Comments by "Regulus" (@xXx_Regulus_xXx) on "They Thought Our Solar System Was Empty Until This Discovery" video.

there are a lot of options for avoiding a genetic bottleneck on a colony ship, all with varying degrees of discomfort. You could freeze sperm and eggs and have mothers give birth to kids who are related to her and some man back on Earth, or have a kid that's not related to her even if you used the eggs. If your tech is good enough you could even store the DNA digitally and then recreate it in a lab so you don't have to worry about radiation damage or the samples thawing out. If you didn't want to do any of that, you could carefully keep track of who's allowed to sleep with who and make sure each couple has some minimum number of kids, and then they go on to repeat the process. Maybe every few generations you deliberately divide people into groups to create distinct populations, and then shuffle the groups before bottlenecking happens. It all depends on what your technology is capable of and how much weirdness people are willing to put up with.
2