Prehistoric demography is the study of the demography of human and hominid populations from the origin of hominids about 6,000,000 years ago through the origin of anatomically modern humans about 200,000 years ago, to the beginning of the agricultural revolution about 10,000 years ago.
Hominid population estimates
It is estimated that the average life span of hominids on the African savanna between 4,000,000 and 200,000 years ago was 20 years. This means that the population would be completely renewed about five times per century, assuming that infant mortality has already been accounted for. It is further estimated that the population of hominids in Africa fluctuated between 10,000 and 100,000 individuals, thus averaging about 50,000 individuals. Roughly multiplying 40,000 centuries by 50,000 to 500,000 individuals per century, yields a total of 2 billion to 20 billion hominids, or an average estimate of about 10 billion hominids that lived during that approximately 4,000,000 year time span.