Evolution’s Toolkit and the Dinosaur on your Thanksgiving Table

If something chases you…run!

jurassic-world-rex-leak-1

Jurassic World opens this weekend and I’ll be there! (go for the fun; critique the science.)

Dinosaur-mania is nothing new. People have long been fascinated with the mysterious bones buried beneath them. When a particularly strong earthquake hit first-century Rome, a series of colossal skeletons was exposed. The locals assumed it was a graveyard for ancient giants, but they dutifully sent the emperor Tiberius one enormous tooth. Tiberius ordered his mathematicians to recreate a to-scale model of the giant, calculated from the “tooth” (probably a mastodon).

The Chinese thought they had found dragon bones; American Indians told tales of the “Thunderbird” (probably skeletons of pterodactyls). The Victorians loved fossils and collected them and identified them in earnest. They collected and reconstructed fossilized skeletons of dinosaurs as well as the dinosaur cousins: the long-neck sea-dwelling plesiosaurs, the shark-like ichthyosaurs, and the flying pterosaurs.

Plesiosaur fossil found by Mary Anning in 1821

Plesiosaur fossil found by Mary Anning in 1821

Dinosaurs in your Backyard

There are three main groups of dinosaurs: the horned and frilled plant-eaters (like Triceratops), the giant long-necked, long-tailed plant-eating sauropods (like Brontosaurus), and the raptor-clawed, razor-toothed meat-eaters called theropods (T. Rex is the most famous in this group).

Almost all (if not all) theropods were feathered – yes! even T. Rex most likely sported at least a fuzzy covering. Feathers helped keep the theropod dinosaurs warm and possibly helped them attract the ladies – theropods didn’t use their feathers for flying.

a shaggy-feathered theropod

Until they did.

The hummingbirds in your backyard, the grackles covering the parking lot, the ducks in the park pond, and the turkey on your Thanksgiving table are all descended from small meat-eating theropod dinosaurs. In most current biology writings, birds are referred to as “avian dinosaurs”.

T. Rex is more closely related to your Thanksgiving turkey than it is to Triceratops.

Wishbones and Dinosaur Moms

In humans and other vertebrates, the clavicles or “collar bones” connect the sternum to the scapula. In birds, however, the two bones are fused together in a “y” shape. The fused bones are called the furcula, better known as the “wishbone” in birds.

The only living animals with a wishbone are the birds.
The only extinct animals with a wishbone were the theropod dinosaurs.

And that’s not all. We have found a wealth of fossilized theropod dinosaur nests – complete with eggs and fossilized dinosaur babies. Some of the fossilized nests have fossilized dinosaur moms, brooding over eggs, arranged nicely in a circle…just like birds.

Fossilized Oviraptor brooding her nest

Fossilized Oviraptor brooding her nest

 

Even the inside of dinosaur bones looks like the inside of bird bones. Both bird bones and dinosaur bones have air pockets. Both also have bone growth rings (like the growth rings of trees), indicating that dinosaurs, like their bird descendants and unlike their reptile cousins, were warm-blooded.

Mesozoic Rock Star

Nineteenth century paleontologists suspected that birds evolved from dinosaurs based on the multiple bird-like dinosaurs that had been found, many with fuzzy-feathery coats.

In 1860, an unmistakable, perfectly preserved flight feather was found in Germany, in Mesozoic rock – far predating any known fossils of modern birds. In the next two decades, more were found, but this time, the feathers were attached to their owners: animals with a wishbone, wings, and feathers but also with teeth, fingers, and a long tail.

One of the rock-stars of the fossil world had been found: Archaeopteryx.

Archaeopteryx looked like a small raptor dinosaur, but with the unmistakable feathers, wings, and bone structure of a bird. In the last few decades, other primitive bird species have been found in China and Madagascar – retaining their dinosaur looks but with distinctive bird features.

Archaeopteryx1140553061

Archaeopteryx

 

No one knows for sure why all of the non-avian dinosaurs were wiped out 65 million years ago but the avian dinosaurs (birds) survived. (Gary Lawson, the undisputed king of dinosaur humor, chalked it up to smoking).

real reason dinos extinct

The avian dinosaurs survived, expanded, and evolved traits seen in modern birds: short tail, no teeth, fused fingers.

