I don't know why that would surprise them. We expect man and his predecessors to be more primitive the further back you go. Hunting and fishing require organization and good tools. Gathering roots, berries and seeds not so much.
The further back you go, the more likely we were carrion eaters. Doesn't take tools or much organization to sneak up on a dead body. Ate your berries, roots, seeds and fruits also of course.
Don't like that idea and don't think it is true? Then tell me why we like aged meat over fresh...