Inconsistent Nature: The Enigma of Life's Stupendous Prodigality - Evolution News & Views

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Inconsistent Nature: The Enigma of Life's Stupendous Prodigality

animal diversity

By the latest reckoning we share this planet with more than 8 million species of fish, birds, mammals, insects, fungi, plants etc., etc. -- with 6,500 new species being described every year. The more notable of recent discoveries include the Eternal Light Mushroom (mycena luxeterna) from Brazil, which emits a bright yellowish light, and the impressive 6-foot-long Golden Spotted Monitor Lizard that had eluded detection in the dense forests of the Philippines.

The prodigality of these forms of life is, of course, stupendous -- where, as broadcaster David Attenborough points out, those spending just a single day in the tropical rain forest may encounter hundreds of different species "moths, caterpillars, spiders, long-nosed bugs, luminous beetles, harmless butterflies masquerading as wasps, wasps shaped like ants, sticks that walk, leaves that open their wings and fly..."

Naturalists have identified 81 different species of frog in a single square mile of the forest in Ecuador and 27 species of woodpecker in Borneo. When beetle expert Terry Erwin spread plastic sheeting on the ground in the Panamanian jungle and sprayed the nearby trees with pesticide, he recovered the bodies of more than eleven hundred novel species.

But that prodigality is also -- as the late Robert Wesson of Harvard University points out -- deeply puzzling, for every seemingly plausible law of biology that might account for it proves, almost whimsically, to be contradicted by numerous countervailing examples. There is no more self-evident imperative than that living things should be fruitful and multiply so as to generate those random genetic mutations that the evolutionary process reputedly requires. And indeed most do on a fantastical scale: the oyster spews out millions of eggs, trees shed countless seeds, and rabbits breed like rabbits.

Yet many species seem reluctant to procreate. Pandas are notoriously uninterested in the joys of sex so their human keepers seeking to breed them in captivity must resort to giving them Viagra or artificial insemination.

Our primate cousins, the chimpanzees, would be much more numerous than they are were it not, as Jane Goodall describes, that they give birth on average just three times during their 21-year lifespan.

Several types of bird (the albatross and golden eagle) and mammals (the rhinoceros and grizzly bear) have far fewer offspring than they might, while, remarkably, the lizard-like reptile Tuatara indigenous to New Zealand has survived for two hundred million years to become a "living fossil" -- despite taking two decades to get round to reproducing and then laying just a single egg every other year.

Or again, the considerable energy and complexities involved in becoming sexually mature should be a prelude to protracted fecundity, but famously many species expire after just a single shot at procreation. It seems distinctly odd that butterflies should undergo the miracle of metamorphosis from one form of life to another (with all that entails) to produce just a single batch of eggs. And, on a much grander scale, the same applies to the salmon and eel whose migration across thousands of miles proves so exhausting that they die after relieving themselves of their sperm and eggs.

Then, while for the most part the cardinal rule of adaptation holds where all living things are beautifully adapted to their way of life (birds and insects for flying, fish for swimming), it seems merely perverse that the fairy wasp and water spider should have opted instead to spend their lives under water or that birds such as the ostrich and emu should have lost the power of flight.

Many species that might seem exceptionally well adapted for "the survival of the fittest" are surprisingly uncommon. The scarce African hunting dog has the highest kill rate of any predator on the savannah, while cheetahs may have no difficulty in feeding themselves thanks to their astonishing speediness -- but are a hundred times less common than lions.

Contrariwise many creatures do much less than they might to defend themselves. "The Tarantula lives by seizing and feeding on insects," writes Robert Wesson. "But when a spider-killing wasp appears it makes no effort to discourage its nemesis from injecting its paralyzing sting."

Perplexing too are those inconsistencies of nature where the powerful instinctive drives for food, shelter and sex become perverted for futile ends -- as with the species of beetle, described by naturalist E.L. Grant Watson, that is powerfully attracted by the sweet scent of nectar but quite unable to satisfy its desire to taste it.

This small creature laboriously climbs the flower stem before positioning itself on a petal facing towards the honey cups at its base. But its mouthparts are not designed to reach the nectar so instead it bites through the petal with its mandibles. "The petal falls off, with the beetle, to the ground. Undeterred by this failure it proceeds to creep up the flower stem once again only for the whole process to repeat itself. It never learns by experience or gets to taste that sweet smelling nectar."

The purpose of such inconsistencies, if there is one, must be to remind us that Nature is too profound to be readily accessible to the finite human mind. And while many aspects of the diverse being and ways of life are more or less well described, hardly anything is really understood.


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