Lucy’s Great Mystery: How Could Australopithecus Survive and Evolve Into Us?

Part One:

She Should Have Been Caught and E A T E N !

Lucy evolved into us. Really, really (to quote “Shrek.”)

Her species, Australopithecus afarensis, or something extremely close, changed over three million years to become Homo sapiens – the species that includes you and me.

So we should treat Lucy with respect…….

….but wait.  There’s a problem. It shouldn’t have happened. Lucy and her whole species should have been gobbled up by a legion of voracious, bloodthirsty carnivores! She shouldn’t have had any time to evolve at all.

Darwin Makes Sense (usually)

Evolution should be logical – when we have enough data. Textbooks used to say that Lucy evolved from an ancestor who was built like a chimp. But Lucy’s knee and ankle and hip bones were NOT chimp-shaped. The design of Lucy’s joints is very close to what we have – so we know that Lucy walked upright, on just her hind legs, with left and right knees close together.

s-Parade-Blog-ColorFine.  Did leg evolution make Lucy better?  Faster? That’s what we’d expect. But it looks like evolution made Lucy  s l o w e r !  Chimps run very fast and can change direction in an instant. These apes zip around on all fours, running on their knuckles. A modern human has great difficulty catching a running chimp – I know, I used to be a zoo-keeper in charge of three boisterous chimps.

Lucy couldn’t match chimps in speed and maneuverability. Since she walked just on her hind legs, her arms were useless dead weight in running. Plus – she was very short in the legs. Her shins and thighs were far shorter than in modern humans. She was not nearly as fast as we are today.

Why would evolution make Lucy slower?

Lucy – Evolved for Holding Babies on the Open Plains?

The standard theory said that Lucy’s upright posture was fit for moving across savannah, open grassland with scattered trees. She could walk for hours and use her hands to hold her babies or an armful of fruit or a big Pliocene salad or whatever.  Meanwhile, her chimp ancestors stayed in the forest. Sounds good……except we have a huge problem. The savannahs were occupied by a whole host of predators  who would love to eat Lucy and her kind.

In fact, Lucy was evolving during the worst possible time. The australopithecine clan evolved between 5.8 to 1.8 million years ago. This interval produced the scariest variety of big feline meat-eaters the world has ever seen.  Here’s what was out there, ready to catch Lucy and her kin.

Leopards
s-Kitties-Blog-ColorLLeopards are stealth felines who lived with Lucy. They had short, wide paws, flexible legs and body. That’s a build excellent for climbing rocks, hiding in burrows, ascending trees – and sudden ambush! Body weights went from 50 lbs to 200 lbs.

Lions & Tigers
Lucy’s neighbors included lion-like cats, huge predators up to 500 lbs, with massive paws that could swat down a water buffalo. Legs were longer, straighter than a leopard’s and speed over level ground was higher. Because of the great weight, climbing was less agile than a leopard’s.

Dagger-Tooth Saber Cats – Homotheres
Lucy’s world was jam packed with saber-toothed cats. The biggest were the Dagger-Tooths, who were built like a cross between a cheetah and a leopard, with long legs, excellent for fast running with some climbing. Sizes ranged from up to 500 lbs. The jaws were like a rattlesnake’s. They opened so wide that the upper fangs were exposed and ready for action. The upper fangs were long, wide blades with very sharp, saw-toothed edges. Homotheres slashed and stabbed so deeply they could kill an elephant.

Long, muscular necks let saber-cats swing their head down like a battle-ax.

How could Lucy avoid these deadly cats?

Imagine that you are Lucy. You’re waking along the savannah, carrying a load of  melons. Then, without warning…..WHAM!  A leopard leaps on you, bites your neck, and you are leopard-kibbles. Or….you’re resting on a rock when…..WHAM!  A pride of lions jump you and tears you apart. Or….you’re plucking figs from a fig tree when…a Dagger-Tooth jumps up from the tall grass. You try to run as fast as you can….but in ten seconds…WHAM! Zip-Zap!  The cat slices you into bite-sized pieces.

