Wait a second. Why did dinosaurs have tails?

Question: Why does T. rex have such a big tail?

Answer: The tail is a counterbalance, so the body doesn’t come crashing down.

Everyone knows this is the right answer. All the books in the volunteer library say so. We’ve been telling kids this since 1907 (or thereabouts).

You can do an experiment. Go to the Museum Store. Buy a plastic T. rex. Cut off the tail with your Leatherman. Watch the plastic T. rex fall. See? Case closed.

Bakker - Tail Blog 1Dr. Bob does say that’s the right answer. But he also says it is the totally wrong answer.

Dang PhD! Doesn’t he know we have to talk to 35 fourth-graders all at once in our Fossil Hall? We need simple, direct answers, not some sort of Talmudic rumination that goes around in circles and ties itself in knots like a philosophical pretzel.

Wait. He does make a good point or two.

First point: Dino tails were made of live bone and thick muscle, tissue that’s expensive for any animal to make. To grow his massive tail, a rex would have to eat lots more protein and minerals than what he would need if he were tail-less. Any rex who could do away with his tail would save 35 percent of his total food bill.

If the only purpose of the tail is to be dead weight that balances the body in front of the hips, it seems silly to build the tail out of such costly material.

Second point: Consider the turkey. Or a free range chicken or ostrich. Or Texas roadrunner. They are just as bipedal as a tyrannosaur or allosaur but they have hardly any bone or muscle in their stubby little tails (tail feathers are very light and inexpensive).

Go out to a farm and chase chickens and turkeys. Come to Seymour and try to catch a roadrunner as it zig-zags between the cactus. You will discover that these nearly tail-less critters run around and maneuver quite efficiently — and hardly ever fall over on their beaks.

Bakker - Tail Blog 2If evolution can make a bird who balances perfectly without a heavy tail, why would Darwinian processes insist on giving dinosaurs such wasteful rear ends? Let’s walk through the history of tails to see how function shifted over the last 380 million years.

Stage One: The Earliest Amphibian, the First Vertebrate with Legs and Toes Fit for Walking.

We trust you’ve been watching “Your Inner Fish” on TV. Go read the book. It’s a great story about how the earliest four-legged fossils were dug in Greenland, stubby-limbed fellows named Icthyostega and Acanthostega. These species retained some very fishy features, like internal gills, tail fins designed for swimming, and heads that had no way to hear airborne sound waves. They did have thick, strong thigh bones (femora) with large joints for the hip socket and knee.

Bakker - Tail Blog 3On the back of the thigh bone is a bump where a major muscle attached — it is the “tail-thigh muscle”, or, if you’re a fossil geek, you can use the Latin caudo-femoralis. Reptiles today have that muscle, as do salamanders.

Next time you are in Grand Chenier, La., go to the Cajun restaurant and order gator tail. The big chunk of meat you are eating is the tail-thigh muscle. It’s immense. It attaches to the side of the tail bones and then runs forward to attach to that bump on the thigh bone.

(More fossil-jargon for paleo-nerds: muscle bumps on the thigh are labelled “trochanters”, and the tail-thigh muscle is hooked onto the “fourth trochanter.” No, I’m not going to explain the other three trochanters; if you must know, get Al Romer’s The Vertebrate Body).

When the tail-thigh muscle contracted in Ichthyostega , it pulled the hind limb back and pushed the body forward. In other words, the tail-thigh muscle was one of the main propulsive organs that let the earliest four-legged animals walk. Top speed wasn’t fast; more of a steady waddle.

Stage Two: Early Reptiles, about 300 million years ago.

Early reptilian legs were much longer than in the early amphibs, and the beasts were far more nimble. The tail-thigh muscle still was the No. 1 propulsive unit, pulling back on the fourth trochanter in every step. The end of the tail was very long and whip-like, so it could be used as a weapon to slap other reptiles or inquisitive amphibians who got too close.

Bakker - Tail Blog  4Stage Three: Land Crocs, Close Kin of Dinosaurs, about 210-250 million years ago.

A major upgrade in running equipment came in the Triassic with the evolution of land crocs (technical label: the “suchia,” from the Greek word for croc). Land crocs did include the direct ancestors of today’s water-loving crocodiles and alligators, plus a dazzling array of land-lubbers. Leg action was even stronger than in the earliest reptiles, and the tail-thigh muscle was of great size.

Footprints show that most types of land crocs walked on all fours. However, the hind limbs were much, much thicker and longer than the front, so the tail-thigh muscle was dominant in thrusting the animals forward, with only a little help from the forelimb.

