The article touches on it briefly near the end, but those estimates of how many breeding pairs you need are made under the assumption that you want to keep the incidents of genetic disease to roughly the same level we have now in the world at large.<p>If you are willing to accept higher rates of disease--willing to conceive more children and abort more diseased ones, then you can get away with a much smaller starting population.<p>Pre-screening the initial population and weeding out as many deadly mutations as possible would also help a lot.<p>Your new population will of course be more vulnerable to diseases as there will be far less variety in their natural immunities so it is tricky, but if the Earth were reduced to just a small handful of people it&#x27;s not necessarily curtains for humanity.  Indeed in ancient times tiny tribes of highly inbred individuals managed to survive and eventually give birth to modern humans.