Why we can't have our own kids

Chimpanzees we are told are 98.5% related to humans.

So how then do we also hear that siblings are 50% related?

It's because siblings only share 50% of the "variable" DNA. Most DNA is fixed, and only at a few sites are there variables.

It means that any two humans are more than 99.9% related and this number is even higher for humans from the same region and background.

So it means that a parent is 99.95% related to their children while a complete stranger is 99.9% related. It means that a parent is only 0.05% more related to their own children than a complete stranger.

To put that another way a completely stranger is 99.9% related to anyone's children.

It means that the complex process of finding a partner, having children and raising them affords us control over only 0.05% of our DNA. A person who does nothing can still see the vast majority of their DNA making it through to the next generation! That seems like a very cost effective approach!

Now evolution depends upon traits being selected for in the next generation but the process is slow as the variability is only 0.05% and sex and reproduction is incredibly conservative. Children are genetically incredibly similar to their parents and everyone else in the generation.

So that feeling of "your" own kids does not really have much of a genetic foundation. It is 99% cultural and derived from Capitalism and ownership. Even if you bring up a complete strangers child you are preserving 99.9% of your own DNA.

Admittedly parents bringing up random children will end the process of evolution as selection will be slowed or stopped. Now compared with another Capitalist population where children are only supported by their own families; it would be hard to say which would "do best." You might argue that rich parents would on average produce more children than poor so the society would evolve to be stronger and more able. But families still mix. A woman in a rich family can still sleep around and "bring in genes" from a poor family. Or perhaps bad genes will evolve randomly in the rich family and get stuck (as in fact we seen with inbreeding in the rich). So there are considerable random effects even in the controlled Capitalist society. It would take some more thought and modelling to really be clear how social organisation actually effects DNA.