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The Fairy Tale World of an Evolution Textbook

Robert F. Shedinger
Photo: This fer-de-lance doesn't belong in a hotel, by Bernard DUPONT / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0).

Editor’s note: Dr. Shedinger is a Professor of Religion at Luther College in Decorah, Iowa. He is the author of a recent book critiquing Darwinian triumphalism, The Mystery of Evolutionary Mechanisms. See also the earlier entries in this series:

I have been reviewing the edited and updated textbook Strickberger’s Evolution. In a text box titled “Coevolution of Plants and Insects,” Brian K. Hall and Benedikt Hallgrimsson tell of how Darwin became aware of strange forms among orchids and postulated that even the most unusual orchid must have a matching pollinator that had coevolved with it. For example, the Madagascar Star (Christmas orchid) had a corolla 25 cm. long but no pollinator was known to Darwin. Years later, however, a giant hawk moth was discovered with a 30 cm. tongue, proving Darwin’s postulate. Hall and Hallgrimsson view these types of coevolutionary relationships as evidence for natural selection. But they do so without considering how such a process would actually work.

The textbook consistently side-steps the problem of the initial stages of variation. That is, if an orchid developed a slightly longer corolla, how could a hawk moth pollinate it if the hawk moth had not yet developed the slightly longer tongue necessary? What was the initial stage of variation that set this coevolutionary process in motion? This problem appears in many different parts of the textbook, most prominently when discussing major transitions in evolutionary history. In these discussions, Hall and Hallgrimsson set aside science and engage in the telling of fairy tales worthy of Hans Christian Andersen.

What Drove the Transition?

For example we are told, “The change from unicellularity to multicellularity occurred a number of times, giving rise to different lineages of organisms.” But what drove this transition? There must be advantages to multicellularity that would be preserved by natural selection. A multicellular organism’s food gathering surface, we are told, increases which ensures a more stable food supply and the ability to attack and digest larger particles of food. This would be accompanied by an increase in gene numbers and regulatory pathways. 

But if by chance some ancient unicellular organism mutated in such a way that its offspring became multicellular, and these multicellular offspring were perpetuated by natural selection due to the advantages they enjoy over their unicellular parents, they would have eventually replaced their unicellular ancestors and the world today would be awash only in multicellular organisms. But as anyone who has battled a bacterial infection knows, unicellular organisms continue today as perhaps the most successful organisms on the face of the planet. Multicellularity somehow evolved, but it does not seem to be because multicellularity confers a clear selective advantage. After all, most multicellular organisms have gone extinct. 

The Fairy Tales Continue 

Hall and Hallgrimsson then consider the increasing complexity of organisms over the course of evolutionary history. For example, early pelagic animals that swam above the sea floor, we are told, became benthic animals that crawled along the sea floor eating accumulated detritus. Why? Because a benthic existence has clear advantages:

A number of evolutionary steps would inevitably accompany a benthic existence. The scattered distribution of food sources would give a selective advantage to organisms that could eat more food more rapidly, leading to an increase in size and the evolution of a mouth and gut that would permit selective digestion.

If this transition took a number of evolutionary steps, how would the first benthic organisms have taken advantage of these new food sources if a mouth and gut had not yet developed? And if benthic existence was such a selective advantage, why do the oceans today teem with large and complex pelagic organisms swimming above the sea floor? (Sharks, anyone?!) The textbook has nothing to say on this.

Life, of course, did not remain in the sea. How did aquatic organisms invade the land? The commonly accepted hypothesis, according to Hall and Hallgrimsson, is that aquatic animals moved onto land due to pressure from increasing numbers of predators and competition for space, food, and breeding sites. That is:

Combined ecological, environmental, and climactic changes provided powerful selective advantages to lineages spending progressively larger periods of time on land.

But if land-dwelling was such an advantage, why did aquatic lineages continue to thrive? And what was the initial stage of variation that allowed for terrestrial existence, given the radically different anatomical and physiological systems required for life on the land. Apparently, natural selection waived its magic wand and fish walked out of the sea!

Eventually, terrestrial animals, which were cold-blooded, discovered endothermy. And this was clearly an advantage since:

…increased aerobic metabolism supports more sustained activity and greater stamina than ectotherms can achieve; ectotherms become rapidly exhausted because they rely mostly on anaerobic metabolism.

A Snake in the Eco-Lodge

Several years ago, my family spent time at an eco-lodge in the Costa Rican rainforest. One morning lodge employees were trying to capture and remove a fer-de-lance from the lodge grounds for safety reasons. But after reading Strickberger’s Evolution, I fail to understand their concern. The exhausted snake should not have presented much of a danger to the superior endotherms staying at the lodge!

In a related transition, why did egg-laying animals give rise to live births? A system that provided maternal care and nourishment, we are told, would have led to smaller eggs and more rapid development of the fetus before hatching. Endothermy would have helped since the hatched offspring could be kept close to maternal body temperature which would have assisted enzymatic activity. Then:

At some point, viviparity (viviparous reproduction) replaced oviparity; it would probably take only a few additional steps for hatching to occur in the oviduct.

Viviparity replaced oviparity? Really?! Then where did my scrambled eggs come from this morning?! 

Breakfast Is Served

Understanding how small incremental variations would be preserved by natural selection and lead to large-scale evolutionary change has plagued Darwinism since its inception. In 1909 the forceful Darwinian August Weismann puzzled over the thickness of limpet shells that protect limpets from the destructive force of ocean waves. He asks:

What proportion of thickness was sufficient to decide that of two variants of a limpet, one should survive, the other be eliminated?

Weismann confesses ignorance on this question but assumes that some measure of thickness must have had selective value because limpets exist. To the larger question of whether small incremental variations can do the work Darwin requires of them Weismann writes:

To this question even one, who like myself, has been for many years a convinced adherent of the theory of selection can only reply: we must assume so, but we cannot prove it in any case. It is not upon demonstrative evidence that we rely when we champion the doctrine of selection as a scientific truth; we base our argument on quite other grounds. [Emphasis in the original.]

What are those other grounds? Later in the same essay Weismann comes clean:

We must accept it (natural selection) because the phenomena of evolution and adaptation must have a natural basis, and because it is the only possible explanation.

Strickberger’s Evolution is clearly making the same kinds of assumptions as Weismann, and likely for the same reason: the philosophical requirement for naturalistic explanation. The textbook wants to tell a story of how major transitions in the history of life were driven by mutations conferring a selective advantage on organisms that out-competed and replaced their “inferior” ancestors. But the data don’t support this narrative. Multicellularity developed, but unicellular organisms continue to exist and thrive. Benthic organisms evolved, but their pelagic ancestors continue to swim in the world’s oceans. Some animals left the ocean to live on land, but their ocean-living cousins have done just fine. Endothermy may have advantages over ectothermy, but I wouldn’t advise taking your chances by picking up a poisonous snake. 

Given the lack of substantive scientific argumentation in these attempts to account for major transitions in the history of life, Strickberger’s Evolution might be a textbook better suited to an English course on fantasy literature. It really doesn’t belong in a science classroom.