New York Times, June 17, 2007 (Week In Review)Link
Eskimo hunters killed a bowhead whale off the coast of Alaska last month and began to chainsaw their way into its blubber. They stopped when the saw hit the tip of an old harpoon lodged deep inside the whale. Historians identified it last week as part of a bomb lance, a harpoon manufactured for only a few years in the late 1800s in New Bedford, Mass. Whalers probably fired it at the bowhead around 1890, when the whale was probably a teenager, and it carried the harpoon for the next 115 years before finally being killed by a modern one.
Whales don't carry birth certificates, so scientists usually can make only rough estimates of their age by examining protein in the lenses of their billiard-ball-size eyes. The bomb lance is pretty clear proof that this particular bowhead whale lived longer than any human on record. Had the whale escaped the second harpoon, scientists say it might have lived another 80 years. Indeed, the age of another bowhead examined by scientists in 1999 was put at 211 years. It holds the record for the longest-lived vertebrate.
But bowheads certainly have competition. Rockeye rockfish can live to be at least 205 years. A Galápagos tortoise named Harriet is reputed to have lived 175 years. At the other end of the spectrum, some animals live eye-blinkingly short lives. The pygmy goby fish in Australia, for instance, lives for only eight weeks. Male Acarophenax tribolii mites live only a few hours within their mothers, just long enough to fertilize their unborn sisters.
Why do bowheads hang on so long, and mites for such a short time? The answer lies in the evolution of aging. Animals can evolve either to produce a lot of babies very quickly, or to live longer but reproduce more slowly. Animals facing lots of risks -- such as getting eaten by predators -- may be better on the fast track. Scientists who have studied the life spans of flies in the laboratory have found that if they kill off lots of flies, the remaining ones evolve to mature faster and reproduce more. But this accelerated life comes at a cost: it damages their cells and they age quickly.
When life isn't so risky, animals often evolve a slower pace of life. They take more time to mature, expending their energy to grow bigger and healthier. They produce fewer offspring, but tend to invest more in their care.
But size alone does not guarantee a long life, says Steven Austad, an expert on animal aging at the University of Texas. He points out that other big whales don't seem to live as long as bowheads. It may be that living in the Arctic Ocean gives them an edge, because they don't face much competition for food in its frigid depths.
Like bowheads whales, humans seem to be something of a long-lived exception among their relatives. Humans live much longer than chimpanzees, for instance, whose DNA more closely resembles our own than any other creature in the animal kingdom. Dr. Austad suspects that this greater longevity evolved as humans, with their bigger brains, constructed social groups that provided protection from predators and other depredations.
Scientists are now investigating the biology of long-lived animals to find ways to slow down our own aging process, but the clues have proved elusive.
Compared to bowhead whales, we clearly have a long way to go in the pursuit of a longer life. But for bowhead whales, longevity has turned out to have a severe downside.
It takes bowhead whales about 20 years to reach sexual maturity. A female bowhead gives birth to a single calf at a time, and it may take four to seven years before it gives birth to the next one. When bowheads began to be slaughtered in huge numbers in the 1800s, the whales could not make up for their lost numbers. They've been slowly recovering, but are still well below their 19th-century numbers and are considered in danger of extinction.
In a human-dominated world, old age may be a luxury few animals can afford.
Copyright 2007 The New York Times Company. Reprinted with permission