Did you know dogs were beasts of burden for thousands of years?  Horses weren’t used in America until the Europeans introduced them for instance.  There and many other places, it was just dogs.  I suppose it shouldn’t have surprised everyone when the first uplifted dogs quite literally started pulling their weight and more.  By the time I grew up, it was common to see army dogs walking around with heavy weapons strapped to their backs.  They can be real intimidating.