It is essential to clarify that in the context of evolution, the concept of "gender" doesn't necessarily apply in the same way it does to human societies today. Gender, as we understand it, is a social and cultural construct that varies among different human societies.
In biological terms, the first forms of life were likely single-celled organisms that reproduced asexually, meaning they did not have distinct genders. These organisms would have undergone simple cell division or other forms of asexual reproduction to create new individuals.
As life evolved and became more complex, sexual reproduction emerged as a more advantageous strategy. Sexual reproduction involves the fusion of genetic material from two individuals, which leads to greater genetic diversity and potentially more adaptable offspring. However, even in early sexually reproducing organisms, the concept of "gender" as we understand it today still didn't exist.
The evolution of distinct sexes, such as males and females, likely occurred in more complex organisms over an extended period of time. The development of separate sexes allowed for a division of labor in reproduction, enhancing the specialization of reproductive roles. This division can be observed in various plants and animals today.
It's important to note that the specific details of the evolution of sex and gender-related traits are complex and can vary significantly across different species. There is no single linear path that leads to the current diversity of sexual and gender-related characteristics found in living organisms today.