Evolution

Lamarcks Theory of Evolution and its Legacy



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Lamarck is an almost forgotten, pre-Darwinian evolutionist. Born Jean-Baptise Antoine de Monet in 1744, he used 'Chevalier de Lamarck' as a pen name. He wrote extensively on botany as well as his findings on the classification of animals. His was a brilliant mind and he paved the way for those who came after him.

One of the most useful things that Lamarck did was to come up with a simple system of identification of animals based on a simple flow-chart arrangement of yes or no answers about the animals attributes. This has largely been superseded by Linnaeus' more complex classification system, but it is still useful for the layman.

Following Erasmus Darwin, Lamarck's work led him to appreciate the way in which very different creatures have underlying similarities, indicating the possibility of them having developed from common ancestors.

In his 'Philosophie biologique' (1809), Lamarck was the first person to publish the theory that complex creatures have developed over time from simple ones. His theory of evolution was based on the idea of 'use' and 'disuse' of organs in response to environment. He put forward 2 'laws' to illustrate this.

The 1st Law is about the principle that use strengthens and disuse weakens. The 2nd Law says that modifications in an organism caused by the first Law are passed on to offspring.

His, (rather heretical at the time) argument was that the pressures placed on a species by their environment caused them to change in response over time. Previously it was thought that animals were created perfect by Nature, or God, and that their attributes dictated the animals behaviour. As proof he points out that environments are constantly changing, and that animals have to adapt to survive. All of this was very progressive thinking, many years before Darwins voyage to the Galapagos on the Beagle.

Somewhat unfairly, Lamarck has largely been ignored by later evolutionary theorists because he could offer no convincing ideas as to the mechanisms of such change. For one thing, the idea that changes caused in the parents by their environment could be passed directly to their offspring was far too simplistic. It doesn't matter how many times you breed rats with their tails cut off, the offspring will still have tails. Lamarck, of course, could have no idea bout genetics or genetic variability. This wasn't to be thought of until well into the 20th century.

One of his ideas was that change was based on what the animal 'wanted'. For example, most famously, he theorised that giraffes developed long necks because they 'wanted' to reach the leaves at the tops of trees, so they educated their young to reach upwards. This has turned out not to be quite as ridiculous as it sounds. Julianne Kaminski, a cognitive psychologist studying language development in Welsh Border collies, has recently said:

'Dogs understanding of human forms of communication is something new that has evolvedbecause of their long association with humans'

She suspects that:

'These collies are especially good at it because they are highly motivated.'

However, the reality is much more complicated. Changes do take place in response to environment, but they take a great deal longer to become inheritable than Lamarck would have thought and have more to do with genetic mutations than the animals wishes. Despite these mistakes in his thinking, he was the first to talk about the process of adaptation to environment.

Lamarck's writings are interesting these days for mainly historical reasons. He came up with the first classification of invertebrates and he was first to bring the word 'biology' into common usage. He was certainly read by the likes of Darwin and Wallace, so that their legacy can also be counted as his. In any case, we can't help but be impressed with what was, at the time, very lateral thinking which paved the way for those who came after.

Sources

Zoological Philosophy, An Exposition with Regard to the Natural History of Animals by J.
B. Lamarck 1809. (Translated by Hugh Elliot, 1914)

Philip Whitfield, 'Evolution: The Greatest Story Ever Told' Marshall Press 1993

Vince Musi, 'Animal Minds' National Geographic March 2008

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