The same is true of most of the flowers we are aware of — probably all the flowers that are colored anything other than green and whose smell is anything more than just vaguely plant-like. Not all the work was done by insects — for some flowers the pollinators that did the initial selective breeding were hummingbirds, bats, even frogs — but the principle is the same. Garden flowers have been further enhanced by us, but the wild flowers with which we started only caught our attention in the first place because insects and other selective agents had been there before us. Generations of ancestral flowers were chosen by generations of ancestral insects or hummingbirds or other natural pollinators. It is a perfectly good example of selective breeding, with the minor difference that the breeders were insects and hummingbirds, not humans. At least, I think the difference is minor. You may not, in which case I still have some softening up to do.

What might tempt us to think it a major difference? For one thing, humans consciously set out to breed, say, the darkest, most blackish purple rose they can, and they do it to satisfy an aesthetic whim, or because they think other people will pay money for it. Insects do it not for aesthetic reasons but for reasons of . . . well, here we need to back up and look at the whole matter of flowers and their relationship with their pollinators. Here’s the background. For reasons I won’t go into now, it is of the essence of sexual reproduction that you shouldn’t fertilize yourself. If you did that, after all, there’d be little point in bothering with sexual reproduction in the first place. Pollen must somehow be transported from one plant to another. Hermaphroditic plants that have male and female parts within one flower often go to elaborate lengths to stop the male half from fertilizing the female half. Darwin himself studied the ingenious way this is achieved in primroses.

Taking the need for cross-fertilization as a given, how do flowers achieve the feat of moving pollen across the physical gap that separates them from other flowers of the same species? The obvious way is by the wind, and plenty of plants use it. Pollen is a fine, light powder. If you release enough of it on a breezy day, one or two grains may have the luck to land on the right spot in a flower of the right species. But wind pollination is wasteful. A huge surplus of pollen needs to be manufactured, as hay fever sufferers know. The vast majority of pollen grains land somewhere other than where they should, and all that energy and costly materiel is wasted. There is a more directed way for pollen to be targeted.

Why don’t plants choose the animal option, and walk around looking for another plant of the same species, then copulate with it? That’s a harder question to deal with than you might think. It’s circular simply to assert that plants don’t walk, but I’m afraid that will have to do for now. The fact is, plants don’t walk. But animals walk. And animals fly, and they have nervous systems capable of directing them towards particular targets, with sought-for shapes and colors. So, if only there were some ways to persuade an animal to dust itself with pollen and then walk or preferably fly to another plant of the right species…

Well, the answer’s no secret: that’s exactly what happens. The story is in some cases highly complex and in all cases fascinating. Many flowers use a bribe of food, usually nectar. Maybe bribe is too loaded a word. Would you prefer ‘payment for services rendered’? I’m happy with both, so long as we don’t misunderstand them in a human way. Nectar is sugary syrup, and it is manufactured by plants specifically and only for paying, and fueling, bees, butterflies, hummingbirds, bats and other hired transport. It is costly to make, funneling off a proportion of the sunshine energy trapped by the leaves, the solar panels of the plant. From the point of view of the bees and hummingbirds, it is high-energy aviation fuel. The energy locked up in the sugars of nectar could have been used elsewhere in the economy of the plant, perhaps to make roots, or to fill the underground storage magazines that we call tubers, bulbs and corms, or even to make huge quantities of pollen for broadcasting to the four winds. Evidently, for a large number of plant species, the trade-off works out in favor of paying insects and birds for their wings, and fueling their flight muscles with sugar. It’s not a totally overwhelming advantage, however, because some plants do use wind pollination, presumably because details of their economic circumstances tip their balance that way. Plants have an energy economy and, as with any economy, trade-offs may favor different options under different circumstances. That’s an important lesson in evolution, by the way. Different species do things in different ways, and we often won’t understand the differences until we have examined the whole economy of the species.

If wind pollination is at one end of a continuum of cross-fertilization techniques – shall we call it the profligate end? – What is at the other end, the ‘magic bullet’ end? Very few insects can be relied upon to fly like a magic bullet straight from the flower where they have picked up pollen to another flower of exactly the right species. Some just go to any old flower, or possibly any flower of the right color, and it is still a matter of luck whether it happens to be the same species as the flower that has just paid it in nectar. Nevertheless, there are some lovely examples of flowers that lie far out towards the magic bullet end of the continuum. High on the list are orchids, and it’s no wonder that Darwin devoted a whole book to them.

Both Darwin and his co-discoverer of natural selection, Wallace, called attention to an amazing orchid from Madagascar, Angraecum sesquipedale, and both men made the same remarkable prediction, which was later triumphantly vindicated. This orchid has tubular nectaries that reach down more than 11 inches by Darwin’s own ruler. That’s nearly 30 centimeters. A related species, Angraecum longicalcar, has nectar-bearing spurs that are even longer, up to 40 centimeters (more than 15 inches). Darwin, purely on the strength of A. sesquipedale’s existence in Madagascar, predicted in his orchid book of 1862 that there must be ‘moths capable of extension to a length of between ten and eleven inches. Wallace, five years later (it isn’t clear whether he had read Darwin’s book) mentioned several moths whose probosces were nearly long enough to meet the case.”‘

Excerpted from ‘The Greatest Show on Earth’ by Richard Dawkins