What evolutionary theory posits that species evolve through numerous small changes over a long period?

The theory that species evolve through numerous small changes over long periods is known as phyletic gradualism. This concept suggests that evolution occurs at a slow and steady pace, with gradual changes accumulating over time leading to the transformation of one species into another. Phyletic gradualism is typically contrasted with punctuated equilibrium, which argues that species remain relatively unchanged for long periods, punctuated by brief periods of rapid change.

In phyletic gradualism, the emphasis is on continuous and incremental changes rather than sudden and drastic shifts in a species' form or function. This perspective aligns with the fossil record in some cases, where gradual transitions can be observed.

Understanding this concept is crucial in evolutionary biology as it reflects a traditional view of how evolution occurs, representing a process that can take millions of years, influenced by environmental factors and natural selection.