Are Primates Really That Similar to Humans?
Most people are aware that primates are the closest living relatives to humans. Chimpanzees, gorillas, gibbons, orangutans and other monkeys all have unique characteristics, but together we are all part of the same order of mammals, Primatomorpha.
This distinct order of primates has evolved in different ways, but their behaviors and even their looks reveal some similarities to modern humans. When it comes down to the finer points — certain habits, emotions, reactions and physical developments — what’s the truth about how similar we are to primates?
How Were Humans and Primates First Linked?
As a species, we have come a long way in 25 million years. Evolutionary specialists, starting with Charles Darwin, have suggested humans evolved from other animals around 150 years ago. This theory was met with indignation by some people, but as more scientific evidence was studied, the similarities between humans and primates became too much to ignore.
From familial behaviors, patterns of learning and tendencies to hunt for food to their desire to provide for others in their group and even show human-like emotions (loneliness, happiness, etc.), humans and primates have a lot of obvious things in common. Taking it to a biological level, archaeological evidence also shows that primate skeletons look remarkably similar to human skeletons throughout the various stages of evolution.
Are Our Brains Alike?
Modern human brains evolved to be larger than primates, but our brains are structurally similar to that of a chimpanzee. And we're not just talking about skull shape. We're talking about cortical areas of reasoning, abstract thought and problem-solving.
In essence, if our primate cousins had the physical ability to speak our language — their mouth and vocal cords aren't developed like ours — then they could talk to us about love, heartache, irritation and happiness. They might even have a sense of humor and tell us jokes!
What Other Physical Similarities Do We Have?
Sticking to the physical similarities for now, one of the most obvious similarities is that most primates can walk on two legs, just like humans. Their feet are more hand-like, which allows them to more easily jump and swing through their natural tree-based habitats. They also use their actual hands for many of the same things that humans do.
This includes gesturing to others, eating, grooming and even pointing and using rudimentary tools. As studies continue into their behavior, we may discover that humans’ similarities to primates go far beyond our genetic make-up.
Which Primate Is Most Similar to Humans?
In terms of physical characteristics and behavior, the chimpanzee is the most similar primate to humans. Geneticists say that chimps share about 98.6% of their DNA with humans. This is significantly more than monkeys and other great apes.
A study from Science Daily found that chimpanzees share 60% of their personality traits with humans too! This includes things like openness (honesty), extroversion and agreeableness. Of course, humans and chimps don't have tails like many other primates, although some humans might agree that a tail would be a pretty cool physical addition!
Who Conducted the Earliest Studies?
Naturally, when humans became more interested — and more convinced — in the similarities between primates and humans, experiments began in a new field of study known as primatology. Many early studies didn’t follow acceptable practices to get answers, but science has come a long way, and many ethical studies in recent years have produced some fascinating results.
Jane Goodall is one of the leading specialists in primatology. She moved to what was then Tanzania in 1960 at the age of 26 to learn more about chimpanzees. Studying these primates became her life’s passion, and she spent more than 55 years observing their unique and individual personalities.
Did Primates Travel in Space?
Sadly, the similarities between primates and humans are so significant that primates were sent into space as test subjects to see if humans could survive the travel conditions. The first primate astronaut, a rhesus macaque called Albert, was sent up to an altitude of 39 miles in a rocket ship in 1948 and died from suffocation.
A year later, Albert II was sent on a similar flight, and the parachute failed. The first monkeys to survive space travel were Able and Miss Baker, a squirrel monkey and a rhesus macaque, who made it back alive in 1959. They flew at an altitude of 360 miles aboard a Jupiter rocket.
Do They Have Emotions Like Us?
Humans convey so much through their facial expressions, and those expressions are seen as uniquely human attributes to convey when we’re happy, sad, angry, excited and more. Primates don't have the same range or the same in depth meaning for facial expressions, but they do have other ways of showing their emotions.
While a chimp's fierce, teeth-baring "smile" is obviously a sign to go away and leave them alone, a slight grimace with the mouth corners pulled back usually shows subservience. Most other expressions are vocalized with grunts, shrieks and hoots as well as body language.
Will Primates Do Tricks or Trade for Food?
What better way to bribe someone than with food? Humans are guilty of promising their children food treats as rewards for good behavior, and monkey trainers — and all kinds of other animal trainers — often enjoy great success using food as rewards during training.
