Just to clarify: the advantages that males have that matter in athletics don't just start with puberty in adolescence. In adolescent puberty, the advantages males have over females become enormous and glaringly obvious, impossible to overlook, but males have advantages that affect sports performance before then too.

Part of this is coz the puberty of adolescence is the second puberty that occurs in a child's life. In the first six months after birth, babies go through a four-five month period (usually from the end of the first month post birth until or into the six month) known as the mini-puberty of infancy. During this time, male babies have testosterone levels at the same levels they will have in the puberty of adolescence. Which is one of the reasons male babies grow faster and are larger and heavier than female babies - a fact long tacitly confirmed by the use of two different charts to gauge babies' physical growth, weight and height, one for males and another for females.

Male children have larger hearts and lungs, higher hemoglobin, better blood oxygenation (and other features) from infancy - not just from the puberty of adolescence. Which is probably amongst the reasons why cystic fibrosis, a genetic disease that occurs equally frequently in both sexes, has a different trajectory depending on a patient's sex: while no one with CF can be said to have good health or a long lifespan compared to people without CF, compared to females with the disease born the same year and with access to the same treatment, males with CF generally are less sickly and live longer.

Also, scientists researching embryos and embryonic stem cells have recently reported that sex differences are evident in the cells of human zygotes at 6-7 days after fertilization; and sex differences can be seen in human embryos prior to the development of male or female gonads (usually in the 7th week) and thus prior to when embryos begin making sex hormones. Many sex differences that long have been assumed to be the product of sex hormones are turning out to predate them and to be independent of them.

Little League - which starts as early as age four - is a good indication of the athletic advantages male children have prior to puberty. LL has been co-ed since 1974. Yet it remains very male-dominated. 7 out of every 8 kids in LL are male. The vast majority of boys in LL play baseball, whereas most girls play softball. Moreover, starting at age four through the late teens, males in LL now have their own male-only softball division. Coz of sex differences that affect performance.

Since LL became co-ed nearly 50 years ago, more than 11,000 boys have made it to the LL Baseball World Series, and only 19 girls.