Behe and bugs: Genesis of a Creationist canard?

Well, the Discovery Institute-sponsored translation of Sermonti’s un-informed and dis-informing book, which I reviewed a few weeks ago here on PT, is out. There isn’t much more to say about the translation that I haven’t said already, but an endorsement by Mike Behe on the back cover does stick out, and I think it’s worth discussing here. Behe says:

With charming prose, Sermonti describes biology which contradicts Darwinian expectations: leaf insects appearing in the fossil record before leaves, insects before plants, and biological forms that reflect abstract mathematical expressions. He shows that there are more things in life than are dreamt of in Darwinian philosophy.

I am sure several readers will wonder what the heck this insect stuff is about. So did I, and looked into it. In short, it means that neither Sermonti nor Behe know much about insect and plant evolution, and more significantly, they are not keen to put any effort learning about them. More below.

Behe’s comment stems from a chapter in Sermonti’s book entitled “The leaf insect before the leaf”, which is such a true masterpiece of bait-and-switch argumentation, that Behe (not a novice of the art himself) fell for the trick. Sermonti starts with discussing the features of biological mimicry, from his usual mystical-structuralist viewpoint. He then goes into the specifics of leaf and stick insects. It is very hard to describe Sermonti’s twisted argument, so I am actually going to quote him verbatim. It’s long, but bear with me:

A strange order of Insects, close to the coleopterans, has been given the name of phasmids (‘phantoms”), indicating their ability to remain invisible to neighbors by imitating the forms and colors of the trees on which they alight. Stick insects and leaf insects belong to this order. These astute animals are taken as examples of mimetic adaptation, but they proved embarrassing when paleontologists started following their fossil traces and found them where they were not supposed to be. How these ghost insects—these incredible mimickers of leaves and sticks—ever came into the world remains a mystery, an unsolved scientific detective story. The reigning utilitarian interpretation would have it that these insects, before they were like leaf surfaces or dry sticks, got mixed up with leaves and twigs and, through mutation after mutation, came to resemble their background, until they arrived at the point of becoming the perfect models we now see (to the point that we don’t see them!) on plants. Unfortunately for them and for the theory, these artful imitators derive no benefit from their mimetic capacity and are prey for their enemies, which have no difficulty in detecting them. But the most unforeseeable surprises have come from paleontology. The oldest phasmid fossils (they go back in Baltic amber to the Tertiary—i.e., about 50 million years ago) look identical to present-day species, showing that no gradations have occurred. It is thought that those phasmids originated from Chresmodids of the Upper Jurassic in Germany, fossils of which are encountered in deposits dating back some 150 million years. But the oldest fossils of stick or leaf insects (protophasmids) go back to even remoter periods, in the Permian (250 million years ago, in the Paleozoic). One might argue that these insects completed the process of imitating leaves at an extremely gradual rate beginning at a still earlier time. Yet things do not work out this way. Plants with flowers and leaves (phanerogams and Latifoliae) appeared no earlier than the Cretaceous—in other words about 100 million years ago, long after the first protophasmids. This chronological anomaly places the imitators earlier in time than the objects of the imitation, leaving entomologists and paleontologists disconcerted. In his Great Book of Nature (Hoepli, 1954), Fritz Kahn asserts that there must have been a mistake somewhere. How could the leaf insect be older than the Latifoliae on which it has modeled itself? I once saw a picture of a leaf insect in a reputable journal, in which the commentator attributed to the artful imitator an ability to “prophesy” something that originated millions of years later!

Leave out mimicry. We have to recognize that phasmids have a tendency to laminate themselves like leaves or elongate themselves like sticks, and they had this tendency prior to and independent of the plants. Who knows? Perhaps phasmids mistake the plants’ leaves and sticks and [sic] for themselves?

The entomologists I have consulted prefer to gloss over the phasmids. The Chresmodids (150 million years ago) have been disqualified as their dubious forebears, and the protophasmids have been excluded from their phylogeny altogether. The exclusion does not change the general picture, however. There were leaf insects and stick insects—“phantasm” insects—over 100 million years before there were leaves or sticks.

