Reader Penelope wants to know if I have any ideas about why herbs, spices, and flavorings — like vanilla — exist at all. Do they serve a purpose in nature? And if so, what is it?
Penelope they certainly do serve a purpose in nature: they are delicious. My personal belief is that God put them there so that we average schlubs might enjoy a decent pot de crème every so often, however I recognize that my theory lacks scientific rigor.
As it happens there is another theory, one which also lacks a certain amount of scientific rigor: the scientific explanation. The central idea here is that chemical compounds contained in a plant which are not essential to the plant’s survival (i.e. which aren’t related to the plant’s growth, metabolism or reproduction) are defensive in nature. Which is to say they are designed to protect the plant from predation by microbes, insects and larger animals, and also protect them from, say, too much exposure to the sun.
These so-called “secondary metabolites” make up an incredibly diverse family of chemicals ranging from phenols (pigments as well as the flavonols and flavonoids that give pods and seeds like vanilla, nutmeg, coffee and chocolate their flavor) to terpenes (the essential oils found in leafy herbs like basil, mint and citrus) to alkaloids and glycosides (everything from the bitter tasting compounds in kale to nicotine, cocaine, heroin and cyanide). There are many others besides.
The idea that pigments protect from the sun and cyanide helps keep large herbivores from eating too much escarole, well, I’d say there’s pretty compelling evidence to suggest those theories are true. Far less is known about what specific pests vanillin or eugenol might protect against. Probably there is some sort of evolutionary answer out there. Until that’s definitively found, though, I prefer that notion that universe wants me, personally, to enjoy my ice cream.