- AP World History - Stearns Chapter 1 ? From Human Prehistory to the Early Civilizations I. Introduction A. Human origin ? 2.5 million years ago 1. 1/4000 of earth?s existence ? 24 hour day ? last 5 minutes B. Human negatives and positives 1. Aggressiveness, long baby time, back problems, death fears 2. Grip, high/regular sex drive, omnivores, facial expressions, speech C. Paleolithic (Old Stone) Age ? 2.5 million to 12000 BCE 1. Simple tools ? increase in size, brain capacity ? Homo erectus II. Late Paleolithic Developments Homo sapiens sapiens ? 120,000 years ago ? killed off others? Population growth required change ? 1 square mile to hunt/gather for 2 people Long breast feeding ? limit fertility