@Char65
I can't say I agree, there maybe elements of learnt behaviour but there is biology too. I know I hit the stereotype, I had a job and not a career as a PP said and became a SAHM at 25 with a husband with a very high powered, high income job but as I said i loved it and looking after out 4 children and wouldn't have swapped it for the world - my only regret is that that they grow up too fast!!!
That's great and fine but surely you can understand that your one personal experience does not establish an infallible biological rule?
For every person who has stayed at home and loved it there is a person who stayed at home and didn't love it (as on this thread). Your enjoyment or otherwise of your role as a SAHM is not hard-wired, it's a complex combination of circumstances which brings to bear factors including your relationship with your spouse, your personality, your level of education, your financial circumstances, your personality, etc etc. It's multifactorial.
Meanwhile, as @ElaineMBenes points out, if its evidence you are looking for, there is some that men are not at a biological disadvantage in looking after children.
That doesn't mean everyone should feel that they have to do a perfectly progressive 50/50 swap approach. Some men will always prefer working in an office and some women will prefer to be at home (and vice versa). And that's all good and well. But please stop saying its biology, it's not. It's a combination of learned behaviour and disposition.