Among fossils: How very old things remind us of our youth

The earth is 4.54 billion years old. That’s a big number to wrap your head around. Spending time among very old things helps, but even then it’s easy to forget that not only the fossils themselves are ancient; so is the rock they came out of, the planet circling a sun that has been around a long time.

Since my childhood, dinosaurs have arrested my imagination like nothing else in science, and what better place to witness the majesty of these ancient animals than the Houston Museum of Natural Science, displaying some of the oldest things on Earth? When I walk through the Morian Hall of Paleontology, I see the bones of creatures that lived millions of years ago, preserved naturally by the processes of geology, like mummies, but embalmed by mud, pressure, and minerals. These aren’t bones, really. They’re rocks, no different from petrified wood or the crystals in the Cullen Hall of Gems and Minerals. They were once creatures of flesh and bone, but the organic molecules and chemicals that made up their bodies, if they didn’t decay, were replaced atom by atom while the rest of life on Earth developed.


Lane, the most complete fossil specimen of Triceratops in the world. 65 million years old.

Mine is a problem of scope, I think. It’s a strange feeling to understand that Lane the Triceratops, the most complete specimen of this dinosaur, was under our feet during the fall of the Roman Empire, was still buried in the time of King Tutanhkamen, and remained undiscovered while Shakespeare wrote his sonnets. This animal died, and life went on as it always does. Its life among presumably millions of others like it was common. Undistinguished. But that specimen is no longer a Triceratops; it’s a skeleton made of rock. Not even a skeleton, but an impression of it. A three-dimensional photograph dug out of the album that is the many-layered dirt of our planet. This animal has become a symbol of history. Now that is rare.


Icthyosaurus mother. At least 146 million years old.

It’s remarkable, this action of preservation that the Earth is capable of. And it’s remarkable that we have developed the science to identify and understand these stones. We had to consider both the life cycle of rock and the taxonomy of life before we could begin to speculate what these samples could mean. But really, so what? They’re just rocks.

It’s the feeling of humility they deliver that makes them fascinating. It’s like walking through modern Rome after living in developing Houston, surrounded by buildings a thousand years old that stood before the United States was even imagined. We’ve been walking around these seven continents for millenia, in the dark about what was under our feet until the birth of paleontology in 1666, when Nicholas Steno identified “tongue stones,” known then only as triangular rocks, as fossilized shark teeth. Dinosaurs were around whether we knew they existed or not. They are as old as the rock we walk on.

Icthyosaur Baby

Impressions of Icthyosaurus pups in the rib cage of this rare specimen suggest this animal died in childbirth.

Now consider this. In 2011, biologists identified 20,000 new species, a large number of them beetles, and most of them invertabrates. That was in a single year. Now take that diversity and multiply it by the age of the Earth. I’m not going to do the math, but that’s the number of species paleontologists have yet to discover. That’s the amount of life we potentially have yet to search for in the rock.

After early hominids, fossils of the first humans date back 1.8 million years, along with mammoths, mastodons, and saber-toothed cats that appear in the rock alongside them. Triceratops lived in the late Cretaceous, discovered in rock at least 65 million years old. Icthyosaurus swam the oceans and gave birth to her young between 245 and 146 million years ago, in the Jurassic and the Triassic. (Their era lasted 100 million years. Again, we’ve been around for 1.8.) Trilobites in our collection have been preserved for between 540 and 360 million years, and the stromatolites, layered rocks formed by ancient bacteria, date back to 3.4 billion years. Not million. Billion. They appeared in the Archaeozoic Eon, about a billion years after Earth solidified out of molten space-rock.


One of the best preserved and most intricate trilobites in the world. At least 360 million years old.

What will the occupants of this planet find after the next million years? We’ve been around for a while, but not nearly as long as these fossils. What will paleontologists of the future, if they still exist, find in another 65 million years? 146? 540? 3.4 billion? The Earth will still be here by then; humanity is another story. Will we still cling to the crags in a different form, the maps unrecognizeable to the once-dominant species of 2015 CE, if they could see them? Will we have preserved our history as well as the rocks have preserved the dinosaurs?


Stromatolite formed by layers of ancient bacteria preserved in rock. At least 3.4 billion years old.

In another 3.4 billion years, the sun will be nearing the end of its life, having expanded into a red giant and swallowed Mercury and Venus. According to many estimations, by the time the sun is 7.59 billion years old, it will engulf the Earth. We are living in our planet’s middle age. It took half the Earth’s life for humanity to arise and build its cities. For the United States to claim its sovereignty.


