I am not arguing that people would start out TRYING to eliminate the two-gender system. I think it would happen naturally as people first got rid of maladaptive differences (aka- aggression, low social skills and low empathy for men; and depression, low risk-taking and low self-promotion for women), which then started a cycle towards one-gender or similar

In other words, one gender (or low gender differences) isn't the original desire of anyone. It's the unintended result.