Jun 12, 2005

screw Dobzhansky: nothing in biology makes sense, period

Mr. Dembski just doesn't get it. Or perhaps refuses to get it. Or gets it, but will never admit it. Or gets it in a parallel universe. One can hope.

Josh Rosenau claimed that evolutionary theory has been useful even to the point of helping save lives. Overblown rhetoric, right?

Wrong.

NewScientist this week, discussing controversial new medications targeted to specific ethnicities, points to several maladies that are thought to have genetic links. Now, unlike Mr. Dembski, I respect NewScientist's subscriber-only policy, so I won't reproduce the article in its entirety. But I'll summarize a key chart below.

Sickle cell anemia is common everywhere except in northern Europe and North America because those continents are largely malaria-free. "The sickle-cell gene has been positively selected because people who inherit just one copy do not have sickle-cell anemia, but they are more resistant to malaria, a disease in which a parasite infects red blood cells."

Caucasians suffer more from cystic fibrosis, for yet-unknown reasons. Puerto Rican children are twice as likely to develop asthma; incidence is as high as 30%, compared to 5-16% in other populations.

Type 2 diabetes is common in the Indian subcontinent, likely because of mixed genetic and dietary factors. A similar mix of environment and genetic effects causes African Americans to suffer from a more aggressive form of prostate cancer.

Alcohol intolerance affects up to half the people of China, Japan, and Korea, due to a mutation in the gene for aldehyde dehydrogenase.

Breast, ovarian and prostate tumors arising from BRCA mutations are more common in Ashkenazi Jews; 1 in 40 carry these mutations, compared with 1 in 500 in the general population. A "founder effect" is the likely cause.

Multiple sclerosis is twice as common among European Americans than among African Americans, and quite rare in Africa. Genes and environmental factors are both implicated.

(Schizophrenia's ethnic connection is a matter of great dispute.)

These are just a few conditions from a gigantic list that are or may be genetic in origin, proximate cause, or effect. I'm sure a more savvy researcher could find far more.

Note that sickle-cell anemia, for example, demonstrates the interplay of mutation and selection. Carry the mutant gene? Fantastic. Now you're at less risk from one ailment, but at greater risk of passing another on to your children. (Or is that the forward-thinking of a beneficient designer?)

I could say more, but why re-evolve the flagellum? Evolutionary theory is useful.

8 comments:

Murky Thoughts said...

I suppose you could rationalize like a medieval person, without benefit of the principle of common descent, that relative to humans, monkeys are more similar than mice, and maybe you'd find it sensible to test drugs on immortal tissue you took from somebody's tumor, but I wonder if you'd bother looking for drug strategies in worms and flies. I imagine a few lives and a lot of misery has been prevented with drugs discovered in organisms you wouldn't think have anything to say about human physiology if you didn't believe in common descent. I don't buy your argument that our understanding of sickle-cell incidence as reflecting selection has saved lives. Knowing a disease is hereditary can save the lives of hypothetical progeny though genetic testing and marriage counseling, but that's not really saving lives and I don't see an assumption of common descent or NS in there.

Jim said...

I don't think of my list as a knock-down argument, which is why I included the link to a more robust description by people who know more than I.

In looking for mutations that affect only certain regions or ethnicities, we are operating in a framework of evolution--change in allele frequency over time, due to mutation, genetic drift, retroviral insertions, genetic duplication , whatever. We look to the genetic variances among different strains of bacteria and viruses to faster develop responses that can overcome their evolving defenses. We attempt to imitate and overcome evolutionary processes through gene therapy.

Mr. Rosenau has further thoughts, which I won't repeat here.

Murky Thoughts said...

Lots of people believe in genetic variabilty and heredity through DNA without believing in common descent, and the fact that HIV is a moving drug target is an empirical fact, the appreciation of and response strategies for which (I'm inclined to think) don't depend on or even benefit from an explanation.

Jim said...

Common descent is just one subset of evolutionary theory.

Murky Thoughts said...

Actually, I think "common descent" more or less says it all. We don't know how much of evolution is adaptation-driven under natural selection and how much is undirected under the influence of genetic drift and the founder's effect. But common descent the hard fact and framework with which we use the interpretive tools of Mayr's modern synthesis. I think rhetorically we'd be in better shape against the creationists if we talked about common descent instead of "evolution." "Evolution" is so abstract that it practically invites dismissal by the ignorant. It's harder to be ignorant of what scientists mean by "common descent."

Jim said...

I disagree mildly, but perhaps it's because I'm not tailoring this discussion to the masses. To my mind, "evolution is shorthand for common descent" is too much like saying "physics is shorthand for the Big Bang." But I'll let you have the last word.

Murky Thoughts said...

What if I say the last word is your momma? (wink)

Vito Papenfuss said...

it was pretty awesome.