Lucy, Australopithecus afarensis, the most complete skeleton of this hominid in the world. 3.18 million years old.

The Earth is old, dude! We never pay this age any mind until we identify something to date it against. Here we have Triceratops, say, a creature that lived in the time when this rock was young, just a pile of sediment on the floor of the ocean or a river. Paleontologists owe a lot to the power of speculation and theory. We may never know for sure what life was like in the era of these ancient creatures. But if we have anything in common with the dinosaurs, ancient mollusks and archaebacteria, it’s that we all grew on this same rock.

In a way, we’re just as old as they are. Our bodies are made up of the same elements that have always been here in some form or another, buried under the crust in a molten mantle, or exposed to the light of the sun that has fueled life on Earth for as far back as the imagination will stretch. As Carl Sagan said, “We are all made of star stuff.”

Digging Sideways For Science

Recently we received the question on our blog, “How far down do you have to dig to get to the Cretaceous-Tertiary boundary?” A similar question that I get in anthropology and paleontology is “How far down do you dig to find a T. rex…..or a Dimetrodon….or an Australopithecus?”

We usually don’t dig down. We dig SIDEWAYS!

Fossils are not that common. You could rent a back-hoe and dig at random in North Texas for a month and not find anything. You need to find those few, special layers that have bones or shells.

So….the best way is to use Nature’s Bulldozer.

Here’s how it works. Nature cuts into rock layers using rivers and streams. River banks and the sides of arroyos show us cross-sections of the rock. We use these natural cuts to search for the layers rich in fossils.

Edaphosaurus pogonias

My HMNS crew has walked, hunched over, for days at a time, scrutinizing the banks of gullies in North Texas, without seeing a thing worth digging. But we must have patience. In the Permian Red Beds, for instance, we do find new sites on average every two days. Last month, we found four spots that had bones of the fin-back Edaphosaurus, one of the earliest plant-eaters that ever evolved.

We didn’t dig those four spots because the bones were few and fragmentary.

But we found a fifth spot in the bank of a gully that had a whole vertebral column of the fin-back Dimetrodon, the top predator of the time. Here we dug in, sideways, and recovered a large part of the skeleton, including hips and shoulder.

To get the CretaceousTertiary transition fossils, we go to Raton, New Mexico. Here steep river banks expose the sediments from 65 million years ago, when the dinosaurs went extinct. We can dig in sideways and excavate thin zones of black clay that preserve pollen and spores from the plants that lived just before and just after the great dino extinction.

To find fossil hominids in Africa, first we’d search aerial photos, looking for cuts made by rivers and streams into sediments laid down about 2 million years ago.

Think “Sideways.”

Lucy’s Great Mystery: Part 3

In Part One we learned the frightening facts: Lucy was surrounded by formidable felines. She was too slow to run away and she didn’t have weapons to repel 150 pound leopards or 500 pound  homothere saber-tooths.

In Part Two we discussed even more of the fearsome predators surrounding Lucy, and began to discuss how futile fighting back would be.

How Could Our Lucy Survive a Legion of Cats and Hyenas?

How did she defend herself?

Here are some suggestions:

She made sharp-edged knives out of broken antelope bones and buffalo horns
Lucy model - faceThis was a popular theory in the 1950’s.  In South African caves, Lucy’s relatives are found with hundreds of broken antelope bones, horse bones, and broken horns form all sorts of hoofed creatures. Conclusion: Australopithecus didn’t make stone tools – they made bone-tools.

Supposedly Lucy and her clan smashed antelope legs and used the sharp-edged ends the way a hockey fan would use a broken beer bottle in a bar-fight. “Poke, whack, stab!”

Broken bones can be nasty weapons, it’s true, but….

Hyenas broke the bones
Careful analysis of the way the bones were broken proved that Australopithecus didn’t do the breaking. Teeth marks on the bones and the style of breakage matched what we see today around a hyena lair. All of those cave bones had been smashed by the big teeth of hyenas and maybe big lion-sized cats. The predators smashed Australopithecus bones too.

Maybe – Lucy Smelled Bad – Or Tasted Bad

Striped Skunk
Creative Commons License photo credit: Charles & Clint

Seriously – this is a theory we must consider. A few animals stink so thoroughly that predators won’t attack. Skunks are a good example. Even mountain lions are repelled by one spray from the stink glands of a Texas skunk.

