Human Evolutionary Change 100 Times Higher in Past 5,000 Years (Today's Most Popular)
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August 13, 2013

Human Evolutionary Change 100 Times Higher in Past 5,000 Years (Today's Most Popular)

 

           Are-your-footprints-ape-like_68200_600x450


"We are more different genetically from people living 5,000 years ago than they were different from Neanderthals," according to John Hawks -University of Wisconsin anthropologist. "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.'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."

In a finding that countered 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.

In 2007, 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. Hawks is Professor of Anthropology at the University of Wisconsin—Madison and Associate Chair of Anthropology, a Howard Hughes Medical Institute (HHMI) Faculty Fellow, and an associate member of both the Department of Zoology and the J. F. Crow Institute for the Study of Evolution. Many of the new genetic adjustments, Hawks observes, 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.

The Wisconsin study was published the Proceedings of the National Academy of Sciences.

The Daily Galaxy via University of Wisconsin and http://johnhawks.net/weblog/hawks/hawks.html

Image credit: http://images.nationalgeographic.com/wpf/media-live/photos/000/682/overrides/are-your-footprints-ape-like_68200_600x450.jpg

Comments

I've been pointing up since the '80s how humans have been changing more quickly than most people think. I was generally laughed off at the time, and now it turns out that I was right.

One doesn't need to be a geneticist to see that racial characteristics of homogenous populations have morphed in the past century. All it takes is a good look at the faces of those populations in photographs from those early days of photography, compared to photographs now.

People are too willing to let "logic" overrule the evidence of their own senses, and so often "logic" has turned out to be both flawed and wrong.

Good comments Bob. There are too many people out there whose attitude is "My mind is made up; don't confuse me with the facts."
That being said, advances in food production, better hygiene and medical skills have allowed the population to expand at an alarming scale which is protection against a massive reduction in the population due to a single pathogen.
Considering this diversity seems to be expanding on a logarithmic scale, it will be interesting to watch the changes in the genome of the next 200 years.

I agree that the mutation is in fact faster than it was in the past, however I submit a mutation to this theory. The evolution is still hampered by the fact that we are humans. If the same population explosion happened to, say Iguanas, the evolution would be unimpeded. Being that we are human puts a wrench in the process. Since humans have a habit of being moral and ingenuitive, they tend to find ways for human all genetic information which would not be limited to the fittest, (survival of the fittest), to be passed on. I am not saying it is wrong, I am just saying it is. An example of this would be a friend of mine, who we will call her Alice. Alice had FFI (Fatal familial insomnia). This is a fatal genetic disease that can kill you. She fell in love got married, had a child. Alice, at the age of 23, passed away. Thanks to us being human, Alice lived long enough to pass on her genetic information which does not necessarily be the best for the species as natural selection had intended.

I've always been interested in changes to neural pathways that may help us cope with technology advancing the way it has. I appreciate that technology being as recent as it is will probably not show up yet in genome studies but surely one would think that as we move from the real to the virtual world; that this new environment would be a cause for adaptation?

Hawks says there is a strong record of skeletal changes. He says our brains are smaller. Now i know what happened to me.

Over dinosaur population causes its extinction. And after millions of years later intelligent (we claim) humans evolved. Now human population is 100s of times greater than then finosaur population and thus we too in the verge of extinction. Some other species would evolve which would be more intelligent than us. I think this is the cycle on the earth until earth extinction.

If the world was populated by Iguanas and not by bipedal homo sapiens, the world would be a much different place. Iguana evolution began to accelerate some 4,000 years ago (some 400 to 600 generations ago; Iguana years). In the beginning of Iguana evolution when Iguana-kind developed in the Galapagos with a paltry number of Neanderthalgans of 5,000 some 40,000 years ago. The population of Iguana-kind number is 6.5 billion. It proven that the population of Iguanas will reach 12 billion by the end of this century. Charlie Darwin, the famed Iguana evolutionist stated in his treaty of Evolution of a species, studying lower primates is Africa, stated that humans as a lower class of primates may have the chance to evolve into something; what that something is he did not know.

So does this mean there is hope?

***I've always been interested in changes to neural pathways that may help us cope with technology advancing the way it has. I appreciate that technology being as recent as it is will probably not show up yet in genome studies but surely one would think that as we move from the real to the virtual world; that this new environment would be a cause for adaptation?***

@ Terry,

Actually, the current trends in developed countries is for negative selection on intelligence. That is because the most educated women tend to have fewer children.

The opposite was the case though previously and there are examples where selection could have lead to increased population cognitive ability. Economist Greg Clark has discussed an example in the case of England before the Industrial Revolution and Steve Hsu also cites an example in the post below.

http://infoproc.blogspot.co.nz/2011/08/demography-and-fast-evolution.html

I am not saying there hasn't been any evolutionary changes. Most have have minor changes in their genes. But ingesting foods we didn't evolve on around 10,000 to 20,000 years ago is a recipe for disease. Most illnesses are from our own immune system attacking itself from eating processed foods. Even our beta cells are attacked from our own enzymes after drinking cow's milk. Most Alzheimers' cases are correlated with sugar destroying Hippocampal cells and etc and etc...


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