo side, however, the vault is expanded and the face is considerably narrower than that of your average australopith. Compare it to this front shot of Australopithecus boisei specimen OH5, taken by David Brill. This lateral flaring of the cheeks is characteristic of all australopithecines to one degree or another and is not found in early Homo at all.

From the neck down, the skull has a mix of australopithecine and early Homo traits. The australopithecine traits include comparatively long arms, a somewhat conical-shaped rib cage and a small stature. On the other hand, it has a pelvic structure much more like later Homo, suggesting even better walking and running abilities.

Berger and his team have, I think, correctly placed this critter in the genus Australopithecus, but it clearly does have some characteristics that presage early Homo. What those mean is not yet clear but there was a general shift toward more modern characteristics in all of these hominids at around 2 million years ago.

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More on the Hominid Discovery

The Telegraph has a larger, more in-depth article on the discovery in South Africa of the early Homo remains. Richard Gray writes:

Experts who have seen the skeleton say it shares characteristics with Homo habilis, whose emergence 2.5 million years ago is seen as a key stage in the evolution of our species.

The new discovery could help to rewrite the history of human evolution by filling in crucial gaps in the scientific knowledge.

Most fossilised hominid remains are little more than scattered fragments of bone, so the discovery of an almost-complete skeleton will allow scientists to answer key questions about what our early ancestors looked like and when they began walking upright on two legs.

This discovery was hinted at months ago but no details had been forthcoming. One of the problems that continually plagues palaeoanthropology research is sections for which the fossil record is not as good as we would like it. There are a number of Homo habilis fossils that show a clear evolution of Homo but only a few instances in which it appears as though there is a clear transition between australopithecines and Homo habilis. This may change that.

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New Hominid from South Africa Fills Gap

Lee Burger has discovered a hominid specimen that fills some of the holes between australopithecines and early Homo. The article by Christopher Szabo, in Digital Journal notes:

The near complete skeleton was found by Professor Lee Burger of the University of the Witwatersrand (known locally as ”Wits”) in Johannesburg. He was exploring cave systems in the Sterkfontein region near Johannesburg in an area dubbed the ”Cradle of Humanity” for all the finds originating there.

More in a bit, I am sure.



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