When we mention staples, we should actually include pepper because there are about 3 billion people who consume this berry daily and they eat its varieties in different ways either raw, cooked, pickled, or powdered. Some people cannot imagine a cuisine without pepper be it the sweet one or the spicy one and this has made the berry very popular for hundreds and thousands of years.
It is a part of the Solanaceae or Nightshade family just like eggplant, potatoes and tomatoes are. Belonging to the capsicum genus which has about 30 genera in it. Depending on how hot a pepper is, it is measured using the Scoville scale which was introduced by Wilbur Scoville, a pharmacologist in 1912 and this scale represent the amount of sugar water 1 gram of the capsaicin extracted from the pepper needs to be dilluted into not be detectable any longer. The more hot the capsaicin, the more sugar water would be needed to not to be able to sense it which means the higher Scoville Heat unit.
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Bell pepper with 0 SHU is at the bottom of the scale while the pepper with the highest SHU is at 2.69 million. The majority of the pepper we consume for cooking are of Capsicum Annuum which originated from Northern South America to Southwestern North America and has been introduced to different part of the globe.
The Jalapeno pepper ranges from 2500SHU to 8000SHU and this is because the heat depends on how and when they were harvested. If the pepper is left to ripen, its Scoville Heat unit would increase and the sooner they are harvested, they less spicy they will be. Cayenne is another pepper and this has a SHU of 30,000 to 50,000.
The burning sensation of pepper on mucous membrane comes from a chemical compound known as Capsaicin. Capsaicin also increases the production of saliva, stomach acid, and stimulates the nerve endings of the skin triggering nociceptors which is meant to identify pain as well as trigger the body to release sweat as it has to cool it. Capsaicin is also used in other applications that are not related to food such as in pepper spray and arthritis cream.
Because you feel the heat from capsaicin in your mouth doesn't mean all creatures also experience the same. Birds do not feel the heat because they lack the receptors to taste it the hotness but rodents on the other hand will have their taste buds burning just like humans when they consume capsaicin.
Habanero pepper "Capsicum Chinense" is another pepper that ranges between 100,000SHU to 350,000SHU and similar to habanero is the scotch bonnet which ranges the same. Ghost pepper is another type of pepper and this is a combination of capsicum chinense and Capsicum frutoscens. It measures at 1,000,000SHU and it is very hot but compared to Carolina pepper, this isn't still child's play. Carolina pepper is 2,000,000SHU on the scale. In all these, the pepper X still rains as the hottest pepper and it is a member of the Capsicum Chinense and it measures at 2,690,000SHU.
Eating these peppers activates the polumodal nociceptor receptors all over the body which is activated by extreme heat. So when we eat chili or any other type of pepper that has a rank on the Scoville Heat unit, the brain begins to react to a burning sensation as it thinks the mouth and the entire body is burning as it is in contact with a heat source.
READ MORE
https://www.menshealth.com/uk/nutrition/a754832/the-ultimate-guide-to-chilli-pics-needed/
https://medium.com/@foodrepublic/fear-the-carolina-reaper-the-story-of-the-worlds-hottest-pepper-2f80c111860d
https://www.nist.gov/how-do-you-measure-it/health-and-nutrition
https://recipes.howstuffworks.com/food-science/scoville-scale
https://gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/peppers-by-scoville-units/
https://www.webmd.com/diet/peppers-health-benefits
https://www.health.com/food/dangers-eating-hot-peppers