G. Sermonti, “Why is a fly not a horse?”, pp.145-147

I think it would be fun to show this passage to an entomologist, and play “spot the errors”, so many there are [1]. But for the issue in question, let’s just consider the basics. Let’s assume for the sake of argument that the phasmids’ ancestors in the Permian already resembled sticks and leaves. Were there leaves and sticks then? Of course! There were luscious, thick forests, made up of tree ferns and leafy gymnosperms (think of stuff like the gingko bilobas on some street near you). There were twigs and leaves all over the place. In fact, by the Permian vascular and seed plants, even tree-like, had been around for – oh, 100 million years or so - seriously. Sermonti has the timeline exactly backwards. (If you need to refresh your memory about geological periods and evolution, check out this figure).

But that’s not all: notice how Sermonti first introduces the Protophasmida as “oldest fossils of stick or leaf insects” – despite their name, that’s simply not true. Protophasmids miss critical synapomorphies (traits that identify a taxon) of Phasmida, and are currently considered probably close to Orthoptera (crickets and grasshoppers). This cladistics-dictated taxonomic assignment, Sermonti suggests, is just a trick of embarrassed entomologists at the end of their ropes. But that makes no sense – as Sermonti himself states, if Paleozoic insects really resembled Angiosperm leaves and twigs, they would be puzzling regardless of their taxonomic position or name. Alas, protophasmids were not twig- or leaf-like: they looked like many other winged bugs (you can see an example of a classic protophasmid in this paper). As for Chresmodidae, their position is also debated, but one sure thing is that they had little resemblance to vegetation. In fact, because of their morphology and some specific leg adaptations, they are considered to have been water-skating insects (for a couple Chresmodida fossil species, see here and here).

So, neither protophasmids nor possibly Chresmodidae were closely related to modern stick- and leaf-insects. Most importantly, they also did not resemble leaves or sticks, and in fact, neither do many modern phasmids. Although many are amazing in their mimicry, others simply have elongated, cryptic shapes and colors, but they do not closely resemble leaves and twigs, and are rather similar to many other non-phasmid insects (see for instance some of the phasmid species in the picture below). Far from being a “mystery”, it is really not hard to imagine that a thin, brownish insect may gradually evolve into a stick-like mimic (center left picture), or that a green insect living among foliage may evolve to resemble leaves (right). This conclusion is further strengthened by the existence of many gradations of stick- and leaf-like crypsis in living insects. Several studies have shown that crypsis and mimicry confer a selective advantage against visual predators [2]. I am not aware of any specific work on bona fide leaf- or stick-like insects, but a 1993 paper on two differently colored forms of the phasmid Timema cristinae, which are more or less cryptic depending on the vegetation they reside on, clearly showed differential predation against the less cryptic morph [3]. I don’t know what study (if any) Sermonti’s comment that phasmids “derive no benefit from their mimetic capacity and are prey for their enemies, which have no difficulty in detecting them” refers to, but taken at face value, it is just silly – gazelles are caught by predators too, but I doubt that Sermonti would claim that for this reason their speed must not be a defense mechanism against predation.

So, Sermonti is engaging in a smoke and mirror trick. He equivocates between flowering plants (Angiosperms, which appeared in the Mesozoic) and leafy vascular plants in general (which are much older), and between Phasmids proper, Protophasmids and Chresmodidae (making the reader believe that the three groups are closely related and morphologically similar). To wrap it up, he ludicrously accuses sneaky paleoentomologists of changing the taxonomic classification of “embarassing” ancestors to purposefully hide the fact these insects shouldn’t have existed. Note also his references for the whole story: a 1954 lay book and an unnamed “reputable magazine” [4]. How about actual scientific sources? None. Real, live entomologists? Sermonti says he asked, but they preferred “to gloss over the phasmids”. More likely, he just didn’t like their answers.

