Abundant literature has demonstrated the critical institutional and social impacts on board gender diversity. This study applies the evolutionary cognitive theory that emerged in neuroscience to explain how the millions of years of evolutionary history have shaped gender cognitions more significantly than the thousands of years of institutional tradition. We conjecture that the labor role division between women as mothers and men as hunters over a deep-long evolutionary history has a profound impact on human neural mechanisms. Such division has led to the following cognitive differences between genders and contributed to the current gender gap on boards: 1) women's focus on building relationships versus men's focus on building tools; 2) women's strong sense of fairness and social compliance versus men's strong drive to win; and 3) women's risk-conservativeness versus men's risk-aggression. Using the U.S. data in 2016 and 2020, we investigate the competing effects on board gender composition between business sectors aligned with gender cognitions and the left-wing and right-wing sociopolitical region as a proxy for institutional variance. Our study results show that women are better represented on boards in the sectors that are people-oriented and more economically stable and are less represented in the sectors that are tool oriented and more economically volatile. The finding suggests that evolutionary cognition has strong explanatory power for women's under-representation on boards than social roles. Our study sheds light on the research of corporate governance and calls for more proactive approaches to improve board gender diversity for the long r