From a biological perspective, the distinction between male and female is fundamentally rooted in chromosomal composition, which subsequently orchestrates the development of specific gonads and their corresponding internal and external genitalia.
Primarily, biological sex is established at conception by the presence of XX chromosomes defining female or XY chromosomes defining male, with the SRY gene on the Y chromosome being crucial for testicular development.
These gonads, either ovaries or testes, then produce sex hormones—estrogens and androgens, respectively—that drive the differentiation of internal reproductive organs such as the uterus and fallopian tubes in females, or the epididymis and vas deferens in males.
Concurrently, these hormonal influences guide the development of external genitalia, leading to the formation of a vulva, including a clitoris and labia, and a vaginal opening in females, or a penis and scrotum in males. While these phenotypic expressions are typically distinct, biological sex development can exhibit variations, often termed intersex conditions, where chromosomal, gonadal, or anatomical features do not align in a strictly binary fashion, highlighting the spectrum of biological sex.
Therefore, while the presence of a penis or vagina represents a key phenotypic marker, the complete biological definition of male and female involves a hierarchical cascade of genetic programming and hormonal signaling impacting multiple physiological systems.
