After studying 2600 species:
Sticky toepads have independently evolved in geckos, skinks and Anolis lizards — producing tree acrobats specially adapted to life in the forest canopy. Scientists have long considered sticky toepads an ‘evolutionary key innovation’ that allow arboreal lizards to interact with the environment in ways that many padless lizards cannot. Yet, some lizards without toepads have adopted the canopy lifestyle, an observation that has puzzled scientists for decades. Biologists Aryeh Miller and James Stroud at Washington University in St. Louis set out to find if lizards with toepads had an evolutionary advantage for life in the trees relative to their padless counterparts. They analyzed data from 2,600 lizard species worldwide and discovered that, while hundreds of different types of lizards have independently evolved arboreal lifestyles, species that possessed sticky toepads prevailed.Washington University in St. Louis, “Sticky toes unlock life in the trees” at ScienceDaily (August 5, 2021)
Now here is where it gets interesting:
Miller, who led the analysis, is the first to find that species have evolved for specialized life in trees at least 100 times in thousands of lizards. In other words, it is evolutionarily easy for a lizard to become a tree lizard.
What’s difficult is sticking around (pun intended!). Toepads don’t evolve until after lizards get into the trees, not before. And padless lizards will leave trees at a high frequency — much higher than padbearing lizards.
“There are hundreds of lizards living in the trees, but over evolutionary time many of those species end up leaving for life on the ground because, presumably, they interact with these padded lizards that have a greater advantage,” Stroud said.Washington University in St. Louis, “Sticky toes unlock life in the trees” at ScienceDaily (August 5, 2021)
Okay, now here’s a question: How, exactly, does the tree lizard “evolve” toe pads just because they would be convenient? It’s not self-evident. Many lizards did not but others did. As Michael Behe would ask, “How, exactly?”
Convergent evolution is often portrayed as a friend to Darwinism but it really isn’t. Not when we look closely at what is being said. No “how exactly.” “Natural selection” is often treated as a magic concept and we aren’t supposed to notice that.
The paper is closed access.
See also: Evolution appears to converge on goals—but in Darwinian terms, is that possible?