Monday, January 19, 2009
Sharon Begley, writing at Newsweek, would have you think that new research is casting serious doubts on the validity of the theories of evolution and molecular biology.
Teamed with genetics, Darwin's explanation of how species change through time has become the rock on which biology stands. Which makes the water flea quite the skunk at this party.That "somehow", as Begley correctly notes, is called a "genetic switch", and the notion that a primitive species like the water flea might use one to determine whether offspring develop "helmets" makes perfect sense -- in the context of Darwinian evolution and the genetic theory of inheritance.
Some water fleas sport a spiny helmet that deters predators; others, with identical DNA sequences, have bare heads. What differs between the two is not their genes but their mothers' experiences. If mom had a run-in with predators, her offspring have helmets, an effect one wag called "bite the mother, fight the daughter." If mom lived her life unthreatened, her offspring have no helmets. Same DNA, different traits. Somehow, the experience of the mother, not only her DNA sequences, has been transmitted to her offspring.
That gives strict Darwinians heart palpitations, for it reeks of the discredited theory of Jean-Baptiste Lamarck (1744–1829). The French naturalist argued that the reason giraffes have long necks, for instance, is that their parents stretched their (shorter) necks to reach the treetops. Offspring, Lamarck said, inherit traits their parents acquired. With the success of Darwin's theory of random variation and natural selection, Lamarck was left on the ash heap of history. But new discoveries of what looks like the inheritance of traits acquired by parents -- lab animals as well as people -- are forcing biologists to reconsider Lamarckism. [minor format edits, bold added]
Clearly, a water flea without a helmet would be ill-adapted to survive in an environment rich in predators. Perhaps not so clear is the fact that a water flea with a helmet has at least one disadvantage to one that does not: That helmet has to come from somewhere. The superior armament will cost it more food. In an environment where there are no predators, then, a helmet-less water flea has an advantage in needing less food.
What solution is best? Predators aren't always a problem for water fleas, so a species that saddled itself with unneeded armament would be wasting precious food. (And, I suppose, creationists would pounce on that as an example of how God was telling puny man that He was in charge.... What Intelligent Designer would fail to sign His work?)
But predators sometimes are a problem. Gosh, perhaps an organism that could either have a helmet or not have one as needed would have an evolutionary advantage! I am no expert on water fleas, but something tells me that they don't live too long, so its best bet as a species would be -- oh, I don't know -- to evolve the capacity to turn the helmet gene(s) on or off from one generation to the next. (News flash: Genetic switches, as "gene regulatory proteins", are encoded in the DNA by genes.)
Well! I'll be switched! That's exactly what happened!
But Begley either does not understand this fully or she is an active, dishonest opponent of the theory of evolution, as we see in another example:
Since 1999 scientists in several labs have shown that an experience a mouse mother has while she is pregnant can leave a physical mark on the DNA in her eggs. Just to emphasize, this is not a mutation, the only way new traits are supposedly transmitted to children. Instead, if mother mouse eats a diet rich in vitamin B12, folic acid or genistein (found in soy), her offspring are slim, healthy and brown -- even though they carry a gene that makes them fat, at risk of diabetes and cancer, and yellow. It turns out that the vitamins slap a molecular "off" switch on the obesity/diabetes/yellow-fur gene. [minor format edits, bold added]Yes, a genetic switch has been thrown, and it affects the physical appearance of offspring. But without the genetic code already in place (including both the regulated genes and the switch proteins other genes encode), neither the range of possibilities nor the switching mechanism we're busy distracting ourselves with would even exist.
In Begley's defense, some of the scientists she draws upon seem not to understand how to hold new data or complicated theories such as evolution and genetics in their proper context, and Francis Crick's foolish decision to refer to his theory of inheritance as the "Central Dogma of Molecular Biology" has not helped. On the other hand, the fact that the phenomenon of epigenetic inheritance has been known about for quite some time indicates that further research was warranted -- on Begley's part.
There is no great controversy here. Epigenetic inheritance, far from being a reason to resurrect older, discredited or -- worse -- arbitrary theories of speciation, actually serves as further evidence in support of Darwinian evolution and molecular biology. Begley just insulted the guest of honor by calling it a skunk!