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Is the Human Species in Evolution's Fast Lane? -A Galaxy Classic

Shutterstock_52302401 "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 new 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 estimates 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.

Related Galaxy posts:

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

Comments

Would things like the use of orthopedic aids, hearing aids, eyeglasses, pacemakers & similar devices affect human evolution ?

People that would not have been allowed to breed or able to breed at one time because they were too weak, too small, disabled, ( such as myself ) etc., are now able to pass their genetic material on to other generations.

It's just a thought.

Well reasoned idea...but....not quite correct on the timescale we are talking about. Every defect you mentioned would take several thousands of generations to even begin to show a marked preference to de-select them. We are talking about hundreds of thousands of years here, no matter what John Hawks thinks.

To Daniel- not enough is known to say for sure, one way or another, that your timescale is any more accurate than Hawks'. Evolution doesn't have a standard bearer. It's irrelevant to say his theories are bunk just because MOST evolution takes longer. Humans are unique in that our "herd" has the ability (via airplanes, boats, cars) to procreate with people all over the world, thus creating a gene pool of magnificent variety.

Hollywood Riot, I don't think it's a question of which idea is more "accurate". Hawks is talking the last five thousand years. Which is still very recent. But the amount of time we've had hearing aids and eyeglasses is only in the hundreds of years or less.

So I'm assuming the ideas from 'Daniel' above, wouldn't be incompatible with Hawks theory.

It might be arguable whether Hawk's civilization has affected evolution but I would think it's extremely unlikely that "modern technological civilization" has had a chance to shape evolution yet.

Who the hell is Scott Maxwell and why is he using my name? I am Scott Maxwell....I feel like I am in a science fiction movie.....my friends call me about a post which I did not make. Call me Scott....we have to work this name duplication out.

Scott

& various vaccines & drugs would affect evolution, too. We don't have cultures like the Spartans anymore who believed in " thinning the herd " of people who couldn't make positive contributions to the society. Maybe a few Stone Age tribes in SE Asia & the Pacific do it, & China has a custom of aborting " superfluous " children, especially females, but it's not so prevalent anymore.

" Modern Technological civilization " is having something of an impact, although it's not felt in the genetic pool just yet.
Look up " Transhumanism " - the people that write about say that humanity began to change in subtle ways when we stopped being hunter -gatherers, using fire, domesticating animals, developing languages, etc., not just designing & building prostheses, crutches as well as rockets & computers.

If this is adapted from another article, why isn't their a link to said article?

And let's not forget sexual selection, you may not be eaten by a sabertooth anymore, but if you're always turned down at the disco, the results are the same as far as natural selection is concerned...

Whaat a joke!

The Alternate Spiritual Community has knownthis for at least a decade, but now that PhDs have caught up, we're supposed to believe it.

The PhDs don't even know the details, and can't or wont even tell you how.

See: Indigo and/or Crystal Children.

Did lyou think that Homo Sapiens Sapiens was the last of the line? If it is, then, we hit a dead end and were doomed. But we've got children now that can be called "Homo Stellaris

Evolution goes on. Always.

Yet, the scientists & tptb, & the communities and parents, are scared to death of these brilliant children, who are bored with the schooling, that passes now for "education"?- so drugs them into oblivion.

And the "Future of the Human Species," our priceless children, are sent to endless wars, to die, or come back maimed in body and mentally. This in turn, devolves the Human Species back.

Perhaps, after all, the tptb, know what they're doing in their petty wars, and poisoning of the food and air and water. Since then, there won't be anybody to take power away from the Elite.

Interesting information, presented in a concise manner.
I'll check back often for more.
Thanks for sharing this.

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