Even materials that seem to be impervious to the harshest conditions over scales of years may actually be degrading in subtle ways: our characterization methods are just not good enough to see whether you have lost a few atoms here and there. Yet over many thousands of years the damage could start to show, letting us know which sorts of materials are best.
Long-term testing would be tremendously helpful for other technological applications as well. Current laboratory and simulation techniques, for instance, cannot predict with confidence how the battery of a new electric car will perform over the next 15 years. Eventually computer simulations may become sophisticated enough to substitute for long-term experiments. In the meantime, though, we need to exercise extra caution when building things that need to last.
Will we eventually wage endless local wars?
Laurence Smith, geographer at the University of California, Los Angeles
100,000 YEARS: WHAT MAKES A NEW SPECIES?
Jerry Coyne, evolutionary biologist at the University of Chicago
Most new species in nature appear when a population becomes geographically isolated from other populations. It then adapts to the local environment and, sooner or later, acquires traits that prevent it from successfully mating with the original species or that would make the resulting offspring sterile, or both. The great open question of evolutionary biology is, Which of these two types of reproductive barriers tends to arise first—those that make crossbreeding difficult or those that lead to nonviable offspring?
Speciation occurs over geologic timescales. Thus, although we can see evidence of it in the fossil record or in DNA, we would have to wait a million years or more to see it reach completion. (Much faster routes to speciation have been documented that do not require geographic separation, but they are the exception rather than the norm.) But if we had, say, 100,000 years, we should be able to reproduce it in the laboratory.
The trick would be to work with an organism that produces new generations quickly, such as Drosophila (fruit flies). Researchers would isolate two or more populations in the lab and expose them to different diets and other conditions. You would then need to periodically test each population for genetic mutations and for changes in its anatomy, physiology, and behavior and once in a while have members of different populations meet to see what happens.
In special cases, my collaborators and I have been able to understand reproductive barriers indirectly by looking at many closely related species at different stages of evolutionary divergence. For geographically separated species of Drosophila, we found that the two types of barriers—mating problems and sterile offspring—evolve at about the same rate. But for species cohabiting the same area, interbreeding barriers seem to evolve quicker. It is not clear, however, whether such results apply to all groups of organisms.
To obtain a new species much faster—perhaps in as little as 100 years—you could beef up the selection pressures to be far stronger than they would normally be in nature. In a landmark experiment in the 1980s researchers bred populations of fruit flies to adapt to different environments—as well as to prefer mating with individuals that shared their habitat preferences—in just 25 generations. Yet the conditions in that experiment were artificial, and it is doubtful whether the two populations produced could be regarded as different species. A very long experiment could be much more definitive.