A great interview with Richard Dawkins who explains why, looking back in our past, there was no first human being and how, instead, your 185 millionth great-grandfather was a fish.
From the Open Culture website:
Imagine pulling out your family genealogy. Now snap a photo of each ancestor going back 185 million generations. What would it show? First off, your very distant grandfather was a fish. Secondly, you can never put your finger on the very first human being, a proverbial Adam and Eve. 185,000,000 snapshots can never capture that one moment.
The above image is a screenshot from the video.