Friday, 29 April 2016

What? No Flood? - Australia's 50,000 Year History

Australian Aborginals have one of the oldest histories of any peoples, dating back 50,000 years.
Photo Credit: Rusty Stewart/Flickr (CC BY-NC-ND 2.0)
Deep Roots for Aboriginal Australian Y Chromosomes: Current Biology

If you are a creationist who insists that Earth is somewhere between 6,000 and 10,000 years old and that everyone save for a single family living in the Middle East were drowned in a global flood about 4,000 years ago, it really doesn't help that you have no evidence for that claim.

Imagine then having to cope with scientists continually coming up with evidence that it couldn't possibly be true! Evidence that modern humans have lived continuously and with little or no contact with other human groups, for 50,000 years in a single continent, for example.

The standard procedure in most creationist circles in these sorts of cases is to fall back on denialism, not so much arguing that the evidence isn't there, has been forged or has been misinterpreted - the sort of denialism that can be objectively refuted - but by arguing that it doesn't count! Most creationist organisations such as the ICR, Answers in Genesis, etc, have a statement of 'faith' (for faith read dogma) to the effect that no matter how good or convincing the evidence is, it must not be allowed to change their belief that the Bible is a literal account of how the Universe, Earth, and life of Earth came into being a few thousand years ago.

So, doubtless that will be the official response to news that researchers from the Wellcome Trust Sanger Institute and collaborators at La Trobe University in Melbourne and several other Australian institutes have shown that the aboriginal Australian population diverged from the rest of the human population some 50,000 years ago, and have live in Australia and the nearby Torres Strait Islands, uninterrupted by any mass extinction caused by a flood, and with little or no contact with the rest of humanity, ever since. The population closest to them, based on genetic evidence, are the people living in Papua New-Guinea.

Highlights
  • We have sequenced 13 Aboriginal Australian Y chromosomes
  • These diverged from Y chromosomes in other continents around 50,000 years ago
  • They diverged from Papua New Guinean Y chromosomes soon after this
  • We find no evidence for Holocene male gene flow to Australia from South Asia
Summary
Australia was one of the earliest regions outside Africa to be colonized by fully modern humans, with archaeological evidence for human presence by 47,000 years ago (47 kya) widely accepted. However, the extent of subsequent human entry before the European colonial age is less clear. The dingo reached Australia about 4 kya, indirectly implying human contact, which some have linked to changes in language and stone tool technology to suggest substantial cultural changes at the same time. Genetic data of two kinds have been proposed to support gene flow from the Indian subcontinent to Australia at this time, as well: first, signs of South Asian admixture in Aboriginal Australian genomes have been reported on the basis of genome-wide SNP data; and second, a Y chromosome lineage designated haplogroup C∗, present in both India and Australia, was estimated to have a most recent common ancestor around 5 kya and to have entered Australia from India. Here, we sequence 13 Aboriginal Australian Y chromosomes to re-investigate their divergence times from Y chromosomes in other continents, including a comparison of Aboriginal Australian and South Asian haplogroup C chromosomes. We find divergence times dating back to ∼50 kya, thus excluding the Y chromosome as providing evidence for recent gene flow from India into Australia.


Copyright © 2016 The Authors. Published by Elsevier Inc. Reprinted under Creative Commons license CC BY-NC-ND 4.0

The study was conducted on the Y chromosomes so strictly speaking shows the phylogeny of the male line. This is the first complete sequencing of the Y chromosome of Australian Aboriginals. One hypothesis which has been lain to rest by this study is that Australia was populated by migration from the Indian sub-continent.

We worked closely with Aboriginal Australian communities to sequence the Y chromosome DNA from 13 male volunteers to investigate their ancestry. The data show that Aboriginal Australian Y chromosomes are very distinct from Indian ones. These results refute the previous Y chromosome study, thus excluding this part of the puzzle as providing evidence for a prehistoric migration from India. Instead, the results are in agreement with the archaeological record about when people arrived in this part of the world.

Anders Bergstrom, quoted in EurekAlerts
This study places the Australian Aboriginal peoples arrival in that part of the world when Australia, New Guinea and Tasmania formed a single landmass called Sahul, and probably several thousand years before modern humans arrived in Europe. This is entirely consistent with a coastal spread out of Africa, firstly into what is now Arabia, then via India to the Malay peninsula and so down into Sahul.

The point about coastal spread is that it is relatively easy compared to migration over uninhabited land, with no major discontinuities such as deserts or mountain ranges. A migrating population, no matter how slowly the migration takes place, needs to sustain itself all the while, so needs a supply of food and fresh water. Both these things are more readily available at the coast than in a desert of mountain range. They would also develop some form of seafaring ability.

This particular migration appears to have been completed only once, creating an isolated population to evolve genetically and culturally without external 'contamination'. It is also consistent with analysis of Dreamtime myths which appear to be very old, originating before the last Ice Age.

An example of the age of this culture may be the depiction of an extinct Thylacoleo in the earliest 'Bradshaw' rock paintings in the Kimberly Range in northern Western Australia. The Thylacoleo was a large marsupial carnivore (the 'pouched lion'). It was a top predator from about 2 million years ago until going extinct about 45,000 - 46,000 years ago. Relatively sudden extinction of Australia's megafauna, especially since there does not appear to have been a major climatic change at about that time, is again consistent with the arrival of humans at that time.

I've probably covered the likely creationists response to this news. It isn't what their superstition requires therefore it doesn't exist or doesn't count. I wonder if one of my creationist reader would confirm this is to be their response, or suggest some other way that they might cope with the cognitive dissonance and not change their minds in view of the evidence that their minds are wrong?

Hat-tip:
Cushla Geary / Sovereign Union via Facebook


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