Human evolution: adaptations to agriculture?

[ttlaitin]

evidence that implies humans have adapted (to a some degree) to handle carbs/straches/wheat during the last 60,000 years.

however, several of these adaptations are only present in non-Africans.



Humans are evolving to resist disease

Evidence that humans will evolve to shrug off diseases such as type 2 diabetes and obesity has emerged.

A survey of the human genetic code has shown that our resistance to malaria, diabetes and other diseases is changing in response to our environment.

Dr Lluís Quintana-Murci of the Institut Pasteur, Paris, and colleagues analysed more than 2.8 million single letter spelling mistakes in the human genetic code to distinguish the usual random changes over the last 60,000 years from those that seem to be occurring in response to the environment, when a genetic mutation gives people an advantage over their peers.
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People are surprisingly similar at the DNA level and the work "abolishes the idea of race" he says.

But when it comes to the few differences, those showing the strongest signature of this effect, called positive selection, are involved in skin pigmentation and hair development, as is already obvious from how white people live in darker climates. "You do not need genetics to know this, but it shows our method works."

In the journal Nature Genetics the team reports that several traits are sometimes linked to the same gene, so that when people in the Far East evolved a different version of a gene called EDAR to sweat differently, the same gene gave them much denser hair and changed their teeth too, an effect he calls "hitchhiking."

Genes that protect against disease are also evolving. For example, one called CR1 helps to cut the severity of malaria attacks and is now present in eight Africans in every ten, yet is absent elsewhere, a novel finding.

Several genes, such as ENPP1, are involved in the regulation of the hormone insulin and in metabolic syndrome - a combination of adult diabetes and obesity. These are present in 90 per cent of non-Africans and their relative absence could explain why African Americans are particularly at risk of obesity and high blood pressure.

The work suggests they are adapted to an African environment and have not adapted to an American lifestyle. "They have not had the time to readapt," says Dr Quintana-Murci.

Prof Steve Jones of University College London comments: "They have shown that man was once more like other animals than we might like to imagine, for Nature imposed her rules on us in the same way as she did on rats or flies.

"There are three great eras of history; the age of disaster, when we were killed by cold or sabre-toothed tigers, the age of disease - the epidemics which began with farming - and the age of decay, in which most of the developed world now lives, and dies of old age.

"DNA now shows how much we were moulded by the force of natural selection during first two; but my guess is that in future, now that we nearly all survive for long enough to pass on our genes, much less will happen. Perhaps you can ask me again in ten thousand years."

An earlier study by a team led by University of Wisconsin-Madison anthropologist Prof John Hawks suggested that humankind has evolved more rapidly in the past 5,000 years, at a rate roughly 100 times higher than any other period of human evolution.

This work counters a common theory that human evolution has slowed to a crawl or even stopped in modern humans, since in modern society the survivors no longer have to be the fittest.

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/02/05/scievol105.xml


Here's another article about the same study: Team Uncovers New Evidence of Recent Human Evolution (http://sciencenow.sciencemag.org/cgi/content/full/2008/204/2)

[M Levac]

So they found the thrifty gene. I wonder if they also found the stupid gene.

[tom sawyer]

Never thought about the possibility that we might never adapt to a high carb diet. I had always thought that it was possible that some cultures (or even women who were more often the gatherers in the tribal division of labor) might be more adapted to carbs than groups with less exposure. But it would seem that the result of carb consumption is delayed past reproductive times and so would have minimal effect on the passing of necessary genes. This is unlike milk consumption where we need the enzymes during breast feeding, and cultures who were shepherds might continue to produce the enzymes after infancy.

How this is some kind of insightful research, is beyond me. Nature usually publishes only the best research, I don't see this being some breakthrough result though.

[Zei]

Maybe they mean all the high-carb eaters with diabetes will die from it and not pass on their genes? Nope. That won't work. You don't start getting the bad health from diabetes until your reproductcive years are over. So I just warn my grown kids they're likely carrying dad and my genetic tendency toward diabetes and to take some serious thought about reducing carbs.

[Nancy LC]

I think Europeans do a bit better on high carb than say... native Americans. The native Americans really, really get sick quickly, the Europeans last a bit longer.

But, like Tom was saying, I don't know that natural selection could help us out here since carbs kill so slowly. It only works if you die before you reproduce (or have children that can reproduce). Or if it keeps you from reproducing, which it does sometimes (PCOS).

[Wifezilla]

I think I figured out why the American government promotes carby eating....

We still live long enough to produce a new generation of tax payers, but we die quicker and save them social security money.

[ReginaW]

Maybe they mean all the high-carb eaters with diabetes will die from it and not pass on their genes? Nope. That won't work. You don't start getting the bad health from diabetes until your reproductcive years are over. So I just warn my grown kids they're likely carrying dad and my genetic tendency toward diabetes and to take some serious thought about reducing carbs.

Such happens over generations, with each being less able to reproduce earlier....and there may be indicators we're seeing it - we're begining to see type II in children as young as three, symptoms of metabolic syndrome are present in an estimated 10% of teens, an estimated 10% of girls have PCOS (often rendering them infertile), and the estimates of insulin resistance in children is down-right scary - some 25% of children already have insulin resistance to some degree, which is highly correlated with infertility in adults as insulin at high levels interferes with reproductive hormones, throwing them out of balance to enable conception and ongoing pregnancy.

[Dodger]

Such happens over generations, with each being less able to reproduce earlier....and there may be indicators we're seeing it - we're begining to see type II in children as young as three, symptoms of metabolic syndrome are present in an estimated 10% of teens, an estimated 10% of girls have PCOS (often rendering them infertile), and the estimates of insulin resistance in children is down-right scary - some 25% of children already have insulin resistance to some degree, which is highly correlated with infertility in adults as insulin at high levels interferes with reproductive hormones, throwing them out of balance to enable conception and ongoing pregnancy.One goal of the medical system is to keep the people who have a problem with the carbs alive as long as possible, hence delaying the genetic adaptation. That will work until the number to be treated exceeds the capacity to treat them.