A gorilla is an ape, not a monkey. Specifically, gorillas belong to the family Hominidae, the same taxonomic family as humans, chimpanzees, and orangutans. This group is commonly called the “great apes.” While monkeys and apes are both primates, they split from a common ancestor roughly 31 million years ago and have been on separate evolutionary paths ever since.
Why Gorillas Are Apes, Not Monkeys
The confusion is understandable because “monkey” gets used casually as a catch-all for primates. But in biology, apes and monkeys are distinct groups. Gorillas sit within the superfamily Hominoidea (the apes), not in the monkey families. Their closest living relatives are chimpanzees and humans, not baboons or macaques.
The simplest way to tell apes from monkeys: tails. Almost all monkeys have tails. Apes do not. A gorilla has no tail, and neither does any other ape. That single trait is the fastest visual shortcut, but the differences go much deeper than that.
Key Differences Between Apes and Monkeys
Monkeys are generally smaller, with narrow chests and bodies built for running along the tops of branches. Apes are larger, with broad chests and shoulder joints that allow a wide range of arm movement, including the ability to swing beneath branches. Gorillas are the largest living primates: adult males weigh an average of 300 pounds and can reach 500 pounds, standing up to 6 feet tall. Adult females weigh 150 to 200 pounds and stand up to 4.5 feet. Most monkey species weigh well under 50 pounds.
Brain structure also separates the two groups. Great apes, including gorillas, have significantly larger brains in absolute terms and show greater development in the prefrontal region, the area associated with complex decision-making and social cognition. This isn’t just about having a bigger head relative to body size. Research in evolutionary neuroscience has found that great apes stand out for their combined investment in prefrontal brain connectivity and overall brain volume, a pattern that distinguishes them from all other primates.
Gorillas also move differently from most monkeys. On the ground, they use a distinctive form of locomotion called knuckle-walking, placing their weight on the backs of their curled fingers rather than on flat palms. Studies of gorilla biomechanics show they distribute weight relatively evenly between their front and back limbs, using an energy-efficient pendulum-like mechanism. Most monkeys that spend time on the ground walk on flat hands and feet.
The Great Apes, Explained
The term “great apes” refers to the four genera in the family Hominidae: gorillas, chimpanzees (including bonobos), orangutans, and humans. Yes, humans are technically great apes too. There are also “lesser apes,” the gibbons, which are smaller and more distantly related but still tailless and classified as apes.
Gorillas themselves are divided into two species. The western gorilla lives in the lowland forests of central Africa, while the eastern gorilla is found in the mountainous and lowland forests of Uganda, Rwanda, and the Democratic Republic of Congo. Mountain gorillas, a subspecies of the eastern gorilla, live in dense forest, bamboo forest, and subalpine grassland across four national parks in those three countries. Both gorilla species are critically endangered.
What Makes Gorillas Distinctive Among Apes
Gorillas live in troops typically led by a single dominant male, called a silverback because of the band of silver-gray hair that develops across an adult male’s back. The silverback makes decisions about where the group travels and eats, mediates conflicts, and protects the troop from threats. Troops usually include several adult females and their offspring.
One of the most recognizable gorilla behaviors is chest-beating. A silverback rises onto two legs, cups his hands, and rapidly beats his chest, producing a deep drumming sound that can be heard from a kilometer away. Research from the University of Barcelona found that this sound is a reliable indicator of the gorilla’s body size: larger males produce lower-frequency beats. The display serves a dual purpose. Rival males can gauge a competitor’s size without risking a physical fight, and females can use the sound to assess potential mates. The full display often starts with short howl-like vocalizations, escalates to the chest-beating, and finishes with the gorilla running on two legs.
How Gorillas and Monkeys Are Related
Gorillas and monkeys do share a common ancestor, which is why both are primates. The lineage that would become apes diverged from Old World monkeys approximately 31 million years ago, during the Oligocene epoch. Asian and African great apes then split from each other around 18 million years ago. So while gorillas and monkeys are distant cousins, calling a gorilla a monkey is about as accurate as calling a human a monkey. Technically we share ancestors, but the evolutionary distance is enormous.
The relationship is often visualized as a family tree. Monkeys sit on one major branch (actually two branches: Old World monkeys in Africa and Asia, and New World monkeys in the Americas). Apes sit on a separate branch. Gorillas, chimpanzees, and humans cluster together on a sub-branch of the ape lineage, sharing a more recent common ancestor with each other than any of them share with orangutans or gibbons.