The Past 5,000 Years Mark a New Epoch in Human Evolution (The Weekend Feature)
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October 17, 2009

The Past 5,000 Years Mark a New Epoch in Human Evolution (The Weekend Feature)


Shutterstock_4160650"We are more different genetically from people living 5,000 years ago than they were different from Neanderthals."

John Hawks -University of Wisconsin anthropologist

In a fascinating discovery that counters a common theory that human evolution has slowed to a crawl or even stopped in modern humans, a study examining data from an international genomics project describes the past 40,000 years as a time of supercharged evolutionary change, driven by exponential population growth and cultural shifts.

The findings may lead to a very broad rethinking of human evolution, especially in the view that modern culture has essentially relaxed the need for physical genetic changes in humans to improve survival.

A team led by University of Wisconsin-Madison anthropologist John Hawks estimated that positive selection just in the past 5,000 years alone -dating back to the Stone Age - has occurred at a rate roughly 100 times higher than any other period of human evolution. Many of the new genetic adjustments are occurring around changes in the human diet brought on by the advent of agriculture, and resistance to epidemic diseases that became major killers after the growth of human civilizations.

"In evolutionary terms, cultures that grow slowly are at a disadvantage, but the massive growth of human populations has led to far more genetic mutations," says Hawks. "And every mutation that is advantageous to people has a chance of being selected and driven toward fixation. What we are catching is an exceptional time."

While the correlation between population size and natural selection is nothing new - it was a core premise of Charles Darwin, Hawks says - the ability to bring quantifiable evidence to the table is a new and exciting outgrowth of the Human Genome Project.

In the hunt for recent genetic variation in the genome map the project has cataloged the individual differences in DNA called single nucleotide polymorphisms (SNPs). The project has mapped roughly 4 million of the estimated 10 million SNPs in the human genome. Hawks' research focuses on a phenomenon called linkage disequilibrium (LD). These are places on the genome where genetic variations are occurring more often than can be accounted for by chance, usually because these changes are affording some kind of selection advantage.

The researchers identify recent genetic change by finding long blocks of DNA base pairs that are connected. Because human DNA is constantly being reshuffled through recombination, a long, uninterrupted segment of LD is usually evidence of positive selection. Linkage disequilibrium decays quickly as recombination occurs across many generations, so finding these uninterrupted segments is strong evidence of recent adaptation, Hawks says.

Employing this test, the researchers found evidence of recent selection on approximately 1,800 genes, or 7 percent of all human genes.

This finding runs counter to conventional wisdom in many ways, Hawks says. For example, there's a strong record of skeletal changes that clearly show people became physically smaller, and their brains and teeth are also smaller. This is generally seen as a sign of relaxed selection - that size and strength are no longer key to survival.

But other pathways for evolution have opened, Hawks says, and genetic changes are now being driven by major changes in human culture. One good example is lactase, the gene that helps people digest milk. This gene normally declines and stops activity about the time one becomes a teenager, Hawks says. But northern Europeans developed a variation of the gene that allowed them to drink milk their whole lives - a relatively new adaptation that is directly tied to the advance of domestic farming and use of milk as an agricultural product.

The biggest new pathway for selection relates to disease resistance, Hawks says. As people starting living in much larger groups and settling in one place roughly 10,000 years ago, epidemic diseases such as malaria, smallpox and cholera began to dramatically shift mortality patterns in people. Malaria is one of the clearest examples, Hawks says, given that there are now more than two dozen identified genetic adaptations that relate to malaria resistance, including an entirely new blood type known as the Duffy blood type.

Another recently discovered gene, CCR5, originated about 4,000 years ago and now exists in about 10 percent of the European population. It was discovered recently because it makes people resistant to HIV/AIDS. But its original value might have come from obstructing the pathway for smallpox.

"There are many things under selection that are making it harder for pathogens to kill us," Hawks says.

Population growth is making all of this change occur much faster, Hawks says, giving a tribute to Charles Darwin. When Darwin wrote in "Origin of the Species" about challenges in animal breeding, he always emphasized that herd size "is of the highest importance for success" because large populations have more genetic variation, Hawks says.

The parallel to humans is obvious: The human population has grown from a few million people 10,000 years ago to about 200 million people at A.D. 0, to 600 million people in the year 1700, to more than 6.5 billion today. Prior to these times, the population was so small for so long that positive selection occurred at a glacial pace, Hawks says.

"What's really amazing about humans," Hawks continued, "that is not true with most other species, is that for a long time we were just a little ape species in one corner of Africa, and weren't genetically sampling anything like the potential we have now."

The recent changes are especially striking.

"Five thousand years is such a small sliver of time - it's 100 to 200 generations ago. That's how long it's been since some of these genes originated, and today they are in 30 or 40 percent of people because they've had such an advantage. It's like 'invasion of the body snatchers.'"

The Wisconsin study is published in the Dec. 10 issue of the Proceedings of the National Academy of Sciences.

Posted by Casey Kazan with Josh Hill. Adapted from a University of Wisconsin release.

Recommended posts:

Stephen Hawking: Have Humans Entered a New Stage of Evolution? 

Bringing Ancient Human Viruses Back to Life: A Jurassic Park or Salvation?
Loren Eiseley on Evolution: Transcending the Cosmos -A Galaxy Insight

Comments


Cool and nice article , but what does it means ???

These guys expert of the so called "human genoma" have mapped various and extensive samples , OK.

BUT what are the spiral sectors of the DNA relating to the acquired-developed & society induced intelligence ?????

And more how many samples thay have of DNA of the men of 5 K Years agò ???
5 or 6 ??

