Human Evolution: The Year 2010 in Review (Part 2)

Make sure you check out part one of my blog, published two weeks ago.

Teeth came up in another story in 2010. Researchers were quoted as saying that modern humans, traditionally thought to have evolved roughly 200,000 years ago in East Africa, now might be 400,000 years old. In addition, they may have evolved in Israel rather than Africa. Twice as old and not from Africa, was the message spread by the media. The evidence? A few teeth found in Qesem Cave.

However, a word of caution is in order here. What was reported in the media was not what the scientists had said. In fact, they had implored the members of the press not to engage in hyperbole and present hypotheticals as proven facts. They were ignored. Someone called the media on this and chastised them for engaging in “science by press release.”

DNA made the headlines several times this past year.  In August scientists announced that they had decoded famous ice man Oetzi’s genome. This is interesting in itself; it would be even more interesting if we could compare his genetic makeup with the genome of the Tarim Basin mummies.  Such a genome has not been decoded yet, so we will have to wait. Imagine, however, the potential such a comparison would present to evaluate the origins of these Caucasoid mummies.

Oetzi the Iceman: as exhibited in Museum Bélesta (Ariège), France;
reconstruction of his equipment. Photo by: Gerbil

What lessons can we draw from all this?

First, it seems that a lot of trailblazing research is now based on minute amounts of evidence, a finger bone here, and a few teeth there.

Second, the fact that we are dealing with minute amounts of information does not detract from the importance of the scientific contributions these data have made.

Third, some of the data are microscopically small. Size notwithstanding, DNA and DNA analysis have become a very valuable component in retracing human origins.

I would like to end with an observation and a comment.

In March 2010, the Smithsonian’s National Museum of Natural History proudly opened its doors on the completely renovated David H. Koch Hall of Human Origins. It is a wonderful exhibit, sharing with millions of visitors the scientific basis of our understanding of human evolution.

On display for the first three months were three original fossils, one Cro-Magnon and two Neanderthals. Their presence was announced with great pride in the original press release.  A review by a leading US newspaper stated:  “Because of the fragility of human remains, only a handful of actual fossils are on display, diminishing the sense of wonder the real thing always inspires.”

Interestingly, the reference to the original fossils was missing in other (presumably later) online versions of that same announcement. Instead, we only find a reference to “a display of more than 75 skulls (exact replicas).”

Here is a photograph as it appeared in the media (AP Photo/Jacquelyn Martin), showcasing two of the three original skulls on display.

Treasured Neanderthal and Original Cro-Magnon
Creative Commons License photo credit: Ryan Somma

The caption read :
“Fossil skulls of La Ferrassie Neanderthal, left, and Cro-Magnon, that are on a three-month loan from the Musée de l’Homme in France, are seen in the David H. Koch Hall of Human Origins exhibit at the Smithsonian’s National Museum of Natural History in Washington. Scientists think DNA analysis of Siberian genetic material may have revealed yet another branch of the human tree.”

In an age where the human attention span seems to be measured in minutes, let alone days or even years, it is good to remember that in 2007, there was another original fossil on display in the US. The venue was the Houston Museum of Natural Science. The original fossil involved was that of Lucy.

In a very savvy media campaign, several leading paleoanthropologists engaged in variations of an ad hominem attack, and used rather unfortunate language to refer to the museum, as well as the curator of the exhibit.

The scientists who opposed Lucy going on display all invoked the same document, a 1998 statement drafted by the International Association for the Study of Human Paleontology. The second resolution in this document declares:

“We strongly recommend that original hominid fossils should not be transported beyond the country of origin unless there are compelling scientific reasons which must include the demonstration that the proposed investigations cannot proceed in the foreseeable future in the country of origin.”

Less than three years after invoking this document, the National Museum of Natural History now finds itself doing the very same thing it once so vehemently opposed. Moreover, an internet search in the days following the opening of the new hall in Washington failed to identify any criticism by the same individuals who in the previous case had brought out the big guns. As the first anniversary of the hall is just around the corner, still not a word of criticism has been uttered.

As someone once said: “Isn’t that special?”

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!

horsesscott-copy

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.