For scientists claim to have found a gene in women's brains that determines the strength of their natural maternal instincts and how much effort they put into bringing up their kids.
Dubbed the 'Good Mother Gene', it is found in a specific group of brain cells and can control crucial biological behaviour such as protecting, feeding or raising children.
When these neurons were reduced in mice, they spent less time licking, nursing and retrieving their young.
The cells are triggered by oestrogen and contain the ER alpha receptor, which receives chemical signals in maternal care and sexual behaviour.
Mice with lowered ER alpha levels responded to their babies differently from normal mice but showed similar aggression when defending nests.
"Manipulation of a specific gene in a specific group of neurons can drastically alter the expression of a biologically crucial behaviour," explained lead researcher Dr Ana Ribeiro, of New York's Rockefeller University.
"These effects are remarkably specific, as even related behaviours are unaffected by these manipulations."
It was previously known the medial preoptic area of the brain controlled aggression, sexual receptivity and maternal care in mice but the underlying mechanisms remained elusive.