CARRY IT ON YOUR HEAD!
My husband told me that in Nigeria women and men, young and old carrying everything on their heads. For the small things it allows them to use their hands for other uses, but if the balance is right they can even carry much larger objects that might usually require two people to carry. E.g. a dining table.
Really, it is a matter of convenience. - say Nigerians. If the weight is carried appropriately you have the opportunity to use your hands - to buy and compare other items on your journey. Sure it is arduous, but the best alternative. Side benefits are wonderful shaped women, able and active throughout their years. Do not forget it is not only a practice of Africans, even the Asians and South Americans employ the same methods, as did we Europeans in past decades. Nigerians also have cultures that carry on the shoulder - that is in their culture - the Gwari's and that is tedious. In Ethiopia, they carry on the back, as a contrary example the method there is pureley cultural.