A natural experiment which shows that being bought up female does NOTHING towards making a male adult feminine. Two articles on the subject are reproduced below:

Startling sex-changes on the island where little sister may become big brother

By SANDRA JOBS0N, in London

On a lush tropical island in a remote area of the Caribbean something, very peculiar is happening. The young girls in one village are turning into boys. This startling sex change is occurring naturally, and a team of scientists sent to the island believes it could throw a new light on fundamental aspects of human nature and sexual identification. It has all been revealed in a fascinating documentary shown recently on BBC television, called The Fight to be Male.

The Caribbean phenomenon has been happening for the past 50 years. In that time 37 village girls have changed into boys around the age of 13. The cause has been traced back to one woman seven generations ago who passed on genetic abnormality to her descendants.

The story of the Batista family is typical of the village. Four out of the ten children in the Batista family have changed from girls into boys. The eldest, Mario, now 29 and married with children, began life as a girl named Antonia. The next daughter Milady. remains a girl. Then came Chichi, now 19, a normal male who started out as a girl called Isobel. Then there is Venecia, a normal girl. And now Virgilio, who is 12 and in the process of changing from a female to a male.

The Batistas do not regard themselves or their affected children as freaks. After all, 22 other families have experienced the same sex transformation over the years. The primitive lifestyle of the village contributes greatly to the relaxed and passive acceptance of “God’s will.” The people of the island are a mixture of Negroid and Creole stock - well-built handsome men and tall, strapping girls able to share the work load of cutting sugar cane, the island’s staple crop.

The Caribbean climate makes life both easy and lazy. So some of the girls turn into boys? Who cares? As long as they are happy. Virgilio’s brothers immediately found girlfriends when they turned into boys. Mario, the eldest, is the father of two children now, living in one of the bigger towns.

“We always brought up our girls as girls” Mr Batista says. “Because that’s what we always thought they were.”

“And some of our girls stayed girls,” adds Mrs Batista, pointing to two of her grown-up daughters who remained girls and are now married with babies of their own. None of the Batista men who were girls appears to show any sign of embarrassment about the change. Even Virgilio, still in the process, did not mind removing his trousers to reveal his sexual parts.

At birth Virgilio and his other sisters who became boys looked just like any other female baby. But the male anatomy was waiting inside his body and the external genitalia began to change at puberty. The testes dropped, as with all pubescent boys. But in the Caribbean children, the testes have to force their way from deep inside the child’s body. The clitoris grew into a normal, full-size male penis.

In Virgilio’s case the process is still half-way and his external sexual organs appear curiously bisexual at present. But soon his tiny, infantile vagina will close up and he will be completely male. I am looking forward very much to being a man” she says through an interpreter. “I have a girlfriend already”.

The phenomenon was first observed by a Spanish doctor who visited the village on holiday soon after it was connected by road to the rest of the island back in 1950. He wrote up his discovery in a Spanish medical journal where it remained unnoticed until 1972 when a team of doctors _came cross the article and decided to investigate more closely.

To protect the families the team will not reveal the name of the village or the island, but a BBC producer, Edward Galdwyn, was allowed to film the children recently. The team, headed by Dr Julienne Imperator-McGinley has pieced together a family tree of all the 23 affected families, tracing them back seven generations to one woman named Altagracia who married four times and produced a large number of children.

All of them carried a mutant gene which shows up only when one of the members of the 23 families marries a cousin. The clue to it all is a chemical called dihydrotestosterone which Virgilio and the other affected children were unable to produce when they were tiny babies. Doctors can now reliably state that it is the chemical which creates the external anatomy of the male.

In the womb all babies have the beginnings of both male and female sex organs. How the child develops, is determined by the “program” laid down by the chromosomes within its cells. If the child has the female chromosome structure, she will develop ovaries, and the male organs will disintegrate, leaving the female organs to grow.

But the Caribbean children had inherited a faulty gene which meant that the testes developed, but failed to produce the chemical which would remove the female parts. The body did not start producing the vital chemical until puberty, and then the children underwent the changes that should have occurred in the womb.

