Choose Your Weapon

Scimitars, sabers, daggers, dirks—which will it be? Long, curved, sharp teeth, the fossil cats had all those weapons handily attached to their top jaws.

An incredible array of cats and pre-cats roamed the earth from 10 million years until relatively recently. One wonders how any primate— much less our smallish bipedal hominid—survived the predation of so many large-bodied, large-toothed felines. The figure on p. 65 diagrams

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A reconstruction of the skull of Megantereon, a fossil saber-toothed cat that roamed Africa when hominids were evolving. (C. Rudloff, redrawn from Hartstone-Rose, et al.)

the who and the when of all these hungry felines; emphasis is limited to large cats that were present where and when hominids were evolving. The entire felid record stretches back much farther in time and also includes many North and South American mega-predators that were indigenous to those two continents long before human arrival occurred.

The extensive array of fossil and modern cat species inhabiting Africa from 12.5 million years until the present (light shading denotes fossil record). (C. Rudloff, redrawn from Hartstone-Rose et al.)

Fossil evidence that will support theories of long-term coevolution (50 million years or more) between the primate order and mammalian predators is uncovered only occasionally. Nevertheless, there are enough of these finds to generate speculation that the very roots of primate origins are buried in episodes of carnivore depredation. For example, Notharctus was a prosimian-like primate living in the Eocene epoch 50 million years ago. The death of one such animal was reconstructed based on the size and shape of skull puncture marks matching the teeth of Vulpavus, an arboreal predator that looked like a large mongoose and was ancestral to all carnivores.15 The holes in the skull of the fossil primate are the perfect fit for the fangs of Vulpavus.

The creodonts are an extinct group of primitive meat-eating mammals, but these fossil predators behaved very much like big cats of modern times and had several saber-toothed varieties, an adaptation for killing large prey that was to reoccur over and over in successions of later predatory species.16 Fossil creodonts and their prey have been unearthed in an area called the Fayum, a fossil-hunter's paradise located in Egypt not too far from Cairo. The Fayum contains fossil primates from the Oligocene epoch, dating in age from 25 to 30 million years. When paleontologists measured puncture marks on Fayum Oligocene fossil primates, they found many tooth holes in skulls and long bones, evidence to the paleo-detectives that the primates had died at the hands (or rather teeth) of predators. Due to this simple forensic device, it was concluded that the creodonts preyed and/or scavenged on these primates.

Relative sizes of fossil cats and bears from the time period 8.5 million to 1 million years ago. Each square measures approximately 20 inches on each side; three squares equal 5 feet. From left to right: giant cheetah (Acinonyx); saber-toothed cat (Machairodus); ancestral leopard (Paramachairodus); bear (Indarctos); saber-toothed cat (Homotherium); saber-toothed cat (Megantereon). (C. Rudloff, redrawn from Turner 1997)

Relative sizes of fossil cats and bears from the time period 8.5 million to 1 million years ago. Each square measures approximately 20 inches on each side; three squares equal 5 feet. From left to right: giant cheetah (Acinonyx); saber-toothed cat (Machairodus); ancestral leopard (Paramachairodus); bear (Indarctos); saber-toothed cat (Homotherium); saber-toothed cat (Megantereon). (C. Rudloff, redrawn from Turner 1997)

We totally agree so far, but this is where we think the detectives lost the trail. Based upon their assumption that predation on living primates is a rare event (a paradigm we're trying our best to undermine), the paleo-detectives concluded that it must also have been rare 25—30 million years ago. The case against the creodonts was dismissed on the evidence that only 9—10% of the primate fossils examined showed evidence of death from predation.17

Hey, that's no small percentage of predation! A 9—10% predation rate is exactly the impact today's large carnivores inflict on the great herds of grazing animals migrating through the Serengeti in East Africa.18 And the Serengeti ecosystem, of course, is the quintessential example of predator—prey interrelationships. Twenty-five to 30 million years ago, the creodonts were having exactly the same effect on the demographics of primate prey as lions and hyenas have on wildebeest, zebra, and gazelles today.

As we move closer and closer in the fossil record to the 7-to-10-million-year mark that may pinpoint when apes and hominids split from a common ancestor, we encounter more evidence of predation in the form of those perfect round holes into which predator fangs will fit. To cite one example: standing on the figurative doorstep of the hominid lineage during the Upper Miocene epoch (approximately 7—10 million years ago) is an extinct primate skull evidencing such bitemarks; these holes—once again—fit the canine teeth of a fossil felid the size of a modern leopard.19

Saber-toothed cats may have used their teeth to stab prey in much the same downward motion as a person would use a knife. (C. Rudloff, redrawn from Turner 1997)

If we cross that figurative fossil doorstep and enter the time zone of the hominids—the Pliocene and Pleistocene epochs that began 5 million years ago and ran until just 10,000 years past—we find more and more evidence of predation on human and non-human primates. At this point in time there were a lot of cats sporting a lot of very long teeth. You might call it the heyday of cats; in fact we don't have nearly the number of cat species in existence today. The large cats that currently exist represent just a few species lucky enough to have survived a dramatic change in world climate about 1.8 million years ago.

