Stardate 20010726.1451 (On Screen): Why is there fruit? For someone who believes in evolution, this appears initially to be a puzzle, since the fruit appears to be an altruistic gift by plants to animals of one form or another. But there's no altruism involved. Take, for instance, apples. You have have noticed that horses love to eat apples, and well they might; they're sweet and tasty and easy to chew and definitely a nice break from tough old grass and leaves. But what's in it for the apple tree? Well, horses (and other grazing animals) don't actually chew all that efficiently, especially when eating something as soft and digestible as an apple. They do chew a bit, but most of the digestion is done in the gut. Apple seeds are small and hard and slippery and there are several in the fruit, and while one or two may get crushed by teeth, most will not be. They're also resistent to digestive processes, and will emerge from the horse undamaged. But where and under what circumstances they emerge is the point: horses tend to move around. By the time the seeds emerge the horse may have moved miles and certainly will have moved hundreds of meters away from the original tree, and the horse deposits the seeds in the middle of a pile of the best naturally occurring fertilizer there is. It's a win for the apple tree.
Some plants optimize their fruits for big ruminants; some for birds; some for squirrels and other climbers. But what is hot pepper optimized for? Why would a plant grow a fruit that is impossible to eat? Research has now found that it isn't actually impossible to eat; it's just impossible for mammals. Birds love the things and aren't affected by capsaicin, the chemical which makes peppers "hot". It's a selective poison. And birds turn out to be the ideal creatures for spreading pepper seeds around.
What they don't mention in this article but which I suspect strongly is that it also repels insects. If a fruit is destroyed by caterpillars, it's not going to be eaten by something larger which will move its seeds unharmed. Defense against insects is, so far as I can tell, the reason why the onion family (including garlic) have a strong flavor, as well as why such things as black pepper and cinnamon bark have the flavors they do. In small quantities, mixed with other things, we humans find these flavors quite pleasant. But eat a full meal of 100% raw garlic or 100% black pepper or 100% oregano leaves and you're going to be deathly ill afterwards. That's what insects would face. (discuss)
