Thursday, June 25, 2009

Lamarckism: Lessons from History   posted by DavidB @ 6/25/2009 03:20:00 AM

In my recent post on Darwin's mechanisms of evolution I was rather dismissive about the Inheritance of Acquired Characteristics (IAC), commonly known as 'Lamarckism'. Darwin himself believed in the existence of IAC but gave it a relatively minor role in evolution. In comments on my post it was pointed out that there has recently been some revival of interest in IAC in the form of 'transgenerational epigenetics'. For a recent review see here. [Note added: as originally posted I somehow inserted the wrong link. Hope this one is now correct.]

Even if all of these reports are true, they don't (yet) amount to more than a small tweaking of evolutionary theory. The main examples seem more like congenital syphilis than 'Lamarckism' in the traditional sense: an animal is exposed to a substance that happens to affect the germ cells as well as the rest of the body. No big deal. But I think biologists should be cautious about accepting such reports without clear independent replication, for two reasons. First, because 'extraordinary claims need extraordinary evidence'. Second, because there is a long and dreary history of unsubstantiated, unreliable, and downright fraudulent claims about IAC. As much of this history is now generally forgotten, it may be useful to recall some of the 'highlights'.


Brown-Sequard was a distinguished if eccentric French physiologist. He achieved scientific fame for the discovery of what are now known as hormones, and notoriety when he claimed that life could be rejuvenated by the injection of crushed animals' testicles. At least he was willing to try it on himself. But the present point of interest is in his neurological experiments. For many years he experimented on thousands of guinea pigs, mainly by severing various nerves. He claimed that the untreated offspring of the experimental subjects showed certain symptoms, such as a liability to epileptic fits, which resembled those of the parents. Charles Darwin accepted the evidence as proving that IAC was at least possible. Darwin's younger friend George Romanes, a supporter of IAC, spent years trying to replicate the experiments, and claimed some slight success, but admitted that on the whole the results were negative. Brown-Sequard's results have never been conclusively explained, but unexplained results are not unusual in science. The Germans have the useful term 'Dreckeffekt' for this kind of thing.


[Apology: I first gave the name as 'William Edward Tower', but on checking my source again I find the initials are 'W. L.'. Apologies if anyone has wasted time following up the incorrect name.]

Tower was an American entomologist who claimed in the early 1900s to have produced inheritable mutations in beetles by changes in temperature and humidity. The pioneer geneticist William Bateson questioned Tower's results and became increasingly critical, hinting at fraud. Tower admitted that there were errors in his reports, and claimed that his original records had been destroyed by a fire in his greenhouse. Hmm.


Kammerer's experiments on the Midwife Toad, made famous in a sympathetic book by Arthur Koestler, led to tragedy when it was discovered that the specimens had been artificially tampered with, and Kammerer committed suicide. There was certainly skullduggery by someone, though whether by Kammerer himself remains controversial.


Heslop-Harrison was an English botanist and entomologist who claimed to have induced heritable melanism in insects by chemical treatments. His claims were questioned by Haldane, Fisher and others. There must be suspicion of fraud, as Heslop-Harrison later became notorious for the unconnected allegation that he (literally) planted evidence on the Scottish island of Rhum to support his botanical theories. [NB Heslop-Harrison must not be confused with his still living son of the same name, also a botanist. ]


McDougall was a leading psychologist in the first half of the 20th century. He carried out a long series of experiments on rats which seemed to show that successive generations became better and better at learning mazes. I don't think anyone has suggested fraud, but subsequent attempts at replication pointed out a major defect in his methodology: the absence of a control group. When a control group was used, whose ancestors had not been trained, they showed much the same patterns of improvement - or non-improvement - as the experimental subjects themselves (see here.) The improvement therefore seems to have been due to some other factor or factors, such as better laboratory or cage conditions, and not to IAC.


No need to comment.


Edward Steele is an Australian immunologist who claimed in the 1970s to have produced inheritable immunological responses in mice. This led to a predictable spate of 'Darwin was wrong' and 'Back to Lamarck' news reports. Less publicity was given to at least three independent replication attempts with negative results.

The moral is - oh, draw your own.