Wilderness Underfoot: Evolution of feathers in dinosaurs (and birds)

Today, a majority of scientists agree birds are direct descendents of—if not living members of—the dinosaurs. In fact, the dinosaurs that went extinct are often referred to as “non-avian” to distinguish them from the “avian” creatures we now recognize as birds. What distinguishes these two groups is feathers, and exactly how feathers evolved is one of the most intriguing mysteries in paleontology.

The most plausible explanation as to why dinosaurs gained feathers at all is for insulation. Feathers are hollow and fibrous, which makes them superbly suited as insulators. The first feathers were shaped more like tiny spikes or downy fibers. They may have evolved from dinosaur scales or scutes.

The strongest initial force that drove the evolution of larger feathers was probably little more than their natural marketing value—that is, for showing off during courtship.

Feathers were the perfect advertising space where an individual dinosaur could display its vigor, dramatic color, or exaggerated brawn and stature.

Later advantages of feathers were probably more accidental. For example, dinosaurs may have used their feathered forelimbs to trap small prey, much like modern birds sometimes do.

Gaining the ability to fly would have come in small steps, with feathers helping to improve lift while running or leaping from trees and ledges—either to catch prey or flee from predators. No doubt these advantages would have improved the survival of avian dinosaurs, helping them pass on their genes from one generation to the next.

from the Oct. 17-23, 2007, issue

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