Lucy Defended Herself With Spears?

An old theory says that Lucy’s kind used spears and rocks for defense. But that notion doesn’t work. We find no stone tools at all with Lucy’s bones, not a spear point or a stone knife.  How about a wooden spear? Chimps today make mini-spears from twigs and impale bugs and little furballs. Sure, Lucy might have picked up a branch and chewed the end to make a point.

But if Lucy poked a  Dagger-Tooth in the butt with her spear, she’d only make him mad.

No, wooden spears aren’t enough to drive away lions and leopard and saber-toothed cats.

Conclusion: Lucy and All Her Kind Should Have Been Massacred by The Big Cats.

We’re left with a big problem. How did Lucy get away?

Please! Help our Lucy!!!!!

Send in your suggestions about how to avoid predators!

Interested in learning more about Lucy? Check out my previous blog posts on Australopithecus afarensis migration.

Lucy, meet Ardi

More than 4 million years since she last walked the Earth and more than 15 years since her discovery was first announced, a distant human ancestor dubbed “Ardi” was introduced to the general public on Oct 1, 2009.  Nicknames abound in this field where long scientific nomenclature is common. So, meet “Ardi”, a member of the genus Ardipithecus.

Who was Ardipithecus? When and where did they live? What can we say about their diet and behavior? How do they relate to later fossils, such as Lucy, as well as to us? Where do they fit in with regards to our closest living primate relatives, the chimps? This is an extensive array of questions, not unusual to find when fossils are discovered. Scientists rely on an equally extensive array of approaches to find answers.

Lets start with the first question: who was Ardipithecus?

The genus Ardipithecus derives its name from an Afar language word, “ardi“, which means “ground” or “floor.” By choosing this term, the scientists involved in the discovery clearly wanted to reflect the place Ardipithecus occupied in human evolution: as close to the very beginning of hominids as possible. Defining “hominid” as any fossil species closer to modern humans than to chimps and bonobos, which are our closest living relatives, Dr. Tim White stated: “This is the oldest hominid skeleton on Earth.”

After their discovery of the first Ardipithecus remains in 1992, scientists had identified the bones of 17 hominid fossils by the end of 1993. These specimens were retrieved from a cluster of localities West of the Awash River, within the Afar Depression, Aramis, Ethiopia. Hominid and associated fossil faunas, including wood, seed and vertebrate specimens, were dated to about 4.3 million years ago.

Over a period of several years, the team followed up with more excavations at the location of the original discovery. They collected 125 fragments of skulls, teeth, arms, hands, the pelvis, legs and feet. In addition to this skeleton, the area yielded a total of 110 other catalogued specimens representing body parts of at least 36 other Ardipithecus individuals.

Ardi is the most complete individual among those found, with about 45% of the skeleton intact. Ardi, an adult female, probably stood four feet tall and weighed about 120 pounds, almost a foot taller and twice the weight of Lucy

Ardi
Ardi, as shown in the Oct. 2 issue of Science.
Image (c) Tim White, 2008

When did they live?

There is more than one species within the genus Ardipithecus. Scientists distinguish between Ardipithecus kadabba (5.8 – 5.2 million years ago) and Ardipithecus ramidus (4.4 million years ago). Both discovered in the Awash valley in Ethiopia, these two species lived after the split between the human and chimpanzee lineages. They represent the earliest known hominids from Ethiopia.

Where did they live?

The remains of Ardipithecus kadabba and Ardipithecus ramidus have been found in Eastern Ethiopia. When they roamed that area, the Great Rift was a well-established geologic feature. The environment 4-to-5 million years ago was very different from that of today. The climate was cool and wet. Ardipithecus kadabba and Ardipithecus ramidus lived in an area of swamps, streams and dense tree cover, rather than in a mosaic of forest and grassland, as originally thought. This evidence has caused a re-examination of the hypothesis on the origin of upright walking.

What can we say about their behavior?

