This is not evidence of evolution at all but adaptation, there is an enormous difference between the two. Adaptation occues naturally in nature and can be seen in everyday life. My chihuahua is an adaptation of a wolf. ... there is not nor ever has been any evidence that my chihuahua could ever adapt into an entire other species.
Apostate Kate....Evolution of a species, or speciation, is not just adaptation but adaptation + a reproductive barrier in the breeding population. A reproductive barrier occurs when a breeding population splits apart into groups that can no longer breed with each other (either through a new adaptation, geographical isolation, etc.). Once a parent population has split into two or more discrete populations, new adaptations would be confined to one group and not spread to the other...and thus both groups descended from a single parent population would accumulate different adaptations and thus "evolve" in different directions (and potentially have their own population splits). What has been described in this article is an instance of adaptation, but since there is no barrier in the human breeding population (since anyone can breed with anyone, and since the time depth of geographical isolation has been so very shallow), you are correct that this is not evidence of speciation. But since adaptation is a primary process of evolution, it certainly is evidence of evolutionary change. The example given of chihuahuas and wolves is evidence that much adaptation can occur within a breeding population; it is not evidence that a reproductive barrier cannot arise. If the time comes when chihuahuas and wolves can no longer mate with each other, then that would precisely be evidence of speciation.
Missing genes cause often fatal flaws such as Downs Syndrome, Marfans, Cystic Fibrosis, cancers, Sickel Cell Anemia, there have been thousands mapped... Mutations show no gain in genetic information.
It is a straw man argument to only point out mutations that have negative consequences, what about all those that have no advantage or disadvantage whatsoever? That is where most mutations lie, in our natural genetic variation that comprises the health of a species. What happens is that a neutral variant can become either a benefit or a detriment in a new ecological setting, and thus become more frequent or less frequent in the general population. Sickle-cell hemoglobin is a detriment in our "first world" ecology where malaria does not really exist, but in countries that are plagued by malaria, it is actually a benefit because it protects people from malaria....hence, it is usually regarded as an adaptation to malaria. I also don't understand why one would claim that mutations "show no gain in genetic information". They produce new DNA combinations which in turn instruct different productions of protein. The introduction of variants into the breeding population precisely represents an increase in genetic information.
I'm left with the opinion that the research teams mentioned in the article are grasping at straws rather than giving a rock solid explanation of why lactose doesn't affect some people like it does others. In my own family, some members can drink lactose-containing products every hour of the day and not be affected while others of us get pain and other digestive problems from merely drinking half a glass of milk.
Frank....Of course that's the case, there is more genetic variation within a population than between populations, and thus it is quite typical that a member of a family would have one variant and another member would have the other (think in terms of Mendelian genetics). Just because one population has the variant and another one lacks it does not mean that all members or even most members of the first population would have the variant.
If we take a drink of something and discover in the drinking that it's poison, don't we decide never to drink the stuff again, if we're fortunate enough to survive? Doesn't plain common sense tell us never to drink it again? And if we care about our children, don't we warn them never to drink it? So what's the chance of our descendants some thousands of years later getting adjusted to the stuff if nobody down the line ever drinks what their ancestors have learned to avoid?
I think you are misunderstanding what the article is saying. Nobody is claiming that "nobody down the line ever drinks what their ancestors have learned to avoid". In fact, prior to animal husbandry, people wouldn't have necessarily "learned to avoid milk" but rather had little opportunity to drink it after weaning (e.g. people didn't sneak up to wild animals to milk them). Nor would people have necessarily "learned to avoid milk" after animal husbandry began. It certainly could have been used with children to substitute for breast milk (thereby helping mothers conserve their nutrition), or at least supplement for it. Children who have been weaned may continue to drink animal milk, and thus continue to drink milk at slightly older ages. Those who have the mutation (the actuation of which could have occurred long before animal husbandry began, which did not begin to confer any advantage until animal milk entered the diet), could thus continue to drink milk at older ages than those without it (who would have stopped drinking milk when production of the lactase enzyme wound down). Since those who had the gene were better fed and better survived childhood mortality, the gene became more and more common in the general population in successive generations, until it got to the point in which those who could not tolerate milk in adulthood (e.g. who continued to switch off lactase production) became the minority in the population. This scenario bears no resemblance to the "drinking poison" scenario in your post.
The article compared ancient groups that imbibed lactose and those that didn't. Lactose was bad for both groups, according to the article. But the group that imbibed the stuff, bad as it was, made improvements, but it took millenniums for it to happen. Based on the article, as I see it, we ought to ignore experts who warn us about poison mushrooms. We may die sooner than we want, but our descendants some thousands of years later will be the better for it.
Again this is much too simplistic, such that this is a straw man argument. It wouldn't have taken millennia for some our milk-drinking ancestors to benefit from milk....indeed, some would have benefitted right away ... such as nursing children and those who already had the mutation. What took time was for the mutation to spread throughout the general population so that it displaced the frequency of the gene that switched off lactase production. Milk was also beneficial for adults in the form of aged hard cheeses which contain little or no lactose. As the mutation became more and more common in the population, adults would more commonly tolerate also softer cheeses, and finally milk itself. And even for those who were lactose intolerant, occasional drinking of milk in famines would have been beneficial (e.g. a little diarrhea, if water is plentiful, is better than starvation). There is no analogy with poison mushrooms. Is there a group in the population that already can benefit immediately from them? Can poison mushrooms be consumed by the average person in some other form? Are poison mushrooms similar to milk for the lactose intolerant person in terms of nutrition outweighing health concerns (bear in mind the famines and very low average life expectancy faced by our ancestors)?
Hi Satanus, I think what Frank is saying is that if a tribe could deduce that milk was fatally harmful then why would they continue to ingest it at all anyway, why would they need to adapt. Is this correct Frank?
GBL....To further respond to Frank, early childhood mortality was already "fatally harmful" to children. A mutation that would enhance the nutrition of children by prolonging the age at which milk can be consumed would naturally confer an advantage over those who became lactose intolerant as they grew up. They have a food source that lactose intolerant children would not have without certain reprecussions. After a number of generations, the "tribe" would be dominated by those who were tolerant of milk because childhood mortality negatively impacted those who were intolerant.