Question

why are our ancestors supposed to shift from tree dwelling mode of life to land life?

Answer 1

Even among all land- dwelling vertebrates, human .... Did our ancestors come down from the trees? ... in the trees in order to start a bipedal terrestrial way of living.

Answer 2

Bipedalism,visual surveillance,long distance walking & foraging & increment of intelligence helped tree dwelling Australopithecus to evolve to Homos.