Hot Peppers – Why Are They Hot?

Plants have been waging a war with animals-and humans alike-for a long time. As herbivores and omnivores rely heavily on plants for nutrients and survival, they can easily live on without us. Due to this, many plants have developed techniques to rebel animals from eating them (e.g. vile smell, thorns, unappealing, difficult to reach, etc.). However, other plants will try to attract animals (e.g. colourful, sweet smell, etc)  to eat their fruits so as to spread their seeds and germinate.

So what makes hot peppers so special?

This peculiar fruit attracts animals through its bright colours and sweet scent. However, as we all know, these signs are misguiding as they fill our senses with a fiery explosion of pain.

The reason for this pain is due to the chemical, capsaicin, which attachs to receptors called vanilloids which are found at endings of trigeminal nerve (sensory and motor fibres in the face). These receptors are typically found inside the mouth and-when bound by capsaicin-creates a sensation of pain.

As researchers began studying on the reasons for this “backwards” phenomenon, they discovered that vanilloid receptors are found in all mammals but not birds.

In this article Bora Zivkovic talks about how:

 Back in 1960s, Dan Johnson had an interesting proposal he dubbed “directed deterrence” which suggested that some plants may make choices as to exactly which herbivores to attract and which to deter. 

Following this proposal, researchers found out that mammals tended to chew, crush or semi-digest the seeds. While birds are able to eat through to the seeds and keep them fertile even after digestion.

For more details, check out:

Hot Peppers – Why Are They Hot? | A Blog Around The Clock, Scientific American Blog Network.