Chip's Place

As I was cooking my typically spiced-up tea (take any food at all, and add one Scotch Bonnet chilli) this evening, I started wondering why chillies were hot. Not "what chemical makes them hot?" (any hot-head knows that's capsaicin), but "why did chilli plants evolve capsaicin-producing fruit?"

It's a given of Darwinian evolutionary theory that "features" of organisms evolve in order to succeed better in their environment, so I expected that capsaicin should confer some competitive advantage over non-spicy fruit.

The only website I could find (read the section on ants) suggests that hotness would deter mammals from eating the fruit (wouldn't work on this particular mammal!), and since birds are believed immune to capsaicin's effects, they would be attracted to the bright red chillies, eat them and then spread the seeds far and wide.

However, this seems an unsatisfactory answer, for two reasons :

1. Why limit your seed dispersal method to just birds? Mammals are perfectly suitable for that too (viz. tomatoes, apples, etc.), and they give you one more angle. Capsaicin seems counter-productive in this case.
2. Not all chillies are red! Green ones would be unattractive to mammals, as discussed above, and also to birds (relative to the red ones).

Anyone got any thoughts on this?
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