Human evolution slower than thought, say scientists

Maybe this explains why there are more apes and chimps around than expected, especially in the business world...?
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Posted: 14 June 2011

PARIS - Humans may be evolving a third as slowly as commonly thought, according to an investigation into genetic changes in two generations of families.

The genetic code comprises six billion nucleotides, or building blocks of DNA, half of which come from each parent.

Until now, the conventional theory among scientists was that parents each contribute between 100 and 200 changes in these nucleotides.

But the new study says that far fewer changes occur. Each parent hands on 30 on average.

"In principle, evolution is happening a third as slowly as previous thought," said Philip Awadalla of the University of Montreal, who led the study by the CARTaGENE group.

The discovery came from a painstaking look at the genomes of two families, each comprising a mother, a father and their child.

The study breaks new ground although its sample size is very small.

If confirmed on a wider scale, it will have a bearing on the chronology of evolution. It would change the way we calculate the number of generations that separate Homo sapiens from a primate forebear who is also the ancestor of the apes.

The study also challenged thinking about whether DNA changes are more likely to be handed on by the father or by the mother.

The mainstream notion is that DNA changes -- known in scientific terms as mutations -- are likelier to be transmitted by the man.

This is because mutations occur during cell division and DNA replication, and thus are much likelier to happen in sperm, for which many millions are made, than in eggs.

In one of the families, 92 percent of the changes were derived from the father.

But in the other family, only 36 percent of the mutations came from the paternal side.

"The mutation rate is extremely variable from individual to individual or...some people have mechanisms that reduce the likelihood of mutations," concluded Awadalla.

This variability could prompt a rethink on predicting the risk of inherited disease, caused by flawed genes bequeathed by one or both parents.

Some individuals might be at risk of misdiagnosis of a genetic disease if they have a higher natural mutation rate than the benchmark rate, he suggested.

-AFP/rt


Taken from ChannelNewsAsia.com; source article is below:
Human evolution slower than thought, say scientists

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Are brains shrinking to make us smarter?

I know that in the individual level, this is true - the billions of cells and full-connection synapses are all there, and in the growing months and years, there is a necessity for much of the cells and synapses to be cut and broken: to give way to learning and strengthening the connections that retain our learning.

And it is observed in the whole human populace as well.

Read on...
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Posted: 06 February 2011

WASHINGTON: Human brains have shrunk over the past 30,000 years, puzzling scientists who argue it is not a sign we are growing dumber but that evolution is making the key motor leaner and more efficient.

The average size of modern humans -- the Homo sapiens -- has decreased about 10 percent during that period -- from 1,500 to 1,359 cubic centimetres, the size of a tennis ball.

Women's brains, which are smaller on average than those of men, have experienced an equivalent drop in size.

These measurements were taken using skulls found in Europe, the Middle East and Asia.

"I'd called that a major downsizing in an evolutionary eye blink," John Hawks of the University of Michigan told Discover magazine.

But other anthropologists note that brain shrinkage is not very surprising since the stronger and larger we are, the more gray matter we need to control this larger mass.

The Neanderthal, a cousin of the modern human who disappeared about 30 millennia ago for still unknown reasons, was far more massive and had a larger brain.

The Cro-Magnons who left cave paintings of large animals in the monumental Lascaux cave over 17,000 years ago were the Homo sapiens with the biggest brain. They were also stronger than their modern descendants.

Psychology professor David Geary of the University of Missouri said these traits were necessary to survive in a hostile environment.

He has studied the evolution of skull sizes 1.9 million to 10,000 years old as our ancestors and cousins lived in an increasingly complex social environment.

Geary and his colleagues used population density as a measure of social complexity, with the hypothesis that the more humans are living closer together, the greater the exchanges between group, the division of labor and the rich and varied interactions between people.

They found that brain size decreased as population density increased.

"As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive," Geary told AFP.

But the downsizing does not mean modern humans are dumber than their ancestors -- rather, they simply developed different, more sophisticated forms of intelligence, said Brian Hare, an assistant professor of anthropology at Duke University.

He noted that the same phenomenon can be observed in domestic animals compared to their wild counterparts.

So while huskies may have smaller brains than wolves, they are smarter and more sophisticated because they can understand human communicative gestures, behaving similarly to human children.

"Even though the chimps have a larger brain (than the bonobo, the closest extant relative to humans), and even though a wolf has a much larger brain than dogs, dogs are far more sophisticated, intelligent and flexible, so intelligence is not very well linked to brain size," Hare explained.

He said humans have characteristics from both the bonobo and chimpanzee, which is more aggressive and domineering.

"The chimpanzees are violent because they want power, they try to have control and power over others while bonobos are using violence to prevent one for dominating them," Hare continued.

"Humans are both chimps and bobos in their nature and the question is how can we release more bonobo and less chimp.

"I hope bonobos win... it will be better for everyone," he added.

-AFP/ac


Taken from ChannelNewsAsia.com; source article is below:Are brains shrinking to make us smarter?

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Monkeys can now see the world in full colour

Image via Wikipedia

PARIS - Two monkeys were cured of colour blindness, thanks to gene therapy that one day may open the way to treating eye disorders in humans, scientists said yesterday.

The ground-breaking technique used a cold virus as a "Trojan horse" to infect cone-shaped cells in the retina, stealthily delivering a gene that provides a pigment which is sensitive to red.

About 20 weeks after the treatment, the two primates began to acquire full colour vision, according to the paper, published by the British journal, Nature.

It thus gives the lie to the belief that congenital vision defects become "hard-wired" through neural connections soon after birth, and cannot be corrected.

Colour vision in the two adult squirrel monkeys has remained stable more than two years after treatment, the paper says.

Red-green colour blindness affects between 5 and 8 per cent of men, and around 1 per cent of women. AFP

From TODAY, World – Thursday, 17-Sep-2009

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