What is the core belief of the fixity of species?

The belief in the fixity of species centers around the idea that species are unchangeable after their creation and that they remain consistent over time without undergoing significant evolutionary changes. This concept was particularly prevalent before the development of evolutionary theory and the understanding of natural selection. Advocates of the fixity of species believed in a static nature of life's diversity, asserting that each species was created in its current form and did not evolve from or transform into other species.

This belief contrasts sharply with concepts such as evolution, extinction, and common ancestry that suggest dynamic biological processes. Evolution posits that species can change over generations in response to environmental pressures, extinction acknowledges the disappearance of species over time, and common ancestry implies that species can share traits and characteristics due to shared evolutionary origins. By understanding the fixity of species, one can appreciate the historical context of biological sciences and how these foundational beliefs have been challenged and refined by discoveries in genetics and fossil records.