When asked what would disprove evolution, the biologist J. B. S. Haldane famously growled: "Fossil rabbits in the Precambrian." What he meant was that evolution predicts a progressive change over time in the millions of fossils unearthed around the world: multicellular organisms should come after unicellular ones; jawed fish should come after jawless ones, and so on. All it would take is one or two exceptions to challenge the theory. If the first fossil amphibians were older than the first fossil fish, for example, it would show that amphibians could not have evolved from fish. No such exceptions have ever been found anywhere.
The discovery of a mammal-bird hybrid, such as a feathered rabbit, could also disprove evolution. There are animals with a mixture of mammalian and reptilian features - such as the spiny anteater - and there are fossils with a mixture of bird and reptilian features, such as the toothy archaeopteryx. But no animals have a mixture of mammalian and bird features. This is exactly what you would expect if birds and mammals evolved from separate groups of reptiles, whereas there is no reason why a "designer" would not have mixed up these features, creating mammals with feathers and bird-like lungs, or furry, breastfeeding ostriches.
“Why are there no feathered mammals or furry, breastfeeding ostriches?”A young Earth would also be a problem for evolution, since evolution by natural selection requires vast stretches of time - "deep time" - as Darwin realised. Some thought evolution had been falsified in the 19th century when physicist William Thomson calculated that the Earth was just 30 million years old. In fact, several lines of evidence, such as lead isotopes, show the Earth is far older than even Darwin imagined - about 4.5 billion years old.
Suppose for a moment that life was designed rather than having evolved. In that case, organisms that appear similar might have very different internal workings, just as an LCD screen has a quite different mechanism to a plasma screen. The explosion of genomic research, however, has revealed that all living creatures work in essentially the same way: they store and translate information using the same genetic code, with only a few minor variations in the most primitive organisms. Huge chunks of this information are identical or differ only slightly even between species that appear very different.
What's more, the genomes of complex creatures reveal a lack of any intelligence or foresight. Your DNA consists largely of millions of defunct copies of parasitic DNA. The inescapable conclusion is that if life was designed, the designer was lazy, stupid and cruel.
Not only that, if organisms had been designed for particular roles, they might be unable to adapt to changing conditions. Instead, countless experiments, both planned and unplanned, show that organisms of all kinds evolve when their environment is altered, provided the changes are not too abrupt. In the laboratory, tweaking organisms' environments has enabled researchers to produce bacteria, plants and animals with all kinds of novel characteristics - even entirely new species. In the wild, human activity is reshaping many species: urban birds are diverging from their country cousins, some fish are getting smaller because fishermen keep only big fish, and trophy hunting is turning bighorn sheep into smallhorns, for instance.
The online version of this special, with lots of extra content and links, can be found at www.newscientist.com/
From issue 2652 of New Scientist magazine, 19 April 2008, page 26
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