Why does no farmer say, "sorry my dear cow A, but the cow, that gives only half the amount of milk, (let us call it cow B) should make babies instead of you"?

I gave another example of robot engineers doing exactly that.
Also cow A and cow B are adapting to their new environment, being human cattle, where production of milk is a fitness criteria. For this fitness "advance", the offspring of the cows will give up other traits that it can't afford energy to because it has to produce more milk, let's say it gives up some immune responses, that aren't really needed in the clean and healthy environment that it is living in (human farms). It wont need to deal with wild predators either, so that can be some other traits that it loses to gain more milk production.
These traits are now WIPED from the cow gene pool.

Then, what would you know, ice age happend, population of humanity shrinks, most cows have to live in the wild again, cows go extinct because they require human assistance to survive. They're using all their fucking body energy on mostly useless milk production.

Meanwhile cow Bs offspring was sent off to some random forest, where they kept some of their wild nature traits which allowed them to barely survive the ice age change of environment.
Sure, CowAs where better in environment 1, but change the environment and suddenly CowBs are better.

Wouldn't the diversity of breeding cow B with other cows increase the overall milk production (at least in the long run), if your theory was correct?

Sure, it could happen. Much could happen. It could also be some random other trait that got boosted, like say lowering of the intake of food to the same energy output, which wasn't intentionally meant to increase milk production, but it just so happened that now the farmer could afford twice as many cows, so individually it didn't "improve", but overall it did? It is random stuff like that and admittedly it is completely random and unknown what benefits you might find. This is why it is called EXPLORATION vs EXPLOITATION. Exploitation is when you try to optimize one local optimum and exploration is when you try to explore the surface, you might find new interesting attributes that are worth optimizing for.
Think of genetics as the surface of the planet.
If you climb the tallest hill in Denmark, you might be king of the hill of Denmark, and you might try to keep climbing that hill to stay on it for generations. But if you go explore Norway or Sweden, by first going down the hill, then you will find much taller hills (mountains).

Exploit = climb a hill (local optimum)
Explore = find new hills (other local optimums)

And sometimes the landscape of the earth changes, new mountains rise, old mountains fall.
What was once the lowest point of Europe (least fit), might be a mountain today (good fit, not necessarily the best or optimum).

Will a retard be the smartest person on earth, because it becomes ice age? No.... what might happen is that the offspring of these retards will get some genes that counter act their retardation. Now if that trait was transferred to normal whites, it could have a positive influence on the overall population. Maybe it would be bad, maybe it would be good. Most mutations are BAD, because they move the individual away from the normal range of the local optimum, but stack those bad mutations and you might end up on a mountain in Norway lol.

T