Living World / Evolution

Life isn't cheap. In evolutionary terms, it's incredibly expensive, says Drew Allen, an ecologist at the University of California at Santa Barbara. Using a mathematical model, Allen worked out exactly how much it costs to generate a new species. The answer: a staggering 10²³ joules, more energy than is released by all the fossil fuels burned on Earth in a year.

Allen looked specifically at foraminifera (right)—tiny, omnipresent, ocean-dwelling plankton that have been plentiful for millennia. His model took into account both an individual plankton's body size and its metabolism's dependence on temperature to quantify how much energy it takes to fuel all the genetic changes that must occur in order for a new species to emerge. He found that although the amount of energy required is constant, new species form more quickly near the equator because heat speeds up both metabolism and the rate of genetic mutations.

Even Darwin noticed that biodiversity is more plentiful in the tropics. "But the idea that temperature affects speciation rates through its effects on molecular-level processes is brand-new," Allen says.

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