- One reason the question keeps coming up is that somewhere, at some time back in the 1970s, a now-forgotten writer made the statement that 75 percent of the people who had ever been born were alive at that moment.

- sounds plausible since we believe most aspects of the 20th century are characterised by expo growth

- What might be a reasonable estimate of the actual percentage?

- Any estimate of the total number of people who have ever been born will depend basically on two factors:

(1) the length of time humans are thought to have been on Earth and

(2) the average size of the human population at different periods.

- According to the United Nations' Determinants and Consequences of Population Trends, modern Homo sapiens may have appeared about 50,000 B.C.

- This long period of 50,000 years holds the key to the question of how many people have ever been born.

- It is difficult to come up with an average world population size over this period. In all likelihood, human populations in different regions grew or declined in response to famines, the vagaries of animal herds, hostilities, and changing weather and climatic conditions.

- One estimate of the population of the Roman Empire, from Spain to Asia Minor, in 14 A.D., is 45 million.

- rates and such

- low because of Blacl Death

- The average annual rate of growth was actually lower from 1 A.D. to 1650 than the rate suggested above for the 8000 B.C. to 1 A.D. period. One reason for this abnormally slow growth was the Black Death. This dreaded scourge was not limited to 14th-century Europe.

- The epidemic may have begun about 542 A.D. in western Asia, spreading from there. It is believed that half the Byzantine Empire was destroyed in the sixth century, a total of 100 million deaths.

- Such large fluctuations in population size over long periods greatly compound the difficulty of estimating the number of people who have ever lived.