LSLGuy
May 2, 2017, 12:50am
49
Back in post #9 of this thread I linked to an earlier thread on topic. I expected a few folks to go read that then comment here. It appears nobody has.
Ref your comment and the several folks farther up-thread who said substantially the same thing …
Here I’ll quote myself from that old thread.
TLDR: It “works” in the sense that selective breeding is selective breeding is selective breeding. It fails at the next level up: making meaningful progress in heritable traits in a meaningful fraction of the stock.
We’ve done this topic several times in the past.
Speaking strictly to the science …
A proper selective breeding program, as is used on domestic animals, requires that no more than a couple percent of your males breed, and no more than 10-15% of your females. From a genetic perspective, the rest of the less desirable population are just pollution.
It also requires a certain number of generations to accomplish anything. Dogs, pigs, sheep, etc. can reproduce at about age 1 year. Humans more like 12 years. Dogs & pigs can produce litters where 4-8 offspring survive in controlled conditions. Sheep & goats usually produce twins (at least teh good breeding stock do). Humans produce twins about 3% of the time. Finally, the gestation period of the domestic animals is shorter, with pigs being just under 4 months and sheep & goats are about 6 months
Said another way, the low lifetime fecundity of humans means you can’t cull as aggressively as you’d want to for genetic change without killing off your entire breeding stock. Which menas that the process of perfection will is even slower than you’d expect looking just at reproduction times & quantities.
The sum of all these factors is that any eugenics effort will take many years and will produce fairly few of the better examples for the next iteration.
Humans are valued mostly for their versatility, not their excellence at narrow things such as height & weight. For farm animals, we try to maximize growth rate & growth amount per unit of food. Damn near nothing else matters. We kill & eat sheep & cows at the equivalent age to a 4-6-ish year old human. They are optimized for only that part of their lifespan.
Designing a human to be the ultimate toddler would be useless. So the problem we face is that we need to optimize across a much wider range of lifecycle traits to achieve super humanness.