...because they die!!!!. I got to thinking about this when I saw this article titled Leaving the Wild, and Rather Liking the Change, about the emergence of an isolated tribal population into the Columbian mainstream. This caught my eye:
Though it is unclear how big the Nukak population once was, anthropologists believe that what little contact the Nukak have had with outsiders has most likely left them reduced by Western diseases, including influenza and the common cold, to which they have no natural defenses.
Read 1491 by Charles C. Mann, and you'll see that unfortunately the decimation of Amazonia is simply an epitaph of a long process that began with the arrival of Eurasian peoples. In fact, Mann appeals to recent archeological finds to suggest that the Amazon might have been more densely populated than it is today, and that it was plague which reduced the human presence until the region was "pristine."
About a month ago I read Land of the Naked People by Madhusree Mukerjee, which chronicles the author's encounters with the natives of the Andaman Islands. It was a difficult read, even discounting the painful patronizing tendencies of the author. The fact is that Indians, South Asian immigrants, are killing the Andaman Islanders with contact. The native peoples simply do not have the immunological defenses to deal with a group of people who have spent thousands of years being sifted through the brutal selective cauldron of the Eurasian pathogen pool. Western visitors to India often have to take cocktails just to not become ill, imagine how people who have been relatively isolated for nearly 30,000 years react!
The author notes that the natives of Nortn Sentinal Island, which is quarantined by the will of the Indian government and the hostility of the inhabitants seem taller than other residents of the archipelago. I don't think that there is a genetic reason for this, I suspect that they are simply healthier and so develop their full height without their body being swarmed by powerful pathogens. Additionally, the Andaman Islanders, like many traditional peoples, do not take well to the alcohol and carbohydrate diets introduced in regards to their health, though they relish them from an epicurean vantage.
I've discussed MHC before, and this is probably an issue for many native peoples. A week ago I was skimming through Evolutionary Genetics: from molecules to morphology, and I stumbled upon this in the chapter on MHC:
...in isolated populations...there has been selection even in the current generations... in the Havasupai, there is a statistically significant deficiency of homozygotes at both the HLA-A and the HLA-B loci, and average of 25.8% over the two loci...other nonselective factors...do not appear to be the cause of this deviation from Hardy-Weinberg proportions.
In short, these populations that are depauperate for HLA polymorphism in the first place and are now placed in the midst of immunologically more fit people are moving through the Neo-Darwinian gauntlet. We aren't talking selection coefficients of a percent or two, we're talking powerful biases which are resulting in massive heterozygote advantage (because most populations are very polymorphic heterozygosity is the norm, only in very homogenous groups is homozygosity a large issue). Reality is known to have a heartless bias.
- Log in to post comments
Won't that make them primitive forever?
Won't that make them primitive forever?
well, i guess dead is forever, huh....
I get the impression that plagues are no longer an issue in previously isolated peoples who have been non-isolated for a long time. The populations of native Americans (even "pure breds") and Australian aboriginals have been increasing for some time now.
How'd that happen?
The populations of native Americans (even "pure breds") and Australian aboriginals have been increasing for some time now.
How'd that happen?
1) "sometime" = within the last century or so. i know this is true for native americans, 1900 was the turning point.
2) well, there aren't really that many "pure bred" native americans. i believe about 1/4 of those who have tribal cards.
3) interbreeding can give you "good alleles." even "pure" indgenes in places like peru or deepest guatemala seem to have something like 5% european genes. that's enough that selection could drive the new alleles up.
4) remember, the last century. public health matters. a vulnerable immune system can be helped a lot by vaccination campaigns.
5) which is the issue re: plagues, in the andamans plague isn't a problem, the common cold is. they can be innoculated against the "big" problems that everyone has to deal with, but what about a population that needs a super weak flu shot that isn't manufactured by anyone?
well, there aren't really that many "pure bred" native americans. i believe about 1/4 of those who have tribal cards
But I think there are specific tribes where it's much higher.
However, points 3 and 4 might suggest some solutions for the Andamans.
Has anyone studied the relative frequencies of European alleles in native American populations? It would be very interesting to see which are being selected for.
Has anyone studied the relative frequencies of European alleles in native American populations? It would be very interesting to see which are being selected for.
greg has suggested that some amerindian natives in guyana are now malaria resistent. that sure isn't indigenous.
some amerindian natives in guyana are now malaria resistent. that sure isn't indigenous
That's interesting, but I was suggesting beginning at the gene-end. If we see an average of 5% European alleles in some population, but a particular allele is at 25% in that population, I think that would be interesting, as it is a very clear indication of very recent selection. It could also shed some light on what happened in 1492.
Only peripherally related, but Amazonia is really terribly fertile from an agricultural point of view. Heavy rains leach minerals from the soil, and constant warm temperatures and dampness foster enormous insect and bacteria populations which destroy both crops and humus. Temperate climates have a shorter growing season, but the winter die-off of pests and the more moderate rainfall are both very good things. (And the long freeze stores moisture for the spring planting, which in well-drained soils is a big plus too.)
Here's my 2002 interview with George Weber, the founder of the Andaman Society that works to save the pygmy negritos of the Andaman Islands, including the uncontacted ones of North Sentinel Island.
http://www.isteve.com/Andamanese.htm
Earlier this year, two Indian fishermen fell asleep drunk in their boat and were washed up on their boat. The natives immediately killed them.
If I recall correctly, that was the island where the Indian government knew the population had survived the tsunami... because when they flew a helicopter over, they got spears chucked at them.
What about amerindians from Peru, Bolivia, Guatemala, there are millions of full blooded amerindians there?
And what abou the 10% of amerindians who survived the diseases brought by the europeans? Why did they survive?
After all modern amerindians descend from them.
What about amerindians from Peru, Bolivia, Guatemala, there are millions of full blooded amerindians there?
a) the population density was higher to begin with.
b) the europeans had documented problems replacing natives at high altitudes. e.g., spanish women miscarred at extremely high rates above a certain elevation.
And what abou the 10% of amerindians who survived the diseases brought by the europeans? Why did they survive?
After all modern amerindians descend from them.
a) any population (usually) has genetic variation. so some of the natives were presumably more immunologically prepared than others. this just like insects developing resistance to pesticide.
b) the introduction of even a few genes from eurasians* can spread very fast via positive selection. the amerindians of the modern period are likely not 'pure' in their blood, even if overwhelmingly amerindian.
* an example might be resistance to malaria in the guyanas. clearly malaria is a eurasian disease, and theyr probably acquired resistance from intermarriage wtih africans (likely 'bush negros').
any population (usually) has genetic variation. so some of the natives were presumably more immunologically prepared than others. this just like insects developing resistance to pesticide.
But you implied that resistance to malaria and other diseases must have been picked up via interbreeding, as opposed to selection for those Amerinds whose genes rendered them immune?
It seems that the native population of the Americas would have one of the smaller gene pools of any large population, having all apparently descended from a rather small population that crossed the Bering Strait just 12,000 years ago. That could be another reason why Eurasian pathogens were so universally effective.