Peppers evolved chemicals like capsaicin to discourage animals from eating them, and that chemical itself can cause internal damage if consumed in large quantities, though this is usually only a concern for the hottest of peppers (which people do eat).

Still, why is it that humans seem to be the only animal that often "like" spicy food?

  • $\begingroup$ Since I can't quote any literature on this I wont write it as an answer. My guess would be that other animals don't have the ability to feel the "rush" we get from punishing ourselves by eating spicy food. For example the burning sensation from chilly releases endorphins which gives you a temporary biological "high". I am also eagerly waiting for an expert to answer this. $\endgroup$ – Roni Saiba Sep 24 '17 at 4:34
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    $\begingroup$ "Peppers evolved chemicals like capsaicin to discourage animals from eating them"... that is not correct. It's to discourage mammals from eating them. Birds eat chili without any problem. $\endgroup$ – user24284 Sep 24 '17 at 4:55
  • $\begingroup$ But the observation remains the same. Humans are mammals and often like spicy food, and there are other animals comparable to humans in many ways which do not like spicy food by their seeming intrinsic physiology. The question still remains: why is it that humans to are an exception from this group? Perhaps its something similar to broccoli where some people taste it as especially bitter and others do not, but you have not provided any formally recognizable answer. $\endgroup$ – DaneJoe Sep 24 '17 at 5:46
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    $\begingroup$ @DaneJoe Not all humans enjoy spicy food. In fact, many don't. And of those that do, there are even fewer who enjoy really spicy food. Your question could very well be asked when only considering humans, which could suggest then that there's nothing inherent to [all] humans having an affinity towards spicy food. This, however, is the basis for your question. BTW, my cousin has a cat that eats spicy food all the time. Also, I believe birds eat all kinds of [spicy] peppers.. $\endgroup$ – Charles Sep 24 '17 at 7:27
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    $\begingroup$ Perhaps the answer is that humans seem to be the only species that is capable of seasoning its food. Very few people eat hot peppers directly (and then it seems to be more of a test of machismo that actual liking, at least IMHO), they use small amounts to season food. Certainly my dogs have eaten such food with every outward evidence of liking. $\endgroup$ – jamesqf Sep 24 '17 at 18:36

I think like many things spicy food became something that we used as a tool. Used mostly for preserving food, those countries where it gets very hot due to a tropical climate you'll find the food tends to be much spicer in areas where parasitic flies and other pathogens would contaminate the food faster. The spicier it is, the longer your food stocks would last. Over generations they developed a higher and higher tolerance.

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    $\begingroup$ Welcome to Biology SE! It'd be great if you can cite your sources. Answers with no references may be challenged or deleted. $\endgroup$ – vkehayas Jan 26 '18 at 20:51

There are really two questions here 1. Why do humans use spices? and 2. Why do some humans eat excessive amounts of this particular capsaicin but not other spices, or only a few others?

I will answer the second question first. The current understanding of why some humans eat so much spicy food is that it is a form of benign masochism. "Some" is the key: only some humans like spicy food in anything but the most minimal amounts. It has been shown that eating spicy food releases endorphins, but only after the burn, so eating spicy food is like going to a scary movie or riding a rollercoaster — initial discomfort followed by a rush. Humans are the only animals that do these things because we know they are not dangerous. It is thrill-seeking.

Now this is not the entire story. Spices in general have their own origins. Many spices inhibit bacteria, and capsaicin appears to do so as well. This alone could be the reason people started using it more widely. We see that more spices are used in warmer climates, the same places where spoilage would be the biggest risk. We also see more use of the spices with the highest inhibitory properties. Interestingly humans may not be the only animals to spice food in this way; bears and bees are both known to mix antibacterial plants into stored food.

Additionally small amounts of many spices, even capsaicin, can improve flavor without generating the burn. This is probably the least understood aspect, but some believe it may be linked to simulating the flavor of better-quality organ meats or increasing bioavailability of some nutrients.

Lastly it has been shown that capsaicin in particular can actually trick the body into cooling itself off even when it would not do so normally. Your body responds to the false signal of heat by cooling itself, which could be a benefit in hotter climates.

  • $\begingroup$ Yes, I was going to answer with "benign masochism" also.. The examples of "from negative to positive" experiences are called hedonic reversal. $\endgroup$ – ermanen Jan 26 '18 at 17:23
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    $\begingroup$ Here is a relevant article and a relevant excerpt about animals: "There is no strong evidence for liking for innately negative experiences in animals. The strongest evidence against animal exemplars is that rural Mexican dogs and pigs that eat food with hot peppers regularly (since they eat human leftovers) do not develop a preference, unlike some hundred million human Mexicans who share their diet (Rozin & Kennel, 1983)" $\endgroup$ – ermanen Jan 26 '18 at 17:25
  • $\begingroup$ Birds for instance can "ingest" spicy food, but that doesn't mean they actually perceive the spiciness in the same way or at all. If someone can't taste the acidity sulfuric acid, they could drink sulfuric acid and say they liked it. $\endgroup$ – DaneJoe Jun 26 '18 at 21:57
  • $\begingroup$ @DaneJoe it isn't spicy to birds, capsaicin only works on mammals. birds don't have the same TRPV receptors as mammals, which works for the plants because birds spread the pepper seeds, mammals destroy the seeds when they eat them (chewing) so the pepper want to discourage mammals but not discourage birds. $\endgroup$ – John Jun 26 '18 at 23:48
  • $\begingroup$ Right, so when people try to argue that birds have no problem with spicy food, the point is moot. $\endgroup$ – DaneJoe Jun 27 '18 at 20:14

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