The purpose of emotions was proven by accident. Emotions exist as a physiological component of the brain to help make complex cognitive decisions on the fly. It is safe to think of this as a short circuit around analysis paralysis, but it also comes at a cost of various cognitive biases.
It should be no surprise that animals have emotions similar to humans since the physiology of many animal brains is not incredibly different from human brains.
It was hard to confirm the discovery because people with no emotion are rare, but some of it was arguably confirmed later through interviews with John Wayne Gacy who demonstrated much of the same behaviors but had learned to compensate and fake it for much of his life.
It should be no surprise that animals have emotions similar to humans since the physiology of many animal brains is not incredibly different from human brains.
The discovery: https://www.smh.com.au/national/feeling-our-way-to-decision-...
It was hard to confirm the discovery because people with no emotion are rare, but some of it was arguably confirmed later through interviews with John Wayne Gacy who demonstrated much of the same behaviors but had learned to compensate and fake it for much of his life.
https://en.wikipedia.org/wiki/John_Wayne_Gacy