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."

Re:take that you intelligent desing thoricists

[higuy48]

I was pondering whether or not to totally theadjack this topic, but it seems you have made the decision for me.

This won't stop them. This is mircoevolution. What they're claiming is that we couldn't have possibly speciated from very simple cells and organisms to what we are today. They are disputing macroevolution.

Nitpick

[Dimensio]

Every living thing is evolving.

Living things don't evolve. Populations of living things either evolve, remain stagnant (which is very , very rare) or die out.

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: [johnhawks.net]

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

Re:Duh?

[brianf711]

Actually, evolution is more complicated than just natural selection.

There are 5 conditions where Hardy-Weinberg equilibrium does not apply and thus evolution is occuring.

While natural selection is one of these, the others include non-random mating, mutations, genetic drift (small populations may be more sensitive to random events) and migration (gene flow).

Since all of these events are occuring at some degree, the short response to the article is of course evolution is occurring, as you pointed out, but not just because of natural selection. What is interesting, and I didn't read the article so bear with me, is whether there is a correlation with "intelligence" and surviving offspring. This is where natural selection would favor or disfavor intelligence. Perhaps more intelligent people have fewer children, but are able to raise them and get them access to medicine and other factors that could enhance their survival, but maybe this isn't the case as well.

Re:Theory or God??

[CurlyG]

Yes, I think you *should* consult a real scientist, and ask them what "theory" means in a scentific context, and then get them to explain to you the difference between a theory and a hypothesis, as you clearly haven't the faintest idea what you're blathering about.

You're welcome.

"Smart Jews"

[Tablizer]

A related and interesting article on "Smart Jews"

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

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

Re:Human evolution has STOPPED!

[John Hawks]

Sure, some of the things that used to kill a lot of people don't so much anymore. People even survive and have kids with CF today.

But selection requires only an incremental increase in reproduction. In a big population like ours, this increase can be as small as tenths or hundredths of a percent. This is so small that practically we will never measure it. Yet in a few thousand generations, this tiny reproductive effect will completely transform a population -- even a population of billions.

That's the problem with predicting the future -- what will be important then, we can't observe happening today. But there is plenty of reason to think that things are happening now. From my weblog [johnhawks.net]:

Today, with 6 billion humans, every one-off mutation from the human consensus genome sequence occurs in dozens of people. Many multiple-off mutations occur in some people. In a larger population, selection is more potent, because genetic drift is weaker. This means that the advantageous variants of the next fifty millennia are already appearing in the world today, and may inevitably be selected. The global population is exploring the entire mutational space, many times over, and novel mutations are no longer likely to disappear so rapidly due to genetic drift. Any near variants that confer an advantage are already on the way to fixation. Many of these may lose their advantage once biomedical technology catches up to them. But others will be more subtle, more difficult to market in pharmaceutical form, and these will slowly, steadily increase.

So if you want to have an effect, get out there and reproduce! --John

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 [scienceinafrica.co.za]

Re:Since when is natural selection called evolutio

[Anonymous Coward]

no, natural selection is the pressures applied to the species that weed out those that are not suited for the environment.

microevolution is the process of small changes appearing within a species
macroevolution is the process of things changing into a different species entirely

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.

What was selected?

[John Hawks]

One of my friends thinks a good candidate for selection would be avoidance of cities, since these were cholera-ridden population sinks for most of history. Maybe so.

Really the reason to think that cognition is involved is that these same genes were selected repeatedly in primate and human evolution [johnhawks.net]:

Both genes underwent repeated adaptive subtitutions in the primate lineages leading to humans: these changes in Microcephalin were concentrated in the ancient hominoid ancestors of humans and chimpanzees; ASPM fixed a new adaptive substitution on average every 300,000 or so years since the human-chimpanzee common ancestor. Disease-causing alleles of both genes are associated with forms of microcephaly. The normal functions of neither have been characterized, although their effects in microcephaly would indicate that one important function is in early neural growth and differentiation. Thus, it is reasonable to think that they may have been involved in the evolution of brain size and structure in humans and other primates.

I suppose it's possible they make you dumber. But then further experiments should show one way or the other.

