Why would anyone be opposed to de-extinction?

[LearningCurve]

83. I assume you didn't watch the video

I'll try to summarize. The video focuses on the mammoths in North America, and lays out 3 possibilities. The first, is climate change. Climate change is discussed within the context of what was occurring in the Americas at the time. The conclusion reached, was was that climate change theory was insufficient to account for the disappearance.

The second, was hunting. The reason for the assumption is partially circumstantial, mammoths disappeared in the Americas shortly after humans arrived. Evidence of clovis points found among mammoth bones, plus use of mammoth bones in tools is contributing evidence to the theory. Additional evidence, is the disappearance of other animals, hunted to extinction by newly arriving humans. Horses had to be reintroduced to the Americas, for instance. There are some skeptics in the video, for some of the reasons you cite.

The third reason, is disease. Evidence for this includes bones of mammoths during times when humans were present, that seemed to show sick mammoths. Possibilities include direct transmission, or from domesticated dogs introduced by newly arriving humans. I am not aware of any current study which still holds to climate change as the reason for mammoth extinction in the Americas.

That being said, I am unfamiliar with studies done in Eurasia. If you are referring to climate change as the reason for their disappearance there, I'm not informed enough to know one way or the other.