Primates have also been observed to understand the concept of using currency in exchange for food. A study at Yale New Haven Hospital trained capuchin monkeys to exchange silver discs for grapes — but that wasn’t all they learned. The researchers were stunned when female monkeys started exchanging sex to get silver discs from male monkeys so they could get more grapes!
What About Junk Food?
Unfortunately, primates seem to have developed the same affinity for junk food as humans. In parts of India and Africa where fast food joints have cropped up over the years, wild primates have been observed rooting through trash to find leftover chips and fried chicken to munch on.
Like humans, primates also prefer cooked food. In a Harvard study, researchers found that chimpanzees understand that the taste and composition of foods change during the cooking process. If given a heating apparatus, they learn to cook foods like meats and potatoes and appear to prefer it.
Do They Know Right from Wrong?
The ability to distinguish between right and wrong is considered to be a concept that is unique to humans and learned in the formative childhood years. However, studies like one conducted by the University of Zurich show chimpanzees are well aware of what behaviors are appropriate.
Part of the study showed that if a chimp watched scenes of a baby chimp being harmed by another chimp, it showed signs of anger and defensiveness. However, if the chimp saw adult chimps fighting one another, the reaction wasn't the same. This showed they knew it was wrong for a stronger adult chimp to hurt a defenseless youngster.
Do Primates Recognize Faces?
Remarkably, primates have been observed to recognize their own faces when they are handed a mirror and look at it, which is something very few other animals can do. This shows that primates do have a sense of self like humans do.
Additionally, primates can also recognize their friends in photos. A study published in the Proceedings of the National Academy of Sciences showed that capuchin monkeys could identify members of their "in-group" on a touch screen when displayed among similar looking members of an "out-group."
Can Primates Understand Humans?
So, we have established that primates, particularly chimpanzees, do indeed experience the world similar to the way humans do. Using similar senses as our own, including touch, hearing, smell and sight, they enjoy food, fun, social interaction with friends and many other things considered "human."
Although their mouths and vocal cords aren't formed to speak like humans, they exhibit similar body language and an ability to read human facial expressions and decipher vocal pitch, which helps them understand what we are trying to express. Many primates have been observed to learn certain words and commands too.
Can They Learn Sign Language?
Among their own social groups, primates use vocalizations and body language to communicate with each other. This includes hugging, grooming, patting, hand-holding and fist-shaking. Even more impressive, they can use body language and sign language to communicate with humans. Koko the gorilla is probably the best-known example of a primate that was taught sign language.
She knows around a thousand signs and shows a good understanding of spoken English. It is estimated that Koko has an IQ level of up to 95 — the average human IQ is 100. Like many of us humans, she is also a fan of kittens!
What Makes Primates Laugh?
Primates have been observed to show a range of positive emotions, from relaxed facial expressions to bursting into laughter and rolling around on the floor! As laughter signals a sense of humor and understanding that something is funny, it’s remarkable that this trait is shared between primates and humans.
Chimpanzees laugh when tickled by other chimps, animals or humans. Interestingly, their ticklish spots are usually the same places as humans: near the underarms and belly. Primates have also been observed to laugh when playing, chasing and wrestling.
How Do Primates Learn?
Just like us humans, the formative years of a primate's life are all about learning. In particular, the first five years of a chimp’s life are the most important time for learning, and they do it through play, copying relatives — especially their mother — and socializing with other chimps.
Not only does this learning build on the innate tools for basic survival — finding food, getting shelter and so on — but primates also learn new things that are useful. This includes learning how to use new tools to access food and, as mentioned above, learning how to cook.
Do They Have Playmates?
Human children spend hours running around playing and having fun — and so do the adorable babies of primates. For most animals, playful behavior such as play fighting is a kind of practice for real-life, adult situations.
However, scientists at the University of Pisa discovered that primate babies and young adults play purely for the fun of it and have playmates that help them form stronger social relationships as well as better attitudes toward being part of a community. Also, like human versions, primate games have been known to have a competitive edge, particularly as they start to get older.
Do Primates Play with Toys?
Primates have been observed to play with sticks, stones and other things in nature. When given human toys, they relish the opportunity to play with them. In a remarkable study conducted by Kim Wallen, a psychologist at Yerkes National Primate Research Center in Atlanta, Georgia, rhesus monkeys actually chose gender-specific toys.
The primates were offered "masculine" wheeled toys, such as toy cars, and more "feminine'" plush toys, such as dolls. In general, the male monkeys opted to play with wheeled toys over the dolls. Interestingly, the female monkeys played with both kinds of toys.
