While deciding upon a partner, it is not mere good looks that come into play, but smell or body odour of the partner as well, a recent study on mandrills has revealed.
Mandrills - a primate cousin of humans - can use body odour to identify suitable mates, found the study.
An international team found an explicit link between a cluster of genes that play a key role in the immune system and an individual's smell.
And Dr Leslie Knapp from the University of Cambridge, who led the research, said the findings support the theory humans may also be able to "sniff out" a good mate.
"Our results strongly suggest that smell allows mandrills to transmit information about their own genetic quality and similarity to one another," the Daily Express quoted Knapp as saying.
"By using smell they can then identify potential partners with the appropriate genes.
"What we can infer for humans is that there are some very old behaviours at play here.
"Our early ancestors may have relied on smell in a similar way, and although we may think choosing a partner has more to do with looks or sound, smell can play an important role in the process," he added.
The team investigated the "major histocompatibility complex" or "MHC" genes - a diverse cluster of genes that play a key role in the immune system.
The study has been published in the Proceedings of the Royal Society B.