Evidence That Human Brain Evolution Was A Special Event

[Dover]

Evidence That 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."

Cont'd

http://www.sciencedaily.com/releases/2005/01/050111165229.htm

[Spinzonner]

1. Then of course there are retrograde cases

like the Bush family

(Sorry to pollute your science thread)

[tridim]

2. How do you explain the Republican brain?

A special case of the special event? I really think there was a branch in the human evolutionary tree a few thousand years ago because my brain is nothing like Bush's brain.

[saltpoint]

3. Maybe it's like microwave popcorn --

-- where not every kernel goes pop, and when you take it out of the microwave, there are always these unpopped rogue kernels rolling around.

Judge Roy Moore comes to mind, and Trent Lott, Jesse Helms, Dan Quayle, Tommie Thompson, etc.

[unpossibles]

7. easy

the NeoCons seem to be controlled by what is sometimes referred to as the Reptile Brain:

<snip>
The most inner section, like the hard seeds of an apple, is called the reptile brain, because it looks like and functions like the brains of snakes, lizards, and reptiles. It computes only basic survival, self-defense and counter-attack. Famous Neuroscientist joke: "The reptile brain computes the four F's of behavior- fighting, fleeing, feeding and reproduction." It merely reacts with the rest of the universe- no thinking, no new ideas- just reacting with the ancient primeval programming "It is 100% competitive consciousness, and only computes 'me-me-me' types of behavior"
</snip>

from http://www.reptilianagenda.com/research/r110699a.shtml

Maybe we should try to find a NeoCon brain and see if it's true physiologically.

[gottaB]

4. It doesn't appear to be particularly strong evidence

I find the evidence of accelerated brain development in primates to be stronger and more intriguing. Homo has made great use of the opposable thumb, but from an evolutionary point of view it would be silly to see that as a characteristic of the genus. To establish the divergence of Homo sapiens from other primates in the matter of brain development, more data will be needed from other species, including of course apes, lesser and great.

The business about developmental vs. housekeeping genes may not say much about brain development in sapiens or any lineage in particular. Neotony is a general trend in primates, probably particularly advanced in humans. One might expect that the longer the period of gestation and postnatal development, the higher the ratio of developmental genes to housekeeping genes that will be subject to evolutionary forces. It would be interesting to compare these ratios in humans and primates to other mammals with pronounced trends towards neotony, and also the ratio of developmental to housekeeping mutations in non-brainy organs and structures. It may well be that a selection for braininess is behind the trend towards neotony and/or the increased proportion of developmental to housekeeping mutations. However, it is possible that other traits are being selected for, and that these observed ratios can be explained as a byproducts of a more vital process.

Finally, Lahn's speculations about anatomically modern humans strike me as racist gobbledygook.

[muriel_volestrangler]

5. 'Racist gobbledygook'?

That's a stretch, considering Lahn says nothing about race, region, or even different human cultures. In fact, I can't see anything racist about what he says at all.

[gottaB]

6. it's a reasonable inference

Examine the final paragraph:

Lahn further speculated that the strong selection for better brains may still be ongoing in the present-day human populations. Why the human lineage experienced such intensified selection for better brains but not other species is an open question. Lahn believes that answers to this important question will come not just from the biological sciences but from the social sciences as well. It is perhaps the complex social structures and cultural behaviors unique in human ancestors that fueled the rapid evolution of the brain. "This paper is going to open up lots of discussion," Lahn said. "We have to start thinking about how social structures and cultural behaviors in the lineage leading to humans differed from that in other lineages, and how such differences have powered human evolution in a unique manner. To me, that is the most exciting part of this paper."

What does it mean to say that "strong selection for better brains may still be ongoing in the present-day human populations"? Does that mean that some populations are brainier than others, and that natural selection will weed out the less brainy? Is this use of "populations" consistent with a natural scientific view, or does it have more to do with the non-scientific concept of race? Lahn speculates that culture has "powered" the evolution of the human lineage. The link between culture and evolution of the brain is an interesting area of study if one is talking about the emergence of Homo or anatomically modern humans. If one applies that sort of argument to modern humans, and views cultural differences as ultimately governed by natural selection, it all too easily degenerates into racist gobbledygook.

I do not know that Lahn is a racist. I do know that his speculations go far beyond what can be supported based upon the evidence he has presented. Given the sorry history of this field of study, I expect evolutionary scientists to be sensitive to how racists, acting within and without the scientific establishment, have abused and misapplied elements of the theory of evolution.