Most of the species that we use as food do not look like their ancestral species anymore. How have humans achieved that?

Through genetic modification/engineering

Explanation:

Most of the species that we use as food do not look like their ancestral species anymore because humans have genetically modified them to suit their desires.

Through genetic engineering, humans have been able to select desirable characteristics or attribute from one organism and transfer it to another organism of similar species that already has some desirable attributes. Thus, the latter organism becomes genetically modified and looks different from its ancestors just to suit the taste of man.