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General interest items edited by Janice Flahiff

Are humans still evolving by Darwin’s natural selection?

Are humans still evolving by Darwin’s natural selection?

From the 28 February 2011 BBC article

n 1859, Charles Darwin published On the Origin of Species, a book which transformed our understanding of how life on Earth developed – but ever since then, scientists have wondered whether humans were resourceful enough to remove themselves from the grip of natural selection.

There is no question that humans are unique in the animal world. We have developed technologies that shelter us from the harshness of the environment in a way that no other creatures have managed.

While polar bears evolved thick coats of blubber to insulate them from the Arctic cold, humans could skin that polar bear, and use the pelt as clothing to keep warm.

Does this mean that, at some point, technological advances have stopped us evolving?

Much of the story is in our genes and the sequencing of the human genome has helped unlock the answers.

By comparing the genes of people from all around the world, scientists can see how different we all are, and therefore how much we have evolved apart from each other since our species first appeared.

Skin colour is the most obvious way we have evolved apart, but there are other examples.

“We are living records of our past,” says Dr Pardis Sabeti, a geneticist at Harvard University. “And so we can look at the DNA of individuals from today and get a sense of how they all came to be this way.”

Another area of recent evolution is how our metabolism has changed to allow us to digest some things that we could not in the past.

The most obvious example of this is lactose, the sugar in milk. Some 10,000 years ago, before humans started farming, no one could digest this beyond a few years of age.

But today, the rate of lactose tolerance in different parts of the world is a clue to the different histories of farming across the globe. While 99% of Irish people are lactose tolerant, in South East Asia, where there is very little tradition of dairy farming, the figure is less than 5%.

So clearly our technology and inventions didn’t stop us evolving in the past. But what about today?

Professor Steve Jones, a geneticist at University College London, said: “In Shakespeare’s time, only about one English baby in three made it to be 21.”

“All those deaths were raw material for natural selection, many of those kids died because of the genes they carried. But now, about 99% of all the babies born make it to that age.”

The bulk of medical and other technological developments which protect us from our environment have come in just the past century. So in the developed world today, what is there left for natural selection to act on?

“Natural selection, if it hasn’t stopped, has at least slowed down,” says Jones…..




March 1, 2011 - Posted by | Health News Items | ,

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