Monday, January 05, 2009

neo-Lamarckism and neo-Darwinism, mainly

Jean-Baptiste Lamarck, sittin and thinkin in front of the jardin des plantes, Paris

Oikumene: As used in Karen Armstrong's A History of God, the Oikumene is the Greco-Roman world or civilisation, blended with Christianity. Within the Greco-Roman tradition it refers to the 'whole world', as opposed to the barbarian fringes which were regarded as not really of this world. The derived term ecumenical takes a more modern meaning of the world; creating a religion for all the world and all ages.

Axial age: a term coined by Karl Jaspers, referring roughly to the period immediately preceding the Oikumene, the era that according to him, gave birth to philosophy, but also many of the 'great' religious writings. 

I've wanted for a while to write about Lamarckism as a subject in the history of evolution, a faulty precursor to the theory of natural selection, and my recent reading of The Blind Watchmaker and especially its final chapter, 'Doomed rivals', has spurred me on, but I've been thrown into a bit of a tizz by listening to Radio National's 'Okham's Razor' the other day. The speaker, Ross Honeywell, wasn’t a scientist, and when he started going on about neo-Darwinian dogmatists and the unchallengeable orthodoxy I was ready to switch off after just having tuned in [I didn’t even know it was Okham’s Razor at first, I thought it was one of those summer season new-age crank shows].

Then the name Lamarck came up. As Honeywell pointed out, all too rightly, Lamarck has received a raw deal from history. An outstanding pioneering biologist [and apparently the first user of the term ‘biology’], founder of invertebrate zoology – the term ‘invertebrate’ was also his coinage – he came up with a theory of evolution via the inheritance of acquired characteristics that seemed plausible, and even self-evident on reflection, to most nineteenth century naturalists, including Darwin himself.

But Honeywell was saying far more than that Lamarck was not just a failed theorist. He was saying that recent evidence showed that some characteristics, acquired during a lifetime, could be passed on to the next generation.  Further, he seemed to be saying that the neo-Darwinists were out to suppress and belittle this evidence. Naturally I was sceptical. Dawkins’s treatment of Lamarckism was pretty damning, or seemed so to a layman like myself. Was it too damning, though? Was there a dogmatism I hadn’t noticed within the careful argumentation?

So I thought I would look again at what Dawkins had to say about Lamarckism in the light of Honeywell’s claims. Dawkins isolates two related elements of Lamarck’s theory adopted by his modern followers; the theory of acquired characteristics and the principle of use and disuse. I’m essentially focussing on the former. One example Dawkins gives is that of the soles of the feet becoming tough and horny after a lifetime of walking on hard stony ground. It was thought that the offspring would acquire tougher soles as a result. Dawkins’ response is that no proof has ever been given that such characteristics are inherited. Presumably the soles of babies born to tough-soled parents are no tougher that those born to soft-soled sedentary parents. In fact, according to Dawkins, no evidence of the inheritance of any acquired characteristic has ever been provided, though he is quick to point out that it may be provided in the future, and Lamarck will then regain his prestige and stand up there with Darwin, for the two theories are quite compatible.

But Dawkins seeks to refute Lamarckism more thoroughly by means of embryology. Honeywell also speaks of embryology, without using the term, when he introduces a concept known as the Weismann barrier. Unfortunately, Honeywell’s description of the concept is clearly flawed and brings out my sceptical antennae.

 For neo-Darwinists, hereditary information comes only from DNA in our sex cells: our germline. Our body cells, the building blocks of our entire being, have no say in the matter whatsoever. It's a one-way street with a brick wall at one end. This is known as the Weismann Barrier, named after the 19th century biologist August Weismann, who proposed that DNA in those very few sex cells, sperm and eggs, remains unchanged as a repository of the instructions that determine the next generation.

The flaw being that Weismann, who died in 1914, proposed nothing about DNA because nothing was then known about the properties of DNA [called nuclein when it was first discovered in the nineteenth century], and little was known about genes in general.

 To be continued.



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