Microbes 3, Humans 2

Face it: We're no match for E. coli.

Let us mince words. When we say "best," we mean some kind of success, implying the existence of goals, which in turn are the exclusive property of organisms and not of species. Where the goal of a runner in a track meet is to break the tape, where a dragonfly succeeds when it snatches a fly from the air for dinner, where even a colon bacterium reverses the spin of its flagella, causing it to tumble and depart in a new direction that leads to dissolved sugar, it takes an organism to have a best.

As a result of natural selection, species -- or more precisely, the organisms composing species -- generally perform brilliantly in the niche to which they are specialized. There are probably 10 million or more species alive on earth. Which are the best at filling their niches? All are, I guess. Consider this Zenlike question: Can a bird fly better than a fish can swim? Live species are by definition all successes, because the losers are extinct, having fallen victim to nature's equivalent of the Foreign Legion command, March or die.

Of course, success by organisms can ultimately be disastrous for their species. Browsing animals, like the American white-tailed deer, can be superlatively efficient and as a result wipe out the plants on which they depend, whereupon the species and the organisms it comprises plunge toward extinction. Or take the same principle in reverse: the most successful parasites are those that least harm their host. The champion human parasites may be the Demodex mites, microscopic spiderlike creatures that live unnoticed on the eyelashes and eyebrows of a large percentage of the human population.

That said, I am unwilling to give up entirely the quest for successful species. So let me use subjective, human-oriented criteria to pin some gold medals on members of the world's fauna and flora.

Most abundant. Bacterial species win this one easily. There are more E. coli and other intestinal bacteria in your colon at this moment than there are human beings who have ever lived.

Longest lived. All living species are in a dead heat, since all have descended from early forms of life that originated more than 3.5 billion years ago. When biologists speak of ancient forms and living fossils, they really mean certain combinations of traits that have persisted for relatively long periods of time in certain lines of descent, like modern horseshoe crabs and coelacanth fish. But the direct ancestry of human beings goes back just as far as these living fossils, the only difference being that the traits that distinguish Homo sapiens as a species are less than one-hundredth as old.

Most likely to survive. Without doubt, bacteria and allied organisms known as archaea win again, especially the species that use photosynthesis or inorganic chemicals to grow and reproduce. If every kind of plant and animal on earth were destroyed, these hardy organisms would carry on. Even if the earth's surface were blasted to a cinder, the inorganic-energy extractors and petroleum feeders would continue their lives many kilometers below the surface of the earth. Given a few billion years, they might give rise to new higher life forms on the surface.

Most social. As an entomologist, I will be accused of insect chauvinism, but I say ants, termites and honeybees win hands down. That is, they win if we use the following criteria: altruism, the complexity of anatomy, instincts devoted to social life and the tightness of the bonds that turn colonies into virtual superorganisms.

Most intelligent. At last, a gold medal for humanity.

Most powerful. Human beings win again. Peering into the future and understanding how the world works, we have acquired the power of life and death over all other higher life forms. Whether we choose life for them and ultimately for ourselves is surely a valid criterion of success. To achieve that goal, however, requires wise management of the environment, an enterprise for which we have so far shown little dedication or talent.