The concept of number and the process of counting developed so long before the time of recorded history that the manner of this development is largely conjectural. It is not difficult, though, to imagine how it probably came about. It seems fair to argue that mankind, even in most primitive times, had some number sense, at least to the extent of recognizing more and less when some objects were added to or taken from a small group, for studies have shown that some animals possess such a sense. With the gradual evolution of society, simple counting became imperative. A tribe had to know how many members it had and how many enemies, and a man found it necessary to know if his flock of sheep was decreasing in size. Probably the earliest way of keeping a count was by some simple tally method, employing the principle of one-to-one correspondence. In keeping a count on sheep, for example, one finger per sheep could be turned under. Counts could also be maintained by making collection of pebbles or sticks, by making scratches in the dirt or a stone, by cutting notches in a piece of wood, or by tying knots in a string. Then, perhaps later, an assortment of vocal sounds was developed as a word tally against the number of objects in small group. And still later, with the refinement of writing, an assortment of symbols was evolved to stand for these number. Such an imagined development is supported by reports of anthropologists in their studies of present-day primitive peoples.