alt Hacker NewsThis is a kinda silly argument. Interstellar colonies would have the opposite problem: they'd cease to be the same species due to genetic drift.
If you look at the (im)practicalities of interstellar travel, it's going to take centuries. That means a generational ship of some kind. That means having a sufficient population to get there, which really means tens of thousands of people. Plus, the kind of ship that would make that would likely host up to millions. That's just not going to create a genetic bottleneck.
Also, you could even mitigate that by bringing frozen genetic material.
I don't know if a generational ship is absolutely required. There's this assumption that interstellar ships would be full of human astronauts who are alive and awake. But that might not be strictly required. You might be able to have everybody go there frozen. Or have a robot ship that gives birth to the colonists from an artificial womb on arrival.