In just one sentence, tell me what this says: 

Throughout the Paleolithic, humans were food gatherers, depending for their subsistence on hunting wild animals and birds, fishing, and collecting wild fruits, nuts, and berries. The artifactual record of this exceedingly long interval is very incomplete; it can be studied from such imperishable objects of now-extinct cultures as were made of flint, stone, bone, and antler. These alone have withstood the ravages of time, and, together with the remains of contemporary animals hunted by our prehistoric forerunners, they are all that scholars have to guide them in attempting to reconstruct human activity throughout this vast interval—approximately 98 percent of the time span since the appearance of the first true hominin stock. In general, these materials develop gradually from single, all-purpose tools to an assemblage of varied and highly specialized types of artifacts, each designed to serve in connection with a specific function. Indeed, it is a process of increasingly more complex technologies, each founded on a specific tradition, that characterizes the cultural development of Paleolithic times. In other words, the trend was from simple to complex, from a stage of nonspecialization to stages of relatively high degrees of specialization, just as has been the case during historic times.
Paleolithic humans were gatherers and hunters, and the tools used by them started off simple and got more complex and specialized. 