Convergence part 2: “exceptions to the rule”

In part 1, I argued that some advocates of intelligent design give a misleading picture of the history of evolutionary thought on the topic of convergence. To hear them tell it, convergence, or at least convergence as a widespread phenomenon is a recent discovery, unknown to Darwin and to the architects of the modern synthesis. For example, Günter Bechly says,

One of the most essential doctrines of Darwinian evolution, apart from universal common descent with modification, is the notion that complex similarities indicate homology and are ordered in a congruent nested pattern that facilitates the hierarchical classification of life. When this pattern is disrupted by incongruent evidence, such conflicting evidence is readily explained away as homoplasies with ad hoc explanations like underlying apomorphies (parallelisms), secondary reductions, evolutionary convergences, long branch attraction, and incomplete lineage sorting.

When I studied in the 1980s at the University of Tübingen, where the founder of phylogenetic systematics, Professor Willi Hennig, was teaching a first generation of cladists, we still all thought that such homoplasies are the exceptions to the rule, usually restricted to simple or poorly known characters. Since then the situation has profoundly changed. Homoplasy is now recognized as a ubiquitous phenomenon (e.g., eyes evolved 45 times independently, and bioluminiscence 27 times; hundreds of more examples can be found at Cambridge University’s “Map of Life” website).

I don’t know who gave Dr. Bechly the idea that homoplasies are rare, but I’m pretty sure it wasn’t Willi Hennig. Dr. Bechly was there, and I wasn’t, but I’m going to go out on a limb here anyway and say that Willi Hennig wasn’t even at the University of Tübingen in the 1980s. I can be fairly confident that this is the case, because Willi Hennig died in 1976.

Willi Hennig

Willi Hennig, 1913-1976. Photo by Gerd Hennig, shared by Wikimedia Commons under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Let’s give Dr. Bechly the benefit of the doubt, though, and assume he meant “had taught” rather than “was teaching”, and focus instead on his main point:

…we still all thought that such homoplasies are the exceptions to the rule, usually restricted to simple or poorly known characters. Since then the situation has profoundly changed.

Since biologists in the 1980s thought homoplasy (or convergence) was rare, the “profound change” Dr. Bechly refers to must be what Arthur Willey had in mind when he wrote

I have failed in my purpose unless it has been made abundantly clear that the influence of convergence in evolution has been widespread, deep-seated, and intimate, more so than is generally recognised. —Convergence in Evolution, pp. 168-169

Just as Dr. Bechly was saying: convergence is more widespread than is generally recognized. In the same book, Willey also wrote of convergence that

…it is, we may repeat, a fundamental phenomenon and consequently of frequent occurrence. –p. 91

and that

It has long been recognised as a dominant factor in comparative morphology. –p. 52

Since the importance of convergence had “long been recognised,” Willey must have written this well after Dr. Bechly’s time at the University of Tübingen. But here we run into the same problem as with his interactions with Willi Hennig in the 1980s. Convergence in Evolution wasn’t published in the 1990s, the 2000s, or even the current decade. It was, in fact, published in 1911.

How can we square Dr. Bechly’s account of his time in Tübingen with Willey having recognized convergence as “widespread”, “fundamental”, “frequent”, and “long…recognised as a dominant factor”? Maybe Willey was an outlier, or maybe the predominant view changed between his time and Dr. Bechly’s. I have already mentioned that Darwin discussed a long list of cases of convergence in the Origin. Let’s check in with some of the 20th century’s leading evolutionary biologists. In 1949, George Gaylord Simpson wrote that

Convergence on a grand scale is seen in the comparison of South and North American mammals. —The Meaning of Evolution, p. 184

In 1953, he wrote that

The very widespread occurrence of parallelism and convergence is the strongest sort of evidence for the efficacy of selection and for its adaptive orientation of evolution. —The Major Features of Evolution, pp. 170-171

In 1963, Ernst Mayr wrote that

The animal world is full of convergences ( and so is the plant world! ) where similar demands by the environment have evoked similar phenotypic responses in unrelated or at least not closely related organisms. —Animal Species and Evolution, p. 609

Willey might have been an outlier, but Simpson and Mayr are both counted among the architects of the modern synthesis (which makes it surprising that Lee M. Spetner would say “examples of convergence are inherently contradictions to the M[odern] S[ynthesis]”). Let’s check in with one more influential evolutionary biologist from the 20th century, who said in 1965 that

Convergence is, in fact, commonly manifested by similar organs having arisen in adaptation to the same functions from different morphological foundations in different organisms.

Want to guess who said that? Here’s a hint: someone who wasn’t at the University of Tübingen in the 1980s. Someone whose photo is in this blog post.

The Discovery Institute is producing a revisionist history. To hear them tell it, convergence is something that evolutionary biologists have either barely heard of or that they “invented” or “made up” to hide problems with the tree of life. Convergence “destroys the tree of life,” it “contradict[s] the [modern synthesis],” and it is “quite unexpected” to evolutionary biologists. All of that is a big, stinking pile of wrong. In reality, biologists since Darwin, and including Darwin, have always appreciated the importance of convergence, have written thousands of papers about it, and have included it in every evolutionary biology textbook I’m aware of.


Stable links:

Hennig, W. 1965. Phylogenetic systematics. Annu. Rev. Entomol. 10:97-116. DOI: 10.1146/annurev.en.10.010165.000525

Mayr, E. 1963. Animal Species and Evolution. Harvard University Press. Google Books:

Simpson, G. G. 1949. The Meaning of Evolution. Oxford And IBH Publishing Co.; Calcutta. PDF:

Simpson, G. G. 1953. The Major Features of Evolution. Columbia University Press, New York. PDF:

Willey, A. 1911. Convergence in Evolution. E. P. Dutton and Company, New York. Google Books:


  1. jazzlet says

    Stuff learning about convergence in evolution at university in the 80s – which I did at Aston University – I learnt about convergent evolution in biology at school in the late70s. At this point in time I can’t remember whether it was for O Level (exams taken at 16) or A level (exams taken at 18), but I know I first learnt about convergent evolution in school as I can remember the teacher that taught us. I think it is more likely to have been taught at O Level as from what I remember convergence was taught as part of the basic course, which I am pretty sure we did at 15 or 16.

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