Dino-Chickens, Anyone?

And just when you thought Jurassic World’s recreation of dinosaurs from mosquitoes trapped in amber was great movie fiction, this: dino-chickens.

Biologists at the University of Chicago recently created chicken embryos with dinosaur-like faces by tinkering with the proteins that build chicken beaks.

Whoa.

In reptiles, there are two bones in the face that form the snout. In birds, the two bones fuse, grow longer, and form a beak. The proteins that form a snout in an embryo reptile are the same proteins that form a beak in an embryo bird. In reptiles, the proteins are active only in two small places on the face. In birds, however, the proteins are active in a wide band across the face.

The biologists blocked the activity of the proteins in dozens of developing chicken embryos. In some of the chicks, the bones only partially fused. In others, the bones were significantly shorter and separate. The biologists did not created full-out snouts in the chicks, but pretty close to it.

Evolution’s Toolkit

The dinosaur-to-bird transition wasn’t straight-forward, all neat and pretty. That’s not how evolution works. Contrary to the famous monkey-to-man evolution poster, evolutionary change does not happen in noticeable leaps from animal to animal. Change occurs in tiny steps that over time, add up.

Evolution is a tinkerer. Every new trait, every new characteristic that eventually results in a new species was fashioned from what was already there. Nature doesn’t start from scratch. Nature modifies old genes for new purposes or reuses old genes in a new way. Evolution doesn’t need new tools – it makes do with what is already in the toolkit.

In the case of birds, a dinosaur didn’t just wake up one morning with a beak instead of a snout. A dinosaur hatchling didn’t break out of its egg with a fully-formed beak. The dino-chicken research demonstrates that something as minor as a small change in protein expression can interrupt snout formation.

Nature’s thriftiness is evident throughout the entire tree of life. In a fascinating trip through the branches of the tree of life, Neil Shubin (author of Your Inner Fish, book and popular PBS series) explains how evolution has re-fashioned and re-purposed structures already in existence: “tinkering with mammal-ness to get whales, tinkering with fishy-ness to get tetrapods”.

Sometimes evolution’s re-purposing has little to do with original function. For example, a light-bending protein called crystallin makes up the lenses of complex eyes. But crystallin existed well before the first complex eyes evolved. Sea squirts, primitive ancestors of vertebrates, also have cystallin. In sea squirts (who have no heads, much less eyes), crystallin forms a gravity-sensing organ.

sea squirt

sea squirt

But Aren’t Some Things Too Complex to Have Evolved?

Creationists (including Intelligent Design advocates) claim that certain aspects of life are so complex they could not have possibly evolved. The eye, the blood clotting system, the bacterial flagellum – these and more are considered “irreducibly complex” – all parts must be in place or the structure is useless.

But that is not how evolution works. Crystallin did not have to be created specially for complex eyes. The protein was already in the ancient toolkit, doing another job. Precursor parts and pieces of the blood clotting system and flagellum have also been identified. Nature doesn’t start from scratch.

A Planet Bursting with Evolutionary Possibilities

Dr. Kenneth Miller is a cell and molecular biologist and the co-author of one of the most widely used biology textbooks in the country – the text at the center of the Texas State School Board’s evolution controversy. He is an outspoken critic of creationism and intelligent design. He has been an expert witness for science in multiple high-profile court cases involving the teaching of evolution.

And he is a committed Christian.

Dr. Miller was awarded the 2014 Laetare medal by Notre Dame University in recognition of his witness to excellence in science and religious belief.

Here’s Dr. Miller:

Like many other scientists who hold the Catholic faith, I see the Creator’s plan and purpose fulfilled in our universe. I see a planet bursting with evolutionary possibilities, a continuing creation in which the Divine Providence is manifest in every living thing. I see a science that tells us that there is indeed a design to life, and the name of that design is evolution.

Kenneth Miller

Kenneth Miller

 

Dinosaurs aren’t extinct – they’re flocking all over town. There may even be some waiting for you in the parking lot when you leave Jurassic World.

Watch them and marvel at a planet bursting with creation.

 

ccat reading

***************
The heavens declare the glory of God;
the skies proclaim the work of his hands.
Day after day they pour forth speech;
night after night they reveal knowledge.
*************

Science Cat

Science Cat

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