Chili pepper
Chili peppers, spicy fruits from the genus Capsicum, originated in South and Central America but have since spread all over the world.
Capsaicin, the chemical that gives chili peppers their heat, originated as a defense mechanism to protect the plant from predators. However, humans have strange tastes, and enjoyed the burning sensation of hot peppers.
Different kinds of chili pepper contain varying levels of capsaicin and thus varying levels of spiciness.
#Human relations
People of the Fifth World prepare peppers much as people do today. They will often dry and grind peppers into a spice to flavor other dishes, or cut up fresh peppers to cook in sauces, curries, and dips. Some mild chilies, they will stuff with ground meat or other fillings. Communities with access to ancient cast-iron frying pans may fry peppers in oil before adding more ingredients, to draw out the spicy flavor.
Horticultural communities living in areas where elephants roam will also plant chili peppers around the borders of their gardens, to discourage the animals from trampling them. (Elephants have very sensitive noses and strongly dislike the smell.)
#Specialization
A community specializing in relationship with chili peppers will invariably tend strongly towards horticulture, and therefore live in settled villages. These communities will practice slash-and-burn agriculture, growing different guilds of plants at different stages and moving around the jungle in a regular cycle. They will likely grow chili peppers at an early stage in this cycle, so the growing peppers can get enough sun.
A community focusing so much on hot peppers as to specialize in them will certainly like spicy food, and possibly participate in endurance challenges or contests over who can handle the spiciest pepper. They may incorporate the ingestion of hot peppers into coming-of-age rituals.
Such a community may trade extensively in various chili powders, infused oils, and possibly even hot sauces. If they make infused oils and hot sauces, they will likely also practice ceramics or glass-blowing in order to make portable containers for these products. They and those with whom they trade may take as much pride in the bottles as the sauces and oils themselves.
If they make clay pots, this would require living near a good source of clay, and possibly camping in that area for part of the year to make pottery there. If they use glass bottles, they may spend a lot of time digging in old landfills to re-use glass bottles from our time. If so, they'll likely collect a number of other ancient curios, and trade those as well -- becoming known not just for their hot sauces, but for their strange and unique antiques.
On the other hand, if they blow their own original glassware, they would require a source of sand; perhaps they live on the edge of a desert, or on the coast. (If they live on the coast, they would have to take care to separate true sand from the plastic sand that now covers every beach.) Glass-blowing requires a great deal of specialized knowledge, which this community likely treasures and may keep secret from others - perhaps even guarding the knowledge in a secret society within the community, or across communities. They probably produce more glassware than just bottles, branching out especially into jewelry.