It's called Symbiogenesis [0] and it's not at all a wild theory. But it's limited to cell components, not multiples organs fusing to create something as complex

It's called Symbiogenesis [0] and it's not at all a wild theory. But it's limited to cell components, not multiples organs fusing to create something as complex as a mammal. [0] https://en.wikipedia.org/wiki/Symbiogenesis https://en.wikipedia.org/wiki/Symbiogenesis