Spare a thought for the poor guppy fish, who lives a miserable existence but teaches us something important about forecasting.

Small, brightly colored, and terrible at defense, the guppy faces an unusually high rate of predator attacks. Birds eat guppies. Small fish eat guppies. Big fish eat guppies. Crabs eat guppies. It’s everyone’s favorite lunch.

How does a species under so much threat avoid extinction?

In short, guppies get busy as soon as they’re born. They can reproduce at seven weeks old, and deliver new offspring every 30 days. By the time a six-month-old guppy is eaten by a bird it might be a great-great-grandmother. The family lives on.

But this evolutionary trick has a nasty flip side.

Knowing how much danger they’re in, guppies expend nearly all their energy on reproducing from the moment they’re born. They grow as fast as possible, then devote a huge portion of their resources to nourishing their young.

That leaves little energy left to care for themselves. Their bodies are thrown together slipshod, like cheap plastic toys, and few resources are available for cell repair and maintenance. By the age of a year or two old it’s a crusty senior citizen, crippled by disease and decline, soon to go belly up. That’s how it should be: No use investing in the future when you’re likely to be eaten anyway.

Now compare the guppy with the Greenland shark, whose life is nearly a mirror image.

The Greenland shark has no natural predator. It (Read more...)