Picture yourself on the stage of a large theatre with room for an audience of two thousand. In your mind’s eye, place your mother in the seat at the end of the front row, to your left, and then her mother next to her and so on – until you have filled the theatre with 2,000 generations of mothers and daughters.
Only your mother and the two or three ladies on her left would have seen motor vehicles. The women in the front two rows would have lived after the first cities came into existence, and those in the front six or seven rows would have lived after farming began. All the other maternal ancestors in the theatre, over 1800 of them, lived in the hunter-gatherer phase of human history.
You could fill five other similar theatres with earlier maternal hunter-gatherer ancestors belonging to the species Homo sapiens.
If you were to carry out the same mental exercise imagining you were in a stadium with seats for 100,000 people, the ladies in the back rows would be australopithecines.