Claus Wedekind is a Swiss biological researcher notable for his 1995 study that determined a major histocompatibility complex (MHC) dependent mate preference in humans.
[4] It has been suggested that MHC plays a role in the selection of potential mates, via olfaction.
MHC genes make molecules that enable the immune system to recognise invaders; generally, the more diverse the MHC genes of the parents, the stronger the immune system of the offspring.
It would obviously be beneficial, therefore, to have a system of recognizing individuals with different MHC genes and preferentially selecting them to breed with.
[7] The hypothesis is that MHCs affect mate choice and that oral contraceptives can interfere with this.