Darwin rarely used the conventional rhetorical device of depicting nature as a person (invariably female in traditional usage). Darwin desisted for two good and personal reasons. First, his central theory of natural selection held that no direct causes worked at such comprehensive levels and that all general, and apparently purposive, patterns arose as a side consequence of struggle among individual organisms for reproductive success. Second, Darwin was not a lyrical writer, and he did not often resort to metaphors that might misstate the proper locus of causality. Thus, we may regard the final sentence of his book on the fertilization of orchids by insects (written in 1862 as his first full work following. the Origin of Species) as unusual and puzzling. Darwin wrote: "It is hardly an exaggeration to say that Nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilization."
I believe that Darwin was driven to this rare verbal device by his awe at the intensity of the phenomenon--at the enormous range of devices, often highly complex, evolved by flowers to assure that pollen does not always fertilize flowers on the same plant, but finds its way to the female organs of other plants, thus guaranteeing cross-fertilization. Darwin wrote: "In my examination of Orchids, hardly any fact has struck me so much as the endless diversities of structure--the prodigality of resources--for gaining the very same end, namely, the fertilization of one flower by pollen from another plant."
(Darwin did not know the genetic reasons for the biological danger of such frequent self-fertilization or of sexual reproduction between very close relatives, but his culture certainly possessed sufficient folk wisdom about frequent hereditary deficiencies in offspring of such unions--and he correctly reasoned that natural selection must therefore strongly favor mating between nonrelatives. He also recognized that the evolution of devices to prevent self-fertilization would therefore operate as a good test for the power of natural selection, for if selection could not insure this most elementary of all biological imperatives, then his favored mechanism of evolutionary change had little power and his entire theory must fail.)
Among many modes evolved by plants to assure cross-fertilization, none is so common, so interesting, so provocative in inspiring endless books on the subject, and so fundamental in structuring our planetary ecosystems as the attraction of insects (and sometimes other creatures, including hummingbirds) to a flower, the development of devices to assure that pollen will be affixed to the visitor, and the evolution of other structures to promote the transfer of this pollen to female parts of other flowers visited later by the same insects. One might even say, to a first approximation, that the most striking characteristics of flowers--their sizes, shapes, and clustering; the beauty of their colors; the sweetness of their odors--exist largely as features evolved to attract animal pollinators. We once thought, in our arrogance, that God had so fashioned flowers for our delectation, but we are only the lucky beneficiaries of an eminently practical arrangement first evolved almost a hundred million years before our appearance on this planet. Going further, most evolutionary biologists would also argue that the evolution of flowers as devices to assure cross-fertilization provides the most important reason for domination of the plant kingdom by the late-evolving group of angiosperms (or flowering plants). Thomas Gray's famous lines may be good poetry and fine metaphor, but they win no prizes for accuracy as natural history:
Full many a flower is born to blush unseen
And waste its sweetness on the desert air.
Gray need not have lamented. That flower probably passed a most useful, if short, existence, attracting insects and securing its Darwinian fitness by having its pollen transferred! …