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Are We Still Evolving?

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In this Spotlight, we ask whether modern humans are still evolving or whether we have stepped out of the path of natural selection.

Charles Darwin published his totemic work on evolution — On the Origin of Species — in 1859.

Based on the concept of natural selection, Darwin’s book provided scientists with a new toolkit for understanding the place that humans and animals occupy in the natural world.

The tome also gave clues as to where their earthly origins may lie.

According to Darwin’s thesis, evolution is slow and incremental with tiny genetic changes spread tens of thousands of years apart gently pushing forward changes in species.

In 2000, the paleontologist Stephen Jay Gould famously declared that “there’s been no biological change in humans in 40,000 or 50,000 years,” suggesting that evolution in humans is imperceptibly slow or has perhaps stopped altogether.

The British naturalist and broadcaster Sir David Attenborough concurred, even arguing that birth control and abortion have contributed to a halt in physical evolution among humans.

“We stopped natural selection as soon as we started being able to rear 90–95 percent of our babies that are born. We are the only species to have put a halt to natural selection, of its own free will, as it were,” he told the British magazine The Radio Times in 2013, adding that our species has instead ensured our continued survival through accelerating cultural evolution:

“Stopping natural selection is not as important, or depressing, as it might sound — because our evolution is now cultural […] We can inherit a knowledge of computers or television, electronics, airplanes, and so on.”

Natural selection requires variation

Both positions have been hotly contested. For instance, Dr. Ian Rickard — from Durham University in the United Kingdom — responded to Attenborough’s claims by pointing out that while abortion and birth control may mean that some people are having children while others are not, natural selection does not end here.

Rather, it places a renewed focus on the genetic material that is being passed along by those who are having children. Writing in The Guardian, Dr. Rickard explains, “Natural selection requires variation. It needs some individuals to thrive more than others.”

“So the improved survival prospects around the world over recent decades and centuries drastically decreases the potential for natural selection to work in those populations. But that is not the end of the argument. Even if everyone survives to the same age, there is still variation for natural selection to work with. Natural selection doesn’t really care about survival.”

source: medicalnewstoday.com

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