The gender gap begins even earlier than we thought.
A study has found that a mother's breastmilk changes quality depending on the sex of your child.
And it turns out that breast is even better for
boys.
Psychologists Nancy Segal and Satoshi Kanazawa carried out the study which they will publish in the April edition of
The Journal of Experimental Child Psychology.
They say that there seems to be an evolutionary pre-disposition for mums to make higher quality milk for their sons
This phenomenon is called the Trivers-Willard hypothesis and a way for parents to preserve their genes for the future.
If mum's 'invest' more in male children they are then strong enough to go out and seek females to mate and have more children and stronger off-spring.
The study compared the outcomes of same-sex twins to opposite-sex twins, figuring that with opposite sex-twins a mother wouldn’t be able to cater differently while breastfeeding both children at the same time.
Speaking to the
New York Times, Segal says:
“We found that breast-fed same-sex twins were indeed either slightly taller or substantially taller than breast-fed opposite-sex twins. Same-sex twins were, on average, nearly one inch taller than their opposite-sex counterparts. Similarly, same-sex twins were substantially heavier than the opposite-sex twins except during the first measurement period. The same-sex twins were, on average, 12 pounds heavier than the opposite-sex twins.”
What do you make of it mums? Breastmilk sex bias - the earliest form of gender pay gap! 