Bakker - Tail Blog 5Land crocs filled the Middle and Late Triassic with a dynamic horde of adaptive variations — we have three examples in the Morian Hall of Paleontology. There were huge predators with heads over a yard long, armed with saw-edged fangs (Postosuchus), who used their hefty tail-thigh muscles to generate fast running speeds. And there were armor-plated plant-eaters (Desmatosuchus) who employed their tails to brace the forequarters when the up-turned snout was busy excavating roots and tubers. And there were immense fish-eaters with long snouts bristling with stabbing teeth up front and, in the rear, steak knife teeth for cutting prey (Smilosuchus and its cousin Rutiodon). These aquatic species developed deep, flat-sided tails that were useful for swooshing underwater, providing locomotion a la croc or a la gator.

Bakker - Tail Blog 6Here are two land crocs featured in our Fossil Hall. The spiky fellow is Desmatosuchus, an herbivore. The big-headed chap is Postosuchus, a predator. Both are common fossils in the Triassic Red Beds of Texas and adjacent New Mexico.

Bakker - Tail Blog 7And here’s Rutiodon, a land croc who modified the tail into a swimming organ. Our Smilosuchus is a close kin. The drawing is by the great S. W. Williston for his delightful book, Water Reptiles of the Past and Present. Williston did all his own illustrations — my hero!

Stage Four: Carnivorous Dinosaurs, about 200 million years ago.  

The first genuine dinos evolved from a quadrupedal ancestor shaped like a Land Croc. The dinos took the trends in limb evolution to extremes. They reduced the size of the front legs even more, and increased the length and thickness of the hind. Voila! The early meat-eating dinosaurs were completely, unapologetically bipedal. Since the tail was already very heavy, it found employment balancing the forequarters.

My old professor Stephen J. Gould would label this event as an “exaptation.” That’s when an organ first evolves to fulfill some initial function — in this case, the tail-thigh muscle developed to power the hind limb stroke — and then, later, turns out to be useful in a new role: balancing.

Bakker - Tail Blog 8See! The long tail of bipedal dinosaurs did NOT first evolve as a counterbalance.

It first evolved in strictly quadrupedal animals, the earliest fishy-oid amphibian. The tail was the attachment for the tail-thigh muscle, a key unit of the hind limb stroke. The tail remained very important in walking and running in early reptiles and then in the close kin of dino ancestors, the quadrupedal land crocs. The first dinos were similar to land crocs except the hind legs were bigger and the fore legs smaller. Since they already had a super-heavy tail, the dinos were equipped to shift into a strictly bipedal style.

Yes, the T. rex tail served as a counterbalance. But all through the evolution of rex ancestors, going back to 380 million years ago, the tail’s main purpose had been as an attachment site for the super-sized tail-thigh muscle.

Where Night at the Museum Goes Wrong. And Black Labs Go Right.

I love the Night at the Museum movie, especially the T. rex skeleton that comes to life. However … the rex does illegal things. He wags his tail like a dinosaurian bloodhound or Labrador retriever.

Wrong. Since the tail-thigh muscle was thick and attached to the thigh, rex-like dinos couldn’t twitch, flip, wag or otherwise wiggle their tail with quick movements. Crocs and lizards have the same limitation: powerful sweeps of the tail are fine, but twitchy movements are impossible.

That’s why pet gators don’t wag their tails — even if you throw them a frisbee.

Bakker - Tail Blog 9Hmmmmmmm … that brings up a mystery. We mammals evolved from an ancestor very close to Dimetrodon, the fin-back reptile of some 285 million years ago. D’dons had thigh bones with huge fourth trochanters, where the tail-thigh muscle attached. And that means the tail was linked to the hind limb and incapable of rear-end wiggle-ness.

Modern mammals are weird. None of us has any connection between a tail muscle and the thigh bone, not even big-tailed species like otters, platypuses, pangolins * or giant red kangaroos. Somewhere between Dimetrodon and the earliest true mammal of the Triassic, our ancestors lost the thigh-tail linkage.

How can we tell when it happened? And how can we tell why it happened? It’s not a rhetorical question — I don’t know for sure. No one does. But I do have a hunch …

Bakker - Tail Blog 10*Don’t know what a pangolin is? “Scaly anteater” is another common name. Google it.

Are we there yet? Dr. John Kappelman discusses Africa and the human evolutionary journey at HMNS

In the history of mankind, there have been three major migrations: two of these happened a long time ago, and one (of the “one small step for man, one giant leap for mankind” type) happened in our own lifetime. 

evolution astronautAbout 1.8 million years ago, hominids we call Homo erectus ventured outside Africa, wandering into Europe and Asia. Our own species evolved in East Africa around 200,000 years ago. About 50,000 years ago, Homo sapiens followed in Homo erectus’ footsteps, with significant numbers leaving Africa. Eventually they crossed Asia and made it all the way into the Americas.