And meat can stink or be poisonous. Toxins in the Fugu fish are deadly – if you go to a restaurant and gulp down the wrong part of your Fugu, you’ll die. So…..maybe Darwinian processes gave Lucy toxic flesh.

But primates don’t evolve super-stink
Today we just don’t find any lemurs, bushbabies, monkeys or apes with toxic meat or stinky glands.  In fact, most stinky mammals are predators – skunks, ferrets, and stink-badgers. So, although it’s theoretically possible, we should not be too enthusiastic about Lucy evolving chemical defenses.

Let’s Review Lucy’s Potential

ChimpUs-frontSkeletonLabelLet’s review what Lucy could do – we have nearly all the bones from the skeleton if we supplement Lucy and other Ethiopian finds with close relatives dug from South Africa. Follow along by scrutinizing our Lucy-chimp-us body diagram.

No Grabber Toe
Lucy’s big toe was like ours – it didn’t face away from the other toes the way a chimp big toe does. So Lucy couldn’t grab a branch and climb like a chimp.

Knees Together
Chimps can’t stand perfectly upright, because their knees slant down and out. But Lucy could stand in a modern posture – her joints were shaped so the right and left thighs came down and towards each other. She’d walk and run like us modern humans too – knees close together.

Strong Shins & Thighs
Lucy did have muscular, short shins and thighs. No, she couldn’t sprint as fast as a modern human but she could accelerate fast and turn quickly. And short legs actually are good for climbing.

Modern Hips
Lucy had wide upper hips, like ours, not narrow hips like a chimp’s. Wide hips are good for supporting guts when standing and running upright. And….wide hips could be good for climbing straight up a tree, if arms and legs work together. We see modern people shimmying up coconut palms this way.

Lucy – NOT America’s Next Top Model – Compact Torso
Today’s humans have long waists – especially in the Hollywood starlets and runway models. Not our Lucy. As the song goes, Lucy had “..strong thighs and shins… and her torso…even more so.” Lucy had no waist. Her barrel chest was set on top of her wide hips.

That gave her a low center of gravity, a design useful for three-dimensional movement. Lucy was a natural gymnast! She could jump and twist and do somersaults.

Shoulder-Socket Half Chimp
Lucy’s shoulder socket was half-chimp, half human. The joint let her raise her arms further up, above her head, than we can – but not as far as a chimp. Raising your arms high is useful for climbing vertically; hand over hand (the way we were taught in gym class in seventh grade).

Long Arms
Lucy is half-chimp in arm proportions too – her whole arm is longer and stronger compared to her legs than what we see among modern people. And strong arms certainly would assist in climbing.

Curved Fingers
So far, our review of Lucy’s anatomical equipment is a surprise – she’d walk like a modern human on the ground, but she might be able to climb vertically much better than we can. However – if she really was supposed to climb, she’d need long, curved fingers to wrap around branches.

Did she? Were Lucy’s fingers more curved than ours?


Australopithecus did have more curve in the digits. Not as much as in a chimps but still more than in modern humans.

So, after reviewing all of Lucy’s potential, we now can give her advice:

LUCY!  To avoid being eaten…..STAY NEAR A TREE!

She wouldn’t have to climb like a chimp, but she would have to be near enough to a tree so she could shimmy up when the cheetah charged or the hyena pack came galumphing over a hill. She wouldn’t have to scoot over a branch, holding on with her big toe, chimp-style. But she could avoid most meat-eaters by going vertical.

The Old Theory Is WRONG! Lucy Did Not Evolve on the Open Plains.

Back to our original problem: the old theory said Lucy and her kind evolved to move over open, tree-less terrain. We now have new evidence – from fossil herbivores – that the theory is incorrect. If Lucy lived in treeless areas, her bones should be found only with hoofed animals adapted to plains– the wildebeests and gnu, for example. And zebras. We shouldn’t find woodland herbivores like black rhinos and mastodons.

In fact, the antelope and rhinos and hippos and mastodons we dig with Lucy are mostly woodland critters, adapted to move over grassy areas with many bushes and clumps of trees nearby.

Mystery Solved! Lucy Evolved to Stay Near an Escape Tree.

Her family could forage on the ground. And climb up and away. And maybe they did use pointed sticks to jab down at any leopard who tried to follow.

Our ancestor, Lucy, was a success because she made her world three-dimensional.

Darwin’s Pony…and the Bulldog Who Loved Horses

Count The Toes on Our Petrified Pony

chi_7740Folks stop and stare at our fossil horse.  It is cute in a coltish way, all gangly and long-legged. And it is dynamic – rearing up as if it just saw you and whinnying a “Hello!” 

