At first glance, primates like this baboon (left) may seem similar to great apes like this gorilla (right), but experts say the two groups are quite different. (Photo by Mark Guitard and Mark Newman via Getty Images)
At the initial stage, the comparison of monkeys and apes seems quite simple: modern primates have characteristic physical features and behavioral aspects that clearly separate them into separate groups.
Starting with living things, these differences are easy to see. Most monkeys have tails; some have prehensile tails, which allow them to grasp and hold objects. These animals walk on all fours, making them quadrupeds. Their limbs are about the same length, and they have flexible spines.
Monkeys can be classified as Old World and New World primates based on where they live. Old World monkeys live in Africa and Asia, while New World monkeys are found in Central and South America, according to the Pan African Sanctuary Alliance. Old World monkeys are also known as Afro-Eurasian monkeys, while New World monkeys are known as Neotropical monkeys.
In contrast, apes do not have tails. Their “upright” anatomical plan allows them to stand upright and has disproportionate limbs with long arms and short legs. In contrast, humans – who are also apes – have long legs and short arms. Apes also have a larger brain size relative to their body mass than monkeys, which plays a key role in their intellectual abilities.
“There is a marked difference in intelligence between monkeys and apes,” Becky Malinski, curator of primates at the Smithsonian’s National Zoo and Conservation Biology Institute, wrote in an email to Live Science. “While monkeys can display complex thinking, their cognitive abilities are generally lower than those of great apes.”
Apes can be classified as great apes or small apes based on their size. Great apes include chimpanzees (Pan troglodytes), eastern gorillas (Gorilla beringei), western gorillas (Gorilla gorilla), and bonobos (Pan paniscus) — all of which live in Africa — and orangutans (Pongo), which are found in Southeast Asia. Small apes include gibbons and siamangs, which are found in Southeast Asia. Although humans are also considered great apes, this article focuses on nonhuman primates.
Monkey vs. Monkey Genetics
However, if you delve deeper into the evolutionary history of apes and hominids, the differences between them become even more blurred.
“On the surface, this might seem like an easy topic to talk about,” Sergio Almecija, a senior research scientist in biological anthropology at the American Museum of Natural History in New York City, told Live Science. “But that superficial perception, I think, is based solely on modern animals.”
According to a 2021 study published in the journal Science, of which Almesia is the lead author, humans diverged from apes — specifically chimpanzees — between 9.3 and 6.5 million years ago.
But monkeys and apes diverged from their last common ancestor much earlier: between 23 and 34 million years ago, according to a 2013 paper published in the journal Nature. The authors analyzed the oldest known fossils of Old World monkeys and primates found in the Rukwa Rift Basin in southwestern Tanzania: a partial jawbone with three teeth from an ape and a single molar from a primate. The team classified these new primate fossils, naming the ape Rukwapithecus fleaglei and the ape Nsungwepithecus gunnelli. Geological dating of the rock layer in
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