Human Evolution Seems to Be Accelerating (Jews evolved from "financing!")

Ok, it wasn’t REALLY the last one. Apparently the experiment you propose has already been done in rats (1990). Rats were given milk past weaning time and compared to control rats who were not given milk they had no difference in lactase levels upon reaching adulthood.

Using the predictive power of Science, and utilizing the knowledge that Rats are around 85% similar in genetic DNA, and that mammals use the same cis acting element near the lactase gene to inactivate the lactase gene after weaning; I would say that giving milk to a Southeast Asian (98% lactose intolerance)past infancy would not lead to any difference in lactase activity from a Southeast Asian who was not given milk past infancy; but you would succeed in giving the poor guy/gal in the experimental group severe gas and indigestion.

1: Exp Physiol. 1990 Mar;75(2):231-8. Links
The effect of continued feeding of physiological amounts of lactose on the level of intestinal lactase and other disaccharidase enzyme activities in the rat.
Tadesse K.
Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, N.T.

Intestinal lactase activity in mammals is high at birth but begins to decline around weaning and reaches very low levels in adult life. The triggering mechanism for this decline is not clear. Because of the association of the decline with weaning, lack of lactose in the diet has been implicated. In 110 growing rats, the effect of continued supplementation of the diet after weaning with physiological amounts of either cows’ milk or a 5% lactose solution on intestinal lactase and other disaccharidase enzyme activities was investigated. In both control and test animals, the specific lactase activity decreased from a peak value of 115 +/- 4 mumol min-1 g-1 protein before weaning to about 10% at maturity. There was no significant difference in the level or the pattern of decline between the groups. Sucrase, maltase and trehalase showed the normal maturational changes without being affected by the test diets. The finding suggests that diet, particularly the presence or absence of physiological amounts of lactose, has no appreciable effect on the age related spontaneous decline of intestinal lactase activity or on the pattern of development of the other disaccharidases.

PMID: 2111152 [PubMed - indexed for MEDLINE]

I’ve been away a bit, thanks allmendream for picking up the ball.

One additional factor I think is assumed by scientists and nt understood by lay people is that when we talk about a new species emerging, it’s not like a car emerging from hte factory. What happens is gradually diminishing mutual fertility with the orginal species.

For an imaginary situation:
At the start: thingy-wampuses 100% fertility among themselves

mutation 1.. taller ones: 90% fertility with the orginal, 100% with each other

mutation 2.. (among the taller ones) big ears: 80% fertility with the original, 90% with taller, normal eared, 100% with each other

mutation 3: short toes among the taller, big eared ones: 70% fertility with the original, 85% with taller, normal eared, normal toed ones, 85% with normal height, large eared ones, 70% with the original.

etc. until fertility with the original becomes zero.

Naturally, in reality the situation is wven more complex, but hopefully this shows the idea.

And also as I pointed out, infertility with the parent population is not at all a requirement for a new species. A Lion and Tiger can produce fertile offspring that could then re-breed into the parent population, but they do not and have not breed in the wild.

The closest example I have ever heard of a sort of ‘instant’ speciation was when some insect produced its sex pheromones from a plant chemical precursor. Some insects moved over to a different species of plant with a different chemical precursor leading to the sex pheromones being different between the populations. Instant reproductive isolation, and also differential selective pressure because each little insect will specialize for the plant it preys upon. If you isolated the two different species, no doubt they would still be capable of reproducing together, but it will no longer happen in the wild and the two now different populations will continue to diverge. Eventually transversions in the genomes will make any crosses that can be produced mostly infertile, then totally infertile. Eventually differences can arise making any reproduction between populations impossible.

· join list or digest · view topics · view or post blog · bookmark · post a topic ·
	Gods Graves Glyphs	Thanks Blam. Blast from the Past. I followed you in here five months ago, but must, alas, have been at work and missed the ping when I got home. Just adding to the catalog, not sending a general distribution. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are Blam, StayAt HomeMother, and Ernest_at_the_Beach
· Google · Archaeologica · ArchaeoBlog · Archaeology magazine · Biblical Archaeology Society · · Mirabilis · Texas AM Anthropology News · Yahoo Anthro & Archaeo · · History or Science & Nature Podcasts · Excerpt, or Link only? · cgk's list of ping lists ·

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.