Study Detects Recent Instance of Human Evolution

New York Times ^ | 10 December 2006 | Nicholas Wade

[Alter Kaker]

A surprisingly recent instance of human evolution has been detected among the peoples of East Africa. It is the ability to digest milk in adulthood, conferred by genetic changes that occurred as recently as 3,000 years ago, a team of geneticists has found.

The finding is a striking example of a cultural practice — the raising of dairy cattle — feeding back into the human genome. It also seems to be one of the first instances of convergent human evolution to be documented at the genetic level. Convergent evolution refers to two or more populations acquiring the same trait independently.

Throughout most of human history, the ability to digest lactose, the principal sugar of milk, has been switched off after weaning because there is no further need for the lactase enzyme that breaks the sugar apart. But when cattle were first domesticated 9,000 years ago and people later started to consume their milk as well as their meat, natural selection would have favored anyone with a mutation that kept the lactase gene switched on.

Such a mutation is known to have arisen among an early cattle-raising people, the Funnel Beaker culture, which flourished some 5,000 to 6,000 years ago in north-central Europe. People with a persistently active lactase gene have no problem digesting milk and are said to be lactose tolerant.

[MEGoody]

Because it's a food source.

True, but so are the cattle that produce the milk, as well as some of the plants the cattle eat.

[Alter Kaker]

Yes, cattle are food, but a society that can milk cattle is stronger than a society that is dependent only on their meat, as it has a more stable food source. Stone age societies couldn't slaughter cattle every day.

[Alter Kaker]

Seems to me that if you can't duplicate, you can't demonstrate.

I take it we haven't demonstrated why the earth revolves around the sun? After all, nobody has successfully duplicated the process.

[GourmetDan]

"Huh? Populations don't go into "catastrophic error-catastrophe" (whatever that is). That violates the principle of natural selection -- more fit individuals will survive, which means that there is constant evolutionary pressure towards greater fitness, not less."

Catastrophic error catastrophe is when a population has too many mutations to clear them via natural selection.

RNA viruses are suspected of being in catastrophic error catastrophe and humans are very close.

"RNA viruses which replicate close to the error threshold have a genome size of order 104 base pairs. Human DNA is about 3.3 billion (109) base units long. This means that the replication mechanism for DNA must be orders of magnitude more accurate than for RNA."

http://en.wikipedia.org/wiki/Error_catastrophe

"Error catastrophe is when genetic errors accumulate in a population faster than they can be rid of. Using data supplied by evolutionists themselves, and their own standard model of evolutionary genetics, one can show that humans are within or precariously close to error catastrophe — even if we give the evolutionary model the incredible advantage of assuming that a full 97% of the human genome is completely inert and unavailable to suffer harmful mutation."

http://www1.minn.net/~science/contents_detail.htm

One of those cases of reality intruding on theory.

[Alter Kaker]

Now please explain to me how error catastrophe can arise in a sexual population.

[GourmetDan]

"I take it we haven't demonstrated why the earth revolves around the sun? After all, nobody has successfully duplicated the process."

That is correct.

Fred Hoyle, as follows:

"The relation of the two pictures [geocentricity and heliocentricity] is reduced to a mere coordinate transformation and it is the main tenet of the Einstein theory that any two ways of looking at the world which are related to each other by a coordinate transformation are entirely equivalent from a physical point of view.... Today we cannot say that the Copernican theory is 'right' and the Ptolemaic theory 'wrong' in any meaningful physical sense."

Fred Hoyle, Nicolaus Copernicus (London: Heinemann Educational Books Ltd., 1973), p. 78

[RobRoy]

>>Because it's a mutation that we can observe in the genetic record. <<

I wasn't wondering why they called it "a mutation we can observe in the genetic record", I was wondering why they called it a mutation at all.

[Mamzelle]

Some excellent models have been created and tested. (But--they aren't natchr'l.) They do manage to get rockets into space, however, based on what they learn from the models.

Are the Dismal Coots at DC getting lonely again?

[GourmetDan]

When error correction schemes are not precise enough to prevent replication errors over a certain threshhold. The larger the genome, the more precise the error correction schemes must be.

The links I included said that.

[r9etb]

I'm just glad they decided to milk the girl cows.

[Gondring]

neverdem posted the following interesting info on another thread...

