Happy 277th birthday, Jean-Baptiste!
It has been customary for me to write a post every 1st of August celebrating the anniversary of the scientist who was, as far as I can see, the first evolutionary biologist. No, not Charles Darwin, but Jean-Baptiste Pierre Antoine de Monet, the Chevalier de Lamarck. Born in 1744 to an impoverished branch of the French nobility, he wrote books on botany, coming to the attention of the Comte de Buffon, who employed him in the royal botanical garden in Paris. After Buffon’s death and the French Revolution, he was appointed to the least important curatorship in the new Museum of Natural History, as curator of “worms”, i.e., invertebrates.
Although originally a botanist, he became fascinated by the structure of invertebrates, and from 1801 on he argued that they had evolved in a treelike genealogy. His theory was propounded in his 1809 book “Philosophie zoologique”. Although it never convinced most zoologists, it influenced many thinkers in the early 1800s, including Charles Darwin.
Lamarck was not a crackpot but an important pioneer of invertebrate biology (he coined the words “invertebrate” and “biology”). He also put forward the first proposal for a mechanism explaining adaptation. No, not natural selection, but use and disuse. This is widely misunderstood, In what follows I want to briefly explain how it is that people who think of themselves as Lamarckians get it wrong.
Lamarck had two processes. One was a rather mysterious inherent complexifying force, which he thought was a basic physical principle of some sort. It does not really explain why a species getting more complex would also be adaptive. And of course even by as soon as 100 years later, when physics and chemistry were much better understood, no one thought that there was any such principle. So the Lamarckians of the late 1800s quietly forgot about that part of Lamarck’s theory.
The other process was use and disuse. Organisms used their various organs, such as eyes, limbs, leaves, etc. to try to cope with their environments, and these strivings were inherited by their offspring in ways that resulted in those organs growing a bit in ways that increased adaptation. As I explain here every year, everyone in Lamarck’s day thought that there were such inherited effects. Lamarck did not invent inheritance of acquired characters, because it was already widely accepted.
And here is where modern Lamarckians go badly wrong. They think that it is enough to show that an environmental effect is inherited, such as by epigenetic mechanisms. And they think that this vindicates Lamarck. But to Lamarck it was the organism’s strivings to cope with its surroundings that brought about the inherited effect. That was what brought about the directionality of the change, in the direction of adaptation. A fish tried to swim, and as it used its fins they grew larger and stronger in its descendants.
Just showing an environmental effect would not give this directionality. If your grandfather experienced a famine, and epigenetic inheritance resulted in some effect on you, why should we think that these would make you more resistant to famine? Rather than, say, increasing your susceptibility to cancer or heart disease?
Modern Lamarckians have not only thrown out Lamarck’s inherent complexifying force, they misunderstand him as merely invoking inheritance of environmental effects. By doing that they also abandon any attempt to explain why change is biased toward adaptation. Lamarck would not recognize their theory. His was wrong, but it at least addressed the big issue, Modern Lamarckians don’t even try to do that.