OVERPOPULATION is, arguably, the greatest challenge facing humanity. It took until 1800 for our numbers to reach 1 billion. Now the human population exceeds 7 billion and is set to reach 10 billion by 2085. Although problematic, it is also a testament to our success as a species. In a world in which people are increasingly well fed, healthy and safe, a population explosion is only to be expected. In fact, the surprising thing about human numbers is that they are not growing faster. Far from increasing rapidly as you might expect under such good conditions, human fertility rates are plummeting all over the planet. The question is, why?
An obvious answer is that access to contraception gives us control over our reproductive fate, allowing us to limit the number of children we have. But why we choose to do this is a puzzle for evolutionary biologists. After all, you ...
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