• Most humans who appear “male” have one X and one Y chromosome
• Most who appear “female” have two X chromosomes
• Some who appear “female” who were born with one X and one Y chromosome but have developed feminine sex characteristics
• Some who appear “male” who were born with two X chromosomes but have developed masculine sex characteristics
• Some born with XX or XY chromosomes have genitals that don’t conform to expectations for “male” or “female” bodies (intersex)
• Some are born with a single X or a single Y chromosome
• Some are born with multiple X or Y chromosomes
• Some are born with female-looking genitalia but develop as male at puberty
• Using brain scans, scientists have determined a cluster of attributes that point to a more “male” or more “female” brain; however, only a minority of humans have brains that look mostly male or female
• The brain scans of transgender people tend to more closely resemble the gender of their identification, not the gender of their birth

Clearly, gender can’t just be split into two separate, non-overlapping groups, which is why gender researchers now say that despite what we learned in biology class, there are not simply two genders. Understanding this can help us better parent our children, whether they conform to gender expectations or not. For more information, visit Gender Spectrum’s page, “Understanding Gender” (search for “Gender Spectrum understanding gender”) or the “American Academy of Pediatrics Policy Statement on Transgender Children” (search for “aap policy statement transgender”).