Why do hot pepper plants exist? Wouldn’t it have been an evolutionary disadvantage to have fruits that were painful for animals to eat?
In: Biology
Capsaicin, the stuff that makes peppers hot, is an irritant to mammals but not avians (birds). Birds can eat the fruit and poop out the seeds, spreading them far and wide.
The animals that are supposed to spread their seeds can not taste capsaicin. It prevents pests like mammals from consuming their seeds.
It only hurts mammals. Birds aren’t able to feel the heat
And then by sheer luck, humans *liked* the way it hurt and now hot peppers are everywhere lol
besides what others have said; many hot peppers are a product of selective breeding by humans and not naturally occurring (at the current levels of spice/heat)
As others have said, spiciness in peppers evolved as an irritant to mammals because it was more beneficial for those plants to have their seeds carried by other animals like birds. Actually, a lot of plants that humans eat evolved traits like this to deter certain animals from eating them. Garlic is another example, it’s poisonous to cats and many other mammals.
To add onto that however, humans started eating and cultivating these plants specifically because of their pest-deterring qualities. If you make all your food super spicy/garlicy then wild animals will be less likely to steal it.
Organisms are not known to self-program their DNA for evolutionary advantage. Instead, genetic mutations happen by accident. Some of the mutations will lead to enhanced proliferation, and others will not.
Capsaicin acts as an antifungal, so it likely originally evolved to protect the plants from mold. This would help in humid, tropical climates.
As mentioned earlier, the high levels of capsaicin in modern plants are mostly due to selective breeding.
The chemical tastes spicy to mammals and has no effect on birds. There’s an advantage to the seeds eaten by things that spread the seeds as far as possible. Even to distant islands and new habitats, which mammals are much less likely to do.
Fruits as a dispersal method is VERY effective, so effective that it sometimes gives plants the leeway to evolve a preference towards certain animals dispersing their seeds.
Birds frequently tend to be very favorable to seed dispersal to many plants over mammals, and as such we end up with a wide variety of fruits, usually berries, that evolved to be poisonous or unpleasant to mammals to some degree, but are harmless for birds.
In the case of Peppers, birds can’t really taste the capsaicin that gives them their heat, which caused fewer mammals to try feeding on them. Its also theorized that capsaicin doubles as a somewhat effective antifungal and deterrent for insects. However obviously capsaicin is overall brief and harmless even if a mammal eats the peppers. Some fruits engage in much more harsh measures to make sure birds are the main consumers, even using potentially lethal toxins, such as Pokeweed or the infamously dangerous Deadly Nightshade(a distant relative of Peppers by the way). If you encounter any sort of berry or small fruit that’s considered poisonous to humans, its probably evolved this way because it wants birds to eat it.
Birds do not react to capsaicin. Pepper plants rely on birds to eat their fruit and fly away and poop out the seeds, thus spreading the plant. In fact, some species of plants specifically evolve to activate the germination of their seeds by being digested by animals like birds, squirrels, rabbits, etc. The capsaicin keeps medium to large animals from eating the fruit and it also is a natural protection against insects and other pests
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