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Originally posted by lamin:

To Thought2 and Rasol. Any comments re Microsephalin and ASPM

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Thought Writes:

Not much to say yet. These studies are very new. It is no big surprise that the human brain changes with time. A good example is the higher rate of calcification of the Pineal Gland in Europeans. Furthermore, is there any evidence that the size of the brain ISOLATE marks human intelligence. How about the ability to successfully navigate between and harmonize the abilities of ones IQ AND so-called EQ?

Thought Posts:

Science, Vol. 309 No. 5741

Microcephalin, a Gene Regulating Brain Size, Continues to Evolve Adaptively in Humans

Patrick D. Evans et al.

The gene Microcephalin (MCPH1) regulates brain size and has evolved under strong positive selection in the human evolutionary lineage. We show that one genetic variant of Microcephalin in modern humans, which arose ~37,000 years ago, increased in frequency too rapidly to be compatible with neutral drift. This indicates that it has spread under strong positive selection, although the exact nature of the selection is unknown. The finding that an important brain gene has continued to evolve adaptively in anatomically modern humans suggests the ongoing evolutionary plasticity of the human brain. It also makes Microcephalin an attractive candidate locus for studying the genetics of human variation in brain-related phenotypes.

Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens

Nitzan Mekel-Bobrov et al.

The gene ASPM (abnormal spindle-like microcephaly associated) is a specific regulator of brain size, and its evolution in the lineage leading to Homo sapiens was driven by strong positive selection. Here, we show that one genetic variant of ASPM in humans arose merely about 5800 years ago and has since swept to high frequency under strong positive selection. These findings, especially the remarkably young age of the positively selected variant, suggest that the human brain is still undergoing rapid adaptive evolution.

[This message has been edited by Thought2 (edited 10 September 2005).]

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Originally posted by Thought2:
Thought Writes:

Furthermore, is there any evidence that the size of the brain ISOLATE marks human intelligence. How about the ability to successfully navigate between and harmonize the abilities of ones IQ AND so-called EQ?

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Thought Posts:

Making Sense of the Research

The main question at hand is whether smarter people have bigger brains. As is the case with many science questions, the answer to this one isn't "yes" or "no" but "kinda," "sometimes," or "not necessarily." As you heard, you can't always tell how big someone's brain is from the size of their head—but the two sizes are somewhat related. The same is true with brain size and intelligence.

The most we can say about brain size and intelligence is that by and large, all other things being equal, people who have larger brains tend to have slightly higher I.Q.'s than people with smaller brains. (I.Q. stands for intelligence quotient; it's a standard measure of intellectual ability.) But a lot of things have to be taken into account. For example, when you compare brain size, you really have to compare brain size relative to body mass. It's not reasonable to expect a 5'1", 100-pound woman to have the same size brain as a 6'6", 280-pound man. You have to ask the question: Is this person's brain larger or smaller than you might expect, given his or her body mass?

Even then, the relationship between brain size and intelligence is pretty weak, and there are lots of exceptions. Anatole France, a French author, had one of the tiniest "normal" brains on record, but he was certainly no dummy. On the other extreme, Jonathan Swift (the author of Gulliver's Travels) had a big honkin' brain, at the top end of all the brains ever measured (though still only twice the size of Anatole France's). Does that mean Swift was the smartest man who ever lived? He was certainly a bright guy, but it's hard to get behind any statement so extreme.

Still, it's hard to dismiss brain size entirely. The weak relationship between brain size and intelligence that shows up within the human population is somewhat more striking across the animal kingdom. Compared to other animals, humans have enormous brains compared to our body size (triple what you would expect in an average animal). Dolphins, other primates, and small whales also have big brains, and they're all pretty smart too. Within birds, parrots have big relative brain sizes, and chickens have tiny ones. And based on lab studies of learning and thinking, parrots are geniuses compared to chickens.

Overall, though, many factors besides mere size probably contribute to how well a brain functions, including the way it's organized, how many nerve cells are packed in per square inch, the quality of nutrition and environmental stimulation that you get while your brain is developing, and a host of other issues. Also, don't forget that these studies measure intelligence in terms of I.Q. score—a useful scale, but not necessarily the final word on how smart someone is. Many successful, shrewd, creative, and intelligent people have only average I.Q.'s, while many people with high I.Q.'s are underachievers.

Thought Writes: