I think, therefore I harm
Many animals wore the name of Saber-Tooth, a generic name which once applied to any animal with long canines. Only one of these was a true cat. These beasts have often been represented in literature and movies, but most often as mythical creatures which don’t really resemble any animal which ever lived.
This second part of the series covers these animals, but emphasizes on the only one which truly deserved the name of Saber-Toothed Cat.
During early paleontology, when DNA was not known, animals found as fossils were classified based on physical characteristics. Animals with similar characteristics were assumed to be related. When dating fossils became possible, entire families and lineages were assumed when creatures with similar characteristics lived in successive periods. Full fossils are rare, and most often only fragments exist. Cranes, and more particularly jaws, happen to be the most frequent fragments found as these pieces more easily survived time. When fossils were found exhibiting long upper canines, they were assumed to be related and classified as different species of a same lineage. But as more fossils were recovered and methods to classify them improved, it soon became clear that all the animals previously classified as Saber-Tooth were in fact part of at least 6 different species, all unrelated.
Classifying species based on physical characteristics and age worked fine in most cases, because nature is very creative and rarely invent the same thing twice. While pretty rare, it sometimes happens that unrelated creatures develop the same traits independently. It may sound unlikely that 6 unrelated animals developed long upper canines, but it is in fact not surprising at all. Given the extremely large amount of carnivores that walked on our planet, it seems fair that, given a similar environment, some of them may have solved a similar problem with a similar solution.
Not very related to cats, the first group to feature the long canines was not even a mammal. The Synapsids, ancestors of mammals, were reptiles which evolved specialized teeth. Some featured the saber shaped canines.
Among the mammals, two Feliformia (cat like) and two marsupials (the family including today’s kangaroos and koalas) showed the long canines. The earlier of which appeared some 42 million years ago, and the last one got extinct 7 millions years ago.
Only one true cat ever evolved long superior canines, and we are coming to this.
As we have seen last week, the Felidae family includes all animals classified as true cats, including today’s felines. It began with Proailurus about 30 millions years ago, giving rise to Pseudaelurus 5 to 10 millions years later. Pseudaelurus is thought to have given rise to two subfamilies, one of which is Machairodontinae. This extinct family first appeared in Africa nearly 20 million years ago, but spawned many species in Eurasia and the Americas. Contrary to a popular belief, these cats are not ancestors of modern cats. A recent DNA study confirms that both subfamilies have a common ancestor, but are from a different lineage.
Machairodontinae had body and legs proportions similar to modern cats, though on closer inspection their legs appear somewhat shorter. However they were generally more massive. They had a very short tail, large paws and retractable claws. They had somewhat longer upper canines. Their size ranged from lion to lynx.
Because of their heavier mass and short tail, Machairodonts probably couldn’t climb in the trees. They were land cats.
One of the later species of Machairodonts was Smilodon, appearing some 2.5 million years ago in North America. Initially about 55 kg / 120 lb, it grew in size and weight. The later Smilodons reached 150 cm / 60 in at the shoulder and weighted up to 360 kg / 790 lb. Some individuals may even have been nearly 500 kg / 1100 lb. They were the largest cats to ever live. Their general shape looked more like bears than modern cats.
Smilodon is famous for its very long upper canines, which reached 30 cm / 12 in, giving it its appropriate surname of Saber-Toothed Cat. These teeth were so long that they couldn’t fit in the mouth when it was closed, and instead protruded on each side of its lower jaw. Smilodon could open its mouth 120 degrees, about double that of modern felines, which was necessary to accommodate eating with such long teeth.
Despite popular view and imagination surrounding these long canines, they probably didn’t make Smilodon a better predator, and if anything probably was in the way for many of the hunting techniques which we know about other cats. The long canines made the Smilodon a specialized predator, as it was probably not able to catch anything smaller than itself. Its preys had to be either its size or larger. In fact, protein studies in fossils reveal that Smilodon’s meals were composed of bison, tapirs, deer, camels, horses, mammoths and mastodons, all large preys.
Modern cats have conic canines, which make them very strong and resistant. They use these canines to hold their prey, but otherwise these teeth have little role to kill or eat. Instead, their molars, the larger teeth located on each side of the mouth, have a double role, used by the cats to crush the throat of their larger preys until they suffocate and die, and to cut the meat into pieces to eat it.
On the other hand, the saber-like canines of the Smilodon were not conical, but were instead flattened. That characteristic made their canines fragile. Smilodon could not use them to catch or hold their prey, in the same manner as the modern cat, as their teeth would break. While some fossils have been found with a broken canine, these were rare. Also, much strength would have been required to push the canines within the throat of their preys. For these reasons, it is unlikely that Smilodon caught its preys at the throat like modern cats do.
To make room for the long and large canines, all of the other side teeth had to move backward and less room was left for jaw muscles. Smilodon had a weak bite, estimated to be about a third of the strength of the lion’s jaw. To compensate for this, however, Smilodon had very strong neck muscles, which could have allowed it to pull its head toward its stomach to compensate for their weak jaw. This technique might have helped Smilodon eating harder and larger preys, but could not have served for hunting.
It is thought that Smilodon did not use its teeth for hunting, and instead made use of its heavy body to catch and hold preys to the ground. Once preys were maintained immobile, Smilodon would then have been able to kill them by either stabbing or bleeding them with its canines, and possibly biting into softer parts of their bodies.
Smilodon was probably a social animal, hunting in packs, more like wolves than cats, as it is unlikely that it could have caught very large preys such as mammoth as solitary animals. Another clue is that many fossils showed broken and healed bones. A broken bone requires that an animal be immobile for several weeks or even a few months, preventing it from hunting. A solitary Smilodon would have died, but the fact that many of them healed completely indicates that other cats probably brought them food, or at least let them join their meal by crawling to it.
Smilodon was among the last few species of Machairodonts, but went extinct about 11,000 years ago, soon after the end of the last glaciation. That period also saw the extinction of most of the megafauna, the group of very large animals common around the world until then.
Glaciations, over the last few millions of years, have been a fairly regular occurrence, about every 10,000 to 12,000 years. It is generally accepted that this one glaciation was not the direct cause of the mass extinction which afflicted the megafauna at that time, as these animals had survived many more before. While it had been previously thought that the last glaciation was more important than the preceding ones, it is now thought that it was in fact very similar and did not make significant changes to the overall environment.
A more probable cause for the mass extinction of the megafauna would have been the major population boom of humans which occurred at the end of the glaciation. It is unlikely that humans hunted Smilodon directly, but we are known for having contributed to the extinction of mammoth through extensive hunting, and we probably hunted other large animals as well. Smilodon, being specialized for large preys, couldn’t adapt to the disappearance of the megafauna and gradually went extinct as its preys became scarce.