David Klinghoffer responded earlier to a Science Daily article where evolutionists from U.C. Riverside said that their findings about a certain species of gecko “serve as good evidence against intelligent design ideas.” The toes of this gecko, they say, are not as advanced as those on tokay geckos. Therefore, they must have evolved by gradualistic Darwinism. We argued that simpler tools, like screwdrivers, are not evidence that they and more complex tools, like power drills, originated by unguided natural processes.
Now with the full paper in hand, what do we find in support of this claim? We don’t find the word “design” or “creation” anywhere. Higham et al. do, however, have a lot to say about evolution. They use the toes of this gecko as props to support sweeping ideas about innovation and the tempo and mode of evolution.
Innovations often involve complex and hierarchical systems of integration of physiology and anatomy. They likely begin, however, with a trigger that provides the focus for further integrated change. Such triggers are generally difficult to identify but can be regarded as key innovations. We have shown that a rather modest morphological transformation, the elaboration of epidermal spinules into frictional adhesion-promoting setae, can serve as the key innovation that acts as the foundation for more complex and elaborate subsequent changes. [Emphasis added.]
That’s a pretty grandiose extrapolation from a lizard’s toe. Many better examples in nature of “complex and hierarchical systems of integration of physiology and anatomy” could be adduced. Some of them, like powered flight in birds and the male reproductive system of whales, have been showcased in Illustra Media’s films. Those all-or-nothing systems with multiple interacting parts are the real challenges to the Darwinian story.
It’s not even clear that gecko toes fit the criteria for irreducible complexity. Recently, Ann Gauger argued on ID the Future that natural selection can work by breaking things. A microbe that can no longer import an antibiotic, for instance, will survive and proliferate, because its import machinery is broken. That’s not really innovation; it’s just luck.
Nonetheless, let’s entertain their arguments. To support neo-Darwinism, they need to prove the following:
This species preceded the tokay geckos that have fully-developed adhesive footpads. (Otherwise, it might represent a degenerative form.)
The spinules represent a true innovation, not just a broken piece of toe skin.
The spinules emerged by mutation: i.e., by chance, with no foresight.
The spinules were heritable when they emerged.
There is a continuous, gradual transformation of the toes over time from simple to complex, each version being adaptive.
Genes flowed between members of the ancestral series (i.e., it wouldn’t serve neo-Darwinism if this species never had contact with tokay geckos).
Each transitional form has been preserved by natural selection to the point where all individuals lacking the trait died out; they could not survive without it.
Intelligent design is incapable of explaining this set of observations.
The authors cite forty-year-old work that says the advanced gecko toe pads involve “musculoskeletal, tendinous and vascular modifications” to work, but it’s not clear this statement supports neo-Darwinism. All lizards already had muscles, tendons, and circulatory systems, whether or not they had adhesive toes. Think of it this way. If you found pieces of adhesive tape stuck to the bottoms of your feet that you couldn’t remove, you might alter your gait to maneuver. You might peel your foot from the heel to the toe and step differently. That doesn’t mean that your muscles, tendons, and blood vessels all evolved when the tape first appeared. Besides, other lizards, such as Anolis, lift their feet in similar ways. It’s not unique to tokay geckos.
Strangely, the authors next claim that “Multiple instances of reduction and loss of the adhesive apparatus have been identified.” Good thing they aren’t planning to argue for evolution by subtraction again:
Despite the plethora of examples that illustrate transitions towards secondary loss of frictional adhesion, a demonstration of the transition from frictional to frictional adhesive attachment has remained elusive. Although it has been noted that some groups of geckos possess enlarged subdigital scales that bear small setae (Russell, 1976), no functional data associated with such presumed transitions are available.
And now! They present their transitional form — a primitive gecko with hopeful beginnings of adhesive pads, promising to bloom into fully-fledged setae for which the ceiling-walking geckos are famous. But, lo and behold, we learn that these geckos already possess pretty advanced setae. Compared to other members of its genus, “its epidermal spinules in the vicinity of the digital inflections are longer and are elaborated into branched, spatulate-tipped setae located on the free distal margin of the sub-inflection scales.” So what makes them think this is an incipient innovation rather than a degeneration? If so many geckos lost adhesion, how do we know most species in this genus lost theirs, and this one is a holdout, like a partially blind cave fish?