--John

Re:Now, wait a second...

[Anonymous Coward]

I suppose you don't know about the racial makeup of Brazil...

Re:Gene distribution

[Michael Woodhams]

There are statistical tests for the "under selection" part. here's [wsu.edu] 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:Can someone explain...

[mattjb0010]

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.

There are similar patterns with respect to alcohol metabolism, based on whether populations boiled water or used diluted alcohol in order to kill bacteria. This also occurs for other drugs, such as warfarin [nih.gov] (a common anticoagulant drug).

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.

Nope.

[aussersterne]

Ever have sex with someone of the opposite gender? Were you attracted to them? For whatever reason? And they you?

Yes?

Congratulations, you just participated in the ongoing process of natural selection. You yourself have applied selective pressure in favor of whatever it was that attracted you to him/her, regardless of what the nature of the attraction was or whether you can even spell it out.

Multiply by six billion and you have the human race... evolving.

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.

Re:Learn the nature of science.

[xerxesdaphat]

It's a basic biological fact, as far past theory as Newton's Laws. (We're also slowly approaching the time when we should call Relativity a law. It's not there yet, but it will be eventually.)

Man. Did you even read the above post? He said, theories don't graduate into laws... they are completely different things. Please actually RTFP before replying.

Re: Theory or God??

[johnnyb]

Actually, hypotheses and theories are quite disconnected, as are theories and laws.

A hypothesis is a testable prediction. A theory is a hypothesis-generating model. A law is a mathematical description.

For example:

Hypothesis: If I throw an object X with a force of Y at a vector of Z, it will land at point Q.

Theory: Gravity is caused by the warping of space by mass

Law: F=G*(m1*m2/r^2)

Note that even with dramatic changes to the _theory_ of gravity, the Law is relatively stable -- it is simply a mathematical description.

Thus, creationists and evolutionists are both wrong when one says "evolution is just a theory, it's basically a guess" and the other says "evolution is a proven fact, just like the 'theory of gravity'". Theories are merely hypothesis-producing mechanisms, and are judged by their usefulness of producing testable hypotheses.

Re: Theory or God??

[johnnyb]

"I wouldn't even call it a conjecture. It's apologetics, almost certainly conceived and propagated dishonestly."

Who in the ID community is being dishonest?

"It's possible that someone could offer "intelligent design" as a conjectural explanation for some poorly understood phenomenon"

Actually, most people offer up "intelligent design" for well-understood phenomena. Would you say that the works of Mozart are not intelligently designed? Or perhaps that the Apache server was not intelligently designed? ID simply says that we can analyze design mathematically, and use the results of that to determine if a given physical system is likely the result of an intelligent agent. In fact, this process is already implicit in Archaeology and in SETI. It's just that biologists don't like it being applied to their neck of the woods.

"They're trying to convince the courts that creationists have sound scientific reasons for their beliefs."

This is incorrect. ID does not want either ID or creationism taught in science classes. In fact, most creationist organizations don't want creationism as a mandatory topic. And all groups I am aware of agree that evolution should be fully taught to students.

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 [erowid.org]
http://www.straightdope.com/classics/a2_229.html [straightdope.com]
http://www.levity.com/aciddreams/samples/chromosom e.html [levity.com]
http://www.serendipity.li/dmt/chromosomes.htm [serendipity.li]

Re:I Think I Missed Something Here

[Ihlosi]

Can one seriously argue that lactose tolerance (or intolerance) increases survival of humans in areas that produce (or don't produce) bovine milk?

Maybe the gene now no longer serves its intended function (which is why it can get replaced with its "faulty" version that allows adult mammals to tolerate lactose).

Having the gene in the first place makes perfect sense to anyone who know a bit about mammalian reproduction physiology. Nursing inhibits ovulation in the female. Forcing the offspring to stop nursing allows for more reproductive cycles. Developing lactose intolerance in early life is a pretty sure way to accomplish that.

Thererefore: Yes, one can perfectly well argue that the lactose intolerance gene makes sense. All that's required is some basic physiology. Just because you can't argue doesn't mean anyone else can't.