Submerged rock art from Papua

In the World-famous diving paradise of Raja Ampat, just West of the Bird’s Head peninsula of Papua (aka New Guinea), there is more than one of the greatest biodiversity areas of the planet. It has been found recently that off the shore of Misool, one of the major islands of the archipelago, there is also abundance of beautifully conserved Paleolithic murals.

The now submerged rock art is found in 13 different sites (so far), most of them sharing an intriguing pattern of location:

• a large and rather high cliff;
• a cavity, cave, overhang or hole around the foot of the cliff;
• a main coloured (red-yellow to red-brown) wide strip pouring out, or reaching down to the cavity;
• a (facultative) step-bank (coral or karst platform) at the foot. 

The art was obviously above the water level until the sea flooded all that area at the end of the Ice Age. 

Sources: World Archaeological Congress, Stone Pages’ Archaeonews.

Update (Feb 24): after being down for days, causing perplexity among some readers and myself, the WAC source site is up again. Exactly as it was four days ago. Just in case this time I’ll upload the images here. 

 

Extremely ancient introgression in Papuans

Melanesians

Neanderfollia mentions today[cat] new genetic research that has found unusual diversity in gene OAS1 among Papuans. They contend that this is caused by extremely old introgression that they estimate in more than three million years (more than the age of the genus Homo).

Fernando L. Méndez et al., Global genetic variation at OAS1 provides evidence of archaic admixture in Melanesian populations. Molecular Biology and Evolution 2012. Pay per view.

Abstract

Recent analysis of DNA extracted from two Eurasian forms of archaic human show that more genetic variants are shared with humans currently living in Eurasia than with anatomically modern humans in sub-Saharan Africa. While these genome-wide average measures of genetic similarity are consistent with the hypothesis of archaic admixture in Eurasia, analyses of individual loci exhibiting the signal of archaic introgression are needed to test alternative hypotheses and investigate the admixture process. Here, we provide a detailed sequence analysis of the innate immune gene, OAS1, a locus with a divergent Melanesian haplotype that is very similar to the Denisova sequence from the Altai region of Siberia. We re-sequenced a 7 kb region encompassing the OAS1 gene in 88 individuals from 6 Old World populations (San, Biaka, Mandenka, French Basque, Han Chinese, and Papua New Guineans) and discovered previously unknown and ancient genetic variation. The 5′ region of this gene has unusual patterns of diversity, including 1) higher levels of nucleotide diversity in Papuans than in sub-Saharan Africans, 2) very deep ancestry with an estimated time to the most recent common ancestor of >3 million years, and 3) a basal branching pattern with Papuan individuals on either side of the rooted network. A global geographic survey of >1500 individuals showed that the divergent Papuan haplotype is nearly restricted to populations from eastern Indonesia and Melanesia. Polymorphic sites within this haplotype are shared with the draft Denisova genome over a span of ∼90 kb and are associated with an extended block of linkage disequilibrium, supporting the hypothesis that this haplotype introgressed from an archaic source that likely lived in Eurasia.

This is what I have been arguing since December 2010: “denisovan” admixture in Australasian and SE Asian aborigines stems from Homo erectus (diverged from our line at least 1.8 Ma ago) or even maybe a most distant cousin (maybe H. floresiensis, argued by some to be more archaic than H. erectus in key elements like the wrist or toes). 

Yet I am a bit skeptic of the age estimate, because, unless the H. floresiensis australopithecine hypothesis could be confirmed, the date is out of bounds for Humankind proper and creates many conceptual challenges, which are admittedly hard to swallow. While the “australopithecine hobbit” hypothesis would fit this scenario, it remains hard to swallow that the two genus would still be inter-fertile just a few dozen millennia ago and then again, why would archaic admixture come from this remote relative and not the much closer H. erectus, which we know lived in East Asia until rather recently. 

Finally I am in general very skeptic of age estimates as such and their ability to be able to inform more than they confuse. Normally I find them too recent but the opposite (too ancient) can also happen, I imagine. They are in any case just estimates: educated guesses and nothing else.

Update:

Got a copy of the paper (thanks again) and I would say that these two figures are of special interest:

Fig. 2 – Median joining network of OAS 1 haplotypes

Fig. 3 Geographic distribution of the deep lineage in A) Old World populations and B) South East Asians and Oceanians.

I find particularly notable that the haplotype has been found at very low frequencies in South Asia and nowhere else West of Wallace Line. It can be backflow but may also be indicator about the possible location of the admixture event.

Certainly nothing seems to suggests in these or other maps (1, 2) of “Denisovan” admixture that the episode could have happened in Altai or nearby areas as some readers, stubborn proponents of obsolete migration models, have insisted on. Instead all the evidence suggests that the admixture episode happened in SE or otherwise Tropical Asia, whether deep in Indonesia or more towards the mainland is debatable indeed.

See also:

• Neanderthal gene flow found in modern humans (on Green 2010)
• Exploring the Neanderthal admixture episode (version 1)
• Denisova hominins, Neanderthals, Melanesians and so on… (on Reich 2010)
• Explaining ‘Denisovan’ and also ‘Neanderthal’ admixture: the simplest scenario (where I first hypothesize that H. erectus and also maybe a relative of Neanderthals like the Hathnora hominin, could be the actual culprits).
• Is X-DNA lineage Neanderthal?
• Denisovan admixture widespread beyond Wallace Line, non-existent elsewhere – but then:
• Minimal Denisovan admixture in SE Asians.
• ‘Denisovan’ admixture may actually be from H. erectus.