So, the first person who was the MRCA-with female lineage only, ie the earliest woman who was the female ancestor of all living people, was 100,000 years ago.
But the earliest ancestor (female / male / mixed lineage) was only 3000 years ago.
(i.e. the first, had to have daughters only, the second, more recent could have daughter then grandson then great-grandson etc)
So, 3000 years before we can say anyone definitely was the ancestor of all, and there would be a lot of them. And 100,000 years before its female lineage. Then pretty much everyone is a common ancestor, back to plankton. And Dinosaurs!
More or less, except 3000 years ago travel was far more of an issue. But, somewhere in the ~2,500-30,000 years it's probably true.
Also, with a population of 1 million people a female line 'wining' is much more likely than with a ~6 billion people population that probably will not happen again for a vary long time without some awesome mutation.
But the earliest ancestor (female / male / mixed lineage) was only 3000 years ago.
(i.e. the first, had to have daughters only, the second, more recent could have daughter then grandson then great-grandson etc)
So, 3000 years before we can say anyone definitely was the ancestor of all, and there would be a lot of them. And 100,000 years before its female lineage. Then pretty much everyone is a common ancestor, back to plankton. And Dinosaurs!