Volume 9, No. 9 - December/January 2000
"At the end of a turbulent and violent century, neo-Darwinism apparently remains impregnable--much like Communism just prior to its dramatic implosion." So write the latest critics of evolutionary dogma. Is neo-Darwinism about to collapse? Certainly the Darwinian view has had its share of challenges during the past century, and has survived them. This challenge, however, comes from a novel direction.
The molecular immunologist Edward J. Steele, based at the University of Wollongong in Australia, claims to have evidence for a Lamarckian hereditary mechanism. He and his colleagues believe they are on the verge of a revolution, but the old-guard neo-Darwinists aren't having any of it.
The French biologist Jean-Baptiste de Lamarck (1744-- 1829) outlined a theory of evolutionary change in 1809, fifty years before Darwin's On the Origin of Species. The basic idea was that organisms make biological changes in adapting to their environment and then pass these changes on to their offspring. Since then, Lamarck has been ridiculed for presumably implying that giraffes developed their long necks by stretching, generation after generation, toward the leaves on trees.
Modern biologists are adamant that nothing of the sort occurs, ever. Steele first claimed to have experimental evidence to the contrary back in 1979, when he and his colleague Reginald Gorczynski were visiting researchers at the Ontario Cancer Institute in Toronto. Together, they injected infant male mice with cells from a different group of mice and watched as the infants' immune systems developed a tolerance to the foreign cells. Then they claimed to observe the same tolerance in many of the mice's offspring.
Biologists in Britain were intrigued enough to try to repeat Steele's experiments themselves. Playing the part of the open-minded scientist, Nobel laureate Peter Medawar told the Sunday Times of London, "I have no idea what the outcome will be but I hope Steele is right." After an impressive effort, however, these experimenters ended up with very different results. What followed was a classic scientific duel. Steele and Gorczynski claimed the new data were being misread. Medawar's colleague Leslie Brent went another round, this time conducting what a commentator called "one of the most serious attempts I have ever seen to reproduce an experimental protocol in detail." Brent reported negative results again. Each group claimed the other had misinterpreted data and made technical oversights.
Without consistent results, Steele had just a brief time in the spotlight. His claims, however, did draw endorsements from such prominent figures as Arthur Koestler and the philosopher Sir Karl Popper, who picked Steele's small book Somatic Selection and Adaptive Evolution as the "most exciting" of 1979. Meanwhile, Steele has continued his work during the past two decades. Most recently, he has co-authored Lamarck's Signature: How Retrogenes Are Changing Darwin's Natural Selection Paradigm (Perseus) with fellow immunologist Robert V. Blanden and technology expert Robyn A. Lindley (who has been married to Steele since 1982).
Steele and his colleagues insist their gripe is not with Darwin; in fact, they enthusiastically point out that Darwin himself advocated the existence of a Lamarckian mechanism in tandem with natural selection. If you haven't heard of his "pangenesis" theory, it's probably because contemporary neo-Darwinists have maintained an embarrassed silence about it. Rather than Darwin, it is the German biologist August Weismann (1834--1914) that Steele and company seek to overthrow. In 1885, Weismann proposed that an uncrossable barrier protected reproductive cells from being affected by changes elsewhere in the body (Koestler later referred to it as a "genetic chastity belt"). Weismann famously "proved" his claim by cutting off the tails of several generations of rats to show that their offspring were not born tailless.
In attempting to revive Lamarckism, Steele and his colleagues have focused their attention on the immune system. The immune system is a mini- evolutionary puzzle of its own: How is it that our bodies can quickly respond to so many different kinds of attacks? Is all this information in the genes? If so, then how does our immune system respond to new diseases?
Steele notes that the altered RNA might then revert itself back into DNA, picking up more typos along the way. Indeed, such "reverse transcription" of RNA back into DNA has been observed frequently in other contexts. In the immune system, the mutations that lead to success in combating disease will multiply. Thus Steele suggests those same mutations will have the best chance to be transferred via reverse transcription back into DNA.
But the difficult leap for Lamarckians is this: Could this new DNA then be carried to the reproductive genes (in the sperm and egg cells), replace the original DNA there, and so be passed on to an organism's offspring? Steele and company have devised an elegant, but speculative, story to describe how this crossing of Weismann's barrier might happen using known biological mechanisms. In short, they believe a virus could carry the altered DNA to the reproductive cells and replace the DNA in those cells.
Hard-line neo-Darwinists (in other words, most biologists) are not so quick to make this leap. They set the bar very high for overturning a central tenet of biology. This strategy is understandable given past attacks on the Darwinian story from creationists and others. And many Darwinians suspect the Lamarckians of harboring a sentimental and unscientific fantasy of overcoming the blind chance involved in evolutionary change. The theory's past associations do little to dispel this worry; at a particularly memorable low point, the Lamarckian Soviet biologist Trofim Denisovich Lysenko coordinated the official arrest and imprisonment of several rival geneticists. Another Lamarckian, the Austrian Paul Kammerer, was accused of doctoring his experimental toads with India ink so that they would appear to have inherited certain telltale characteristics.
But might the neo-Darwinists be skeptical to a fault? Interestingly, Richard Dawkins, neo-Darwinism's most ardent champion, found Steele's work worthy of comment in his book The Extended Phenotype (1982). Instead of casting doubt on Steele's hypothesis, Dawkins argues that it is not really Lamarckian at all. "Far from being uncomfortable for neo-Weismannists, it turns out to be deeply congenial to us." Dawkins is not disturbed by the prospect of RNA from the immune system being read into DNA in the reproductive cells. He simply insists that the selection of which mutations get written into the genetic code must occur according to Darwinian principles of undirected trial and error, as Steele agrees is the case within the immune system.
But even if the process Steele and his colleagues describe is possible, does it ever actually occur? Evolutionary mechanisms are never observed directly, so we must make do with circumstantial evidence. Steele and his colleagues claim recently to have found such evidence--a "signature" of past events. It is "written all over the...genes" that carry instructions for immune system responses. They claim that a distinct pattern of mutations concentrated in particular areas of these genes "strongly suggests" that in the past, information from the immune system has been transferred into DNA and in the reproductive organs.
Other biologists are not so easily swayed. Laurence Hurst, a professor of evolutionary genetics at the University of Bath, suggests there may be other, less radical explanations for the pattern of mutations that Steele cites. "I remain to be convinced that Lamarck's signature is not easily mistaken for someone else's," he wrote recently in the New Scientist. Moreover, if Steele and his colleagues turn out to be right about the immune system, it is not clear that a similar mechanism operates elsewhere. Organisms may be able to pass on an acquired immune system tolerance to their offspring, but can they pass on anything else? A long neck? A fondness for strawberries?
Nevertheless, Steele and his colleagues have opened up an intriguing area of research. For example, independent of any Lamarckian phenomena, their work may eventually help to explain how the immune system copes with a diverse array of invaders. Blanden admits that "the hard-liners are very unlikely to change." But he and the others believe that young immunologists, whose work does not directly bear on evolution, might be more open minded. Indeed, there is at least some evidence that times may be changing. "I have not been shouted down in a seminar since 1994," says Steele.
Mark Parascandola is a historian and philosopher of science. His article "Philosophy in the Laboratory: the Debate over Evidence for E.J.Steele's Lamarckian Hypothesis" appeared in Studies in the History and Philosophy of Science (1995).
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