Evolution: Back in time?

This has been a difficult but very cool subject. National Jewish is not only a clinical center but seems to have a "think tank" quality to it as well.

Evolution has been accepted as a product of Darwin and natural selection but with recent discoveries of the human genome, genetics, evolution and molecular biology there may be some devolution in evolution. Before I start let me tell you about a scientist by the name of Jean Baptiste Lamarck. He lived a generation before Darwin and worked as a French biologist. His theory of adaptation in animals contradicted Darwin, or vice versa. Darwin, in his theory including natural selection, argued that the environment selects out survivors who then pass their surviving genes on to the next generation, who pass their genes on etc. With mutations and the like that may make generations even more resilient in the future.

Lamarck believed that organisms adapt to their environment within the lifetime of the organism. For example a giraffe may grow a longer neck if it finds itself in an environment with tall trees. Darwin and his colleagues debunked this theory and we have his thoughts lasting through history until now.

Well, in fact the two may act in accordance with each other. Nature v. nurture, it seems, is being defined in a way that makes scientific sense, not just in a way that would make sense to your mother. Mine would say, "you don't need science to know that." But it's nice that science can prove it...I think.

Dr. Choudry of the University of California, San Francisco, studied Latinas from Puerto Rico and Mexican-Americans. Puerto Ricans have individual ancestry predominantly from Africa and Native Americans and Mexicans have individual ancestry from Europeans and Native Americans. Under all measures asthma severity was more prevalent in Mexican Americans when compared to Puerto Ricans. And there seemed to be a correlation between the amount of European ancestry in Mexican Americans and asthma severity. Interestingly, there was a reverse correlation based on the amount of Native American ancestry in both groups, i.e. the more Native American ancestry one has the less severe asthma. This suggest that ancestry plays a role in asthma. But, Dr. Busse of the University of Wisconsin, and others, have shown that "stress" can lead to changes in the immune system, airways and the brains of those with asthma leading to more severe asthma attacks when confronted with something that precipitates asthma. Nature v. nurture.

In tuberculosis, Dr. William Stead showed that that African-Americans in prisons and nursing homes were more prone to be infected with TB than those of European ancestry. But both groups developed active TB at the same rate. Interesting? Why? Nobody seems to know but many believe that it depends on the genetic make up of the different groups. This seems to be the nature part of nature v. nurture. The part that Darwin may have been very attentive to. The Europeans were apparently the first to encounter TB on a large scale because of their propensity to live with cows and to drink milk. TB is thought to derive from cows long ago. Over generations Europeans may have been passing genes on that are protective against TB infection. An extreme example of "genetic protection" occurred in New Guinea in the 1950s when TB was introduce to their island and decimated many. They were naive to TB and did not have the generations of exposure for natural selection to occur.

I have been a true believer in the predominance of natural selection in evolution until now. It seems that a certain Lamarckian aspect to evolution is creeping into the thoughts of scientists. These are people, who unlike me, probably don't go to many movies or watch sports every week-end because they work. These incredibly smart scientists, like Dr. David Schwartz at National Jewish, are presenting data that suggests the environment may actually change the way genes are expressed in things and this may change the way an organism adapts to its environment, not over generations, but within the life of the organism. This would be the nurture part of nature v. nurture. Although when I asked him specifically about Lamarck he did not think we would go back to that thinking, back to that idea that a giraffe could grow a longer neck to get to the leaves.

But the literature seems compelling enough to at least make me think that pure natural selection may not be so accurate in the evolution of organisms. Although I had a hard time understanding the detail of papers presented on this subject I did glean some useful information to make me believe in a more Lamarckian bent.

The building blocks of genes are nucleic acids and genes contribute to the production of amino acids that are the building blocks of protein, which in turn are the building blocks of organisms. Genes can be turned on and off depending on many things, many I don't understand, but it seems that the level of methylation (a methyl group looks like this...-CH3, where C is carbon and H is hydrogen) and the array of histone acetylation (histones are proteins that wrap around and within genetic material and an acetyl group looks like this...-COOH, where O is oxygen) play a significant role in interpreting what should be made.

In identical twins that look the same at birth it has been shown that over time they will diverge in appearance, much like my friends the Golden brothers who are identical twins. They are both bald, sorry guys, but have different appearance such that it is possible to tell them apart at their ripe age of 47. Dr. Frage, in a paper from Spain, showed that the level of methylation and histone acetylation is different in identical twins of old age and this change occurs as a consequence of environment. Not only that but once a cell has changed it will continue to divide with these changes intact. These changes of methylation, etc. are called epigenetics and epignetics can change the way proteins are made in a gene structure that is exactly the same. This can be observed in plants as well. When a blooming plant is taken to high altitude or to a cold environment it will bloom differently than one in your house. This is thought to be related to the way biochemistry changes at altitude or with temperature. Carbon, oxygen, nitrogen and hydrogen act differently depending on the environment. The Goldens look different because they have had different lives, one is a lawyer and sailed in the navy, and the other has been a fireman in the Midwest.

Finally, if you give pregnant mice a diet high in folate, a vitamin that will induce methylation of genes, the offspring will come out with differing colored coats depending on the level of folate given.

So I am becoming more convinced that the old adage nature AND nurture contribute to the appearance of an organism, and perhaps the way it may respond to disease, and Lamarck may have been onto something when he thought that an organism can "change" within its lifetime to adapt to its environment. I still respect Darwin. Now let's talk religion...