Patagonian monsters: December 2013

Thursday, December 26, 2013

Diabetes Neanderthals and modern Latinos

A paper published in Nature on Christmas titled: Sequence variants in SLC16A11 are a common risk factor for type 2 diabetes in Mexico puts forth the idea that Latin Americans share a genetic risk factor picked up from Neanderthals, which is not very common outisde of the American continent and which makes them more prone to diabetes:

Below is the keyline:

The risk haplotype carries four amino acid substitutions, all in SLC16A11; it is present at ~50% frequency in Native American samples and ~10% in east Asian, but is rare in European and African samples. Analysis of an archaic genome sequence indicated that the risk haplotype introgressed into modern humans via admixture with Neanderthals.

Once again a genetic marker linking Amerindians to Neanderthals but, unsurprisingly skipping their alleged East Asian "ancestors" who hardly share any of these key markers with American Indians. It is clear that current East Asians are not the stock that led to the peopling of America.

The paper explains why Latinos are almost twice as likely to develop Type 2 diabetes as Caucasians and African-Americans

I am working on a long article on these gentetic links and differences which I hope to post soon.

My previous post on Neanderthals and Amerindians

Saturday, December 21, 2013

Denisovans interbred with Homo Erectus

A paper published in Nature tells how a team (Prüfer, Racimo et al)sequenced the genome of a Neanderthal from Denisova and came up with some interesting findings.

Our interbreeding ancestors

The most unexpected finding results from a comparison of genomes. We, the modern African Homo Sapiens never left the continent and therefore were never in the territories occupied by Neanderthals or Denisovans. They therefore had no chance to mix with them and as a consequence, their MtDNA does not have traces of Denisovan or Neanderthal MtDNA. Any similarities between the DNA of all three comes from a common ancestor to all which should be equally distant to all. Well, it isn't.

The Denisovans have sequences that are more distant than expected. This can only be explained if the Denisovans interbred with some other population that had split from their common ancestor with modern African humans about 1 Million years ago.

The only candidate within this time frame is our old friend: Homo erectus who left Africa around that time. And this is what the team suggests: Denisovans mated with H. erectus.

Between 2.7 and 5% of their genome comes from H. erectus. Now, saying that y% of your genome comes from H. erectus means that the percentage of Denisovan's H.erectus parentage is much higher than y% because most of the genome would overlap, and maybe some lineages became extinct so we have no trace of it. How much greater than 2.7-5%? I can't say, but let's take a guess and place it at 10%.

This means that a considerable ammount of inter species intercouse took place (if the MtDNA is erectus, then the female erectus passed on their genome to hybrid offspring. So Denisovan males mated with H. erectus females.

So, did the lice of Homo erectus move from them to us directly (humans mating with erectus) or indirectly: Denisovans mated with H. erectus, got their lice and then we mated with them and caught their lice?.

Neanderthals and Denisovans split from our line about 400 kya. They split between them (Denisovans and Neanderthals) happened about 300 kya.)

So this is the current model:

Hominids appeared in Africa
A group left the continent (H. erectus)
Those that remained in Africa kept on evolving. Some left for Asia (They became Denisovans and Neanderthals)
In Asia they had sex with Homo erectus and got some if its MtDNA into its genome
Modern Humans then left Africa and bred with both Denisovans and Neanderthals, getting their MtDNA into our genome
Modern African Humans did not mix with anyone.

We already knew that Papuans and Australians had a Denisovan influx in their Genes (about 6%), now the paper mentions that Amerindians (0.2% approx.) and Asians also have Denisovan mTDNA. Which means that the modern humans who passed through Altai on their way to Western Asia also had sex with female Denisovans.

From my point of view, the fact that H.erectus survived to intermingle with Denisovans about 40 kya is amazing, and it is likely tht H. erectus or even Denisovans reached America long before the modern humans did. Perhaps a small Denisovan population interbred with H. sapiens paleoindians in the American continent and passed on their mTDNA to them there and not in Asia.

Perhaps the gene influx is even older (how about H.habilis?), see my post The first Asians were not Homo erectus.

Lets wait and see what further gene sequencing tells us.

See Supplementary information 16a on page 139. There is a lot of data if you are interested.

A Merry Christmas an a Happy new Year to all!

Sunday, December 15, 2013

On Yetis and Polar Bears

A very short post to share an article I found online about the DNA analysis of some alleged "Yeti" (abominable snow man) hairs.

Summary

The article is this one: The Yeti Comes in from the Cold.

And below is the quote:

DNA analysis of two “yeti hair” samples, one collected from the western Himalayas and one from Bhutan, has uncovered a genetic match to a species of ancient polar bear. Professor Bryan Sykes, the Oxford University geneticist who conducted the analysis by comparing the hair DNA to a polar bear jawbone found in Norway, has called the finding “exciting and completely unexpected.
The dazzling discovery raises the possibility that a mysterious beast previously unknown to science indeed roams the peaks, and not just the fevered imaginations of locals. Professor Sykes offers two alternative explanations as to how an animal living today in the Asian mountains shares its genes with a Nordic polar bear that existed between 40,000 and 120,000 years ago: the creature is possibly a sub-species of brown bear that shares a common ancestor with the polar bear, or there has been recent interbreeding between brown bears and descendants of the polar bear.

The text was not too clear. Where did the samples come from? Who provided them? So I Googled "Prof. Bryan Skyes" and turned up more data... below is from National Geographic:

One of the most promising samples that Sykes received included hairs attributed to a Yeti mummy in the northern Indian region of Ladakh; the hairs were purportedly collected by a French mountaineer who was shown the corpse 40 years ago. Another sample was a single hair that was found about a decade ago in Bhutan, some 800 miles (1,290 kilometers) away from Ladakh. According to Sykes, the DNA from these two samples matched the genetic signature of a polar bear jawbone that was found in the Norwegian Arctic in 2004. Scientists say the jawbone could be up to 120,000 years old.

That made some sense... a "Yeti mummy" and the single hair could belong to some extant descendant of this yet unknown bear species.

The match with a 120 kya jawbone may be due to the time both species split: polar bears going, well, to the North Pole and surrounding areas an the other one moving into the Himalayan glaciers.

The daily The Telegraph added:

Professor Sykes added: “This is a species that hasn’t been recorded for 40,000 years. Now, we know one of these was walking around ten years ago. And what’s interesting is that we have found this type of animal at both ends of the Himalayas. If one were to go back, there would be others still there.”
Both hairs were brownish in colour. The Ladakh remains suggested a creature that would have been around 5ft tall – shorter than the towering figure of mythology. However, Professor Sykes suggested the animal could have displayed other characteristics which would have fitted with the yeti myth.
He added: “The fact that the hunter, who had great experience of bears, thought this one was in some way unusual and was frightened of it, makes me wonder if this species of bear might behave differently. Maybe it is more aggressive, more dangerous or is more bipedal than other bears.

Comment

If true, it supports my "theory" that "Myths are based on something real". Which does not mean that the real and mythical part are identical. A dragon may not be a dragon but a large lizard, a "water bull" may actually be a deer and so on.

What counts is that a "fact", something "real" originated the myth. The key is to find the actual "real" thing. That is what cryptozoology is all about.

New, July 2014, Bryan Skyes and his team published a paper which studied different hair samples from alleged Yeti and Bigfoot, finding them to belong to extant creatures and, this archaic polar bear. I have posted on this paper that claims Bigfoot is a fake.