Evolutionary Theory
While the fixity of species was the generally accepted view before Charles Darwin, he was not the first to propose that evolution, understood as the transformation of one species into another, occurred. The ancient Greek philosopher Anaximander maintained that people had evolved from fish, and the zoologist and botanist Jean-Baptiste Lamarck (1744–1829), as well as Darwin's grandfather, Erasmus Darwin (1731–1802), were also proponents of evolution.
Lamarck, for instance, argued, in his Philosophie Zoologique (1809), that life resulted from ongoing spontaneous generation and that each lineage, beginning with simple forms, was driven by an inner tendency to complexity and perfection. On his view, more complex creatures belonged to older lineages, with our own the oldest. Adaptation and diversity was explained by the inheritance of acquired characteristics. Different environments caused organisms to have different needs in response to which they would use or not use their various organs: Use would cause an organ to develop, enlarge, and strengthen, whereas disuse would cause it to shrink, deteriorate, and eventually disappear. Lamarck believed that these changes were inherited by offspring, who would in their turn continue to adapt to their environment, thus leading to transformation of the lineage. The term Lamarckism (or Lamarckianism) is now used to refer to the idea that a trait that was not inherited, but was acquired within the life of an individual, could be inherited by that individual's descendants.
This is a free page. This page contains 201 words. This
article contains 5,086 words (approx. 17 pages at 300
words per page).
Read the rest of this Article with our Evolutionary Theory Access Pass.