Homo erectus model displayed at the Westfälisches Landesmuseum, Herne, Germany in 2007 (Image Wikimedia)

Homo erectus model displayed at the Westfälisches Landesmuseum, Herne, Germany in 2007 (Image from Wikimedia).

 On July 20, 1969, Homo sapiens marked another milestone, with the first step on the Moon. Today, we have a permanent presence in space, albeit it on a very limited scale. We have come a long way indeed.

Long before Homo erectus left Africa, other bipedal creatures roamed Africa. Among these was Australopithecus afarensis, a hominid first discovered in Ethiopia. In 1974, Donald Johanson and his team uncovered a well preserved specimen who was nicknamed Lucy, and shortly afterwards also Dinkenesh. 

AL 288-1, Australopithecus afarensis. Also known as “Lucy” or “Dinkenesh” (Image by Viktor Deak).

AL 288-1, Australopithecus afarensis. Also known as “Lucy” or “Dinkenesh”
(Image by Viktor Deak).

Lucy and her species have been the subject of many scientific studies. However, when she traveled to the United States for the second time in 2007 (the first time was in 1975, to the Cleveland Museum of Natural History), she underwent a scientific procedure never before applied to her: for 10 days, she resided on the campus of the University of Texas at Austin, where she underwent a high resolution CT scan.

The scanned data was handed over to the government of Ethiopia and Mamitu Yilma, director of the National Museum in Addis Ababa. The successful completion of Lucy’s scan meant that the specimen is now safely archived in digital format — one of the reasons behind the scanning.

A small but dedicated team participated in the scanning project in Austin: 

Members of the scanning team included (from left) Ron Harvey, conservator, Lincolnville, Maine; Alemu Admassu, curator, National Museum, Addis Ababa, Ethiopia;  John Kappelman, UT Austin; and Richard Ketcham, UT Austin.  The team used the ultra high-resolution Xradia MicroXCT scanner (background), for some of the scans.

Members of the scanning team included (from left) Ron Harvey, conservator, Lincolnville, Maine; Alemu Admassu, curator, National Museum, Addis Ababa, Ethiopia; John Kappelman, UT Austin; and Richard Ketcham, UT Austin. The team used the ultra high resolution Xradia MicroXCT scanner (background), for some of the scans.

Dr. John Kappelman has had a long-standing relation with the Houston Museum of Natural Science. He was one of many scientific advisors to the curator of anthropology when the exhibit featuring Lucy was prepared. His own research into human evolution is the topic of an upcoming presentation at the museum.

To find out if we are “there yet,” come listen to Dr. Kappelman on Tuesday, May 13 at 6:30 p.m.

HMNS Distinguished Lecture
The First Big Trip – Are We There Yet? Africa and the Human Journey
John Kappelman, Ph.D.
Tuesday, May 13, 2014, 6:30 p.m.
Click here to purchase advance tickets.

This lecture is cosponsored by Archaeology Institute of America – Houston Society as part of its 2013-2014 Innovations series.

How mammals became mommies: Learn about the evolution of mothering over 200 million years in this Distinguished Lecture

My mom is a wonderful person. Most people think the same of their own mothers and, at least in my case, it’s true. She is always supportive, she let me win at board games (at least until I was an adult — now she shows no mercy), and she made sure I was able to visit museums and go watch Shakespeare plays.

When we think about mothering, certain preconceptions come to mind. We might think of an SUV full of kids being taken to and from different events. We might think of a working woman coming home from the office, or even a mother at home with a newborn. Would it surprise you to know that the idea of motherhood has changed over time?

via zooborns.comVia the cute-collectors over at zooborns.com

There are two stereotypes currently dominating the idea of the ideal mother: soccer moms and supermoms. Soccer (or hockey, basketball, or other hobby-supporting) moms have a large vehicle full of kids and equipment and they go from plays and practices to games and recitals. There is also the supermom, who works 60 hours a week and still has another 40 for her kids.

In the ’70s we were introduced to child-rearing experts. They gave us the latest and greatest that science had to offer. Dr. Spock was a predominate example. This came as a reaction to the mother-knows-best attitude of the early 20th century, which, in itself, was a response to patriarchal child raising, where the mother deferred to the father to make sure her “womanly disposition” didn’t damage the child.

In early centuries, a well-to-do woman would not lower herself to raise a child — such tasks were for the help while a lady went to dinner parties. And throughout the Dark Ages, a child was thought of as a little demon who had to be restrained until they were able to behave.

