Pillars of Darwinism

By Eva Jablonka and Marion Lamb

Project Syndicate

This month marks the 150th anniversary of the publication of Charles Darwin's ``On the Origin of Species." The evolutionary theory he presented in that great book rests on two pillars: the idea of descent with modification, and the idea of natural selection.

Darwin believed that present-day organisms are descendants of much simpler ancestors: they are the products of unbroken lines of heredity that stretch back to the origin of life.

Today, we have a mass of evidence, ranging from studies of ancient fossils to the latest discoveries of molecular biology, that supports this theory.

Darwin, however, did not invent the idea of descent with modification. Fifty years earlier, Jean-Baptiste Lamarck had suggested that living things are products of a long historical process of transformation.

But the evolutionary mechanisms he proposed, which included the inheritance of characteristics induced by the environment,