Who were the cat predators that lived with, around, and on the early hominids?20 First and foremost, there were the "true" saber-toothed cats. These true sabertooths used their teeth to stab prey in much the same manner that a person would hold a knife in hand and jab with a downward motion. Those long teeth were too delicate to sever spinal cords or inflict other killing bites used by today's robust-toothed wild cats. Instead, the super-sized sabers were used to slice into soft flesh and rip apart prey animals so they would die of massive blood loss.

Machairodus—one of the saber-toothed cats of Africa and Eurasia— had very elongated and stout upper canines with fine serrations. This species was stoutly built and stood about 4 feet tall at the shoulder. Certainly one of the most successful of the saber-toothed lines, individuals in the genus Machairodus roamed large areas of the world for an incredibly long stretch of time (earliest fossils are dated at 15 million years and the most recent ones are 2 million years old).

Homotherium, a lion-sized saber-toothed cat with impressive upper canines serrated like a steak knife, is often called the "scimitar-tooth cat" due to its broad saber-canines. It also possessed long, slender legs adapted to the pursuit of prey. Three separate species of a cat smaller than Homotherium (but still at 200 pounds, larger than modern leopards) were known as Megantereons. The saber-toothed canines of Megantereons were long, slender, dagger-shaped, and devoid of crenulations. These cats show a bit of an innovation for protecting those slender daggers—a bony flange right on the chin protruded from Megantereons' lower jaw. It was covered with a fleshy pad, and the cat's delicate fangs nested on either side of this protective device. Megantereons' limbs were short and robust, and great strength lay in powerful front paws that probably made them quite adept at climbing trees. While Homotherium was fleet-footed, Megantereons was the sumo wrestler of the ancient cat world.

In North America, Smilodon (of Rancho La Brea tar pit fame) was the ultimate in saber-toothedness—its teeth evolved to the maximum size of any known true cat. Just how long were those teeth? Extremely long. To give you a sense of just how long extremely long is, African lions have canines that measure 2 and one-half inches; Smilodons' were in excess of 6 inches in length. This snow leopard—sized predator was built like a Mack truck; powerful limbs and lower back speak to the fact that it did not chase its prey but waited in ambush for mega-herbivores. The enormous gape allowed it to tear out the throat of its prey with blade-like teeth. Being a North American species, Smilodon (sometimes referred to as a dirk-toothed cat) naturally did not interact with the earliest hominids. But it survived until 9,500 years ago, thousands of years after humans advanced into the North and South American continents. As Hans Kruuk commented, "it was around for long enough for it to have seen a good deal of primitive man, and vice versa." (An extinct North American cheetah and lion also survived until between 10,000 and 20,000 years ago.)

Any comparison of saber-toothedness quickly decays to the point of ridiculous relativity: they all had gargantuan teeth! However, another group of felids have been deemed false saber-toothed cats. At least four species of Dinofelis are called "false" sabertooths because their upper canines were not exaggerated to the degree of the true saber-toothed cats, although both upper and lower canines were still more developed than modern-day lions and tigers. The fangs in the Dinofelis group are not as curved as the true saber-toothed cats; they appear to have been more like straight-edged daggers. Size-wise, the false sabertooths were heavily built animals. With heavier front than hind limbs, they may have been midway in size between a modern-day leopard and lion. A particularly fine, intact skull dated at 1.5 million years ago was found at Kromdraai in South Africa, a site also yielding australopithecine remains. Some paleontologists classify one of the false saber-toothed species, Dinofelis barlowi, as a potential specialist at baboon and hominid killing.

Starting at about 3.5 million years ago the direct ancestors of today's lions, leopards, and cheetahs (called the conical-tooth cats) existed alongside the saber-toothed varieties. Panthera is the taxonomic classification containing all today's modern large cats except the cheetah. The epochs spanning the time between 5 million and 10,000 years ago sported a much wider range of pantherine species than exists today. The oldest fossil record of a lion is dated at 3.5 million years and was found at Laetoli in Tanzania where the famous trail of Australopithecine afarensis footprints were discovered. The first record of the extant leopard is also from this same site.

Many species of lions, leopards, and cheetahs did not survive until the present day. One example is the European cave lion. There's a cave by the name of Chauvet in the south of France that contains drawings of 73 cave lions; the drawings can be dated by carbon decay at precisely 32,000 years ago because piles of the charcoal used to make the drawings still lie on the cave floor as if the artist had just stepped away for a moment. The European cave lion was a different species from lions that now roam Africa; it might have been a quarter again larger and heavier than the modern variety. Some of the charcoal drawings at Chauvet are exquisitely accurate in detail and exhibit a fine-tuned knowledge of wildlife behavior, while others are obviously meant to be surreal depictions of a beast that was probably both a dangerous predator and a competitor of human hunters for large herbivores— European bison, mammoths, and giant elk.

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