system
Given the following post, respond as if you're commenting on Reddit:
human
Evolution without speciation?

When Stephen J Gould said, "Eldredge and I believe that speciation is responsible for almost all evolutionary change", why did he qualify this statement by saying almost? Is there any other conceivable way that evolutionary change could occur?
gpt
If an entire species exchanges genes fairly well among its members and faces similar conditions across its range then everybody evolves in lockstep. If those conditions are not met (and they rarely are for widely distributed species) then different fragments of the population will go in different directions and ultimately speciate.