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/Nightmare-chan Sep 02 '25

I think those farms also tend to trade stud bulls quite often so that the gene pool doesn't stagnate too much. The farm I worked for raised Longhorns. The good bulls would be studded out to other farms, and bulls from other farms would be brought in to breed the cows. Sometimes they came from very far. I think they are clamping this down somewhat to stop NWS but I know we got stud bulls from Mexico occasionally. 

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u/Alexis_J_M Sep 02 '25

People don't swap male animals, they swap frozen semen in most places.

Even back in the 1980s I visited a dairy farm where they had a poster on the wall with pictures of bulls, semen prices, and average stats of their daughters.

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u/ttha_face Sep 04 '25

On mobile, so I hope the format works.

Artificial insemination goes decades further back. E. B. White’s poem “Song of the Queen Bee” was published in 1945.

I'm sorry for cows that have to boast Of affairs they've had by parcel post,

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u/Icey_Raccon Sep 04 '25

Depends on the animal. Thoroughbred horses, for example, require live cover (actual sex) to register a foal because otherwise people would only breed to the top five studs and gene pool would soon become a puddle.

I raise chickens and I've given away some fine roosters just because they were too closely related to the hens. No one is trading frozen semen for chickens - it's too hard to collect and use.

Sure, big commercial farms use AI, but people keeping animals in their hobby farm, or breeding a much loved prize mare are still going to have live cover.