But sharp-eyed visitors take a second look. Our Merychippus demands a digital double-take. Count the toes. There’s one big hoof on each foot, as there should be. It’s a horse, of course. The French word is “solipede”, meaning “Single Toe Foot.”  Today, among all animals domestic and wild, horses and only horses have just the single, solitary toe to run on. 

Wait – look closely. There’s more. Our Merychippus has too many toes. There are extra digits, little ones, on the inside and outside of the main hoof.  The mini-toes have hoofs too but they’re narrow and pointed.

I imagine I’m petting our Merychippus along its muzzle, like I do to my neighborhood ponies. And I’d feel another odd thing – Merychippus has a more delicate, lightly-built face and nose. If you stare at the fossil, you see a row of molar teeth far smaller than any horse-owner would expect.

Those small molars and accessory digits tell a story that’s literally earth-shaking. Back in the 1870’s, Merychippus and the other three-toed horses shattered the scientific status quo. The side-toes made Archbishops fume and fuss and get red in the face. German philosophers smiled and puffed their pipes with satisfaction.

You see, Merychippus proved that Darwin was right.

Europe and Its Multi-Toed Equine Puzzles.

Down through the ages, since the time of the Babylonians, folks who could afford to own horses loved them.  Ditto for asses, mules and donkeys – all the solipedes were extraordinarily useful. Once they were domesticated, the equines offered farmers a powerful engine to pull a plow. Donkeys could carry produce to the market. Mules could turn the grinding stones. And war horses made the chariot the instrument of ancient Blitzkriege.

Since wealthy men had time to think about science, it was the horse-owning sector of society that pioneered the new discipline of Paleontology in the late 1700s and early 1800s.  Naturally, these men wondered how fossils could explain modern horse anatomy. Fossils were proving three great truths about the Earth: 1) It was very old. 2) It had gone through many ages, each with it own fauna and flora. 3) With each successive age, the animals got more and more modern.  Horses belonged to the most recent, most modern age. Horses with single hoofs were dug up only in rocks from the last slice of geological time, the Ice Age, when equines galloped around herds of giant mastodons and were chased by saber-tooth cats.

The mammoths and saber-tooths went extinct at the end of the Ice Age. Horses survived.

Anchitherium and Hipparion – Steps Up in Time?

hipparioncolor-copyIn the 1830s, some puzzling equine fossils were dug in older strata, European layers with more primitive cats and mastodons. The skeletons looked mostly equine…..but there was something wrong with the feet. Inside and outside were tiny extra toes.  This very first discovery of thee-toed horses received a name that would be famous: Hipparion.  The Hipparion-like horses were world-conquerors. They invaded Africa and Mongolia, China and India.

(We now know that our ancient human ancestors, Lucy and her Australopithecus relatives, thrived in African woodlands that had teeming herds of Hipparion.)

Further digging in France revealed a second horse-surprise. Long before Hipparion, there was a three-toed horse with extra digits that were far larger: Anchitherium. Radical scientists who defended the new idea of evolution seized upon the two fossil horses as evidence:

“SEE!  Fossils show that horses evolved!  First there was Anchitherium with big side toes….then after thousands of generations the toes got smaller, making a Hipparion, and finally the extra digits were GONE!  Voila! Modern horses had evolved!”

Evolution: A Theory Full of Horse-Holes!


Many learned people thought it was bunk. “Too many holes in your story. There’s too much difference between Anchitherium and Hipparion!”  Skeptics were right. Anchitherium was way different from later horses. The face was short and the molar teeth were much too shallow top to bottom. And the molar crowns were simple.  Modern horses – and Hipparion – are renowned for their molars. The crowns are incredibly tall top to bottom and have crowns with complicated zig-zag patterns of enamel, an excellent design for chopping up tough grass.

Anchitherium had very low, very small molars that wouldn’t do at all for chewing grass. Anchitherium must have been forced to eat only soft fruit and succulent leaves. Dentally, it was NOT a horse.

Centennial USA – Darwin’s Bulldog.

Paleontological speculation about species evolution had begun in the 1820’s and ‘30’s, mostly in Paris. When Darwin published his “Origin of Species” in 1859, the topic boiled over – because Darwin offered a simple explanation for how evolution worked. Animals produced far too many offspring in every generation, so only those with superior genetic traits survived. That was “Natural Selection.”  The Establishment pooh-poohed and harrumphed and tried to stamp out Darwinian ideas. A brash young scientist, Thomas Henry Huxley, fought back. He knew anatomy and he knew fossils.

