What triggers wanting to throw up / gagging when you see someone else throw up?

Question

What triggers wanting to throw up / gagging when you see someone else throw up?

In: Biology

Answer 1

Humans evolved as social animals. Our ancestors shared food and water. Seeing a member of our social group throw up may mean the food we shared was tainted. So we evolved the instinctual mechanism that seeing someone emesis (vomit) primes us to do the same. Dogs have a similar instinct as they evolved in social groups as well.