It seems that Ardi was equally at home on the ground as she was in the trees. Her feet, pelvis, legs, and hands suggest she walked upright on the ground but moved around on all fours when in the trees. The large, flaring bones of the upper pelvis were positioned so that Ardi could walk on two legs without lurching from side to side like a chimp. Ardipithecus gives us a close look at an upright walking being and a chance to evaluate the mechanisms that may have caused this behavior to evolve and remain until today.

Traditionally, scientists suggested that the evolution of upright walking was closely related to the disappearance of the forest cover and its replacement by grasslands. Creatures adapted to living in trees were now forced to cross grasslands in order to go from one island of trees to another, the thinking went. However, crossing through the grass would make them very vulnerable to predator attacks. Walking upright allowed one to see predators sooner, thus representing a beneficial adaption to a changing environment.  We now know that the origins of upright walking pre-dates the widespread disappearance of the forests and their replacement by grasslands. Bipedalism did not evolve as an adaptation to receding forest cover and expanding grasslands. Back to the drawing board, in other words.
Bipedalism is now thought to have evolved in a tree environment.

Questions remain: how and why? Among living non-human primates, researchers have observed bipedal stances in creatures such as orangutans as they move around in the trees, while chimpanzees most often stand upright when they feed on small objects in the trees. Early human ancestors, such as Ardipithecus, who lived in a tree environment, may have had similar adaptations.

The discovery of the genus Ardipithecus and the study of the environment in which they once lived have caused us to revisit and refine the thinking on the origins of upright walking. However, we can’t be sure that bipedalism first emerged in the Awash Valley. Its origins may lie even further back in time.

Upright walking may also relate to another aspect of Ardipithecus’ behavior: monogamy. Here is where a hypothesis originally dating back to the 1980s has found new traction. Dr. Owen Lovejoy suggests that instead of fighting for access to females, a male Ardipithecus would supply a “targeted female” and her offspring with gathered foods and gain her sexual loyalty in return. Walking upright freed his hands to carry the food, thus helping him to achieve this goal.

Lucy fossil
The fossil Lucy.

How does Ardi relate to Lucy?

Ardi pre-dates Lucy by more than a million years. She was larger and heavier than Lucy. Lucy was a more adept upright walker than Ardi. Both Ardi and Lucy lived well before stone tools were in use. Their brain size was similar to that of a chimp. Both were found in the same region of Ethiopia, with Ardi’s site just 46 miles (74 kilometers) away from where Lucy’s species, Australopithecus afarensis, was found in 1974.

What traits does Ardi share with us, Australopithecines and chimps?

Like chimps, Ardi had an opposable big toe. However, she was probably not as agile in the trees as a chimp. Unlike chimps, however, she could have carried things while walking upright on the ground, and would have been able to manipulate objects better than a chimp. And, contrary to what many scientists have thought, Ardi did not walk on her knuckles, White said.

Ardi was not a chimpanzee, but she wasn’t human,” stressed White, who directs UC Berkeley’s Human Evolution Research Center. “When climbing on all fours, she did not walk on her knuckles, like a chimp or gorilla, but on her palms. No ape today walks on its palms.”

Moreover, Ardi’s small, blunt, upper canine teeth, very likely reflect amicable relationships, leaving open the possibility of pair-bonded couples living together in social units. Ardi’s dentition contrasts sharply (no pun intended) with the much larger canine teeth found in chimpanzees and gorillas, animals known for their teeth-baring threat behavior. The latter statement is a good example of how paleoanthropologists rely on various sources of information in their attempt to reconstruct past behavior, including comparative primatology. In this case, similarities in dentition between fossil and living primates form the basis for suggested similarities in behavior both past and present. While Ardi’s canines were smaller than those of chimpanzees and gorillas, Lucy’s canines were even smaller in comparison.

Ardi’s teeth also revealed her and her ilk to be omnivores, eating a wide range of foods rather than specializing in a more restrictive diet of fruit or leaves. Being an omnivore is another trait that sets Ardi apart from chimps, animals that eat primarily fruits, and and gorillas, which eat primarily leaves, stems and bark. The research team surmised that Ardipithecus spent a lot of time on the ground looking for nutritious plants, mushrooms, invertebrates and perhaps small vertebrates.