So eloquent was Huxley that he acquired the nickname: “Darwin’s Bulldog.” Of course Huxley used the European horse fossils as arguments…but still, those big gaps around Anchitherium were annoying.

Meanwhile, across the Atlantic, a new university was being built in Baltimore to revolutionary ideas: professors would do research in labs, graduate students would be given preference over undergrads and – Horrors! – WOMEN would be enrolled. 

This new institution was The Johns Hopkins University. Its official opening was set for the nation’s centennial, 1876. Bad news from Montana – the Sioux had wiped out General Custer – didn’t dampen the festivities. Johns Hopkins officials invited the best known biological scientist from Europe to give speeches – Thomas Henry Huxley.

Huxley advocated Darwinism in Baltimore. Then he took a fateful train ride north to New Haven, Connecticut. He visited the Yale museum where Professor Marsh supposedly had fossils from the American West that were close to European Anchithere-type horses.

Astonishing Riches in a Yalie’s Drawers.

Marsh opened up a museum drawer. There were hundreds of Anchither-style bones. Amazing. Another set of drawers had hundreds of Hipparion-like horses.  Doubly amazing.  Huxley was flabbergasted. “But…do you have missing links between Anchitheres and Hipparion? With a smile, Marsh had a whole room full of drawers opened up. Thousands of teeth, hundreds of skulls, dozens of full skeletons.
merychippuskin-copyYale drawers contained not one but a dozen missing links. There were tiny horses that must have been ancestors of Anchitherium. And tinier still ancestors of those ancestors.   The smallest, most primitive Yale ponies were no bigger than a poodle and had – count ‘em – four toes in the front paw.

Huxley made a suggestion. “When you dig the very first horses, the ones even earlier than these, why not call them the ‘Dawn Horse,’ Eohippus.”  Marsh did dig even earlier horses, and he did christen them Eohippus.

Marsh had already excavated links connecting Anchithere-style species with more primitive four-toed critters and with Hipparion-like species. His smallest three-toed link he called the “Middle Horse,” Mesohippus. Check out the Houston Mesohippus, mounted as if it were escaping the attack of a saber-tooth cat.

Most beautiful of all Marsh’s specimens were delicate skeletons the size of Shetland Ponies. The side toes were splendidly intermediate between Anchitheres and Hipparion. Bigger than in Hipparion, smaller than in the earliest Anchitheres.

But the teeth were better still. These horses had molars halfway between early species and the grass-eaters. The molar crowns were taller than in Anchitheres but lower than in Hipparion. Marsh had named this equine link “Merchippus.”

And to top it all off, the sediment layers in Nebraska and Wyoming just screamed: “Darwin is RIGHT!

The series of horses were buried in a series of layers, with the simplest molars and biggest side toes in the earliest levels.  Each American rock layer was like a frame in an old-fashioned movie, a slice of the Darwinian picture of change through millions of years.

Finally, Huxley knew why the European fossil horse story was full of gaps. “Horses evolved mostly in America… and only every once in a while species spread from here to the Old World!”

Dead right.

Merchippus and Modern Science.

Merychippus continues to tell its story in the 21st Century. A hundred times as many fossils have been dug.  Missing links are filled all the time – and gaps in the sequence of evidence are filled.  The horse family tree turned out to be a family blueberry bush, with many short branches going off sideways. 

The main theme of the equine saga is straight forward: Natural Selection was caused by climate change, as the old, warm, wet forests gave way to drier, cooler woodlands and plains. Horses had to evolve better teeth for tougher vegetation. And the feet had to change too.

Big side-toes were ideal for moving over soft, moist soil. But the shift to sun-baked plains demanded better shock-absorbing, and that meant a bigger central toes and smaller side toes. There were side branches too – some horse species specialized in the remaining patches of well-watered forests. Anchitherium was one of those forest-loving equines.

On the other hand, Merychippus was well on its way towards the new lifestyle. It was the direct ancestor of later, more advanced species, that led to Hipparion and then to all modern single-hoofed horses.

Salute to the Three-Toed Horse!

Take a moment to wave at our Merychipus. It was a fine, lively critter in its own time – one of the fastest hoofed animals and one of the best in eating the tougher leaves that were taking over the environment.

And give it a special tip of the cowboy hat for testifying to the central secret of Nature: Animals are NOT boring and static. Feet and molars are remolded by Nature to keep forests and plains full of creatures most wonderfully fit for their environment.