It's been extrapolated from observations of adaptation taking place to fill niches, with similarity between species and genera. It's evidenced by fossil records demonstrating the development of a species over time. We can see it in vestigial body parts that no longer serve a purpose but haven't been eliminated. It's ostensibly the only model that fits, and it fits quite well. In fact, besides subscribing to a fantastical notion that god created the animals instantly, which no Western religion explicitly teaches, then there's really no other alternative to evolution.
I can ask my sister who has a master's degree in anthropology, if you'd like an off-the-cuff response from an actual scientist.