Sunday, 10 August 2014

Human Evolution - Completing the Picture

Neanderthal family (artists impression) Photograph: Nikola Solic/Reuters
To me, watching a science grow and develop is what makes it more like an adventure than a dull, academic subject. Discoveries are made and fed into the mix; ideas and opinions are contributed by people who are experts in the field; old ideas are revised, reviewed and discarded if necessary and eventually a new consensus emerges which is, in the long run, a little closer to the truth. All the while the picture grows in clarity, sometime becoming more complex that we thought and sometimes simpler.

How unlike religion where the entire effort is devoted to excusing yet again that which is nothing more than evidence-free dogma, finding new and ever-more creative workarounds for the fact of no evidence, and inventing new ways to bamboozle a diminishing following into believing that, despite the overwhelming evidence to the contrary, and despite the enormous gains of science and its contribution to human welfare since the enlightenment, their Bronze-Age belief in magic is the best explanation of reality.

A couple interesting articles in this week's New Scientist illustrate how our knowledge of human evolution keeps being added to and our understanding of is revised and refined accordingly.

The first, by Andrew Coghlan, comments on a paper published in Scientific Reports last March which shows that Neanderthals living in a cave in Gibraltar had roast rock doves (Columba livia ) on their menu.

Feral Pigeons have colonised all corners of the Earth, having developed a close association with humans and their activities. The wild ancestor of the Feral Pigeon, the Rock Dove, is a species of rocky habitats, nesting typically on cliff ledges and at the entrance to large caves. This habit would have brought them into close contact with cave-dwelling humans, a relationship usually linked to the development of dwellings in the Neolithic. We show that the association between humans and Rock Doves is an ancient one with its roots in the Palaeolithic and predates the arrival of modern humans into Europe. At Gorham's Cave, Gibraltar, the Neanderthals exploited Rock Doves for food for a period of over 40 thousand years, the earliest evidence dating to at least 67 thousand years ago. We show that the exploitation was not casual or sporadic, having found repeated evidence of the practice in different, widely spaced, temporal contexts within the cave. Our results point to hitherto unappreciated capacities of the Neanderthals to exploit birds as food resources on a regular basis. More so, they were practising it long before the arrival of modern humans and had therefore invented it independently.


Rock dove Columba livia http://www.wildlifeinsight.com
The significance of this discovery is that it shows that Neanderthals were either agile enough to scale up the cliffs where the rock doves nest to take the young from nests, or were ingenious enough to make nets or traps to catch the adults with. The number of rock dove bones found rules out the occasional chance catching of a sick or injured bird or finding a dead one. Both these things run counter to previous assumptions about Neanderthals, although we have been revising our idea that they were not smart enough to catch anything other than big game by herding it over a cliff. Although Neanderthals were undoubtedly more heavily built that modern humans, this does not necessarily mean they lacked the agility to climb a rock-face.

There is absolutely no doubt that this was the Neanderthals. And they could not have learned this from modern humans because there weren't any modern humans in Europe 67,000 years ago. They must have come up with this on their own.

Clive Finlayson, director of the Gibraltar Museum
And of course we can't rule out the possibility that they captured and domesticated rock doves - the ancestors of the domestic and feral pigeons.

The second article, by Catherine Brahic, raises the possibility that we may have the details of exactly when modern humans came out of Africa wrong. It is widely believed that we came out as a single migration about 60,000 years ago and spread quickly via the Middle East across Europe and Asia and down into Austronesia, reaching Australia about 40,000 years ago.

It was also assumed that one of our ancestors, Homo erectus, had left Africa and made it all the way to Southeast Asia and Indonesia, as did the ancestor of H. floriensis (the 'hobbit') found on the Flores Islands, which may or may not have been H. erectus.

Now we are beginning to see tentative evidence that H. sapiens may have come out of Africa much earlier and may have reached China 100,000 years ago - admittedly only tentative but enough to raise a few questions.

The first piece of evidence is two teeth from Luna cave in Guangxi Zhuang, China, discovered by Christopher Bae of the University of Hawaii at Manoa, Wei Wang of the Guangxi Museum of Nationalities in Nanning, China, and colleagues. Based on the proportions of these teeth they argue that at least one of them must be from an early H. sapiens.

