Source: Atheist Universe, Ch5, Miracle of life on earth By David Mills
Creationists often cite the human eye as evidence of God’s design. We are told that the human eye is more complex and advanced than the most modern digital camera.
Rhetorically we are asked, “If the camera requires a designer, then how could the human eye arise by random accident?”
The answer is that the human eye did not “arise by random accident.”
Nor did any evolutionary biologist ever make such a claim. Creationism thrives by setting up and knocking down imaginary straw-men—i.e., self-evidently ridiculous assertions about evolution that no scientist proposed in the first place.
It’s easy to topple an argument erected specifically for demolition.
Evolution, by definition, is a gradual accumulation of functional adaptations. Evolution has only three essentials for success:
(1) time, (2) genetic variety among offspring and (3) a mechanism for preserving only beneficial variation.
“Today, the theory of evolution is an accepted fact for everyone but a fundamentalist minority, whose objections are based not on reasoning but on doctrinaire adherence to religious principles.”
—JAMES WATSON, Nobel Prize-winning biologist and co-discoverer of DNA’s structure
Such a mechanism is called natural selection, and was first proposed by Charles Darwin in 1859.
First, let’s explain a creationist misunderstanding of the phrase “theory of evolution.” Creationists would have you believe that evolution is called a “theory” because scientists are unsure whether it’s a fact. Such a misunderstanding of the term “theory” reflects creationism’s total estrangement from the scientific community.
Scientists use the term “theory” to mean “explanation.” We have Cell Theory, which explains the structure and function of living cells. Yet no scientist doubts that cells exist. We have Atomic Theory, which explains the behavior of atoms. Yet no scientist doubts that atoms exist. We have Gravitational Theory, which explains how celestial objects are attracted to each other.
Yet no scientist doubts that gravitation is real. Evolutionary Theory, therefore, explains evolution—its subtleties and processes. As we shall see, science considers evolution as undeniable as cells or atoms or gravitation. And the evidence for evolution is just as solid.
When isolated from creationist propaganda and distortion, the Theory of Evolution by natural selection is easy to understand and easy to accept. In many ways, evolutionary theory is a case of stating the obvious.
“Which is it: is man one of God’s blunders, or is God one of man’s blunders?”
—FRIEDRICH NIETZSCHE (1844-1900), in Twilight of the Idols
Many creationists grudgingly admit that evolution by natural selection—or “survival of the fittest”—is clearly evident in the reproduction of bacteria or farm insects or peppered moths. But creationists rarely concede that evolution by natural selection also applies to human beings.
Again, we are asked, “How could evolution account for the human eye?”
To explain such complexity in Nature, Charles Darwin observed that virtually all species exhibit a strong tendency toward overpopulation. Competition is therefore extremely intense within the species for limited nutrients and for other scarce essentials of life.
Any members of the species that possess even the slightest advantage in competing for these essentials will likely survive to produce offspring, which inherit this tiny advantage.
Any awareness of the environment provides a tremendous competitive advantage. If light, for example, could be sensed by skin cells, a lifeform could: (1) orient itself vertically, (2) be aware when a possible source of nutrition eclipsed the light source, and (3) be aware when predators cast a shadow.
A lifeform without eyes produces offspring without eyes. But suppose that a few of the offspring possess a small number of light-sensitive skin cells.
These offspring would enjoy a competitive advantage and would perpetuate this characteristic throughout the species. Suppose now that a few offspring begin concentrating these light-sensitive cells into a single location, thus amplifying their sensitivity. Again, this competitive edge would quickly spread throughout the species. Offspring that did not display this characteristic would die without contributing to the gene pool.
Next, let us suppose that a tiny percentage of offspring are produced with a slightly concave shape to their light-sensitive regions. This rounder shape would allow the lifeform to better discern the direction from which light was emanating, again providing a reproductive advantage. Finally, let’s recall that cells are filled with semi-transparent liquids. So it wouldn’t be too surprising if this liquid occasionally found itself within the concave surface of the light-sensitive region. The liquid would thus serve as a very primitive lens, helping to focus light.
“Truth, in matters of religion, is simply the opinion that has survived.” —OSCAR WILDE (1854-1900),
In this manner, step by step, millennia after millennia, natural selection accumulates beneficial adaptations while discarding the remainder. “What is impossible in a hundred years, may be inevitable in a billion,” said Carl Sagan.
The human eye required almost four billion years to evolve. Regarding the evolution of bodily organs and appendages, creationists often ask, “What good is half an eye?” or “What good is half a wing?” In other words, until such body parts are fully functional, they produce no survival advantages. Natural selection therefore would not perpetuate an eye or wing that was “under construction” or “on the verge of working.” Creationists believe thus that conscious, end-result planning and design were necessary to produce functional organs and appendages.
Nature herself, however, flatly contradicts the creationists’ all-or-nothing argument. For within Nature, we find eyes in all stages of development.
We find lifeforms with:
(1) no eyes at all,
(2) eyes that sense only the presence or absence of light,
(3) eyes that focus light extremely poorly, such as the mole’s,
(4) eyes that cannot see more than a few feet,
(5) eyes that cannot see color, such as most dog breeds,
(6) eyes that are humanlike, and
(7) eyes that are far superior to human eyes, such as the bald eagle’s.
Within Nature, we find a smooth and unbroken continuum of visual capabilities among the various animal species.
What good is 50 percent of an eye? It enjoys a decided advantage over 49 percent or 37 percent or 8 percent in the struggle for survival. The creationist argument—that partially developed anatomical structures produce no survival advantage—
ignores the real-world diversity of Nature. Moreover, the terms “fully developed” and “partially developed” are relative.
Bald eagles may pity human beings for their “partially developed” eyesight and wonder how natural selection perpetuated such “unfinished” organs.
But what if genetic variation or mutation does not produce the beneficial adaptations upon which natural selection may act?
In such a case, the species would show no evolutionary progress, and would likely become extinct. Extinction is as much a part of evolution as natural selection. Looking back over Earth’s geological history, over 99 percent of all animal species have failed to adapt successfully to their environments—and have therefore fallen victim to extinction. If creationists want to believe that all lifeforms were carefully and purposefully designed by a Creator, then they must accept the Creator’s abysmal 99 percent failure rate. Any watchmaker whose product similarly failed would be dismissed as incompetent.
Source: Atheist Universe, Ch5, Miracle of life on earth By David Mills