Final answer:
Research predominantly found no significant cognitive differences between males and females that would suggest gender is solely biologically determined; instead, it emphasizes the role of cultural factors in shaping gender.
Step-by-step explanation:
The excerpt provided suggests that one reason gender is understood to be partially biologically determined is based on the observation of cognitive abilities in males and females. One example cited by biologist Anne Fausto-Sterling in her book 'Myths of Gender' is the review of research on cognitive and behavioral sex/gender differences that mostly found no statistically significant difference between the cognitive abilities of boys and girls. When differences were noted, they were minimal, emphasizing that factors other than biological sex predominantly account for cognitive variations.
Another perspective provided in the text comes from sociobiology, which in the 1970s claimed that evolution had shaped men and women differently, resulting in natural gender roles and abilities. However, this viewpoint has been challenged by the majority of research findings indicating minimal or no significant cognitive differences attributed to biological determinants. This refutes the notion that gender roles and abilities are solely defined by biology, leaning towards the interpretation that gender is a complex trait influenced by both biological and cultural factors.