Why Weren’t Plants Created  100% Efficient at Photosynthesis? (OR: Why Aren’t Plants Black?)

Why Weren’t Plants Created 100% Efficient at Photosynthesis?
(OR: Why Aren’t Plants Black?)

Author: John Woodmorappe
Subject: Biology

John Woodmorappe’s Articles
About John Woodmorappe
“If God made the world,” runs a common argument for evolution, “then why didn’t He. . . ?” Most creationists, we expect, can supply the next clause: “. . .give pandas better thumbs? Or improve the design of the human spine? Or make seed production more efficient?”

This “God-wouldn’t-have-done-it-that-way” argument for evolution appears to many to be among the most compelling in the theory’s favor. But rarely do evolutionists give the argument the careful thought it requires.

Consider the notion of perfection. If God is perfect, asks the naturalistic evolutionist, then shouldn’t His biological productions be perfect as well? Perfection, however, is an exceedingly tricky concept.

What, for instance, would be a perfect wristwatch? The naturalist might claim that no intelligent designer would make a watch that loses one second a month, or accumulates dust and rust, or has a case that tarnishes with time, or can be affected by magnets, or cannot withstand a sledgehammer blow. Why stop there, however? With a little imagination, one can also ask why an intelligent designer would make a watch that fails to forecast the weather, or does not have a vibrator alarm in case the wearer is deaf, or does not have tactile hands in case the wearer is blind, or cannot function in a vacuum in case the wearer wants to use it on the moon, or cannot get up and put itself on its owner’s wrist . . .and so on.

“Well, I meant a reasonable concept of perfection,” the naturalist might reply. This move only brings us around however to meet the same problem, in another form. What would or would not be reasonable for God to create? The philosopher Robert Adams has argued that God is under no compulsion to make perfect creatures (Adams, 1987). He points out that God is not accountable to anyone for His actions, and that He is in no way unfair to His creatures if He does not make them perfect. (This issue can also be approached by considering the primary attributes of God. If creatures were perfect, then they no longer would be simply the image of God. They would BE God. If God alone is infinite, for example, then His creatures must, at some point, be finite. If God is omnipotent, then even the most powerful created object must be finite in its power.)

But the difficulties inherent in the concept of perfection are perhaps best illuminated by biological thought experiments. When anti-creationists assert that God should have made perfect creatures, they seldom think through the engineering consequences of that assertion.

For instance, they object to the fact that the human digestive system is not 100% efficient. Yet if our digestive enzymes had been created so potent that they dissolved virtually any organic substance as do concentrated hydrochloric and nitric acids, then our digestive tracts would themselves be dissolved by these ultra-potent enzymes. It thus might have been more expedient, from an engineering perspective, for God to have created weaker enzymes. And human beings do not exist in ecological isolation: optimizing our design might create problems for the rest of God’s creation.

An analogous situation holds for photosynthesis. If plants were 100% efficient in photosynthesis, they would be black in color, to absorb as much radiation as possible. But this would have diminished the color contrast of the terrestrial landscape, since plants would then have (roughly) the same color as soil. God might then be faced with a different engineering problem: soil would require a different color in order to maintain the contrast with black plants. Once again, solving one apparent engineering problem only generates a new problem.

Recently, Leonard (1993, p. 47), writing from an evolutionary viewpoint, discussed the photobiological effects of light on plants. Absorbing more light is not necessarily better, he argued, because light in large quantities generates reactive chemical species, such as superoxides and radicals. These reactive chemical species are associated with the electron-transport system in the chloroplast. An increase in these reactive chemical species damages the plant, and results in photoinhibition:

Black plants, absorbing most or all of the light spectrum, might be open to this kind of inhibition at even relatively low levels of light. I am not surprised that nature has chosen to be a little more selective. For “nature,” the creationist reads “God.” Had God created plants 100% efficient at photosynthesis, He might have been faced with extraneous engineering problems to solve with regards to photobiology. Perhaps the very properties of light itself would require “tweaking” in addition to other problems a moment’s reflection will reveal.

We should bear in mind that the qualities of being optimal or perfect, and being designed, are theoretically and evidentially distinct. Is the piece of furniture on which you are sitting optimal? That depends on a host of factors, without knowledge of which the question is impossible to answer.

But is the furniture designed? Of course. The information needed to answer that question definitively is much easier to come by, and does not require knowledge of optimality.

Both creationists and evolutionists should remember that questions of perfection involve one immediately in theological difficulties. These are genuine controversies (and ancient: see the Book of Job). To enter those controversies cavalierly, however, is to tumble into a pit of sophistry.

Why aren’t plants black? Try creating an entire universe from scratch, and you might find the answer.


Adams, R. M., “Must God create the best?” in Morris, T. V., ed., The Concept of God (Oxford: Oxford University Press, 1987), pp. 91-106.

Leonard, P., “Too much light,” New Scientist, 139 (1993): p. 47.

Topics: Divine omnipotence, dysteleology, teleology, dysteleological arguments, strange but true, paradoxes of religion, attributes of God, puzzles of nature, purposelessness of the universe (not), minimum solution systems (not), jury-rigged systems (not), arguments from poor design, misunderstood theories, arguments about sloppy design, purposelessness of nature (not)

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