All you have to do is look at the bell curve for IQ and see where this all leads, and its nowhere pretty.
A person with an 85 IQ or below is too dumb to even be in the Army, even doing the most basic of tasks. Turns out, a military force with advanced computerized weaponry requires smart people. Now here's the kicker... 85 and below is something like 16% of the population.
That's 1,250,000,000 people that will, in the coming years / decades, be totally unable to function in the economy in any worthwhile way. And I'm sorry, I just do not trust the "benevolence" of the human race to fix this problem when our technology advances to the point that people of 100 IQ and below aren't useful. There is no way that 50% of the people with 101 IQs and above are going to spend money to keep the other 50% of the human race alive.
I doubt there'll be "mass exterminations" like we've seen of ethnic groups throughout history, but more likely the unemployable will be left to their own devices; after all, out of sight, out of mind.
As higher and higher IQ individuals are keeping the same company more and more and self-segregating, I suspect we're going to see the development of an overclass of individuals that will eventually grow resentful of spending X percent of their income, whatever number "X" ends up being, for keeping those who aren't able to provide for themselves alive. That's a pretty common human emotion. The tribe works fine when every tribe member is even minimally capable. When half the tribe members are literally dead weight? Nothing good, I'm afraid.
More than 25% of people OF WORKING AGE aren't part of the labor force in almost all western economies [1]. And another 20-30%+ of the population is too old to be part of the labor force / retired [2].
This is well over 16% with too low of an IQ to contribute in a theoretical economy. It doesn't seem hard to shift priorities - the age for retirement, the people who qualify for welfare, etc...
Since 2015, the US and France already spend over 30% of GDP on social programs [3].
Horses also can learn to provide different value, just up to a threshold lower than that of humans. But humans still have a threshold.