In ancient Rome, being a mother raised your social capital and marked a closer tie to your husband’s family and distancing of your own. (But if you could afford it, you’d have someone else raise the kid.)

The Greeks had a yearly celebration for mothers. It was a spring festival dedicated to the goddess Rhea. Mothers in Ancient Egypt were also well-regarded — several mothers of pharaoh were the real power behind the throne.

But is mothering confined to human culture? Do other animals do it? Chimpanzees have the longest childhood of the animal kingdom. A baby can stay with its mother for up to seven years. Elephants, which have the longest pregnancy at 22 months and some of the largest babies at 250 lbs, use the herd to help raise a baby, with the other females working together as babysitters.

And motherhood is not confined to mammals.The alligator is noted as a caring mother.  The temperature of the nest determines whether the babies will be boys or girls, so the alligator knows in advance what color onesies to get. After hatching, the mother will carry her babies around in her mouth and protect them from other animals.

A mother octopus will spend months hovering around her 50,000 to 2,000,000 eggs to protect them from predators and to make sure enough water goes by to provide enough oxygen. During that time, she’ll not leave the eggs even to get food and resorts to ingesting an arm or two. We should at least give her a hand.

Earwigs, one of my least favorite insects, are also caring mothers. Instead of just laying her eggs and leaving, she will hang around and keep her eggs warm and fungus-free. She will stay for months after they hatch and continue to provide safety and substance.

If mammals, reptiles, and even insects mother, what part of mothering is cultural? Is it a genetic need to make sure that our progeny survive? Which parts are nature and which nurture? Join us on April 2 at 6:30 p.m. and hear Dr. Robert Martin from The Field Museum talk about the evolution of mothering.

WHAT: HMNS Distinguished Lecture, “Evolution of Mothering: The Natural Heritage from our Deep Mammalian Past”
WHO: Robert Martin, Ph.D., Field Museum
WHEN: Tuesday, April 2, 6:30 p.m.
WHERE: HMNS Main, 5555 Hermann Park Dr., Houston, TX 77030

Sponsored by The Leakey Foundation 

Mammals, whose name comes from the Latin “mamma” for teat, are defined by suckling. Mothering began 200 million years ago with the first mammals and developed to become a hallmark of ancestral primates. Taking evidence from anthropology, archaeology and genetics, this presentation reviews the long evolutionary trajectory of human mothering. Reconstructing that history throws light on the natural basis for our own maternal behavior and highlights sources of problems encountered by modern mothers.

via the Leakey Foundation

Dr. Robert Martin is curator of biological anthropology at the Field Museum in Chicago. He has devoted his career to exploring the evolutionary tree of primates, as summarized in his 1990 textbook Primate Origins. Dr. Martin is particularly interested in reproductive biology and the brain, because these systems have been of special importance in primate evolution. His research is based on broad comparisons across primates, covering reproduction, anatomy, behavior, paleontology and molecular evolution. The Leakey Foundation Lecture Series is sponsored nationally by Wells Fargo Bank and locally by The Brown Foundation, Inc.

Watch Dr. Martin speak about his work and experience as a biological anthropologist below:

Deep Ancestry: Our Story

Anyone who is interested in family history, or anyone who has ever gone to a library or archive to undertake genealogical research knows that while the subject is an exciting one, the work can be tedious and the resulting picture often fuzzy.

This is where we stand with regards to family research writ large, that of modern humanity. To be sure, we have come a long way since we humans even became aware of the fact that we had a very long history, or a deep ancestry. Consider the day, now more than 180 years ago, when people went into a cave in Belgium and encountered remains later identified as belonging to a Neanderthal individual. Compare that against our current understanding of human evolution. How we got here is an interesting story and it is an interesting tale to relate,. Where we go from here is equally intriguing.

Here is part one: how did we get here?

Traditionally, we rely on three main sources of information when studying human origins, our origins. These sources are: the material remains of that past (including both fossil remains and man-made tools), genetics and comparative primatology. The latter refers to observation of current non-human primates and possible correlations between their habitat and behavior with the environment in which our ancestors once lived and their behavior. If there is one constant in the picture generated by these sources is that it is always being refined and updated. Such is the nature of scientific endeavor: it never stands still. Thankfully, our thirst for greater understanding is never slaked either. There is always more to investigate.

