CK12 Life Science

We don’t know all the answers yet, but by looking at population growth through history and
by examining population growth in different countries we may see some patterns emerge.
For example, if we look at worldwide human population growth from 10,000 BCE through
today, our growth, overall, resembles exponential growth, increasing very slowly at first, but
later growing at an accelerating rate and which does not approach the carrying capacity
(Figure23.10).

However, by looking at different countries’ population growth over history, we see more
complexity. The history of human population growth can be divided into four stages and we
can see snapshot views of these stages in countries today. Human populations pass through
these four or five predictable stages of growth (Table23.3):

Table 23.3: The Stages of Human Population Growth

Stage of Human Population Growth Description

Stage 1 Birth and death rates are high and popu-

lation growth is stable (i.e. early human

history)

Stage 2 Significant drop in death rate, resulting in

an increasingly rapid rise in population size

(exponential growth)(i.e. 18th and 19th

century Europe)

Stage 3 Population size continues to grow

Stage 4 Birth rates equal death rates and popula-

tions become stable

Stage 5 Total population size may level off

In looking ahead to the future, projections by the United Nations and the US Census Bureau
predict that by 2050, the Earth will be populated by 9.4 billion people. Other estimates pre-
dict 10 to 11 billion. The Cornucopians believe that more people are good for technology and
innovation. The 5-stage model above predicts that when all countries are industrialized, the
human population will eventually reach stability and a carrying capacity of sorts. However,
many scientists and other Neo-Malthusians believe that humans have already gone over the
Earth’s carrying capacity for resources and habitat, and that this will eventually lead to
famine, epidemics, or war, thus causing a population crash or even extinction.

Which of the above theories makes sense to you? What ways can you think of that people
might use to avoid reaching Earth’s carrying capacity?