Ever wondered why Earth is such an ideal place for humans? Creationists think it’s because God designed all of this for us, but that’s arrogant and silly. Sure, gravitational forces are strong enough but not too strong. Likewise, temperatures are nearly perfect. The oxygen content of Earth’s atmosphere is also good for humans. We can find food and water almost everywhere except in arid deserts, frozen polar habitats and high up in the mountains. All of this couldn’t be mere coincidence, could it?
Rather than suspend reason and succumb to an irrational system of belief, consider a more sensible scientific alternative. Quite simply, our planet is hospitable to us because, like every other denizen of this planet, we evolved here and have thus become adapted to Earth’s conditions by natural selection. Humans are extremely versatile, and although we seem to think that we can exist outside the laws of nature, we cannot. We are Earthlings first and foremost, and space and other planets will always remain hostile environments for us.
Until recently, spaceship Earth has provided a rather nice place for us to live. But now, Earth’s life support systems are failing. We have overpopulated the planet and fouled its atmosphere — the resultant pollution is contributing to global weather change. Earth is warming rapidly; ice caps are melting and ocean currents are changing. Polar bears and penguins are facing extinction and though many refuse to face the facts, humans might not be far behind.
In fact, we have not been “designed” intelligently. Numerous attributes of individuals are poorly designed carryovers from our ancestors who had very different ecologies. Adapting an ancestral aquatic fish into a land-dwelling mammal necessarily involved many changes of function, some of which led to elements of poor design. Melbourne physiologist professor Derek Denton was right to point out that “Knowledge of gravity has not been a strong point in the repertoire of the intelligent designer.” The drainage holes at the top of our sinuses and the way our intestines and other organs are attached by membranes to our backbone are examples. Both designs were fine for four-legged creatures, but now that we have evolved to walk upright, this “design” leads to clogged sinuses and hernias. Another such blatant example is the crossover between our respiratory and ingestion tubes, resulting in a maladaptive lung/esophagus arrangement (one that has led to many thousands of choking deaths). What a sense of humor our “designer” must have had to place an entertainment center right on top of a sewage disposal outlet.
Both vertebrates and cephalopod mollusks have independently evolved complex camera-like eyes complete with an aperture, lens and retina. Prominent anti-Darwinian Charles Hodges once suggested that the vertebrate eye was too complex to have evolved by natural selection and therefore must have been “designed.” However, vertebrate eyes are poorly designed as compared to cephalopod eyes. In vertebrates, nerve fibers pass in front of the retina creating a blind spot, whereas nerves lie behind the retina in the superior cephalopod eye, which does not have a blind spot. It seems the “intelligent designer” gave mollusks a better eye and has failed us once again.
<em>Pianka is a professor of integrative biology.<em>