Friday, September 24, 2010

Lamarck as Darwin's antagonist in Origin; Darwin had related ideas

As suggested by Professor Ogden in lecture (9 Sept 2010), when looking for antagonists while reading Origin, one candidate is Lamarck.


Darwin takes multiple opportunities to diminish the ideas of Jean-Baptiste Lamarck ('inheritance of acquired characters' where actions lead to heritable physical changes - a common example given is an individual giraffe wanting to reach high leaves, so it stretches its neck, leading to longer necks in its offspring, and thereby to longer necks in the population over time).


Darwin also had similar ideas himself: namely, his theory of pangenesis. In Origin, Darwin refers to the disuse of organs leading to their reduction or absence in populations over time. He lists, for example, the loss of upright ears in domesticated animals and the loss of sight in cave-dwelling creatures.

The subject is summed up nicely in Richard E. Leakey's introduction to The Illustrated Origin of Species

On the basis of his experiments with domesticated species, Darwin wrote a two-volume treatise on domestication, published in 1868, in which, he developed a theory of heredity which he called 'pangenesis'.

In this theory Darwin postulated that each organ of the body gives off microscopic particles which he called 'gemmules' and that these gemmules are collected in the reproductive organs where they can influence the corresponding shape, size, and functions of the organs of the offspring. Darwin wanted to account for his belief that some characteristics or habits acquired during a parent's lifetime could affect the corresponding attributes of its offspring. This he usually called 'use-and-disuse heredity': the more familiar phrase is 'the inheritance of acquired characters' or 'Lamarckism', named after Jean Baptiste de Lamarck. However, Lamarck's theory was rather different in that he postulated a desire for change, or besoin, which caused that change to happen in the organism itself and then to be passed on to its offspring. In Darwin's time this aspect of Lamarck's theory was not generally accepted, but virtually every scientist believed that characters acquired by use or disuse could be inherited.

Darwin developed his theory of pangenesis in order to describe how use-and-disuse inheritance could occur. But he realized his theory was purely speculative and therefore put little faith in it. When it was soundly criticized by his cousin Francis Galton (himself an eminent psychologist, statistician and student of heredity), Darwin quietly dropped pangenesis, though he continued to accept the inheritance of acquired characters.

As evidence of Darwin's continuing influence, a 2009 article posted on the Institute of Science in Society site indicates that even 150 years later, researchers are still drawing connections to Darwin's pangenesis theory. The article details blood transfusions between different coloured birds, resulting in plumage colour changes over generations.

Interestingly, there is also ongoing research by Nishihara (Verification of Use and Disuse theory of Lamarck in Vertebrates Using Biomaterials) to test Lamarck's theory as well, as published in Biogenic Amines in 2003.


Taking a step sideways, the notion that genes are not the only carriers of human legacy is a popular one. In Richard Dawkins influential neo-Darwinian book The Selfish Gene , the last chapter of the original edition takes a radical departure from genetics and introduces the concept of memes as the mechanism of cultural transmission. "What, after all, is so special about genes?"

Defined as "a unit of cultural transmission, or a unit of imitation ... Examples of memes are tunes, ideas, catch-phrases, clothes fashions, ways of making pots or of building arches. Just as genes propagate themselves in the gene pool by leaping from body to body via sperms and eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation."

Dawkins suggests religion as a prime example of a meme:

Consider the idea of God ... Probably it originated many times by independent 'mutation' ... How does it replicate itself? By the spoken and written word, aided by great music and great art. Why does it have such a high survival value? ... its great psychological appeal. It provides a superficially plausible answer to deep and troubling questions about existence.

As shown by the recent article referring to Darwin's gemmules, and by Dawkin's extension of neo-Darwinian genetic theory to cultural transmission by memes, it is clear that Darwin's ideas continue to inspire research, discussion, and ideas. Far from being antiquated and outdated, Darwinism remains relevant and as this blog's title asserts: 'Darwin Kicks Butt'.

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