Most people have a special interest in the order of mammals known as primates, for the simple reason that most people (well, all people, actually) are primates themselves.01of 10
The Word Primate Means "First Rank"
Just how egocentric are human beings? Well, it's telling that "primate," the name employed for this order of mammals, is Latin for "first rank," a not-so-subtle reminder that Homo sapiens considers itself the pinnacle of evolution. Scientifically speaking, though, there's no reason to believe that monkeys, apes, tarsiers and lemurs-all of the animals in the primate order-are more advanced from an evolutionary perspective than birds, reptiles or even fish; they just happened to branch off in a different direction millions of years ago.02of 10
There Are Two Major Suborders of PrimatesGetty Images
Until recently, naturalists divided primates into prosimians (lemurs, lorises and tarsiers) and simians (monkeys, apes and human beings). Today, though, the more widely accepted split is between "strepsirrhini" (wet-nosed) and "haplorhini" (dry-nosed) primates; the former includes all the non-tarsier promisimians, and the latter consists of tarsiers and simians. Simians themselves are divided into two major groups: old world monkeys and apes ("catarrhines," meaning "narrow-nosed") and new world monkeys ("platyrhines," meaning "flat-nosed"). Technically, therefore, all human beings are haplorhine cattarrhines, dry-nosed, narrow-nosed primates. Confused yet?
Primates Have Bigger Brains Than Other MammalsGetty Images
There are many anatomical characteristics that distinguish primates from other orders of mammals, but the most important is their brains: monkeys, apes and prosimians have larger-than-average brains compared to their body size, and their gray matter is protected by comparably larger-than-average craniums. And why do primates need bigger brains? To process the information required to effectively employ (depending on the species) their opposable thumbs, prehensile tails, and sharp, binocular vision.
The First Primates Evolved at the End of the Mesozoic EraPlesiadapis is one of the earliest identified primates. Getty Images
The fossil evidence is still disputed, but most paleontologists agree that the first ancestral primates evolved during the middle to late Cretaceous period; a good early candidate is the North American Purgatorius, followed ten million years later by the more recognizably primate-like Plesiadapis of North America and Eurasia. After that, the most important evolutionary split was between old world monkeys and apes and new world monkeys; it's unclear exactly when this happened (new discoveries are constantly changing the accepted wisdo), but a good guess is sometime during the Eocene epoch.
Primates Are Very Social AnimalsGetty Images
Perhaps because they rely more on their brains than on their claws or teeth, most primates tend to seek the protection of extended communities, including male- or female-dominated clans, monogamous pairs of males and females, and even nuclear families (mom, dad, a couple of kids) unnervingly similar to those of humans. However, it's important to realize that not all primate communities are oases of sweetness and light; murder and bullying are distressingly common, and some species will even kill the newborns of other members of the clan.06of 10
Primates Are Capable of Using ToolsGetty Images
You can write an entire book about what constitutes "tool use" in the animal kingdom; suffice it to say that naturalists no longer claim this behavior only for primates (for example, some birds have been known to use branches to pry insects from trees!) Taken as a whole, though, more primates use more tools than any other type of animal, employing sticks, stones and leaves for various complicated tasks (such as cleaning their ears and scraping dirt from their toenails). Of course, the ultimate tool-using primate is Homo sapiens; that's how we built modern civilization!
Primates Develop at a Slower Rate Than Other MammalsGetty Images
Bigger brains are both a blessing and a curse: they ultimately aid in reproduction, but they also require an extended amount of time to "break in." Newborn primates, with their immature brains, would be unable to survive without the help of one or both parents, or the extended clan, over the course of months or years. Also, like humans, most primates give birth to only one newborn at a time, which entails a larger investment of parental resources (a sea turtle can afford to ignore its hatchlings, by contrast, because only one newborn out of a clutch of 20 needs to reach the water in order to perpetuate the species).
Most Primates Are OmnivorousGetty Images
One of the things that makes primates so widely adaptable is that most species (including great apes, chimpanzees and human beings) are omnivorous, feasting opportunistically on fruits, leaves, insects, small lizards, and even the occasional mammal. That said, tarsiers are the only primates to be entirely carnivorous, and some lemurs, howler monkeys and marmosets are devoted vegetarians. Of course, primates of all shapes and sizes can also find themselves on the wrong end of the food chain, preyed on by eagles, jaguars and even human beings.09of 10
Primates Tend to Be Sexually DimorphicGetty Images
It's not a hard and fast rule, by any means, but many primate species (and most species of old world monkeys and apes) exhibit sexual dimorphism-the tendency for males to be bigger, nastier, and more dangerous than females. (The males of many primate species also have differently colored fur and larger teeth.) Curiously enough, human beings are among the least sexually dimorphic primates on the planet, males outweighing females by an average of only 15 percent (though you can make your own arguments about the general aggressiveness of human males vis-a-vis females).10of 10
Some Primate Species Have Yet to Be DiscoveredGetty Images
Of all the orders of mammals on earth, you'd think that primates would be the best accounted for: after all, they're far from microscopic in size, and most human naturalists have a special interest in tracking the comings and goings of our closest relatives. But given the predilection of smaller primates for dense, remote rain jungles, we're only fooling ourselves if we think we've collected them all. As recently as 2001, for example, there were 350 identified primate species; today there are about 450, meaning that about a half-dozen new species are discovered every year, on average.