An evolution paradox

Fittest Males Don't Always Get the Girl

Here's an article from ScienceDaily discussing about a (seems simple) question: if males who are more aggressive and can win more fights and have more offspring, why human and many animals are not selected extremely aggressive nowadays?

The answer given in the article is that aggressiveness is not always the best strategy under all circumstances. Or rather, there is no "best" strategy. Yet the author noted that the female may not always choose the strongest male. Is the need for diversity "hard-wired"? Or is the female choice simply based on the availability and scarcity of males? In other words, does the diversity of environment drives species to diversify their possible strategies, or females mate with not-so-competent males just because they have no chance to get better ones?

Another explanation that I can offer to the lack of extremely aggressive behaviour in today's gene pool is that more aggressive individuals tend to have more fights and higher mortality in their most productive age. This of course is compatible with the two hypotheses above. This is an interesting question anyway.