Reporter and Curator: Dr. Sudipta Saha, Ph.D.
Biologists may have been building a more nuanced view of sex, but society has yet to catch up. True, more than half a century of activism from members of the lesbian, gay, bisexual and transgender community has softened social attitudes to sexual orientation and gender. Many societies are now comfortable with men and women crossing conventional societal boundaries in their choice of appearance, career and sexual partner. But when it comes to sex, there is still intense social pressure to conform to the binary model.
This pressure has meant that people born with clear DSDs (difference/disorder of sex development) often undergo surgery to ‘normalize’ their genitals. Such surgery is controversial because it is usually performed on babies, who are too young to consent, and risks assigning a sex at odds with the child’s ultimate gender identity — their sense of their own gender. Intersex advocacy groups have therefore argued that doctors and parents should at least wait until a child is old enough to communicate their gender identity, which typically manifests around the age of three, or old enough to decide whether they want surgery at all.
As many as 1 person in 100 has some form of “DSD” with or without external manifestation. Diagnoses of DSDs previously relied on hormone tests, anatomical inspections and imaging, followed by painstaking tests of one gene at a time. Now, advances in genetic techniques mean that teams can analyze multiple genes at once, aiming straight for a genetic diagnosis and making the process less stressful for families. Children with DSDs are treated by multidisciplinary teams that aim to tailor management and support to each individual and their family, but this usually involves raising a child as male or female even if no surgery is done.
The simple scenario that all learn is that two X chromosomes make someone female, and an X and a Y chromosome make someone male. These are simplistic ways of thinking about what is scientifically very complex. Anatomy, hormones, cells, and chromosomes (and also personal identity convictions) are actually not usually aligned with this binary classification.
More than 25 genes that affect sex development have now been identified, and they have a wide range of variations that affect people in subtle ways. Many differences aren’t even noticed until incidental medical encounters, such as a forty-six-year-old woman pregnant with her third child, found after amniocentesis that half her cells carry male chromosomes. Or a seventy-year-old father of three who learns during a hernia repair that he has a uterus.
Furthermore, scientists now understood that everyone’s body is made up of a patchwork of genetically distinct cells, some of which may have a different sex than the rest. This “mosaicism” can have effects ranging from undetectable to extraordinary, such as “identical” twins of different sexes. An extremely common instance of mosaicism comes from cells passing over the placental barrier during pregnancy. Men often carry female cells from their mothers, and women carry male cells from their sons. Research has shown that these cells remain present for decades, but what effects they have on disease and behavior is an essentially unstudied question.
References:
https://www.ncbi.nlm.nih.gov/pubmed/25693544
https://www.ncbi.nlm.nih.gov/pubmed/25091731
https://www.ncbi.nlm.nih.gov/pubmed/1695712
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