Material remains have been the backbone of paleoanthropological studies. After all, what could be a better illustration of human evolution than a fossil of an ancient ancestor, or a tool made by a distant relative of ours? By carefully plotting where these remains have been found, we can reconstruct a picture of human evolution, we can start to see where our earliest ancestors once arose, evolved and eventually migrated from. By studying their tools, we can see human inventiveness at work. At first this is a tediously slow process, but eventually we see it picking up pace to the point we are today: new gadgets developed on a daily basis.

For a while, as people were studying fossil human remains, others were investigating genetics. However, initially the practitioners of these two pursuits did not know of each other’s work, or, did not realize how their work could benefit from the other person’s insights. And so we see how Mendel and Darwin were contemporaries, but their respective scientific insights and breakthroughs did not cross over and inspire the other.

DNA rendering
Creative Commons License photo credit: ynse

Our genetic makeup is the result of millions of years of evolution.

Since the Human Genome Project was completed in 2003, we have learned a lot about our genetic makeup. Since then, the chimp genome, gorilla genome, and the orangutan genome have been finished; by the way, the latter was sequenced in our own backyard here in Houston. This provides a nice platform to start comparing our genetic makeup with that of our close primate relatives, and find out where we differ, and, more interestingly, how similar we are below the surface. It turns out we are quite similar.

The difference 1% makes.

Differences, no matter how ostensibly small, remain important. One can be in awe about the fact that we share around 99% of genes with chimps. One could also turn that around and say “See how much difference 1% makes?” That difference, in turn, may help us figure out when in time we started to go our own way, after the split from a common ancestor. This is where the notion of a molecular clock comes in. This concept has been used to “to investigate several important issues, including the origin of modern humans, the date of the human/chimpanzee divergence, and the date of the Cambrian explosion.”

Thus we see in the literature that orangutans, with whom we share around 97 % of our DNA, split from the family tree around 16 to 15 million years ago. Humans and chimps became their own branches on the family tree around 6 to 5 million years ago.

As one researcher recently put it: “There remain signals of the distant past in DNA, and our approach is to use such signals to study the genetics of our ancestors.”

The concept of the molecular clock continues to be refined as our understanding of its potential and limitations has grown. For better or worse, however, it provides us with a tool to help situate major branching events on the family tree. This brings us to our own immediate past, our place in history, when modern humans appeared on the scene.

Modern Humans

Discoveries made in East Africa date the emergence of modern human beings to about 200,000 years ago. Two skulls, found in 1967 in Ethiopia were recently identified as the earliest known modern humans. While that makes all of us Africans, it data from mitochondrial DNA have suggested that our ancestors did not make it out of Africa until 60,000 years ago. The archaeological record seems to disagree, however. Man-made tools twice that age have recently been found in the Arabian Peninsula.

It is at times like these, when dates provided by genetics and archaeology diverge, that we hear voices criticizing the invalidity of this approach. What we will see happen, however, is that this apparent disjunction between two sets of data, will spur on researchers to find where the source of this disparity lies and resolve it. Were that to be impossible then we would have to go back to the drawing board and rethink our ideas about human evolution and the timing of critical events related to it.

Now for part two: where do we go from here?

As people become more mobile, we are now finding our mates much further away than we did just a few generations ago. This means that it will become more difficult to check that box on the census form asking for our ethnicity. It also means that we are slowly becoming more homogenized. Indigenous cultures are disappearing and language follow suit.

To get an idea of how exhilarating and mind-boggling this pursuit of science can be, I would like to invite the reader to attend an upcoming lecture.

On March 7, the Houston Museum of Natural Science will host Dr. Spencer Wells, lead scientist of the Genographic Project.

His lecture, entitled “Deep Ancestry: Inside the Genomic Project,” is brought to us by the Leakey Foundation. Dr. Wells is an Explorer-in-Residence at the National Geographic Society and Frank H. T. Rhodes Class of 1956 Professor at Cornell University. Dr. Wells will share with us how the Genographic Project, using data from hundreds of thousands of people, including members of the general public, the Genographic Project is deciphering the migratory routes followed by early humans as they populated the Earth.

I look forward to this lecture, and hope to see many of you at the museum that evening.

In the meantime, a pop quiz.

Q: What do the following individuals have in common?

Brazilian indian chiefs, Kaiapos tribe, during a collective interview.
Left to right: Raony (state of Mato Grosso), Kaye, Kadjor, Panara (Pará)
Creative Commons License photo credit: Valter Campanato, Agência Brasil (ABr). April 17, 2005
Ethiopian Orthodox Christian woman – Lalibela, Ethiopia
Creative Commons License photo credit: Dirk Van Tuerenhout
Lake Titicaca – Uros people
Creative Commons License photo credit: Dirk Van Tuerenhout

A: They are us. We are them. This is us.