The second of Behe’s claims is actually even more simple to explain. First of all, Behe misinterprets (or perhaps over-simplifies) the issue when he says “insects before plants”. Plants (including green algae) of course appeared very early, and even if Behe retricts the term to land plants, he should probably know, or imagine, that they long preceded animals on land (indeed, land colonization by plants dates at least to the Silurian). What Sermonti refers to is actually the mouth apparatus of insects, which extant species generally use to feed on Angiosperm plant material. So far so good. The supposed “mystery” here is that a 1993 paper by Labandeira and Sepkoski showed that “by the middle Jurassic [the earliest commonly accepted date for the origin of Angiosperms] 65% (low estimate) to 88% (high estimate) of all modern insect mouthpart classes were present”. Note here: what was present before Angiosperms was the basic conformation of the mouthpart classes, not the actual highly adapted, specialized apparatuses that are often currently found in existing species. In a sense, this was surprising at the time because the prevailing theory assumed that the current insect feeding apparatuses had coevolved with the plants on which they are used now. However, it is hardly an unsolvable mystery: remember that there were plants with sap, leaves, seeds, spores and pollen in the Paleozoic, long before flowering plants appeared. Indeed, Paleozoic fossil plants already bear the hallmarks of insect feeding activity, and these feeding patterns look so remarkably similar to those observed in current plants, that paleobotanists and paleoentomologists can reasonably infer what type of feeding behavior caused the damage. Conrad Labandeira himself talks about this in a 1998 review paper, in which he describes: “spore feeding and piercing-and sucking”[in the early Devonian], “External feeding on pinnule margins and the intimate and intricate association of galling”[in the Carboniferous], “hole feeding and skeletonization” [in the early Permian], “surface fluid feeding”, and possible but inconclusive evidence of “mutualistic relationships between insect pollinivores and seed plants” by the end of the Paleozoic. In other words, insects pierced, sucked, gnawed, crushed, lapped, imbibed, scraped and otherwise fed on non-Angiosperm plants then, much as they do on Angiosperms today (the only exception being the current highly specialized flower-feeding apparatuses, which not surprisingly appear in the fossil record at about the time of flowering plants).

Sermonti asks:

How did it happen, then, that these complex and delicate apparatuses existed millions and millions of years before they had a job to do? Ibid., p. 148

Because bugs were just as hungry then as today, that’s how. Sermonti knows this, but seems to suggest that those apparatuses were not really necessary:

But those insects still had to feed themselves, for hundreds of millions of years, among mosses, ferns, cicadas and conifers, in the empire of great reptiles. And eat they did: They had knives and forks and spoons, richer and more sumptuous than their lean and wooden fare required. Ibid., p. 149

“Lean and wooden fare”? Why is that? With the exception of flower nectar and “classic” fruits (some gymnosperms however make fruit-like arils), the Paleozoic plant world offered pretty much the same menu opportunities as modern plants, and Paleozoic insects partook of the feast in pretty much the same way as modern insects do.

There are many Creationist myths and canards, from very crude to more sophisticated: Paluxy River tracks, the bombardier beetle, unevolvable irreducibly complex molecular systems, etc (most of them are listed and answered here). They are all made up pretty much the same way as these: abundant use of outdated and third-hand sources, misinterpretation of scientific evidence, mistrust of expert opinions, a good amount of personal ignorance of the subject (and no effort to correct it), and a lot of artfully crafted misleading statements – et voilÃ: leaf insects before leaves, insects before plants. All these myths exist because of the Creationists’ never-waning hope to find that elusive silver bullet that stops the “evolution werewolf” cold. So Behe, without checking the facts, eagerly announces that Sermonti shows that there are “more things in life than are dreamt of in Darwinian philosophy” - but the dream is only his own.

Acknowledgements: Thanks to Oliver Zompro and Erich Tilgner, two entomologists with expertise on Phasmids and allied groups and their taxonomy and evolution, for their patient explanations and copious references; to the Phasmid Study Group for allowing me to use some of their phasmid photographs; to Reed for setting up the Geologic Time Scale page and PT crew members for comments, suggestions, and for refreshing my Latin.

Notes and References [1] For real info on phasmids, their taxonomy and their evolution, check out the following sources: Tilgner E, Systematics of Phasmida, 2002, PhD Thesis in Entomology, University of Georgia (available online at this UGA site, searching for “Tilgner”); Grimaldi D, Engel MS, Evolution of the Insects, Cambridge University Press, 2005; and references therein

[2] Ruxton GD, Sherrat TM, Speed MP. Avoiding Attack: The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry. Oxford University Press, 2004.

[3] Sandoval, CP 1994. Differential visual predation on morphs of Timema cristinae (Phasmatodeae: Timemidae) and its consequences for host range. Biol. J. Linn. Soc. 52 : 341-356.

[4] Kahn’s 1952 “Das Buch der Natur”, which as far as I can tell was never translated into English, apparently was a two-volume encyclopedic overview of the whole of natural sciences, with volume 1 on Physics/Astronomy/Chemistry/Geology and volume 2 on Biology. As for the “reputable magazine”, from another online article by Sermonti I suspect he’s actually referring to a 1983 issue of the Italian travel/geography magazine “Atlante” (sort of like the Italian “National Geographic”). While both are indeed reputable sources, they certainly are neither up-to-date nor necessarily reliable on the scientific details.