A lot of people misunderstand figurative bottlenecks too.
The "7 women" does not mean anything like "only 7 women existed at the time". Particularly:
* other women existed who only had sons, or whose daughters only had sons, etc. See https://en.wikipedia.org/wiki/Galton%E2%80%93Watson_process (about surname extinction, which is basically the same thing other than sex-specific polygamy effects)
* other tribes existed (or split off) who later faced extinction due to being outcompeted by these 7 tribes.
The "7 women" does not mean anything like "only 7 women existed at the time". Particularly:
* other women existed who only had sons, or whose daughters only had sons, etc. See https://en.wikipedia.org/wiki/Galton%E2%80%93Watson_process (about surname extinction, which is basically the same thing other than sex-specific polygamy effects)
* other tribes existed (or split off) who later faced extinction due to being outcompeted by these 7 tribes.