The Evolution of Evolution: From Ancient Theories to Modern Understanding

From the ancient Greeks through the early Christian era, the concepts of evolution were actively discussed. However, this dialogue ceased during the Middle Ages, giving way to the dogma of Biblical scriptures, which posited that living organisms were fixed and unchanging since creation. The discovery and increasing accumulation of fossils in the 1700s prompted several prominent naturalists to question whether life forms had remained static since creation or had undergone evolution.

Though the theory of the inheritance of acquired characteristics is most commonly associated with Lamarck, its roots can be traced back to ancient Greek philosophy. This concept was later expanded upon by Erasmus Darwin, the grandfather of Charles Darwin, in his two-volume work Zoonomia (1794–1796), in which he proposed that the Earth was millions of years old—contrasting sharply with Irish Bishop Ussher’s 1654 calculation of creation in 4004 BCE.

Jean-Baptiste Lamarck, a soldier in the French army, a distinguished botanist, and the foremost expert on invertebrates of his time (a term he coined), presented his ideas in his seminal work Philosophie zoologique (1809). He argued that living beings did not evolve through a series of catastrophic events and recreations but instead underwent gradual changes. Lamarck theorized that as environmental conditions changed, organisms would adapt to survive. If a particular body part was utilized more frequently, it would increase in size or strength during the organism's lifetime, and these enhancements would be passed on to its offspring. For instance, he suggested that a giraffe stretching its neck to reach higher leaves would result in its neck growing longer, which its descendants would inherit, perpetuating the trait through generations. Similarly, he posited that wading birds evolved long legs by stretching them to keep their bodies out of the water, while disused body parts would shrink and eventually disappear, explaining how snakes lost their legs.

Despite his significant contributions, Lamarck’s theory faced challenges and was ultimately rejected by both religious and scientific communities during his lifetime. He died blind, in poverty, and largely unrecognized. In more recent years, however, Lamarckism has been revisited in the context of epigenetics, where traits can be inherited through mechanisms that do not involve changes to the underlying DNA.

Lamarck cited the giraffe as a key example of how acquired physical characteristics can be passed down through generations. He theorized that the giraffe's long neck evolved from its ancestors stretching their necks over time to reach the highest leaves in trees.