Mom Demands School Go Peanut-Free For Allergic Child

[Silent3]

396. Genetics doesn't work that way

Rare mutations aside, the genes you're born with are the genes you pass on to the next generation. An environmental condition might change whether or not an allergic predisposition encoded into your genes is expressed or not, but it doesn't re-encode your genes so that a new genetic predisposition to that allergy becomes more inheritable than it otherwise would have been.

The cruel way of nature and genetics is we avoid passing on genetic weaknesses mostly by dying before we can reproduce, or, if not dying, then for some other reason becoming infertile or being unable to acquire a fertile mate. We now pass on many more genetic weaknesses than our ancestors could have gotten away with simply because we survive those weaknesses better with the aid of medicine and technology, making our descendents more dependent on similar medicines and technologies.

It's possible that there's a little more to inherited traits than survival of the fittest, some more complex mechanisms than the basics of either passing on or not passing on the genes you're born with (say, occasional naturally-occurring gene splicing via viruses and bacteria, or a selective influence on which sperm cells survive) that occasionally come into play, but it's not like, say, pumping iron to give yourself big biceps makes it more likely, genetically speaking, that your kids will have big biceps too.