Final answer:
Alfred Russell Wallace is credited as the co-discoverer of the theory of natural selection along with Charles Darwin, both having developed the concept independently.
Step-by-step explanation:
The individual credited as the co-discoverer of the theory of natural selection alongside Charles Darwin is Alfred Russell Wallace. While Darwin is often acknowledged as the father of the concept, both he and Wallace independently developed the idea of natural selection. They presented their findings together in 1858 at the Linnean Society. Darwin's extensive observations, especially during his voyage on the HMS Beagle, and the subsequent publication of 'On the Origin of Species' have made him the more prominent figure associated with the theory. However, Wallace's contributions are significant, and he remains recognized for his work in the field of evolutionary biology.