Humans (Homo sapiens) are the most abundant and widespread species of primates, characterized by bipedality and large, complex brains enabling the development of advanced tools, culture and language.

The Chromosomal Theory of Inheritance was consistent with Mendel's laws and was supported by the following observations: Even though male and female gametes (sperm and egg) differ in size and morphology, they have the same number of chromosomes, suggesting equal genetic contributions from each parent.