Have you ever had some annoying person approach you, insisting, on how we were all females as embryos? If so, here’s my argument.
Firstly considering genetics or sex is determined at the end of spermatogenesis in your dad’s testis . Each sperm is either male or female, equal distribution of both. In essence you are fated to be one or the other before you even exsist (excluding turner’s, super male , klinefelter syndrome etc.).
If you then go on the gonadal definition of sex I believe this isn’t true either. As you can see above there is a common origin of both the male and female external genitalia and one may say that it looks closer to the female end product than the male, however, realistically it is neither. It is neither male or female external genitalia so you can’t claim it was either. If you go on the gonadal definition of gender (which I don’t) you can say we were both the same as embryo’s but it is unfair to claim that somehow we were all females. That is utterly untrue.