This feels like a classic case of overthinking. Suggestion: maybe twin sisters care more about their own children than their nieces because they are the ones whom they carried in their womb and then nurtured and actually raised as their own children. Genetics inform our behaviour but ultimately what they do align us to is something like “you shall be attached to cute little baby like things you spend a lot of time raising”. That holds for our babies, it holds for babies born with other people’s sperm/eggs, it holds for adopted babies, heck it even transfers to dogs and cats and other cute animals.
The genetically determined mechanism is not particularly clever or discerning. It just points us in a vague direction. There was no big evolutionary pressure in the ancestral environment to worry much about genetic markers specifically. Just “the baby that you hold in your arms” was a good enough proxy for that.
This feels like a classic case of overthinking. Suggestion: maybe twin sisters care more about their own children than their nieces because they are the ones whom they carried in their womb and then nurtured and actually raised as their own children. Genetics inform our behaviour but ultimately what they do align us to is something like “you shall be attached to cute little baby like things you spend a lot of time raising”. That holds for our babies, it holds for babies born with other people’s sperm/eggs, it holds for adopted babies, heck it even transfers to dogs and cats and other cute animals.
The genetically determined mechanism is not particularly clever or discerning. It just points us in a vague direction. There was no big evolutionary pressure in the ancestral environment to worry much about genetic markers specifically. Just “the baby that you hold in your arms” was a good enough proxy for that.