With people and other life forms–I think–in large enough populations DNA-mixing allows individuals (phenotypes?) to die, because it prevents recessive genes to come to the fore for further reproduction. (As you can tell from the weird grammar, I have no Bio knowledge since HS.)
How do ant colonies work, then? I understand, sort of, how Darwinian evolution might have come up with social colonies, but how do the colonies stay stable in the evolutionary short term, which can be quite long indeed?
As I recall, the queen is fertilized, before establishing a nest, by a drone born in a nest other than hers. Then she digs the beginning of her nest, starts laying eggs, and does little else for the rest of her life.
I’m not sure exactly what your question is. However, the only reproductive individuals in an ant colony are the queens and males. When it comes time for colony to reproduce, it produces large numbers of winged females and males, which leave the colony on a nuptial flight. Normally these flights are coordinated between colonies (often triggered by events like a heavy rain storm). Females from one colony often mate with males from another, so there is cross-fertilization. The fertilized queen then founds a new colony, laying eggs and raising the larvae. This first brood becomes sterile workers that then raise all subsequent broods.
Yeah, I don’t really understand the question either, so I’ll just point out that ants are one of the most successful life forms on earth, with thousands of species found on every continent except Antarctica. So whatever it is that you think is a problem, it’s not really.
I think the OP may be wondering about the effect of all the individuals in the colony all having the same DNA, so there’s a lack of mixing of genes and lack of genetic diversity within a colony.
The mixing occurs before the colony is founded. If the new queen happens to have a bad set of genes, her colony fails or struggles, just like if an individual has bad genes, they may die or not reproduce.
From an evolution point of view, it might help to think of the colony as an individual, rather than as a gene pool.
Yes, ant colonies are effectively superorganisms. The workers can be regarded as body cells, while females and males can be regarded as reproductive cells.
One genetic peculiarity of ants, like members of the order Hymenoptera including bees and wasps, have a haplodipliod method of sex determination. Females have two sets of chromosomes (dipliod), one each from each parent, while males have only one (haploid). As a consequence, females are actually more closely related genetically to their sisters than they are to their own daughters (see the link for the explanation). Evolutionarily, workers may be better off helping to raise reproductive sisters (the new queens that go on nuptial flights) than having offspring of their own.
Terrific answers. And nice rephrasing of my bumbling question, from which you dug out the meaning.
Never new “they” mated every now and then from other colonies. That’s the answer for me.
Colibri’s final response I have to work on.
I have E.O. Wilson’s book on wasps, but basically I love to flip through it and look at the pictures. 
One thing to keep in mind is that the queen may mate multiple times. I’m almost sure this is so in honey bees, and I’m pretty sure this is so for other hymenoptera. Thus, adding to Colibri’s answer, the workers (diploid females) all have the same mother, but possibly different fathers, and the drones (haploid males) have only a mother (the queen).
It’s amazing how we can overthink things sometimes.
That’s a very valid point. I hadn’t really thought of it that way.