It's not really that healthy though. The continuous impact can really mess your joints up long term.
Run with proper form, don't ramp mileage and intensity too fast. Humans are built for long distance running.
I prefer cycling. Running has wrecked me multiple times (100m & 200m training). I'm not built for long distance which is a shame because I could hold pace with the best amateurs over middle distances when fit (sub 3 min kms).
Humans evolved on the plains of Africa, hunting animals by running them down to exhaustion[1].
I think some of the bare foot running purists become cult-like in their views, but I think Chris Mcdougall's "Born to Run"[2] book is worth reading and thinking about. It's an easy, well written and entertaining read too.
[1] Watch the amazing Attenborough clip of them running an healthy, fully grown male antelope down. https://www.youtube.com/watch?v=826HMLoiE_o
[2] http://www.chrismcdougall.com/born-to-run/the-barefoot-runni...
But nor is it settled that running causes damage, and I think the endurance running hypothesis provides an interesting reason to consider the counter-case.
For one, AFAIK humans rarely aged beyond 40 in those times, so it is entirely feasible that the accumulated wear and tear starts to hurt the joints after that age.