well SVF biologically speaking the only way that a person and living creature is "fit" according to darwin's principles is if it is able to procreate and pass the genes down into the next generation. That is our sole "biological" mission in life...and it's why we were born. Having a big variety of genes passed through is important to the process of evolution...as we saw new epidemics can strike anywhere at anytime so having a large pool of genes available out there means more chances of a gene combination strong enough to resist a certain epidemic or able to adapt better to a changing environment or what have you.