Reproduction is divided into two categories sexual and asexual.
This attempt is made by every organism whether the best fit or not, but it is only the environment that will select the successful one. As the organism wants to be as successful as possible, the partner selection will be on the basis that the first organism must believe that to get as far as possible in the generation line, the other half of the genetic material must come from an other organism believed to be equally or more successful than itself. The only explanation is that maybe they are not running the same race or that they both took off at different tangents.