LOW fertility and frequent pregnancy complications may be the price that we have paid for evolving a large brain.
For the fetus to get enough nutrients to grow a hefty brain the placenta has to aggressively invade a mother’s uterus, says a new theory. But that can also provoke her immune system, causing dangerous complications.
However, recent research suggests that exposure to a man’s semen helps a women’s immune system prepare for pregnancy (Â鶹´«Ã½, 9 February, p 32). So low fertility in humans reduces complications during pregnancy by giving a woman’s immune system more time to adapt.
Human…
