Sex determination is the biological process by which an organism develops into male, female, or in some cases hermaphrodite. In genetics and evolutionary biology, two broad mechanisms are recognized: chromosomal sex determination and environmental sex determination. Both play critical roles in shaping evolutionary strategies and reproductive success among organisms. Chromosomal sex determination involves the presence of specific sex chromosomes that direct the development of sexual characteristics. In humans and most mammals, the XY system operates, where individuals with XX chromosomes develop as females and those with XY chromosomes develop as males. The Y chromosome carries the SRY gene, which triggers male differentiation by promoting the development of testes. Birds, however, exhibit a ZW system in which males are homogametic (ZZ) and females are heterogametic (ZW). This highlights that the roles of heterogametic and homogametic sexes can differ across taxa. Another example is found in insects such as Drosophila melanogaster, where sex is determined by the ratio of X chromosomes to autosomes rather than by the presence of a Y chromosome. Thus, an XX individual develops as a female, while XY or XO individuals develop as males. In some reptiles like snakes, the ZW system is also present, whereas in