[magduf]

>Having only one of the genes doesn't give you a deadly condition and protects against an infection that rampantly killed people in Europe historically.

>So it is entirely possible that after designer babies become a thing and we remove too many "bad" genes from the gene pool, someday this will come back to bite us for some reason.

Maybe, but unlikely. Those infections were a problem back then because we lived in huts and didn't have antibiotics or anything resembling modern medicine. A comment below says that this gene helps protect against cholera, for instance. Well cholera isn't a problem in places with proper sanitation, so this gene isn't really a help for people living in rich, industrialized nations. Sickle cell protecting against malaria might be useful to people living in malaria-prone areas still, but we do have immunizations against malaria these days, and in the future it's really not going to be a problem at all.

Finally, with "designer babies", presumably we'll be at the point where we'll just be able to genetically engineer ourselves to deal with any remaining environmental problems/diseases directly, instead of relying on some accidental mutation that gives us a little better resistance at a huge cost.

[DoreenMichele]

we lived in huts and didn't have antibiotics or anything resembling modern medicine

When antibiotics were discovered, the world announced the end of disease. Today, there are endless articles about the rise of antibiotic resistant infections, plus dystopian fiction about a post antibiotics world.

I'm not 100 percent convinced we are as clever as we imagine ourselves to be.

[magduf]

You've got to be kidding. Just because we haven't achieved perfection as far as medical science, you think we're still just as well off as the days where people routinely died young from various infections?

Antibiotics aren't going away, they're just having to get better to cope with the evolution of bacteria.