IF so what kind of statistics is theirs ????

On what facts and proof they talks about human genoma's massive evolution in the last 5KY ?????
INFERENCE ????? Deductive reasoning ????

Genoma and inherited factors are estimated to represent some 30% of human intelligence (or less) as a whole of sapiens-sapiens (us modern men).

Human intelligence is mostly developed and NOT inherired...expecially in modern societies.

So what the study means in practical terms ?? That our genoma is much different from that of ancient egyptians or sumerian that lived some 4 to 5 KYears before us ??? NOT credible or totally wrong.

What are the differences in term of Human genoma between the brain of Einstein (samples as known are available) and that of a normal country side farmer ?????

These guys study genomas as if this is the explanation of the men intelligence : WRONG.

Nice article and well assembled but highly disputable theory.

regards

Actually, if you consider the fact that they have lots of remains from mummies in egypt and across the middle east, and mass graves from the same time period, they probably have tons of DNA from people 5000 years ago.

I would also like to point out that its Genome and Genomes not genoma and genomas

I think you missed the point; they are not talking about intelligence, therefore studying the genetic differences between Einstein and farmers is irrelevant to their study. As an aside, you assume farmers are idiots, and this may well not be the case.

What they ARE talking about is measuring the proportion of the genome which has changed in recent times (~4000 years), compared to humans in periods prior to this. They don't go into much detail, as this is an article, NOT a scientific paper, but they do say that the rate of change is 100-fold higher than previous eras. Plus they put the proportion of human genome containing new mutations at 7%. while that 7% may not account for a full 7% of 'new' or adapted genes, it is a large proportion of the genome to have changed (& been retained) in such a relatively short time span of human history.

As for intelligence, I didn't spot them talking about that (maybe I missed it?), but they do talk about tangible genes such as those giving resistance to diseases, which are usually less complex in terms of the number of genes involved and their interactions to give a phenotype. Intelligence is an extremely complex trait that likely involves many genes, and is, as you point out, not completely heritable.

Just a brief point to summarise; read the article, but if you're going to take the time to try to dissect the original researchers work, then firstly actually read their paper. Secondly, don't suggest they should have been studying something else entirely, intelligence in this case obviously wasn't something they were studying. If you've got brilliant ideas, do the research & publish it yourself!

The fotoes documented by Eric von Daniken , still can't be refuted by paleontologist; they are pix of human footprints side-by-side with dinosaur footprints. Mr von Daniken doesn't believe in evolution theory (at the time when he wrote his book) but the the earth had been visited by ET aliens.
Unfortunately the riverbed in Texas that had those footprints has been erased but those footprints had been confirmed to have existed.

Fascinating stuff... but wouldn't all of this fall under Micro-evolution vs. Macro-evolution (?)

What a great big steaming pile of BS. Of course, when the population increases genetic mutations increase. Whether these changes are beneficial or not is not revealed until a bottleneck is encountered which serves to separate the wheat from the chaff.

Such a bottleneck is approaching (it is inevitable) and it will involve a reduction of the human population on the order of 75 - 90%. While such a reduction will remove the bad mutations and preserve the good mutations the Earth which the good mutations shall inherit won't serve to preserve the species from extinction.

When a species destroys its only home it brings extinction upon its own head. Humankind happens to be the last remaining member of an extinction-prone family (which explains why it was possible for our ancestors to claim separation from the nest of nature) and there isn't any reason to imagine that humankind is immune from extinction.

Whereas circumstance brought about the extinctions of humankind's ancestors, humankind's own foolish activity will bear responsibility for humankind's extinction. Resource depletion, toxins in the environment, global warming, the destruction of entire ecological niches ... these are the sorts of damage which will serve to make life impossible for whatever remnant of humankind still remains in the years ahead.

Nature will recover from all of these damages, of course, as Nature always has recovered from catastrophes. Unfortunately the time involved in Nature's recovery greatly exceeds the time available for humankind's survival. This is very much like dying from an incurable disease before medical science can succeed in inventing a cure.

Fascinating article. I often wonder if this could relate to what some term the "indigo children", extremely intelligent and emotionally sensitive kids that are allegedly being born to the current generation.

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What a load of nonsense. Remember when we were mostly 'junk genes' and now they're not so sure? Well, they STILL don't know anything about us, yet we're supposed to believe that all the kinks have been figured out, not just on humans, but humans 5000yrs and neanderthals. Nice try!
I'll take bets that this guy is in favour of population control/reduction. Think that's a strange leap? Listen to Alan Watt and look up eugenics.

I'm just curious, why do the commenters on this blog seem to be so much pissier and hacked off at every post than on other blogs. I really don't understand it.


"JUNK DNA" is anything BUT junk...It controls various aspects of genes (such as switching them on or off). Dont attempt to debunk a subject you know nothing about.


The CCR5 gene actually exists in all humans. It is a specific variant of the gene, CCR-delta32, that gives resistance to R5 HIV-1 infection. Also, the gene underwent selection pressure (that made it more common) more than 5000 years, as discussed in the following article:
P.C. Sabeti et al., The case for selection at CCR5-Delta32, PLoS Biol. 3 (2005)

Charles Darwin was a very important man in the history of science.

"JUNK DNA" is anything BUT junk...It controls various aspects of genes (such as switching them on or off). Dont attempt to debunk a subject you know nothing about.

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.It controls various aspects of genes (such as switching them on or off).

A very good post ,I like it very much ,hope you will give another post asap

nteresting. I wonder how that intertwines with the study showing that people prefer equality in incomes

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