Saturday, September 07, 2013

The Antiquity of Blonde Hair

Case reopened.

Humans today are a mix of several species from the Homo genus - at least 3 (Homo sapiens, Homo Neanderthalensis, Homo denisova) and probably more when all is said and known.

A graphic from this article [New DNA Evidence ...] shows that linkage between modern Melanesians (who frequently exhibit blonde hair) and archaic Denisovans occurred around 40,000 years ago.

This article [Blonde Melanesians ...] provides some additional interesting information on the antiquity of Oceanic blonde hair, asking the question, "is this trait an independent occurrence of de-pigmentation in Oceania, or was it due to introgression of European alleles?"

The author (Razib Khan) answers his own question:

First, one must note that this is not an isolated feature in Oceania. Rather, blondism crops up in the Solomon Islands, in New Guinea, as well as among some Australian desert groups. This in itself should make us skeptical of the model of [modern human - my addition] European admixture. Additionally, blue eyes, which exhibits a higher frequency in Europeans than blonde hair, is not similarly common in these populations.

Though some scientific studies have reported Melanesian blonde hair to be tied to a recent selected mutation in the TYRP1 pigmentation related locus found among Melanesians, it doesn't close the case that blondism in Melanesians is also linked to deep ancestry rather than solely to a population-specific mutation in the TYRP1 locus (a mutation which is not found in Europeans).

 Khan goes on to write:

But there’s a very good reason I never expected there to be recent selection driving this anyhow: Australian Aboriginals sometimes manifest blonde hair, and the best genetic data suggests separation from Melanesians of at least 10,000 years. Additionally, the Solomon Islands were not part of Sahul, so that’s a conservative estimate. We don’t know if the Aboriginals have the same TRYP1 mutation, but there’s the same tendency toward dark skin and light hair amongst them. It also seems rather suspicious to me that the highest frequency of blonde hair outside of West Eurasia is all amongst Oceanian populations, who are phylogenetically a distinct clade [as are European populations - my addition].

What I am suggesting then is that this pigmentation mutation is an old feature of the Oceanian populations, on the order of tens of thousands of years. 

... and what I am suggesting is that the "tens-of-thousands of years old feature" found amongst Oceanic groups (whatever specific mutation or mutations is are responsible for overt phenotypic expression of the trait) is indeed connected to their shared Denisovan ancestry (linking these populations around 40,000 years ago before the Melanesians and the Aboriginal Australians split genetically around 10,000 years ago).

Flipping Genetics!

As surprised as I was to learn that my Denisovan ancestry was greater than my Neanderthal ancestry despite my overwhelming Homo sapien European genetic ancestry, it is equally surprising to me to learn that modern East Asians typically have more Neanderthal DNA than do modern Europeans, despite that Neanderthals were largely concentrated in Europe (though their range extended into Asia).

This is flipping weird!

According to David Reich, a geneticist at Harvard Medical School and a member of the research team, the new DNA sequence also shows that Native Americans and people from East Asia have more Neanderthal DNA, on average, than Europeans. [Source]

H. Denisova not an H. Erectus Lineage?

Both modern humans and neanderthals are believed to be human lineages of Homo heidelbergensis via Homo erectus. There is hot debate within the scientific community as to the origin of the Homo denisova species - and there is evidence that the Denisovan species is too old to be of the H. heidelbergensis lineage and that the Denisovan species of human may be a lineage of human not within the H. erectus evolutionary line (as modern humans and neanderthals are thought to be).

Friday, September 06, 2013

Southeast Asian Genetic Admixture of Denisovans with Modern Humans

In follow-up to an earlier post, this scientific lecture reports that Denisovan genetic admixture with modern humans took place in Southeast Asia.

The Mysterious Guti

The ancient Indo-European homeland has been postulated to be connected to an ancient Near Eastern people called the Guti. Interesting to me, my own deep genetic ancestry (as discovered in my ancestral DNA results from DNA Tribes) is in Sweden, where Guti is an old Swedish-Nordic name on the surface meaning "Gotlander".

The Mystery of Archaic Denisovan DNA in Me

Why am I Denisovan?

I've been a bit puzzled by my Geno 2.0 archaic hominin genetic ancestry result which reported that I have 2.3% Denisovan genetic ancestry - greater than my Neanderthal genetic ancestry which weighs in at a mere 1.9%. This particularly perplexes me in light of the fact that my autosomal genetic ancestry results indicated that I am significantly and overwhelmingly of European stock (97% - 100% in most studies). Given the overwhelming European-ness of my genetic profiles, coupled with the fact that in the scientific literature archaic Denisovan genes have been found to exist (so far) only in modern populations of Aboriginal Australians and the Melanesians of Papua New Guinea, I didn't expect to have any Denisovan ancestry.

Then comes Teutonic me, with 2.3% Denisovan genetic ancestry. As a daughter of Europe (mostly Northern and Northwestern Europe even more specifically), I expected to have much more European Neanderthal in me and no Asian-Australian Denisovan. But surprise! - I have more Denisovan than Neanderthal! So, what gives with this?

Comparable with others of primarily Celtic-Germanic ancestry (matching the modern German and British reference populations), Geno 2.0 did report that I do have some genetic ancestry admixture from Southeast Asia. Papua New Guinea, home to the Pacific Islanders known as the Melanesians, is in East Asia - so this gets me closer to an answer as to why I have Denisovan DNA.

Like some of Nordic descent, I was born with white blonde hair, though it darkened to a dark blonde as I became an adult. Though I don't have blue eyes, my father does. So, it's clear that some of my ancestors had blonde hair and blue eyes stereotypical of Nordic types.

Interestingly, like me and like some others of Nordic ancestry, blonde hair is also found in high frequency among Melanesian children - those very same children with Denisovan genes. Like me.

So, while it may be that my Homo sapiens sapiens homeland may be Europe by way of Africa and the Near East, it may also be that my Denisovan ancestry homeland is in Australia - maybe that's why so many modern Brits live and love in Australia - our ancestral folksoul (Britain is one my ancestral homelands) is tied to that land as well.

Dare to be true to yourself.