I once knew a family running a dojo & health school on a nearby farm. I was never formally involved, but came to know the family well. The sensei there told me that plain simple walking was the most balanced form of exercise - which makes sense to me in a where-we-come-from kinda perspective : our bodies evolved to function most efficiently doing what we had to do in our natural state in order to survive, namely mostly gather food and water from our environment, mostly walking, with occasional spurts of higher activity either hunting, or fleeing from danger.

So I guess the closest we can get to that is quite a few hours worth of walking every day, with a few running spurts in between - which no-one can afford in the 8 to 5 (at least) enslavement paradigm we are presently trapped in. I guess one should also intersperse the walking part with some reach and dig type exercises, as those would have been part and parcel of the daily routine out in the wild.

Anyhow, I was at my fittest in present day circumstances over a period of more or less ten years when I deliberately chose to do all of my daily traveling by bicycle, with all of my daily destinations being within about a ten km radius.