“hill to hill” is probably the correct answer. But, still, they had to head in a generally consistent direction (south) and not go in circles over the years. It’s fascinating looking at the early human migrations out of Africa, through the middle east, across the inhospitable steppes and mountains of the Asian continent, up to the bitter cold of the north (which makes no sense), then across the Bering land bridge and eventually south again. Most migrations would logically be toward more abundant hunting and foraging. Going north to the frozen wastes doesn’t make sense.
Think of the Nile, Amazon, Misissippi, Ohio, Great Lake tributaries.
The hill are for safety. The water is necessity.
It does if you are moving to get away from another group who perceives you as an enemy, or has superior weaponry and wants the spot where you happen to be living at the time.
The spread of migration in the Americas shows the leading group as very primitive, with "technologically superior" waves pushing them along. Compare the "indigenes" of Tierra del Fuego with the Eskimo. Very similar climatic conditions, very different technology level.
#13 Some real estate agent said the land up north was called Greenland so they went after leaving a deposit with the agent.