system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do women look different than men?

I understand the need for wider hips / breasts, but what's the point of creating two distinct creatures (one with a normally larger and muscular frame) and another with a smaller and more 'aesthetic' face and body?

Wouldn't the human race be simplified by just having a single organism that can reproduce with itself?
gpt
Men and women look different (sexual dimorphism) because of the presence or lack of the Y chromosome and different gonads which in turn leads to different hormones. Natural selection has selected certain features in males and females which made them reproductive successful. Males for example are larger and stronger because they often had to physically compete for females. 

>Wouldn't the human race be simplified by just having a single organism that can reproduce with itself?

Not quite sure what you mean by simplified. Generally speaking sexual reproduction gives an evolutionary advantage because it allows for genetic diversity.