Want to attract a good mate and ward off unknown relations? Secrete a smelly substance from that gland on your chest and rub it all over. At least that’s what a mandrill might do: A recent study suggests that the baboon-like primates may use their smelly secretions to distinguish compatible mates from family.

After taking swabs from mandrill sternal glands, researchers genotyped each sample to determine the monkey’s major histocompatibility complex (MHC)–a unique genetic signature related to the animal’s immune system. They also, using a sorting technique called gas chromatography–mass spectrometry, determined each secretion’s chemical makeup, and thus its stink bouquet.

As the study’s leader Leslie Knapp of Cambridge University told the BBC, more “genetically diverse” mandrills, i.e. unrelated, have different MHCs and chemically-speaking different scents..