OCEAN 320 Chapter Notes - Chapter Unit 1B: Black Death, Infant Mortality
Unit 1B: The Human Ocean
The Total Human Footprint
• Modern Homo sapiens first walked earth 500,000 years ago; 108 billion of our species
have been born since, currently 7.5 billion living
• Estimate: by 2050, 113 billion people will have ever lived on earth
o Rough estimate because we cannot account for prehistoric populations or their
increase rates, but we can imagine based on gathered data
o depends on two factors: the length of time humans thought to have been on Earth
and average size of human population at different periods
o hard to fix a time when human species first came into existence; latest findings
show they could have existed at early as 50,000 BC
o at dawn of agriculture (8,000 BC), human population was about 5 million, but it is
expected than regional populations varied in increase and decline based on their
immediate conditions
o life expectancy during most of human history was only 10 years; this puts the
birth rate at 80 live births per 1,000 people
o complications: infant mortality rate was high in early human history, meaning
there had to be many more births to compensate for infanticide, which alters our
estimate of those “ever born”
o most population estimate of early times are imprecise, though, and estimates
range drastically in numbers
o 1650: world population is 500 million, which seems to be an alarming slow rate
until black plague is accounted for; huge plagues like this make the estimate of
humans ever born even less precise by leaving huge population gaps
o 1800: population hits 1 billion
o Modern population increase is possible because of advancements in medicine and
nutrition, which have slowed the death rate, allowing more people to live into
reproductive years
• To determine estimates, we must apply a presumed birth rate to different known
population sizes throughout antiquity
o Can be challenging to determine if population grows at a steady rate, or
fluctuates; but most scientists use a fixed rate model
o Result: estimate of about 108.4 billion births since the dawn of the modern human
race
o Period 8,000 B.C. to 1 A.D. is key to the magnitude of our number, but hard to
gather accurate data on that entire era
▪ Possible reasons why: current theory of birth rate model might
underestimate the amount of births or average population size at the time,
humanity also could have started earlier (but again, we don’t know that
that would explain the significant increase)
find more resources at oneclass.com
find more resources at oneclass.com
