Re: Mitochondrial Mutations May Have Aided Brain Evolution
From: Rich Travsky (_at_hotmMOVEail.com)
Date: 11/29/04
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Date: Sun, 28 Nov 2004 21:16:27 -0700
Marc Verhaegen wrote:
>
> Thank you very much, runner down of small antelopes in less than 26 miles.
> Ever asked why "Humans are an extreme example of this: they have very large
> brains and a high quality, energy-dense diet"? By running down small
> antelopes in less than 26 miles? :-D Where do you find high-quality
> energy-dense food without having to run down small antelopes in less than 26
> miles? Where do you find mammals with un expectedly large brains? Yes,
> indeed. At the beach. Good answer. Nice boy. :-)
Wrong answer. Go sit in the corner and wear the dunce hat.
Gona - tools and bones in association.
>
> "Rich Travsky" <" traRvEsky"@hotmMOVEail.com> wrote in message
> news:41A80F17.29DA1CFB@hotmMOVEail.com...
> >
> > http://www.nature.com/news/2004/041122/full/041122-5.html
> > Published online: 23 November 2004; | doi:10.1038/news041122-5
> > Energetic cells may have boosted the brain
> > Did rapid mutation of cell powerhouses guide our neural evolution?
> >
> > A good brain needs lots of energy in order to function, and human
> > brains are exceptionally good. Now geneticists have found that
> > humans may also be exceptional in terms of the energy output of
> > our cells, and are wondering whether this is linked to our
> > intellectual prowess.
> >
> > Brains use more energy than one might expect. In humans this organ
> > makes up only 2% of a person's body weight, on average. But it is
> > estimated to account for about 20% of the energy used by the body
> > at rest.
> >
> > One solution to providing more energy is simply to have more cells.
> > In the development of the human brain, "the obvious difference that
> > everyone talks about is the huge increase in size," says John Kaas,
> > a neuroscientist at Vanderbilt University in Nashville, Tennessee.
> >
> > But there are limits to how much more power size can provide. Bigger
> > brains come with additional overhead costs and problems with heat
> > exchange. Something else must have helped to improve our brains.
> >
> > Within each cell, tiny structures called mitochondria are responsible
> > for producing the energy-carrying molecules known as adenosine
> > triphosphate or ATP. ...
> >
> > One solution to generating more energy in a single cell, therefore,
> > is to increase its numbers of mitochondria. But in the brain, cells
> > have long, thin arms called axons for connecting to other cells, and
> > scientists suspect that these cannot physically accommodate ever
> > larger numbers of mitochondria.
> >
> > So where did our brain cells get the power they needed? Lawrence
> > Grossman, a biologist at the Wayne State University School of Medicine
> > in Detroit, and his colleagues think it may have come from improvements
> > inside the mitochondria themselves.
> >
> > Grossman and his team studied the genes for a protein in the electron
> > transport chain known as complex IV, or COX. They compared the genetic
> > sequence across many different mammalian species and found that the
> > human lineage has undergone an exceptional number of changes.
> >
> > For example, there have been 11 changes in the part of the DNA that
> > codes for a certain protein subunit in the past 58 million years,
> > compared with just one change in the 25 million years before that. None
> > of the rodents, lemurs or other mammals that they examined showed more
> > than two or three changes in the same time period.
> > ...
> > He suggests that these changes could have given human brain cells a
> > serious evolutionary boost, by increasing the amount of energy available
> > to them. He and his team describe their theory in Trends in Genetics1.
> >
> > The group's findings fit with a growing body of evidence that our brains
> > evolved with the help of a better energy supply. Research in modern
> > primates has shown that there is a strong correlation between quality of
> > diet and relative brain size, says Bill Leonard, who studies energetics
> > at Northwestern University in Evanston, Illinois.
> >
> > "Humans are an extreme example of this: they have very large brains and a
> > high quality, energy-dense diet," he says.
> > ...
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