How will longer lives affect world population? Certainly anything that keeps people alive longer will increase the number alive at any given point. However, the details of population growth can be rather counterintuitive. Consider that today the countries with the longest life expectancies at birth have populations that are remaining steady or even shrinking. For example, the UN Population Division expects the populations of Japan, Italy, Germany, and Spain to all decrease over the next 50 years, despite the fact that Japan has the highest life expectancy of any large country, and the Western European nations are not far behind. At the other extreme, the countries with the fastest growing populations are those with relatively low life expectancies - countries like India, China, Pakistan, and Nigeria.
Throughout most of human history, birth rates and death
rates were both extremely high. In the year 1000 AD, birth
rates were around 70 births per 1000 people per year, and
death rates were about 69.5 deaths per 1000 people per year.
So each year a town of 1000 people would on average increase
its population by half a person. That's a 0.05 percent rate
of growth.
As societies advance, nutrition, sanitation, and medicine
all serve to lower the death rate. When births outstrip
deaths, population soars, as happened through the twentieth
century. But in the last few decades the birth rate has also
dropped sharply, particularly in the rich developed nations
of the world. As countries gain in wealth and education, and
especially as women in those countries gain greater rights,
resources are increasingly devoted to education and career,
rather than raising a family. This demographic trend is
spreading from Europe, Japan, and North America to the rest
of the world. Worldwide the birth rate is now 21 births per
year per 1,000 people. The death rate is around 10 deaths
per year per 1,000 people. So overall the world population
is growing at roughly 1 percent, slower than at any time in
the last few centuries.
Because the birth rate is double the death rate,
phenomena that affect fertility can have a far larger impact
than similar size effects on the death rate. For example,
between 2000 and 2050, the UN expects around 3.7 billion
people on earth to die, while another 6.6 billion are born.
Cutting the death rate in half would increase population by
around 1.9 billion people. Doubling the birth rate would
increase population by a further 6.6 billion. Thus the birth
rate is a more significant lever on the size of the
population.
Projecting population growth into the future is a tricky
thing. It depends on just how quickly economic growth
improves healthcare, sanitation, and nutrition. It also
depends on how quickly those important birth rates come
down. The United Nations Population Division produces high,
medium, and low estimates for future population. Birth rates
and death rates differ by just a few percent between the
scenarios, but over decades it adds up. In 2000, world
population stood at 6 billion people. Looking forward, the
UN predicts that in 2050, world population will be somewhere
between 8 billion and 11 billion, with a "medium" prediction
of 8.9 billion.
8.9 billion people is half again as many as are alive
today. Yet in real terms it represents a growth rate about
half as fast as the last 25 years. World population grew by
50 percent between 1975 and 2000. The next 50 percent
increase is predicted to take until sometime after 2050,
around twice as long. Ultimately the UN's "medium" model
projects world population hitting a plateau of 10 billion
people in 2100. Of course, projections 100 years in the
future are perilous. They rely on a generally smooth
progression of current trends. They don't take into account
the possibility of global plagues, world wars, or
technologies that radically alter mankind.
Life extension is just one of those technologies, yet its
impact on population is surprisingly small. Demographer Jay
Olshansky, despite being a pessimist about the prospects for
slowing human aging, has shown that extending human life
would have an incremental, rather than exponential, effect
on population. "The bottom line is that if we achieved
immortality today, the growth rate of the population would
be less than what we observed during the post World War II
baby boom", he says. If everyone were made completely
immortal today, he calculates, and taking into account
declining birth rates, global population would hit about 13
billion in 2100, rather than the 10 billion currently
projected.
The immortality Olshansky is talking about isn't
achievable. If we halted all aging, accidents, homicide,
suicide, and infectious diseases would still kill people.
Nor is complete halting of the aging process in our sights
today. More likely, we'll achieve the technology to slow but
not halt the rate of aging in the next 10 to 20 years. Then
it will take additional years for people around the world to
gain access to the technology. Even then, the impact on
population won't be instant. Those who are already old won't
benefit much from techniques that slow their aging rate.
Instead, it will be the middle aged and young who reap most
of the benefits. The combination of those factors suggests a
gradual impact on worldwide population.
Here's a simple mathematical way to look at this. We
can't predict exactly when life extension techniques will
first be available or how quickly they'll spread, so we'll
need to make some guesses. Imagine that life extension
techniques first appear on the market in 2015. In the year
after that (2016), let's say the overall death rate around
the world drops by 1 percent as a result. And let's say that
it decreases by another 1 percent each year thereafter, so
that in 2017 age-slowing techniques have reduced the global
death rate by 3 percent, and that by 2050 they've reduced it
by 35 percent. That's quite an optimistic scenario. It
implies that by 2050 we've managed to increase life
expectancy in the developed world to around 120, and in the
developing world to around 113 - an unprecedented rise in
life expectancy, even compared to what's happened in the
last two centuries.
If this extremely optimistic rise in life expectancy
occurred, how large would the impact on global population
be? If we simply reduce the number of deaths the UN
forecasts each year by the percentages above (1 percent in
2016 climbing up to 35 percent in 2050), we get a total
population in 2050 of 9.4 billion people, instead of the 8.9
billion the UN projects.
Five hundred million additional people are nothing to
sneeze at, but as a proportion of the projected world
population for 2050, it's less than 6 percent. To put this
in context, that's less than the percentage change in world
population between 1970 and 1973 - a noticeable change, to
be sure, but not a catastrophic one.
It's also worth noting that some demographers believe
that birth rates in the developing world will drop faster
than the UN's middle scenario. Just a 5 percent lower birth
rate yields a scenario where global population tops out at
around 8 billion in 2050, and may come back down to below
the year 2000 level of 6 billion in 2100. Achieving this is
entirely plausible if the right resources are applied. A
plateau and eventual reduction in global population depends
on the spread of wealth, education, and freedom in the
developing world. For example, the UN expects the population
of Europe (not counting immigration) to shrink by about 0.4
percent per year between now and 2050. The overall
population of the developed world (again not counting
immigration) is expected to remain fairly constant. If the
developing world can attain the present level of affluence
of the developed world by 2050, we'll see overall world
population level out and begin to drop.
|
|
Excerpted from
More
Than Human © 2005 Ramez Naam.
Published by Broadway Books, a division of
Random House. For information about other
Broadway books and authors, see our web site
at
http://www.broadwaybooks.com.
Ramez Naam is a fellow of the IEET, and author of More than Human, and a senior technologist at Microsoft.
Print •
Email •
permalink •
Discuss in Forums •
Send to: ¡
 ¡
COMMENTS
YOUR COMMENT
Next entry: The Legal Road Ahead
Previous entry: Human Changing
|
|
IEET Blog