They say that it “lacks the modifications of the digital musculotendinous, circulatory, and skeletal systems that are generally considered to be essential for the operation of a gekkotan adhesive apparatus,” but that’s the opinion of one of the co-authors, Anthony P. Russell, who has been working on the problem for over forty years. Again, all lizards today have muscles, skeletons, tendons, and circulatory systems, with or without the adhesive toe pads. It’s not a case of irreducible complexity. You can lose the toe pads and the other systems will still work, just like you can remove the tape from your foot and still walk. The authors even claim, furthermore, that “all lizards exhibit digital hyperextension,” the toe-lifting behavior corresponding to adhesion.
From there, they showcase their phylogenetic analysis and their lab tests of the walking and climbing abilities of G. humeralis. But failing to establish that this innovation is an irreducibly complex system, their case is already weak. And if the extant species in this genus lost their adhesive toe pads by devolution, that fact wouldn’t likely be evident from the fossil record.
Additionally, they have to assume evolution to claim that the fossil and living species in their tree are related by Darwinian common descent. The software used to build phylogenetic trees requires inputting many assumptions. As we have shown, one can get contradictory results in such exercises depending on which genes or molecules are compared. They also don’t establish that there was gene flow between all the species included. So we don’t find the ancestry argument convincing, especially since their tree shows G. humeralis sitting out there all by itself, disconnected from other contemporaneous genera possessing adhesive toepads. Where did it evolve from? Where is it evolving to?
Gecko adhesion, finally, is not an all-or-nothing innovation on which survival depends. The authors point to another lizard in the same environment that has well-developed adhesive toe pads, yet G. humeralis did not go extinct in competition with it. Other members of the genus without the toepads seem to get along just fine in their specific niches. Given this background, the authors’ paragraphs of data about body masses, frictional forces, and movies taken with high-speed cameras, while admirable, are irrelevant to the Darwinian, anti-ID claims.
The results of the present study are consistent with G. humeralis exhibiting the initial stages of a key transition from friction-enhanced to frictional adhesion-enhanced traction, thus providing a window into the evolution of the adhesive system of geckos.
But how can this be, since another species in the same genus survives just fine, despite not being able to climb as steep a slope as G. humeralis? The conclusion is not coming from the data, but rather from the authors’ desire to demonstrate a transitional form to shame ID.
Informatively, we found G. humeralis to sometimes occupy vertical bamboo shoots in its natural habitat (Fig. 2), whereas other species in the genus generally employ rough tree trunks, rocks, fallen palm trees, and fronds, as well as even the ground. Thus, the present study reveals not only the existence of a morphologically and functionally intermediate stage between frictional and frictional adhesive attachment, but also the ecological and biomechanical implications of such a transition. The adhesive system of G. humeralis not only is structurally simple relative to that of other geckos, but also is indicative that slight modifications in form can dramatically influence functional outcomes and the ecological niches that can be exploited.
OK, perhaps so. But it’s hard to call this Darwinian survival of the fittest when this lizard’s cousins are doing just fine in the same habitat. It’s not a case of “Run for the vertical bamboo shoots or die!” The stars of the show only “sometimes” occupy the vertical shoots.
Looking over the eight requirements to prove their case, not one has been demonstrated to our satisfaction. It seems highly audacious for them to compare this to “the origin of terrestrial locomotion in vertebrates,” appealing to Neil Shubin’s fish-a-pod Tiktaalik as a comparable demonstration of evolution. Embarrassingly, they admit that
Evidence for intermediate forms during the loss of a structure (or structures) is prevalent…. Fewer examples, however, are known that highlight intermediate forms during the evolutionary gain of novel structures, especially those that can be regarded as key innovations.
Here’s their claim in a nutshell: tiny setae on one species of lizard in Trinidad, which allow it to climb steeper angles than other members of its genus which survive just fine in the same environment, demonstrate evolution in action. And this, ladies and gentlemen, is how bacteria became humans.
Now, the fine print:
We are not advocating that this intermediate form will necessarily lead to a fully developed adhesive apparatus, although it can be taken to represent middle ground between the absence of frictional adhesive capability and its full expression as exhibited by pad-bearing geckos. Overall, Gonatodes offers a number of attractive possibilities for assessing the origin of evolutionary innovations….
And yet the world should be filled with billions of clear transitional forms if Darwinian evolution were true. They shouldn’t even need to scramble to find “attractive possibilities” here and there. Let them tackle the origin of life and the Cambrian explosion before suggesting they have “good evidence against intelligent design ideas.”
Photo: G. humeralis in Trinidad, by Timothy Higham, U.C. Riverside.