Today I have for you a guest post from a fellow science afflicted author who I’ve had some very cool biology conversations with on a writing forum we both frequent. If you ever wanted to know the how something as amazing and sophisticated as flight evolved, read on!
How Dinosaurs can fix the Evolution of Flight
by Daniel Bensen
When I pitched my “How Dinosaurs can fix your…” series of essays to the good people of the Codex writers’ forum, I expected (and mostly got) requests for writerly advice such as “How Dinosaurs can fix your Routine” or “How Dinosaurs can fix your Need for Speed“, but Coral just wanted to know about the evolution of flight. I’m not sure how that relates to writing, but it is pretty cool, so here goes.
The classic story of the origin of flight goes like this: dinosaur-like critter climbs trees, evolves elongated scales to catch the wind and glide, scales evolve into feathers, gliding evolves into flapping. Simple. And wrong.
The first problems with this theory appeared in the 90’s with the discovery of Sinosauropteryx, a small bipedal predator with fluffy, downy feathers and little bitty arms. This thing was no flier. It couldn’t even climb, and it showed no evidence of climbing (let alone flying) ancestry. Other feathered dinosaurs like Beipaosaurus, Yutyrannus, and Kulindadromeus drove the point home: dinosaurs evolved feathers (technically known as “dino-fuzz”) very early in their evolution as a means of staying warm. That was step one.
Step two was probably sex. Pennaceous feathers (that is, the flat, oblong thing you probably think of when you hear the word “feather”) first appeared on the tails of dinosaurs like Epidexipteryx, as long, ribbon-like display-structures. Other dinosaurs like Caudipteryx had display-feathers on their forearms as well as their tails. Others, like Anchiornis had these structures on their legs.
As an aside, Epidxipteryx‘s relative Yi also had insulating fuzz and display ribbons on its tail and…flaps of skin on its arms like a flying squirrel or a bat. Obviously bird evolution didn’t go with skin-wings, but other small climbing dinosaurs were making similar experiments. Microraptor had feathers all the way down its tail, forming a broad paddle, and feathers on arms and legs forming what could only have been wings. As in, Microraptor could use its feathered wings (all four of them) to glide.
Now, some caveats. It’s possible that animals like Microraptor returned to the ground, evolving into the secondarily flightless (or glide-less?) Caudipteryx and kin. That would mean that gliding came first, then sexual display. Fine. There’s also the fact that modern birds (even flightless chicks) flap their arms when running up inclines in order to get more oomph. Perhaps running dinosaurs evolved feathers on their arms for the same purpose, then took off from the ground, then nested in trees, then glided back down again. Eh. I’m not crazy about the idea, but it’s out there.
Anyway, there were a lot of different animals climbing, running, and gliding around the Jurassic forests, some of them with skin wings, some with four feathered wings, some with two like Archaeopteryx. Teeth were lost at least twice, finger claws were lost and re-evolved and lost again, bones fused together (but never quite the same way twice), tails got short a whole bunch of times. But not all of the experiments pulled through. By the end of the Cretaceous, almost all birds were two-winged (with feathers, not skin) with short tails. Fuzzy skins, fingers, and teeth were still abundant, but for whatever reason all the birds that had them died in the Cretaceous extinction that killed all the other dinosaurs.
The only two bird groups that made it into the age of mammals (paleognaths like ostriches and neognaths like everything else) are toothless and finger-less (unless they’ve re-evolved fingers like ostriches and hoatzins) covered with contour feathers as well as down to insulate their bodies.
So that’s how flight evolved. Insulating fuzz, sexual display, climbing trees, gliding, flying, with many dead ends and loops back around. Much less a march of progress (or taxi before take-off?) than evolution’s usual strategy of throwing things at the wall and seeing what sticks. Or what, in this case, flies.
Uh, anyway, buy my book!
Groom of the Tyrannosaur Queen is a time-travel romance with dinosaurs, available now as a kindle book.
Former soldier Andrea Herrera isn’t happy with where her life’s taken her. Specifically, to Hell Creek, Montana, 65 million years before the present. As far as careers go, making sure the dinosaurs don’t eat her paleontologist clients comes in a pretty dismal second choice to serving her country. But when their time machine malfunctions, Andrea and her team are trapped in a timeline that shouldn’t exist with something a hell of a lot more dangerous than terrible lizards: other humans.
Here’s where you can find Daniel: