At celebrations of Charles Darwins 200th birthday,Lamarckismthe inheritance of acquired traitswill be the skunk at the party
By all rights,2009 should be his year,as books,museums and scholarly conclaves celebrate his 200th birthday and the 150th anniversary of On the Origin of Species. Darwins explanation of how species change through time has become the rock on which biology stands. Which makes the water flea the skunk at this party.
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 necks to reach the treetops. Offspring,Lamarck said,inherit traits their parents acquired. With the success of Darwins 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 parentslab animals as well as peopleare forcing biologists to reconsider Lamarckism.
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. If mother mouse eats a diet rich in vitamin B12,folic acid or genistein (found in soy),her offspring are slim,healthy and brown. This was the first evidence,now confirmed multiple times,that an experience of the mother can reach into the DNA in her eggs and alter the genes her pups inherit. There can be a molecular memory of the parents experience,in this case diet, says Emma Whitelaw of Queensland Institute of Medical Research,who did the first of these mouse studies.
The new Lamarckism doesnt mean that human moms who work out will pass along toned abs to their children,or that human dads who dye their hair red will have red-haired children. But evidence suggests Lamarckism acts in people,too. In 2005,scientists in London found that the grandsons of men who had abundant food when they were boys (the study was done on men in a small town in northern Sweden) were much more likely to have diabetes and to die an early death than were the grandsons of men who suffered food shortages as boys.
The existence of this parallel means of inheritance,in which something a parent experiences alters the DNA he or she passes on to children,suggests that evolution might happen much faster than the Darwinian model implies. Darwinian evolution is quite slow, says Whitelaw. But if children can inherit DNA that bears the physical marks of their parents experiences,they are likely to be much better adapted to the world theyre born into,all in a single generation. The new Lamarckism promises to reveal how the environment affects the genome to determine the ultimate traits of an individual, says Whitelaw.