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MA: It seems simple. To follow the perfect example of a perfect “k-selected” species - we would simply expand to the limits of our environment or as we often say - the habitat's carrying capacity - we would then modulate our birth rate to equal our death rate and live in the land of milk and honey.

But it is, as are many things in complicated systems, not that easy.

James, we now understand that there are both “k-selected” and “r-selected” traits in many populations. Our is riddled with such contradictions.

Let's start with a simple concept like rate of population growth.

While it is true that the overall human rate of increase is modulating - that is not true for all components of that set.

Most European countries have low growth rates. In the United Kingdom, the rate is 0.2%, in Germany it's 0.0%, and in France, 0.4%. Germany's zero rate of growth includes a natural increase of -0.2%, without immigration, Germany would be shrinking, like the Czech Republic.

The Czech Republic and some other European countries’ growth rate is actually negative (on average, women in the Czech Republic give birth to 1.2 children, which is below the number to yield zero population growth, approximately 2.1 children). The Czech Republic's natural growth rate of -0.1 can not be used to determine doubling time because the population is actually shrinking in size.

So in these numbers we have a very strong trait for “k-selection”.

But there is another current equally as strong - if not stronger.

Many Asian and African countries have high growth rates.

Afghanistan has a current growth rate of 4.8%, representing a doubling time of 14.5 years.

If Afghanistan's growth rate remained the same (which is very unlikely and the country's projected growth rate for 2025 is a mere 2.3%), then the population of 30 million would become 60 million in 2020, 120 million in 2035, 280 million in 2049, 560 million in 2064, and 1.12 billion in 2078.

This is a ridiculous expectation. But it is very much in line with a “r-selection” strategy.

J: MA I thought “k-selected” species also had rapid population expansion?

MA: Child I do believe you are paying attention. That is an excellent observation.

The answer is yes, of course “k-selected” species have periods of rapid population expansion. But the kicker is the conditions under which this occurs.

Do you remember the brief phrase I said summarized the k vs r selection?

J: Was it quantity vs quality?

MA: That is correct. But what it also means is that these two strategies are designed to function in different environments.

Your K species uses the rapid growth to take advantage of a stable environment with ample resources (colonization for example) while the R species responds to a disturbed environment by mass reproduction - obviously hoping that some members will survive the certain crash that always occurs.

So it is not just the growth rate but the environment that frames that growth that really defines which strategy is in play.

See the difference?