Convergent adaptation of human lactase persistence in Africa and Europe

A SNP in the gene encoding lactase (LCT) (C/T-13910) is associated with the ability to digest milk as adults (lactase persistence) in Europeans, but the genetic basis of lactase persistence in Africans was previously unknown. We conducted a genotype-phenotype association study in 470 Tanzanians, Kenyans and Sudanese and identified three SNPs (G/C-14010, T/G-13915 and C/G-13907) that are associated with lactase persistence and that have derived alleles that significantly enhance transcription from the LCT promoter in vitro. These SNPs originated on different haplotype backgrounds from the European C/T-13910 SNP and from each other. Genotyping across a 3-Mb region demonstrated haplotype homozygosity extending >2.0 Mb on chromosomes carrying C-14010, consistent with a selective sweep over the past 7,000 years. These data provide a marked example of convergent evolution due to strong selective pressure resulting from shared cultural traits—animal domestication and adult milk consumption.

[Alter Kaker]

*Ping* to an interesting article surrounded by an ocean of creationists.

[MEGoody]

Stone age societies couldn't slaughter cattle every day.

True, but it's doubtful they all domesticated cattle at the same time.

[Gondring]

What's the connection with Vitamin D? It would take several quarts of raw milk to meet the daily requirement of Vitamin D--that's why processed milk tends to be fortified with Vitamin D.

[AndrewC]

I understand that, but lactose digestion is normal(what I am saying). It is "shut down" later in life as a "normal" condition of some mammals including man(what you are saying). Lactose tolerance is "returned" by not "shutting down" the mechanism that metabolizes the sugar. If you look at the genome on gene 2 you might see something related to your answer. Again note that turning something on or off requires a mutation(change) to the mechanism coded in DNA.

LAC, 2q21

Also HYPOLACTASIA, ADULT TYPE has a good explanation of the topic

[abishai]

So if I have a friend who is lactose intolerant, can I tell her that she is the missing (now found) link between humans and apes?

[dogbyte12]

OK, just one question: Why did our ancestors bother to domesticate milk cows, when they couldn't digest the milk in the first place? Did they know that some day, they would become lactose tolerant? If this is evolution, wouldn't that mean our ancestors had to be drinking milk, as adults, for a long time, in the hope that some day their children, or grandchildren, etc, would mutate that gene? Wow, our ancestors were VERY forward thinking.

No, our ancestors probably were mixed in who could or could not drink milk. Some could, some couldn't. Something happens, where other food sources are in bad shape. Just say plants other than grasses are killed off. The cow milk is a great source of fat. Those who were able to consume it, survive the drought and then reproduce. The classic study on this phenomena is the brittish rabbit and butterfly population. White was the dominant color, with some charcoalish too but in a vast minority. Once industrialization came, the air got really sooty. The whites got eaten off quickly by predators, now darker colors were more predominant. Then they stopped using so much coal, and it switched once again. If the recessive trait was totally killed off, the species might have died.

[Alter Kaker]

So if I have a friend who is lactose intolerant, can I tell her that she is the missing (now found) link between humans and apes?

Is that an attempt at humor?

[GourmetDan]

"I understand that, but lactose digestion is normal(what I am saying). It is "shut down" later in life as a "normal" condition of some mammals including man(what you are saying)."

Except that you are ignoring the fact that lactose digestion is normally shut down later in life and I am not. The system is normally more complex than you acknowledge and is disabled by mutation. Disabling complex systems would not be consistent with a goo-to-you evolution model.

"Lactose tolerance is "returned" by not "shutting down" the mechanism that metabolizes the sugar.

Au contraire, it is not 'returned'. It never left in those individual genomes where the shut-down sequence is disabled.

"If you look at the genome on gene 2 you might see something related to your answer."

Sorry, I make it a habit not to try to interpret for people. I figure that if they have something to say, they will say it.

"Again note that turning something on or off requires a mutation(change) to the mechanism coded in DNA."

What we are dealing with here is a complex system that supposedly arose (or was created) that enabled lactose-tolerance early in life and then shuts it down. That the shut-down sequence is disabled by mutation is a loss-of-function mutation. Much simpler than the turn-on sequence which required that the system be built.

[muawiyah]

Modern practice is to fortify milk with Vitamin D. Not so long ago that was not the practice ~ that's mostly because no one knew that we needed Vitamin D, or what a vitamin might be, or that milk was something other than a tasty liquid.

The deal is that the further North you go the less opportunity there is to bare the skin to expose it to sunlight so the body can make its own vitamin D. So, what you do is drink cow's milk (or the milk of some other mammal) to make up for the deficiency. That way you can move even further North (to exploit the resources).

Of course, you eventually run into a situation where your skin can't get lighter (to allow in more sunlight), and the cows can't live. So, what to do?

Other sources of Vitamin D are fish and seamammals.

Early man conquered the North by drinking the milk of wild mammals, eating lots of fish, and hunting for seamammals like walrus, seal, porpoise, and so on.