Lamarckism: The First Scientific Explanation of Evolution

Lamarckism: The First Scientific Explanation of Evolution
French biologist Jean Baptiste de Lamarck (1744 to 1829; Figure 6-2) authored the first complete explanation of evolution in 1809, the year of Darwin’s birth. He made a convincing case that fossils were remains of extinct animals. Lamarck’s proposed evolutionary mechanism, inheritance of acquired characteristics, was engagingly simple: organisms, by striving to meet the demands of their environments, acquire adaptations and pass them by heredity to their offspring. According to Lamarck, the giraffe evolved its long neck because its ancestors lengthened their necks by stretching to obtain food and then passed the lengthened neck to their offspring. Over many generations, these changes accumulated to produce the long necks of modern giraffes.

We call Lamarck’s concept of evolution transformational, because it claims that individual organisms transform their characteristics to produce evolution. We now reject transformational theories because genetic studies show that traits acquired by an organism during its lifetime, such as strengthened muscles, are not inherited by offspring. Darwin’s evolutionary theory differs from Lamarck’s in being a variational theory, based on the distribution of genetic variation in populations. Evolutionary change is caused by differential survival and reproduction among organisms that differ in hereditary traits, not by inheritance of acquired characteristics.