system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Mitochondrial Eve - How can it be that we are all descendant from a single person?

If the population at the time of Mitochondrial Eve was ten thousand people, how can all the other lines of descendants disappear, and how can we know that they did without testing every single human alive?
gpt
Mitochondrial Eve isn't a real single person, it's a concept for a theoretical person, but the actual person isn't known, and would constantly change with time.  It's not really useful to think of it as an actual person.