Abstract

We present two previously unreported hominin permanent teeth [one right upper second molar (M2), one left lower second molar (m2)] from Lunadong ("dong" = "cave"), Guangxi Zhuang Autonomous Region, China. The teeth are important because: 1) they were found in situ; 2) at least one (M2) can be confidently assigned to modern Homo sapiens, while the other (m2) is likely modern H. sapiens; and 3) the teeth can be securely dated between 126.9 ± 1.5 ka and 70.2 ± 1.4 ka, based on multiple MC-ICP-MS uranium-series dates of associated flowstones in clear stratigraphic context. The Lunadong modern H. sapiens teeth contribute to growing evidence (e.g., Callao Cave, Huanglongdong, Zhirendong) that modern and/or transitional humans were likely in eastern Asia between the crucial 120–50 ka time span, a period that some researchers have suggested no hominins were present in the region.


There is solid evidence of modern humans at Tam Pa Ling [in Laos] around 50,000 or 60,000 years ago, and the Zhirendong mandible has modern features, so yes, modern humans were present in at least south-east Asia and south China by somewhere in this time range.

Erik Trinkaus, Professor of Physical Anthropology, University of Washington in St Louis, MO, USA
However, it is not so clear-cut as the authors suggest that these are teeth from H. sapiens. Erik Trinkaus, Professor of Physical Anthropology at the University of Washington in St Louis, MO, USA argues that they are not diagnostic because we don't yet know how teeth evolved in H. erectus in Asia. It could be a simple case of convergent evolution.

As I said, the evidence is tentative.

The second piece of evidence is more convincing. It is a piece of jawbone with two molar teeth found also in a cave in China at Zhirendong, Guizhou. This is over 100,000 years old and has a chin suggestive of modern humans.

Abstract

The 2007 discovery of fragmentary human remains (two molars and an anterior mandible) at Zhirendong (Zhiren Cave) in South China provides insight in the processes involved in the establishment of modern humans in eastern Eurasia. The human remains are securely dated by U-series on overlying flowstones and a rich associated faunal sample to the initial Late Pleistocene, >100 kya. As such, they are the oldest modern human fossils in East Asia and predate by >60,000 y the oldest previously known modern human remains in the region. The Zhiren 3 mandible in particular presents derived modern human anterior symphyseal morphology, with a projecting tuber symphyseos, distinct mental fossae, modest lateral tubercles, and a vertical symphysis; it is separate from any known late archaic human mandible. However, it also exhibits a lingual symphyseal morphology and corpus robustness that place it close to later Pleistocene archaic humans. The age and morphology of the Zhiren Cave human remains support a modern human emergence scenario for East Asia involving dispersal with assimilation or populational continuity with gene flow. It also places the Late Pleistocene Asian emergence of modern humans in a pre-Upper Paleolithic context and raises issues concerning the long-term Late Pleistocene coexistence of late archaic and early modern humans across Eurasia.


But again we see objections from other experts, and come up against the possibility of convergent or parallel evolution in two closely related species, as pointed out by John Hawks, Vilas-Borghesi Distinguished Achievement Professor of Anthropology, University of Wisconsin-Madison, USA.

The third piece of evidence comes from a genetic analysis bublished last April by paleoanthropologist Katerina Harvati and colleagues of the University of Tubingen, Germany.

Abstract

Despite broad consensus on Africa as the main place of origin for anatomically modern humans, their dispersal pattern out of the continent continues to be intensely debated. In extant human populations, the observation of decreasing genetic and phenotypic diversity at increasing distances from sub-Saharan Africa has been interpreted as evidence for a single dispersal, accompanied by a series of founder effects. In such a scenario, modern human genetic and phenotypic variation was primarily generated through successive population bottlenecks and drift during a rapid worldwide expansion out of Africa in the Late Pleistocene. However, recent genetic studies, as well as accumulating archaeological and paleoanthropological evidence, challenge this parsimonious model. They suggest instead a "southern route" dispersal into Asia as early as the late Middle Pleistocene, followed by a separate dispersal into northern Eurasia. Here we test these competing out-of-Africa scenarios by modeling hypothetical geographical migration routes and assessing their correlation with neutral population differentiation, as measured by genetic polymorphisms and cranial shape variables of modern human populations from Africa and Asia. We show that both lines of evidence support a multiple-dispersals model in which Australo-Melanesian populations are relatively isolated descendants of an early dispersal, whereas other Asian populations are descended from, or highly admixed with, members of a subsequent migration event.


