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Human Evolution Accelerating
Researchers estimate evolution now 100 times faster than before
Serena Gebert (Serena)     Email Article  Print Article 
Published 2009-10-16 12:45 (KST)   
Researchers now think that human evolution is accelerating, contrary to popular belief, according to new scholars at the University of Wisconsin.

A team of anthropologists at the Madison campus, headed by John Hawks, found that humans have actually evolved at a rate 100 times faster in the last 5,000 years than ever before.

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Shrinking bodies and brains, were not signs of slowed evolution, they said. Instead this evolutionary change tells us size and physical power are no longer necessary to survive.

Previous theories that human evolution had slowed or stopped were based on the ideas that it is now easier to find food, humans lack predators, and have no competitors.

Hawks counters these theories, arguing that natural selection has actually intensified. Not only is the environment different, but the priorities have changed as well. What is important now may not have been a concern thousands of years ago.

Living in cities has exposed us to pathogens and diseases that didn't exist before, and humans have evolved new kinds of resistance.

"Disease is the number one cause of evolution today," said Hawks.
Thus, advantageous traits now are very different than they were just 300 years ago. Reproduction is important now, whereas in the past survival was the most important quality.

The technical definition of evolution is a change in gene frequencies over time. Using the human genome project, Hawks has been able to look at genes that are increasing in frequency because of natural selection.

"If gene frequencies are changing at a particular rate that's a natural measurement of how fast evolution is happening," said Hawks. "But if we look across the genome there are lots of genes and different genes are responding to different forces. So some of them might be evolving fast, some might be evolving slowly, and some probably aren't changing at all."

Hawks said that there are around 3,000 genes currently undergoing evolution in humans. The majority are involved in pathogen defense, immune system responses, and diet adaptations.

One such genetic change allows us to drink milk. This change involves the body's production of lactase, the enzyme used to digest milk. The gene that produces lactase usually languishes after childhood since milk is no longer needed. But Europeans have a genetic variation that allows lactase to be made throughout a person's entire lifetime. This variation has only been present in humans for the last 10,000 years -- around the time humans shifted from hunters and gatherers to agriculture.

Evolutionary changes also help humans resist disease. Only in the last 5,000 years have some populations developed malaria resistance, for example.

A specific evolutionary change Hawks studies is hair in human's ears as an example of evolutionary change. The hairs, or cilia, in the ear vibrate to send signals to the brain about duration, intensity and frequency of sounds.

"Hairs in the ear have been changing in humans for around the last 15,000 years," he said. "But language didn't originate 15 or 20 thousand years ago, we've been talking for a long time. This is probably that humans are getting better at hearing. They're put into situations where they're hearing different people... more voices at a time and having to learn at an earlier age. Language is a complex adaptation. It's hard to make all the genetic changes that are necessary and we still have the potential of getting better at it."

Hawk said exponential human population growth has also accelerated the evolutionary process, as bigger populations have more opportunity for genetic variation and natural selection.

Since 0 A.D., the global human population grew from about 200 million to more than 6.5 billion in the most recent count. Along with this population growth comes change in environment.

"Why does a species evolve?" Hawks asked. "It evolves because its environment doesn't fit it very well. You can adapt or become extinct."

So why does the research show we are evolving at a faster rate, when only four or five years ago human evolution was thought to have stopped?

"[This research was] not possible until the last two or three years," Hawks said. "It's really been a marked shift in the availability of information about our genetic variation. The human genome project outlined what one person's genome looked like. It turns out to be really easy to use for our purposes... what happened to genes in the past so that's been really important. There is one element that could not have been done [before the genome project] and one theoretical element that could have been done but wasn't."

Despite these advances, Hawks was wary of drawing any conclusions about the future.

"It's impossible to predict," Hawks said.
©2009 OhmyNews
Other articles by reporter Serena Gebert

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