Researchers Say Human Brain is Still Evolving

Oleg Alexandrov writes "Two genes involved in determining the size of the human brain have undergone substantial evolution in the last 60,000 years, researchers say, suggesting that the brain is still undergoing rapid evolution. The discovery adds further weight to the view that human evolution is still a work in progress, since previous instances of recent genetic change have come to light in genes that defend against disease and confer the ability to digest milk in adulthood."

Comments

Re:It's remarkable how wrong this is

[John Hawks]

Well, it sure might look that way, but these genes strongly suggest that something related to cognition was under strong selection throughout history.

One of the two genes, ASPM, appears to have come under selection only 5800 years ago; but it is now at around 20 percent, with a frequency of near 50 percent in some Near Eastern populations. Whatever this allele does, it had a selective advantage of more than 5 percent. They don't know it necessarily makes people smarter, but it's hard to think what else it might be.

That's really the neat part; that it shows that this idea of "survival of the dumbest" is apparently not what has been happening. Instead, there is every reason to think we have been getting smarter.

The submission doesn't mention the most problematic part: These alleles are high frequency in some populations, but absent or low frequency in others -- suggesting there may be adaptive differences in the brain among human populations. From my weblog post:

Geneticists are increasingly finding genetic variants that affect behavior. Several of these variants are now known to vary in frequency in different human populations. These alleles are two; the 7r allele of the dopamine receptor D4 (DRD4) gene is another that influences ADD/ADHD susceptibility (Harpending and Cochran 2002). The selective structure underlying DRD4 variation may be frequency-dependent, with different alleles correlating with alternative behavioral strategies that pose greater or lesser advantages in some populations. It is not clear whether such a mechanism is true of ASPM and Microcephalin; the selected alleles have risen to such high frequencies in some populations that it seems they are not mere alternatives; they are unilaterally advantageous -- at least where they have become common already.

--John

"Smart Jews"

[Tablizer]

A related and interesting article on "Smart Jews"

http://www.economist.com/science/displaystory.cfm? story_id=4032638

It seems that discrimination in Europe may have led to higher intelligence.

Re:Can someone explain...

[ozmanjusri]

what is significant about the ability to drink milk during adulthood?

Most of the world's population can't digest lactose (milk sugar) after the age of about 4. The ability to digest lactose appears to have evolved along with dairy farming. Those parts of the world which did not practice dairy farming remain lactose intolerant.
http://www.scienceinafrica.co.za/2002/june/lactose .htm

This isn't stopping evolution...

[Dimensio]

...this is just changing the selection pressures. Ultimately, advances in medical technology alter the environment in such a way that it is less hostile to the reprodutive success to a given genetic range.

Re:Gene distribution

[Michael Woodhams]

There are statistical tests for the "under selection" part. here's the first summary I found. It changes the frequencies of nearby neutral mutations which get to "ride the coat-tails" of the advantageous mutation.

The "related to brain size/function" is somewhat speculative, in that the gene could have additional unknown functions.

That the mutation makes us smarter is much more speculative. (Indeed, I don't think the paper's authors went this far.) It could, for example, make us 0.1% less smart, but reduce the brain's metabolic cost by 0.5%.

(Note: I've only read the linked article, not the scientific paper.)

Re:It's remarkable how wrong this is

[magarity]

there ought to be some standard for parenthood
 
While I'm glad I'm an Alpha, I clearly see the need for Gammas and Deltas. And for them to be in greater numbers than the Alphas and Betas. That reminds me; trash truck comes tomorrow AM...

Re:Hoist by your own petard

[AJWM]

Natural selection must not only mean that the possession of some combination of attributes confers both survival and the opportunity to procreate, the absence of those attributes must mean the opposite.

No, it's virtually never that clear cut. There'll be some attribute(s) that confer a marginal increase or decrease in the likelihood of individuals to reproduce, or not. It's not all or nothing. Over a hundred generations, though, even a 1% marginal difference adds up to a significant population shift.

Re:Learn the nature of science.

[Decaff]

Now, since we don't have a time machine, we CANNOT falsify historical evolution. It's just a theory, and absent a time machine we won't ever be able to test it.

Of course you can test it. You can make predictions about the way things could have evolved and what intermediate forms may have been present. You can then look for such forms in fossils. For example, there have been several theories about the lineage of whales, and fossil finds have helped test these theories.

In this sense evolution is a lot like cosmology. We can't go back to the early stages of the universe, but we can predict what should be there then look at distant (effectively 'fossil') light with telescopes.

LSD is NOT a mutagen/teratogen...

[Ellis D. Tripp]

Regardless of what they might spew in DARE classes...

http://www.erowid.org/chemicals/lsd/lsd_writings4. shtml
http://www.straightdope.com/classics/a2_229.html
http://www.levity.com/aciddreams/samples/chromosom e.html
http://www.serendipity.li/dmt/chromosomes.htm