KB01:

\That's news to me. I've always been under the impression that all the evidence suggests humans go back to about 200,000 years ago.

I'd also be curious to see how you define "primary caregiver". For most hunter-gatherers and horticulturalists, gender roles were not as well defined as what you're depicting.

Modern humans have been around about 250,000 (possibly as much as 800,000), years with other hominids (also usually referred to as humans) going back much further. Here's a link to a Nature article about a 3.7 million year old human footprint. <link>

More importantly, you won't find an exact point in history where humans "go back to" because evolution is...you know...gradual.