You make a fair point so, let's look at that.
McBride's statement notwithstanding, what does science say?
Well science basically says this; and I'll simplify for you:
All Ovum have a single "X" chromosome. All Sperm have a single chromosome that can either be an "X" or a "Y." If a sperm with the "X" chromosome fertilizes the egg the baby will be a girl. If a sperm with the "Y" chromosome fertilizes the egg the baby will be a boy. And, while it takes a few weeks for sexual organs to start forming, this fact is immutable.
Several sources stated this, in as many words:
"A person’s sex is determined at conception. Males have a set of XY chromosomes and females have a set of XX chromosomes. These sex chromosomes determine whether the embryo develops as a male or female. Initially the gonads in both male and female embryos can develop as either testes or ovaries. Starting at 8 weeks gestation, an embryo with a Y-chromosome produces a factor known as SRY that simultaneously causes the gonads to begin maturing as testes and prevents them from maturing as ovaries. The testes, in turn, produce two important hormones: testosterone and anti-Mullerian Hormone, or AMH. In males, the testes starts producing and releasing testosterone by 10 weeks. Testosterone allows the primitive male anatomy to mature, while AMH causes the primitive female structures to shrivel. The male internal ducts consist of a pair of tubes called the mesonephric ducts that will mature into the vas deferens and epididymis. The epididymis stores sperm, and the vas deferens is the sperm duct. "
Other than being a transgender with an obvious stake in the answer, I'm not sure what McBride's credentials, in the field of human development might be. Do enlighten me.
Not defending the EO. At first, and still, your point is well-taken. I simply think McBride is misrepresenting the fact that AT CONCEPTION, if the sperm (the smaller of the two reproductive cells) fertilizes the ovum (the larger of the two reproductive cells) and is carrying an "X" chromosome, the resulting human will only be able to produce the larger reproductive cell, making it a female. If, on the other hand, the sperm is carrying a "Y" chromosome, when it breaks on through to the other side, the resulting human will only be able to produce the smaller reproductive cell, making it a male.