London, Dec 10 (IANS): Believe it or not but our forefathers were way smarter than us when it came to wooing the opposite sex for mating. According to a new study, Neanderthals learnt how to smile and make expressive faces in order to attract less-aggressive mates.

Researchers from the University of Milan focused on genetic samples from Neanderthals, which showed that gene mutations might have led humans to "self-select less aggressive mating partners".

This behaviour finally led to the "self-domestication" of ancient humans.

The study suggests that modern humans domesticated themselves after they split from their extinct relatives -- Neanderthals and Denisovans -- approximately 600,000 years ago, reported sciencemag.org citing the study that was published in the journal Science Advances.

Giuseppe Testa, a molecular biologist at University of Milan in Italy, and colleagues knew that one gene, BAZ1B, plays an important role in orchestrating the movements of neural crest cells.

Most people carry two copies of this gene.

Significantly, one copy of BAZ1B is missing in people with Williams-Beuren syndrome, a disorder linked to cognitive impairments and extreme friendliness.

Genetic data was gathered from human stem cells taken from the remains of two Neanderthals and one Denisovan.

These two groups of prehistoric ancestors lived around the same time and there is even evidence to suggest they interbred.

"BAZ1B" is the gene which allows dogs to make their eyes expressive in a way wolves cannot, reports NYPost.

"It is thought that selected breeding patterns of some Neanderthals led to the BAZ1B gene and could have contributed to Homo sapiens developing distinctively expressive faces".

When the researchers looked at hundreds of BAZ1B-sensitive genes, they found that in modern humans, those genes had accumulated loads of regulatory mutations of their own.

This suggests natural selection was shaping them.

According to The Sun, Williams-Beuren syndrome causes humans to have what same people perceive as a welcoming expression with a wide mouth and a small nose.