Foetus As Parasite Means Lots Of Sex

So apparently human foetuses expend more energy developing their brain than any other animal. This causes
problems because the foetal placenta has to aggressively invade the maternal body, seeking nourishment. And this should trigger a more violent immune reaction than often seems to emerge. The secret? Lots of sex! Frequent infusions of male sperm — with its invader genes — conditions the female immune system to respond less violently to the foetus, which contains half of this foreign DNA.