This suggests that the widely accepted route out of Africa via the Middle East may not have been the only route. Early modern humans may have left Africa by crossing from the Horn of Africa into the southern Arabian Peninsula and from there, by coast spread across the Strait of Hormuz into India and thence into Southeast Asia, Indonesia and Austronesia. Later on they mixed with and interbred with other humans who came out of Africa at the normally accepted time and by the normally accepted route.

So, that's the emerging picture of human evolution. If there is anyone religious, especially a creationist, who has survived to the end of this article, let's see a similar objective treatment of the emerging archaeological evidence that the Bible, especially the Old Testament, was made up; that large parts of it simply never happened but were invented around the 7th-century BCE to lend credence to a pretentious emergent political power amongst the different hill tribes of Canaan. How will you fit this discovered evidence into your notion of a book of inerrant truths upon which your entire faith rests?

Reference:
Cunning Neanderthals hunted and ate wild pigeons - life - 07 August 2014 - New Scientist
Human exodus may have reached China 100,000 years ago - life - 08 August 2014 - New Scientist

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1 comment :

  1. Talking of Neanderthals, it's also worth mentioning that they in fact seem to have interbred with Homo sapiens. See for example: http://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals/interbreeding .

    And then some interesting questions arise, for example: 1) Did Neanderthals have an immortal soul? 2) If YES, does that mean that also Neanderthals are welcome to the Christian Heaven? 3) if NO, how about interbreeding between a Homo sapiens (who has got an immortal soul according to Bible apologetics) and a Neanderthal (whose soul maybe is NOT immortal)? Will such hybrids get a mortal or immortal soul? 4) Can the omnipotent and omniscient Creator accept such hybrids in His Heaven?

    That sort of questions are often debated at many web forums, for example this one: http://forums.catholic.com/showthread.php?p=2891017 .

    I also recommend this site: http://pandasthumb.org/archives/2014/03/svante-paabo-on.html . There you can read an excerpt from page 221 in the famous and well-known Swedish paleogenetic biologist Svante Pääbo's (or Paabo in English) book Neanderthal Man: In Search of Lost Genomes. Basic Books; First Edition (February 11, 2014), 288 pages http://www.amazon.com/Svante-P%C3%A[…]e/B00GJ9XR7O .

    I quote: There were many others who were interested in the Neanderthal genome – perhaps most surprisingly, some fundamentalist Christians in the United States. A few months after our paper appeared, I met Nicholas J. Matzke, a doctoral candidate at the Center for Theoretical Evolutionary Genomics at UC Berkeley. Unbeknownst to me and the other authors, our paper had apparently caused quite a flurry of discussion in the creationist community.

    Nick explained to me that creationists come in two varieties. First, there are “young-earth creationists,” who believe that the earth, the heavens, and all life were created by direct acts of God sometime between 5,700 and 10,000 years ago. They tend to consider Neanderthals as “fully human,” sometimes saying they were another, now extinct “race” that was scattered after the fall of the Tower of Babel. As a consequence, young-earth creationists had no problem with our finding that Neanderthals and modern humans had mixed.

    Then there are “old-earth creationists,” who accept that the earth is old but reject evolution by natural, nondivine means. One major old-earth ministry is “Reasons to Believe,” headed by a Hugh Ross. He believes that modern humans were specially created around 50,000 years ago and that Neanderthals weren’t humans, but animals.

    Ross and other old-earth creationists didn’t like the finding that Neanderthals and modern humans had mixed. Nick sent me a transcript from a radio show in which he [meaning Hugh Ross] commented on our work, saying interbreeding was predictable “because the story of Genesis is early humanity getting into exceptionally wicked behavior practices,” and that God may have had to “forcibly scatter humanity over the face of the Earth” to stop this kind of interbreeding, which he compared to “animal bestiality.”

    Clearly our paper was reaching a broader audience than we had ever imagined.

    MY OWN REFLECTION: Really? Is it all about “animal bestiality"? Can't creationists come up with a better explanation that that?

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