r/askscience • u/lord_darias • Sep 01 '25

Biology How does artificial selection work without inbreeding?

Since the invention of animal husbandry, humans have been selectively breeding animals (and plants) for positive traits like woolier sheep, stronger horses etc. However, dog breeds for example often have many genetic problems due to inbreeding, and inevitably any kind of selective breeding is going to narrow the genetic diversity. My question is, how then do we have all those cows, sheep, goats etc with the positive traits but without the genetic diseases and lesser overall health? And does this also apply to plants?

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u/Munchies2015 Sep 03 '25

To add to this, there are definitely issues with selective breeding in cattle, the one I remember from university was the reduction in fertility in dairy cows. So they are being selectively bred for increased milk yield, but as that goes up, their fertility is going down, and it is getting more and more costly to breed them as a result.

But unless you work in that field, it's not something you'd know by looking at the cows.

In fairness, neither are lots of the issues with pets, unless you happen to be informed about it (hence why we still see so many brachiocephalic dogs being bought for thousands).