If you’ve consumed cannabis, you’re probably familiar with the munchies, also known as hedonic eating. This impulse to raid the pantry while high isn’t unique to humans - it turns out even tiny worms will pick calorie-dense, tasty food when under the influence, thanks to a thing called cannabinoids. Cannabinoids are compounds found in weed; they make us hungry because they mimic the compounds that run our endocannabinoid system, which helps regulate many biological functions, including eating.
When researchers wanted to know how long we’ve had this system, they turned to an old reliable lab friend - the nematode C. elegans. They exposed these worms to endocannabinoids to investigate just how far back the evolution of the system goes. Exposure to endocannabinoids increased C. elegans’ preference for the yummiest, most nutritionally-dense foods, while causing them to ignore inferior grub.
So that means our endocannabinoid receptor pathways are older than the last ancestor we shared with nematodes - over 500 million years ago.