Orthogenesis

Orthogenesis is a concept in evolutionary biology that proposes that evolution occurs in a predetermined direction or along a single track, driven by an inherent force or tendency within organisms. This idea suggests that evolutionary change is not random but rather follows a specific path, often leading to increasing complexity or specialization. Proponents of orthogenesis believed that species were destined to evolve in a particular way, regardless of environmental pressures or natural selection.

Historically, orthogenesis was a significant idea in the late 19th and early 20th centuries, particularly as an alternative explanation for the apparent progression observed in the fossil record. It was seen as a way to reconcile evolutionary theory with the idea of purposeful development. However, modern evolutionary biology largely rejects orthogenesis as a primary mechanism. The prevailing understanding is that evolution is driven by mechanisms such as mutation, genetic drift, and natural selection, which are largely contingent on environmental factors and random chance. While some lineages may show a degree of directional change over time, this is generally attributed to selection pressures rather than an intrinsic, predetermined path. The concept has been largely superseded by modern evolutionary synthesis.