One of the threats to modern science is the persistence of faith-based beliefs about the origin of life on Earth, such as the concept of intelligent design which holds that the natural world was created by an intelligent designer – who may or may not be God or another deity. Intelligent design, like other forms of creationism, is incompatible with the theory of evolution formulated by English naturalist Charles Darwin in the 19th century. But, in asserting that complex biological systems defy any scientific explanation, believers in intelligent design fail to understand the basic features of evolution.

The driving force in biological evolution, or descent from a common ancestor through cumulative change over time, is the process of natural selection. The essence of natural selection is that, as in human society, nature produces more offspring than can survive, and that variation in a species means some offspring have a slightly greater chance of survival than the others.  These offspring have a better chance of reproducing and passing the survival trait on to the next generation than those who lack the trait.

A common misconception about natural selection is that it is an entirely random process. But this is not so. Genetic variation within a species, which distinguishes individuals from one another and usually results from mutation, is indeed random. However, the selection aspect isn’t random but rather a snowballing process, in which each evolutionary step that selects the variation best suited to reproduction builds on the previous step.

Intelligent design proponents often argue that the “astonishing complexity” of living cells and biological complexes such as the bacterial flagellum – a whip-like appendage on a bacterial cell that rotates like a propeller – precludes their evolution via the step-by-step mechanism of natural selection. Such complex systems, they insist, can only be created as an integrated whole and must therefore have been designed by an intelligent entity.

There are several sound scientific reasons why this claim is fallacious: for example, natural selection can work on modular units already assembled for another purpose. But the most telling argument is simply that evolution is incremental and can take millions or even hundreds of millions of years – a length of time that is incomprehensible, meaningless to us as himans, to whom even a few thousand years seems an eternity. The laborious, trial-and-error, one-step-at-a-time assembly of complex biological entities may indeed not be possible in a few thousand years, but is easily accomplished in a time span that’s beyond our imagination.     

However, evolution aside, intelligent design can’t lay any claim to being science. Most intelligent design advocates do accept the antiquity of life on earth, unlike adherents to the deceptively misnamed creation science, the topic for next week’s post. But neither intelligent design nor creation science offers any scientific alternative to Darwin’s mechanism of natural selection. And they both distort or ignore the vast body of empirical evidence for evolution, which includes the fossil record and biodiversity as well as a host of modern-day observations from fields such as molecular biology and embryology.

That intelligent design and creation science aren’t science at all is apparent from the almost total lack of peer-reviewed papers published in the scientific literature. Apart from a few articles (such as this one) in educational journals on the different forms of creationism, the only known paper on creationism itself – an article, based on intelligent design, about the epoch known as the Cambrian explosion – was published in an obscure biological journal in 2004. But one month later, the journal’s publishing society reprimanded the editor for not handling peer review properly and repudiated the article. In its formal explanation, the society emphasized that no scientific evidence exists to support intelligent design.

A valid scientific theory must, at least in principle, be capable of being invalidated or disproved by observation or experiment. Along with other brands of creationism, intelligent design is a pseudoscience that can’t be falsified because it depends not on scientific evidence, but on a religious belief based on faith in a supernatural creator. There’s nothing wrong with faith, but it’s the very antithesis of science. Science requires evidence and a skeptical evaluation of claims, while faith demands unquestioning belief, without evidence.

Next week: Why Creation Science Isn’t Science