I thought everyone knew this. Tasks based on sex were not so prevalent until high cultures formed and people started settling down instead of being nomadic.
Men are faster and stronger. Men don't spend a good portion of their lives growing children and breastfeeding them. So more free time to hunt. Men's eyesight is literally better at picking up motion than woman's and men have better reflex's and hand eye coordination. Men outperform woman in almost all aspents of what it takes to be a great hunter back in the early human days.