Friday, December 24, 2010

Origins of Indians: Version 8.4

Coastal Migration Theory and I:
A new paper on another archaic hominin species and their admixture in Homo Sapiens is out[2]. According to the study, hominin species labeled as 'Denisovans', remains of whom found in Siberia, were related to Neanderthals. Let me call our old friend Neanderthals as N. Euskaria and these Denisovans as N. Siberia.

A previous study found N. Euskaria admixture in all of Eurasian Sapiens but not in African Sapiens[3]. This was considered as a proof of early Sapiens meeting with N. Euskaria in middle east and their subsequent dispersal to all over the world.

Now the new study has found N. Siberia admixture in Melanesians but which supposedly missing in other Euraisans and Africans. These two studies have a bearing on my model of the northern route migration of Homo Sapiens.

Until now I have based my opposition to the coastal migration theory on two counts.
- Lack of common sense in the model considering India is a tropical country like Sapiens' original home in Africa and there was no pressing need for further migrations to SE Asia and Oceania. I have proposed that the movement thro' temperate landscape would develop the wanderlust that our ancestors have been famous for in occupying the whole of Eurasia in a quick time. They migrated in search of a tropical climate until they reached SE Asia.

- The second factor is genetic. The lack of uniparental lineage Y-Haplogroup D, associated with the coastal migration, in India and the uniform distribution of Y-Haplogroup C (which is now strangely considered as "intrusive" Ancient North Indian or not part of the original gene pool -which has been called Ancient South Indian- in a recent study[4]) cannot be overlooked. Along with the fact that India's so-called oldest mtDNA lineage M2 is mostly observed in East India. This of course gives evidence for migration from SE Asia to India (and then further into Middle East and Europe).

Probably, I need to give add one more factor or probably replace the common sense approach to more circumspect scenario.

Now we know that N. Euskaria and N. Siberia interbred with us. We also know that we don't have N. Euskaria an N. Siberia Y-Haplogroup or mtDNA lineages.  There could be two scenarios.
1. Male Sapiens and Female Neanderthal species mated and produced only fertile males and sterile females. Therefore, only Sapiens' uniparental lineage survived.
2. Female Sapiens and Male Neanderthal species mated and produced only fertile females and sterile males. Therefore, only Sapiens' uniparental lineage survived.

We really don't know whether both scenarios were in vogue or only one of them had occurred. But since both N. Euskaria and N. Siberia were Neanderthal species we could see that above two scenarios have been found consistently true.

I would propose the reason for Sapiens' rapid migration along northern route from middle east to Siberia and from there to SE Asia along western east Asia is related to the second scenario.

It has been observed that Neanderthal communities always had lower percentage of females or lacked enough females so all males could have sex and/or procreate, a situation similar to Haryanvis. It was a common practice for a Neanderthal group to abduct females[5]. In contrast the oldest Sapiens had excess females[1]. So what would happen when a Hominin with enough females meet another Hominin that has scarcity.

Evidently there was a very strong evolutionary pressure on Neanderthals to abduct Sapien females than vice versa. This had resulted in Sapiens' rapid migration from middle east to central Asia to escape from N.Euskaria. But unfortunately for them there they would meet N.Siberia who had similar evolutionary pressure since they were also a branch of Neanderthals.

So, we do see Siberia admixture among one of the Y-Haplogroup C population in Oceania, Melanesians. Since the admixture is clearly because of a species related to Neanderthals and not any Erectus branch in SE Asia,  we can say that northern route was taken by the early Sapiens.

References:
1. Estimators of the Human Effective Sex Ratio Detect Sex Biases on Different Timescales
  - Emery et al. (2010)
2.Genetic history of an archaic hominin group from Denisova Cave in Siberia
  - Reich et al (2010)
3. A Draft Sequence of the Neandertal Genome
  - Richard E Green et al. (2010)
4. Reconstructing Indian population history
  - Reich et al (2009)
5. The documentary I saw either on Discovery or National Geographic channel

3 comments:

Maju said...

"N. Euskaria"?

After googling "Euskaria" I could only find a handful of items all in Basque language, what implies that you are using this term as Indoeruopeanized form of Euskal Herria or Basque Country. However the normally and historically most common form is Vasconia, from a different non-native ethnonym (exonym probably at first).

There's no particular reason to believe that Neanderthals evolved in the modern Basque Country or near it, though it's indeed possible. Also there is no reason to consider non-sapiens hominins as a different genus ("N." - Neanderthal?)

Finally in the biological nomenclature these parts of the name are invariably produced using Latin declensions, so it'd be "Siberiensis" and "Vasconensis"/"Europaeus" or whatever...

Regardless Denisovans are as population loosely related to Neanderthals but their mtDNA makes them as distant from them as of us and likely H. erectus in this aspect. All this clearly means that Denisovans were a hybrid Erectus-Neanderthal (or Erectus-Heidelbergensis) population and not an species on their own right.

Their geographic position at the crossroads of Eastern Asia (H. erectus) and West Eurasia (H. neanderthalensis), their use of Mousterian tech, the fact that Neanderthals inhabited other caves in the same region... support this reasonable theory. But the key evidence is genetic: their mtDNA is clearly pre-Ergaster, hence Erectus.

Denisovans therefore are genetic representatives, at least in part of H. erectus, what means that the component found in Melanesians at low levels (4.8%) is signature of an Erectus introgression at about half those levels (2.4% maybe). This component is more likely to have been picked in Sundaland or otherwise in Tropical Asia than in Siberia, where no H. sapiens lived before the colonization of Australia.

The very dark pigmentation of Melanesians clearly indicate that they never lived (at least for long) in non-tropical areas. Compare with tropical Amerindians, who have completely lost the "black" (dark brown) color and can only achieve a light brown tan. This surely applies to other "black" populations of tropical Asia such as so many Indians, Andamanese, Negritos of Malaysia and Philippines...

manju said...

There's no particular reason to believe that Neanderthals evolved in the modern Basque Country or near it, though it's indeed possible. Also there is no reason to consider non-sapiens hominins as a different genus ("N." - Neanderthal?)

Let's say what's there in a name. I just wanted to make Neanderthal east/west distinction. No, I'm not referring to separate genus..they are subspecies (of subspecies ...maybe).

But the key evidence is genetic: their mtDNA is clearly pre-Ergaster, hence Erectus.
Well, until a new study declares it so, I don't have any reason to think Denisovans are hybrids.

Maju said...

It's evident. We're only missing direct comparison with some H. erectus mtDNA and/or nuclear DNA.