From the Howard Hughes Medical Center
Genes that control the size and complexity of the brain have undergone much more rapid evolution in humans than in non-human primates or other mammals, according to a new study by Howard Hughes Medical Institute researchers.
The accelerated evolution of these genes in the human lineage was apparently driven by strong selection. In the ancestors of humans, having bigger and more complex brains appears to have carried a particularly large advantage, much more so than for other mammals. These traits allowed individuals with better brains to leave behind more descendants. As a result, genetic mutations that produced bigger and more complex brains spread in the population very quickly. This led ultimately to a dramatic speeding up of evolution in genes controlling brain size and complexity.
One of the study's major surprises is the relatively large number of genes that have contributed to human brain evolution. For a long time, people have debated about the genetic underpinning of human brain evolution, said Lahn. Is it a few mutations in a few genes, a lot of mutations in a few genes, or a lot of mutations in a lot of genes? The answer appears to be a lot of mutations in a lot of genes. We've done a rough calculation that the evolution of the human brain probably involves hundreds if not thousands of mutations in perhaps hundreds or thousands of genes and even that is a conservative estimate.
It is nothing short of spectacular that so many mutations in so many genes were acquired during the mere 20-25 million years of time in the evolutionary lineage leading to humans, according to Lahn. This means that selection has worked extra-hard during human evolution to create the powerful brain that exists in humans.
Varki points out that several major events in recent human evolution may reflect the action of strong selective forces, including the appearance of the genus Homo about 2 million years ago, a major expansion of the brain beginning about a half million years ago, and the appearance of anatomically modern humans about 150,000 years ago. "It's clear that human evolution did not occur in one fell swoop," he said, "which makes sense, given that the brain is such a complex organ."This, and some follow-up articles, constitute some interesting stuff. For one thing, I may well be forced to reconsider my views on SETI - something which actually pleases me greatly....
Human Brain Evolution Was a 'Special Event'
Genes that control the size and complexity of the brain have undergone much more rapid evolution in humans than in non-human primates or other mammals, according to a new study by Howard Hughes Medical Institute researchers.
The accelerated evolution of these genes in the human lineage was apparently driven by strong selection. In the ancestors of humans, having bigger and more complex brains appears to have carried a particularly large advantage, much more so than for other mammals. These traits allowed individuals with better brains to leave behind more descendants. As a result, genetic mutations that produced bigger and more complex brains spread in the population very quickly. This led ultimately to a dramatic speeding up of evolution in genes controlling brain size and complexity.
People in many fields, including evolutionary biology, anthropology and sociology, have long debated whether the evolution of the human brain was a special event, said senior author Bruce Lahn of the Howard Hughes Medical Institute at the University of Chicago. I believe that our study settles this question by showing that it was.
Lahn and his colleagues reported their data in a research article published in the December 29, 2004, issue of the journal Cell.< -- snip -- >
One of the study's major surprises is the relatively large number of genes that have contributed to human brain evolution. For a long time, people have debated about the genetic underpinning of human brain evolution, said Lahn. Is it a few mutations in a few genes, a lot of mutations in a few genes, or a lot of mutations in a lot of genes? The answer appears to be a lot of mutations in a lot of genes. We've done a rough calculation that the evolution of the human brain probably involves hundreds if not thousands of mutations in perhaps hundreds or thousands of genes and even that is a conservative estimate.
It is nothing short of spectacular that so many mutations in so many genes were acquired during the mere 20-25 million years of time in the evolutionary lineage leading to humans, according to Lahn. This means that selection has worked extra-hard during human evolution to create the powerful brain that exists in humans.
Varki points out that several major events in recent human evolution may reflect the action of strong selective forces, including the appearance of the genus Homo about 2 million years ago, a major expansion of the brain beginning about a half million years ago, and the appearance of anatomically modern humans about 150,000 years ago. "It's clear that human evolution did not occur in one fell swoop," he said, "which makes sense, given that the brain is such a complex organ."
