[remixff2400]

That's the thing: we're _only_ 8 billion and amongst that we only have so many researchers and people who have the knowledge to do anything like that. We have limited capital to pursue any major initiative, so wasting it on unfeasible and non-beneficial initiatives like starting a Mars colony just wastes time we could do doing something more useful i.e. reforming deserts, stabilizing ecosystems, developing cheaper materials for various industries, etc.

I'm not sure how dangerous "de-extinguishing" a species would be, but we've had numerous faux paus with destabilizing ecosystems by introducing non-native species (i.e. lionfish, as an invasive species). These cause extensive environmental damage and can be irreversible if not contained in time. The worst thing that could happen is losing control over the population of de-extinct species and damaging an ecosystem(s).

That all being said, I'd be stumped if we somehow lost sight of a woolly mammoth... and I'd be lying if I said I didn't want to see one myself, so...