Interesting article but my thought was...what if there were 19 adult males and 20 adult females? I don't as easily picture the guys upping their game...I picture guys inventing video games or beer or sports or wandering off into the woods. Or working together with the other males to make rules about who has access to females. That sounds familiar.
I believe that they too will try to compete, but in a different way. Forgive me for this non-politically correct generalization what I am about to make, but historically women choose men in part based upon who can provide enough money for the family, whereas men select women in part based upon attractiveness, which suggests fertility.
Having too many men vs women is becoming a problem in countries that abort a disproportionate number of girl babies, thus creating a population of young men that will never get married. I believe in China these "bare branches", as they are called, tend to be the ones least economically successful, and there is concern they will cause unrest in the future.
I realize we are getting off topic, so that's all I will say about this.