Usually, Begley is reasonably good on science, but her latest piece is one big collection of misconceptions. It reflects a poor understanding of the science and of history, in that it confuses long-standing recognition of the importance of environmental factors in gene expression with a sudden reinstatement of Lamarckian inheritance, and it simply isn’t — she’s missed the point of the science and she has caricatured Lamarck.
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.
She’s describing real and interesting phenomena, but it isn’t new and it isn’t revolutionary. These are results of plasticity and epigenetics, and we aren’t having heart palpitations over them (you’re also going to have a difficult time finding any “strict Darwinians” in the science community who are even surprised by this stuff). We load up pregnant women with folate and maternal vitamins and recommendations to eat well, and we tell them not to get drunk or smoke crack for a few months, because it is common sense and common knowledge that extra-genetic factors influence the health and development of the next generation. Genes don’t execute rigid, predetermined programs of development — they are responsive to the environment and can express radically different patterns in different contexts. The same genes build a caterpillar and a butterfly, the difference is in the hormonal environment that selects which genes will be active.
It’s the same story with the water fleas. Stressed and unstressed mothers switch on different genes in their offspring epigenetically, which lead to the expression of different morphology. It’s very cool stuff, but evolutionary biologists are about as shocked by this as they are by the idea that malnourished mothers have underweight babies. That environmental influences can have multi-generational effects, and that developmental programs can cue off of the history of the germ line, is not a new idea, especially among developmental biologists.
This is just wrong on evolution:
Water fleas pop out helmets immediately if mom lived in a world of predators; by Darwin’s lights, a population of helmeted fleas would take many generations to emerge through random variation and natural selection.
It misses the whole point. The population of water fleas have a genetic attribute that allows the formation of spines under one set of conditions, and suppresses them under others. This gene regulatory network did not pop into existence in a single generation! If it did, then Begley would have a big story, evolution would have experienced a serious blow, and we’d all be looking a little more carefully into this ‘intelligent design’ stuff. The pattern of gene regulation was the product of many generations of variation and selection; only the way it was expressed in a phenotype experienced a shift within a single generation.
It’s also not Lamarckism. It’s another of those short and simple-minded myths perpetuated by high-school textbooks that Lamarck and Darwin had competing explanations for the same phenomena. They did not. This story of giraffes stretching their necks is an example of the purported inheritance of acquired characteristics … and here’s some headline news, Darwin proposed exactly the same thing! Darwin did not have a solid theory of heredity, and he himself proposed a mechanism of pangenesis which permitted the inheritance of characters by use and disuse and by injury or malformation. The key difference is that Darwin proposed that these variations could lead to the formation of new species; Lamarck believed in the fixity of species, and thought that a species would merely express a constrained range of forms in differing environments.
Both were wrong. A concept called the Weismann barrier emerged in the late 19th century, which suggested that the only influences that can be transmitted across generations are those that affect the germ line, the cells that give rise to sperm and egg, and that modification of the somatic tissues alone would not propagate. This is correct, and it’s still true: nothing in these reports suggest anything but that when perturbed by environmental stressors, gametes can switch on different genetic programs.
I think epigenetics and plasticity are important and play a role in evolution, certainly, but these kinds of elaborations on how cells interact do not imply in any way that there is a revolution in evolution, or that evolutionary biology has had it all wrong, or that this is heresy in progress. It’s also annoying to see all the vague handwaving about discrediting a “Darwinian model” — what Darwinian model? These discoveries are about mechanisms of genetic inheritance, and Darwin didn’t have a valid mechanism in the first place. In that sense, the only real heresy that counted was Mendel’s.