Early Concepts of Evolution: Jean Baptiste Lamarck (1 of 2)

Jean Baptiste Lamarck

Darwin was not the first naturalist to propose that species changed over time into new species—that life, as we would say now, evolves. In the eighteenth century, Buffon and other naturalists began to introduce the idea that life might not have been fixed since creation. By the end of the 1700s, paleontologists had swelled the fossil collections of Europe, offering a picture of the past at odds with an unchanging natural world. And in 1801, a French naturalist named Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck took a great conceptual step and proposed a full-blown theory of evolution.

Lamarck started his scientific career as a botanist, but in 1793 he became one of the founding professors of the Musee National d’Histoire Naturelle as an expert on invertebrates. His work on classifying worms, spiders, mollusks, and other boneless creatures was far ahead of his time.

Giraffe neck extension
Lamarck believed that the long necks of giraffes evolved as generations of giraffes reached for ever higher leaves.
 

Change Through Use and Disuse
Lamarck was struck by the similarities of many of the animals he studied, and was impressed too by the burgeoning fossil record. It led him to argue that life was not fixed. When environments changed, organisms had to change their behavior to survive. If they began to use an organ more than they had in the past, it would increase in its lifetime. If a giraffe stretched its neck for leaves, for example, a “nervous fluid” would flow into its neck and make it longer. Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations. Meanwhile organs that organisms stopped using would shrink.


Learn more about the fact and fiction of Lamarck.


Right: Lamarck also proposed that organisms were driven from simple to increasingly more complex forms.

Organisms Driven to Greater Complexity
This sort of evolution, for which Lamarck is most famous today, was only one of two mechanisms he proposed. As organisms adapted to their surroundings, nature also drove them inexorably upward from simple forms to increasingly complex ones. Like Buffon, Lamarck believed that life had begun through spontaneous generation. But he claimed that new primitive life forms sprang up throughout the history of life; today’s microbes were simply “the new kids on the block.”

Lamarck's arrow of complexity

  • Lamarck image courtesy of Dennis O'Neil, Palomar College. next page


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