The shape of Ardi’s upper pelvis and aspects of muscle attachment in that part of the hip resemble much more an upright walking human than a knuckle walking chimp. However, the lower pelvis is much more primitive than anything found in other hominids.

Why the buzz?

When the news about Ardi was released, it generated quite a buzz, underscoring the great interest in the study of human origins. Hundreds of media outlets covered the story. Predictably, creationist outlets use the sentiment that Ardi has overturned our understanding of human evolution to make their point that scientists “do not agree” when it comes to human evolution.  In making this statement, they display a fundamental misunderstanding of how the scientific process works. Fortunately, there are a number of excellent sites that make the process of understanding the latest news both easier and much more palatable.

Quite often, scientists were quoted stating that this find was “far more important than Lucy.” It also showed that “the last common ancestor with chimps didn’t look like a chimp, or a human, or some funny thing in between.”  Questions also abound about what this will do to Lucy’s preeminent status in the world of paleoanthropology. Now that we have an older creature also capable of walking upright, so the thinking goes, will “Ardi” now become the buzzword du jour, instead of Lucy?

In my opinion this is not the right question to ask. We are not dealing with a beauty contest among fossils. Each of these finds has substantially increased our understanding of human evolution. Lucy taught us that bipedalism pre-dates the expansion of the human brain as well as tool making. With Ardi, the most important contribution seems to be that we now need to look beyond chimps (the 98% genetic overlap between humans and chimps notwithstanding) as a model for a common ancestor. What this common ancestor may have looked like and when and where it lived, remains, as of now, a great unknown.

Lucy’s Monstrous Misfits II: Upside-Down Mastodon

Dr. Bakker’s series on Lucy continues below. Check out  Part 1: Lucy – Out of Africa. Not! and Part 2: Lucy’s Monstrous Misfits: The Moose-Giraffe.

Why did some of Lucy’s neighbors score big bio-geographical successes, spreading over many continents?

Three More Cases: Hairy Monsters With Tusks & Trunks

Elephant bull 2
Creative Commons License photo credit:
Tambako the Jaguar (on the sea)

The Order Proboscidea includes all elephant and elephant kin – large to giant to super-giant herbivores with long upper lips transformed into trunks, plus long tusks. Tusks can sprout from the upper jaw or the lower jaw or both jaws.

Regular Short-Tusked Mastodons – “The Ohio Incognitum”

Regular Mastodons were the first fossil Proboscidea to be discovered – way back in the early 1700’s.  The legs looked like elephants’. The teeth looked like giant pig teeth.  Explorers in the Ohio Valley called the monster the “Unknown  Creature (Incognitum) from Ohio.” Formal name: Mammut.

By the late 1700’s full skeletons showed the whole beast – it was very like an elephant but shorter with a low forehead and short, stout upper tusks.  Lucy lived with Regular Mastodons who were very close to the Ohio Beast.

Regular Mastodons – The Long-Tuskers (Anancines)

DeinoAnancine copyLiving side by side with the Ohio Regulars in Lucy’s Africa was a close relative: The Long-Tusked Regulars. Technical name: the Anancine mastodons. In the Anancines, the super-long tusks stuck out so far we’d expect the beast to trip itself if it ran fast.

Upside Down Mastodon.

Now for the maximum weirdness among proboscideans: the Deinotheres.  Large to super large, Deinotheres had a long, long history in Africa, beginning way before Lucy or any other australopithecine. Body was elephantine – but the feet were small, with tiny side toes and three big ones in the middle.

The astonishing feature was the curved tusks. They were upside down. Instead of being in the upper jaw and curving up, the way they did in all normal mastodons, Deinothere tusks curved down and were in the lower jaw.

What good were upside-down tusks?

Old-timer scientists speculated:

“Maybe they hauled themselves out onto ice flows, like walruses do.”

Wrong. Deinotheres never lived in cold regions.

