"A mile a day? Really?"
Not that surprising. Assuming humans traveling less than 1 mile per day, it would only take about 10,000 years to go half way around the planet.
Huh? Better check your math.
Less than a mile a day?
You assuming they were dragging Barca Loungers and entertainment centers?
Whoever they were, they did nothing but walk and run. On a migratory trek they could do way better than that.
One of the positive things JFK did was establish the Presidential Fitness Program for schools with various goals for pullups, rope climbing, etc. Included running and walking milestones to be achieved. One of the tests was to hike/walk 26 miles in 8 hours or less. Our HS JROTC did 2 of these, with BSA knapsacks carrying lunch, extra socks, and canteens of water...was a walk in the park, even in street shoes and the thin soled tennis shoes of the day.
Check out some of the historic marches of Alexander the Great and Roman Legions carrying war paraphernalia etc.
Ymmv
;>)