Evolution News & Views

You may recall the "complexity by subtraction" theory from 2013. It's back. Three researchers from UC Riverside with two other colleagues have a new way to get animals to evolve: take away a "remarkable innovation" so that they are free of the constraints and costs that the innovation generates. Case in point: subtract the adhesive gecko toe pads that are the envy of biomimicry engineers. That way, the lizards can run faster.

The theory is presented in a paper in the Proceedings of the National Academy of Sciences. Higham et al. studied different genera of geckos and paid special attention to the ones that had lost their adhesive toe pads.

Innovations permit the diversification of lineages, but they may also impose functional constraints on behaviors such as locomotion. Thus, it is not surprising that secondary simplification of novel locomotory traits has occurred several times among vertebrates and could potentially lead to exceptional divergence when constraints are relaxed. For example, the gecko adhesive system is a remarkable innovation that permits locomotion on surfaces unavailable to other animals, but has been lost or simplified in species that have reverted to a terrestrial lifestyle. We examined the functional and morphological consequences of this adaptive simplification in the Pachydactylus radiation of geckos, which exhibits multiple unambiguous losses or bouts of simplification of the adhesive system. We found that the rates of morphological and 3D locomotor kinematic evolution are elevated in those species that have simplified or lost adhesive capabilities. This finding suggests that the constraints associated with adhesion have been circumvented, permitting these species to either run faster or burrow. (Emphasis added.)
How did that "remarkable innovation" arise in the first place? Never mind about that. A look at how they use the word "innovation" in the paper might lead you to think it does so by magic. "Structural innovations involving coordinated changes in multiple anatomical systems" (that almost sounds like irreducible complexity) "...are associated with the diversification of many groups of vertebrates." But how do those innovations, involving coordinated changes in multiple systems, arise? Well, they just do. They occur. They evolve. They are acquired from the "Acquisition" Department:

Many such innovations often occur repeatedly within, as well as between, clades. One example is the evolution of the prehensile tail, which has arisen in primates, nonprimate mammals, seahorses, amphibians, and several groups of lizard, allowing its possessors to move through the environment in novel ways. Although the acquisition of such innovations is often implicated in both diversification and ecological specialization, much less is known about the causes and consequences of their secondary reduction and loss.

More Complexity by Subtraction: The Case of the Gecko - Evolution News & Views
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