We're Underestimating the Risk of Human Extinction

[GliderGuider]

5. Funny you should mention that.

One of the books on my bedside table right now is "Tragedy in Mouse Utopia" by the Canadian ecologist Jack Vallentyne.

The book starts from a discussion of John Calhoun's famous mouse experiment at NIMH in 1968. Four breeding pairs were introduced to a safe, closed environment with plenty of food, water and fresh air, well-arranged sleeping and social quarters, no predators and no disease - a true mouse utopia. They were left to breed at will.

Over 560 days the colony grew from 8 to 2200 mice. It then entered an inexorable downward curve that ended 1000 days later - not with a stable lower number of mice, but with the extinction of the entire colony.

The culprit seems to have been behavioural changes brought on by the marginal overcrowding. There was always plenty of space available, but the level of involuntary interaction may have gotten too high and overwhelmed their social instincts.

The implications it raises for our own future are disturbing, given that we're seeing a similar situation with regard to human populations, intense urbanization and declining species-wide birth rates.

The message that I take from it is that the recent drop in our birth rates may not herald the happy days of Stages 3 and 4 of the Demographic Transition Model , but may instead be the precursor to a behaviour-mediated decline in our numbers, potentially ending at 0. But that's just me...