Does Speciation Demonstrate Large-Scale Evolution?
New species and reproductive isolation have been observed, but critics may argue that speciation generally involves divergence within an existing type of organism rather than the origin of fundamentally new anatomical structures. Does observed speciation really demonstrate the larger transformations proposed in evolutionary history?
Why This Matters
Speciation is important because it demonstrates that populations can separate into independently evolving lineages. Large-scale evolutionary histories require such branching, but lineage separation and the origin of major biological novelty are not exactly the same question.
Response
Laboratory and field research documents the development of reproductive isolation and identifies genetic, ecological, behavioral, and chromosomal mechanisms that can contribute to it. Speciation is therefore an observed biological phenomenon and should not be dismissed simply because the resulting organisms may remain morphologically similar.
However, speciation alone does not explain the origin of every new structure or body plan. It provides the branching populations within which further changes can accumulate. Explanations for major innovations must additionally address the genetic and developmental changes responsible for those innovations.
Question That Remains
How well can documented mechanisms of lineage divergence be connected with the genetic and developmental changes associated with particular major anatomical innovations?