I think having a high savings rate, all else equal, is actually a boon. Low time preference means that more ambitious, longer term projects can be realized. This raises the wealth of the population overall, further increasing the fraction of money that can be saved, and creating a virtuous circle of civilization.
By not eating all the food they had and saving it, the first humans were able to not go hunting/gathering for a while, and dedicate that free time to building better tools. Those tools further increased the productivity of hunting/gathering, and enabled them to save an even greater portion of their food, freeing even more time to build even better tools, etc.