Monday, August 24, 2015

Human Population Growth: Earth's Push Back Time

Humans are entering the top of our population growth curve. 

Partly because some of us have chosen to limit births, but also because, for the very first time in human history, earth is limiting our births for us. 

It’s a biological given that populations have an s-shaped growth curve.

At first, growth is exponential, starting slow and increasing at a faster and faster pace.

Sound familiar?

Until recently, this is what all the human population growth charts looked like:

Doomsday scenarios say if we keep reproducing at greater and greater rates, we will soon run out of food, water, and space.

For most biological populations, though, the rate of growth starts off exponential. Then it slows and eventually stops. The top of the curve becomes flat, making that characteristic s-shape.


Most critters are no smarter than people. They don’t choose to limit how many babies are born.

The environment limits births for them.

Populations race exponentially upward until the critters have filled their environment. Then the environment pushes back. 

The critters' waste products pile up. A poison to them, their waste damages their fertility and vitality. Meanwhile, predators--including disease organisms--settle in for a steady munch. The result? Population growth slows, then levels off.

The human population is still growing, but our growth rate is going down.

We have entered the top of our growth curve.

Now, some of that is sociological. For people in rich countries, kids are expensive, social services means you don't need them to take care of you in your old age, and better medical care for children means you no longer need a bunch to have some reach maturity. So people choose to have smaller families.

But there may also be a more biological explanation.

Think about it.
  1. We are the only true world-wide species. (Other world-wide species, like Norwegian rats, live off us).
  2. If the whole world is our environment, we have only just filled it.
  3. As we cover the earth, our waste products spread--primarily industrial and agricultural pollutants. These decrease our health, and many act like hormones to decrease our fertility.
  4. As a global monoculture, we are fast food central for human disease organisms.
Humans are not really better than other critters. We are not immune to normal, biological processes. 

Neither are we worse. 

In fact, we’re just the same, and we’ve finally filled our environment: the whole earth.
Giving the earth a chance to push back.

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