Sexual selection is one facet of natural selection, and a complex one. The Peacock is spending energy and increasing personal danger in order to take advantage of sexual selection. On the other hand the population of pre-giraffe mammals who discover the untapped food resources to be had by reaching up to browse are choosing a path of resource based natural selection. Sexual selection may subsequently occur, with females choosing partners whose physical attributes have allowed them to pursue this feeding strategy to greater health and vitality, and it's hard to tease the two apart.

Birds gain so much advantage in resource gathering with their ability to fly that often mere physical vitality is not sufficient to attract a mate. The surplus energy available to all can start a cascade of purely sexual selection through sexual display, whereas with the giraffes an improved feeding strategy may create enough improved vitality to drive selection without producing obvious secondary sexual traits like showy plumage.

Humans and bees may be on parallel and non interactive selective paths. For the flower, exhibiting "beautiful" shapes and colors to attract the bee has obvious selective advantage, for the bee the ability to perceive intriguing patterns of color and shape may lead them to more efficient collection of resources. For the human, employing similar neural and visual pathways to create an emotional response to intriguing shapes and colors may add selective advantage by increasing "zest" and enjoyment felt in interactions with the natural environment that provides all resources...food for thought;)