What is particularly significant is that all of the Caribbean children were brought up as normal girls. They were taught the ordinary female village tasks: Washing the clothes, cooking, fetching the wood, and they played with dolls.

But when they reached the age of l0 they suddenly felt the urge to be male. Young Virgilio explains: “I began to feel like a man in my muscles.” Virgilio’s father explains: “When they turn into men they change into different clothes. Soon everybody forgets. They find girlfriends very quickly.” Indeed, the affected children become more muscular and virile than their normal brothers.

The easy adjustment of the Caribbean children led the scientists to challenge the usual view that our “male” or “female” behaviour is determined more by the way we are brought up than by our physiology. They suggest that there may be a part of the brain which is different in males and females and which governs much of what we think of as sex-role behaviour.

(From the Sydney “SUN-HERALD” JUNE 17 1979, p. 41)

Another version of the same story:

“In the south-west corner of a tropical Caribbean island live Belarmino and Benilda Batista and their family of ten children. Four of them were born as girls, grew up as girls but, at puberty changed into muscular men. Their eldest child, Mario, now aged 29 began as a girl called Antonia. Chichi, now a male 19-year old, began as a girl called Isobel. All ‘changing’ children were born with normal female genitalia and grew to have the normal female body shape; until at the age of twelve their vaginas healed over, two testicles descended and they grew full-sized penises. Their ten-year old, Virgilio, is in the process of changing from a female to a male.

After their change, the boys are on average more muscular than their normal brothers. They take on the tough jobs in the local quarry. They marry and lead a normal male sexual life - even though they have not been fertile.

The Batistas are just one of 23 affected families in their village, in which 37 children have changed. In the society of the village - a deeply religious Catholic community - these children’s change has been seen as part of God’s mysterious ways. They are accepted and allowed to be themselves in a way which couldn’t happen in Western society.

In conversation with Dr Gautier, director of the children’s hospital on the island, the parents were quite clear about their feelings towards the children. They spoke of their pride in their new sons, of the extra money the children would bring home as boys rather than girls; and they insisted that the children’s adjustment to their new gender roles was immediate. Benilda admitted having feelings of sadness and worry; but, supported by a devout community, she came to see the phenomenon as God’s will: “If WE made children with our own hands we would make them perfect, beautiful and complete. But God knows what he is doing.”

Although girls had been changing into boys since 1930, it was not known outside the district until the first doctor went on holiday there. He published his findings about the children in an obscure Spanish journal, where it lay unnoticed until 1972. Dr Gautier’s attention was originally drawn by a patient who had been in his hospital when about eight years old, and whose behaviour had then seemed completely female. And some time later he met that person working in the mountains cutting wood, and his behaviour was as a male. Dr Gautier was so surprised that he and a group of scientists began investigating the change and how it came about.

When scientists put all the family pedigrees together, they began to see the interrelationship between one family and the next. They ended up with an enormous family tree, showing 23 families going back seven generations to one woman - Altagracia Carrasco. She lived in the mid nineteenth century, and she is the commonest ancestor of the affected families. The mutant gene has been passed down from her - but shows only when both parents carry it. How these children develop in the womb has been worked out by the scientists, and it gives a new twist to the story of how male genitals form.

The egg is fertilised by a Y sperm and it first develops to a foetus with normal testes. Perfectly normally, they absorb the female parts, and testosterone preserves the male ducts. But in these children’s cases, it doesn’t change the external anatomy, because in their bodies the children miss a critical chemical step.

Normal men are able to process cholesterol through to testosterone - and on to a mysterious hormone called dihydrotestosterone. No-one knew what its function was. But because the Caribbean children cannot make it, and because injecting it into them stimulates their genital growth, it is clear now that dihydrotestosterone creates the male external anatomy. The pubertal surge of testosterone in these children forces up the dihydrotestosterone level and growth that should have happened ten years before, in the mother’s womb, takes place at last.

(From The Fight To Be Male from Horizon, At The Frontiers Of Medicine, Ariel Books, BBC 1983. Reproduced here)