“Maybe they killed their prey with a downward jab.”

Wrong.  Deinothere molars were vegetable choppers, designed to munch big leaves and branches. All deinotheres were vegetarian.

“Maybe they used the tusks to cash down onto branches to break them off.”  “Maybe they fought each other in the mating season.”

Maybe.

World MapDeino

As global travelers, Deinotheres are intriguing. They were like hippos. Deinotheres spread over Europe and India and China. But they never conquered Siberia and never entered the New World, via the Bering Land Bridge.

Makes you think……

Why?

Lucy’s Monstrous Misfits: The Moose-Giraffe

Dr. Bakker’s series on Lucy continues below. Check out Part 1: Lucy – Out of Africa. Not!

Our Lucy and her kin were surrounded by hairy monsters – there were more kinds of multi-ton mammals than at any other time in Darwinian history.

Lots looked “normal.” There were a half-dozen species that were elephant-shaped, more or less. And there were rhinos, both black and white, who would look perfectly acceptable today in the Bronx Zoo.

Then there were the Evolutionary Misfits.  These fellows seemed put together from the front half of one species and the rear from another – with odd legs and horns thrown in.

Perfect Misfit Example – The Moose Giraffe

Sivathere copyThis beast was first discovered in Pakistan and northern India where it was christened “Sivatherium” – for the Hindu God Shiva.  The Moose-Giraffe did look like something out of a mythological-theological  fantasy. Sivatheres were the tallest and fastest of the maxi-monsters, up to fifteen feet or more, hoof to eyeballs. Their body was bulky, in the elephant size-range.  Sivatheres were faster than elephants – they had long, strong legs that combined features of Cape Buffalo and a giant moose. If Lucy ever saw a bull sivathere charging downhill in a hurry, she’d have to get out of the way, fast.

Sivatheres had moose-muzzles. The upper lip and nostrils were carried in a bulbous, muscular schnoz that could grab branches or lift out water plants from ponds.

When Antlers are Not Antlers

At a distance, you’d think sivatheres carried moose-antlers, heavy bone growths that branched and re-branched.  One difference: both male and female sivatheres had them (only male moose today are antlered.) And…if you got close, you’d see something else that was un-moose-like. There was no drop-spot. Moose are deer, and all deer shed their antlers after the breeding season. The main antler falls off, leaving a stub attached to the skull. There’s a rough zone on the top of the stub where the main antler is shed and a new one will grow up next year.

Sivatheres had no drop-zone. Their “antlers” kept growing and growing, all through life.

Therefore – we can’t call the sivathere horny growths “antlers.” We have to call them “horns.”

Plus – Moose Giraffes have too many horns. There are the big, tall, branched things in the rear. And then smaller, sharper, pointier horns in front. Those front horns look like……giraffe horns.

Horns – Hard on the Inside, Soft on the Outside

Beautiful Giraffe
Creative Commons License photo credit: Rennett Stowe

That was the tell-tale clue. Details of teeth told the same story. Sivatheres were part of the giraffe family and NOT moose relatives. Giraffes today grow horns like a sivathere’s but smaller and less complicated. The giraffe family builds their horns in a unique way. Most horned beasts today – antelope, cows and buffalo – have an inner horn made out of bone and an outer horn made out of very hard, tough, dead skin. Giraffe horns are built differently: there’s an inner bone horn but on the outside is a layer of soft skin.

What kind of outer horn did sivatheres have? Skin rots before fossilization. Still, we can tell what kind of covering sivathere bone horns had. Sivathere fossil horns have the same texture on the outside that giraffe horns do – a pattern of small pits, for blood vessels. This texture proves that sivathere horns had soft-skin on the outside.

World MapColSiva copyNo Entry Into the New World

Sivatheres are a geographic puzzle. They spread all over India and Pakistan and Central Europe, then down through Africa. But they avoided northern Asia and Europe. And Moose-Giraffes were shut out of North America.

Why?

If we can figure out what stopped sivatheres, we’d have help figuring out Lucy’s travels.