Denton’s Challenge: Are Leaf Shapes Adaptive?
Evolution News & Views
In his new book Evolution: Still a Theory in Crisis, Michael Denton provides a cavalcade of examples of non-adaptive forms in nature. On page 77, he points to angiosperm leaves as a case visible to everyone.
It is not only the unicellular world that abounds with what appear to be abstract formal patterns. Even on the most cursory and passing observation of some of the most familiar natural forms, such as the forms of leaves and the variety of phyllotactic arrangements that might be observed in any suburban garden, it is hard to resist concluding that a vast amount of botanical order serves no specific adaptive end. [Emphasis added.]
Our film Biology of the Baroque explores this further starting at 4:20, showcasing the wide variety of leaf shapes in a forest. Each plant has its own shape in the same environment, yet they live side by side. “But for Darwinian evolution to explain the shape of these leaves,” the narrator states:
…there ought to be some reason why that specific shape caused one organism to live and another to die in a given environment. Yet there appears to be no functional reason why there are so many different leaf shapes. Much like Baroque architecture, these shapes seem extra, perhaps even decorative. They’re not needed to survive. They are simply beautiful.
Enter Current Biology to the rescue of Darwinian functionalism. In “Evolutionary and Environmental Forces Sculpting Leaf Development,” evolutionary botanists Daniel H. Chitwood and Neelima R. Sinha try to give adaptive reasons for leaf shape…
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