Do Primates Get Angry Like Humans?
It has been regularly observed that primates can become angry and irritated, which is a typical fear or dominance response. Furthermore, primates, particularly chimpanzees, are the only species besides humans that have been observed in studies spanning 50 years to make coordinated attacks on other members of their own species.
This is akin to starting a war. As with humans, this is often done as a territorial strategy, with predominantly males showing aggression toward males from rival communities nearby. Chimps can also make and use weapons from stone and sticks.
Do Primates Express Control and Calm?
Biologists in the U.S. studied primates by using a game of "Ultimatum" and discovered that they share the same aversion to injustice as humans do. In the game, where equality prevails over benefits, the chimps would make fair offers and only accept fine and egalitarian offers from their peers.
This is ultimately because cooperation benefits them and their wider community. It also shows that given a choice, primates will choose fairness and consideration over resorting to violence, showing that they know when to calm themselves and when to encourage measured choices and reactions.
Do They Get Protective Like Humans?
Monkeys do indeed get highly protective. This often applies to basic things such as food and environment, including not allowing other animals or rival primates to invade their territory and steal their food. Most significantly though, it applies to their protectiveness of their young. Adult primates have been known to kill young primates, either as revenge, an act of cruelty or elimination of a perceived threat.
Therefore, mothers often form socially monogamous pairs to protect their young from violent fathers. In these pairs, the males can mate with other females but then live as a socially monogamous duo with just one other female.
Do Primates Like to Cuddle?
Primates that are classed by primatologists as being more "socially competent," such as bonobos, use cuddles and affection to calm others in distress. Along with other sympathetic reactions studied in bonobos, this leads to them being nicknamed the "empathetic apes."
The findings published in PNAS described footage where young or teen apes rushed over to their younger peers who were screaming and upset after being attacked — just as human children do. What's more, the bonobos that received comforting cuddles were more likely to emotionally recover from emotional distress more quickly than others that didn't get a cuddle.
Do Primates Pair for Life?
When it comes to choosing a friend or partner, studies from the University of Vienna found that primates can be quite selective. Like humans, they often choose a partner who shares similar personality traits, such as shyness or bravery, and are naturally drawn to the most social primates in order to better fit into the community.
When it comes to pairing for life, however, individual ape species are quite different. Gibbons are monogamous, which means they pair for life, at least to some extent. Shockingly, there are sometimes instances of infidelity! Chimpanzees, on the other hand, can be quite promiscuous, leading to the next question.
What About Sex?
With primate behavior being so similar to human behavior in terms of socialization, power struggles and a whole load of emotions, it’s not surprising there are similarities in our sex lives. Primates have been observed engaging in deception to get what they want, including the attention of a female, and sometimes even apologize to the injured party if they cause upset.
More importantly, primates don't just have sex for reproduction and dominance. They do it for their own pleasure. It has even been observed that both females and males sometimes seek self-pleasure.
Do They Mourn Like Humans?
Heartbreakingly, primates display significant signs of mourning when they lose one of their friends or family members. Due to their strong social bonds and their need for a strong community, there's an element of social preservation in play, but deeper than that, primates become visibly upset on a personal level when they lose someone close.
This is most significant when a mother loses a baby, and it’s easy to see that she understands that the baby has died. She will continue to carry it around and even groom it for a time until she is ready to say goodbye.
Their Memories Can Fade Like Humans
One element of being human is that no matter what we do to fight it, we know as we get older that we will experience inevitable deterioration with age. Of course, primates show physical signs of aging — aching joints, failing eyesight, etc. — but this also occurs with cognitive function.
The University of Kyoto tested the memories of young, five-year-old chimpanzees using number sequences. They found that the ability to recall the numbers was much better than for older chimps. This type of remembering is called eidetic memory. Like with humans, it functions better in childhood and young adulthood and declines with age.
Do They Have a Hierarchy?
As well as being aware of particular ways to act to gain and keep friends and maintain harmony in a group, primates use social skills to their advantage to gain prestige. If primates know what others in their community want and they act on that, they know they can gain more status.
There is always a pecking order in a group with a dominant male at the top, and that highest ranking member gets all the girls and makes the main decisions. His status is usually achieved by asserting aggression. There are often one or more alpha females in a group too.
Primates Get Excited by New Things
Just like human babies, primate babies are fascinated by the new world around them, and they want to touch, feel, taste and play with all sorts of things to figure them out — even if it means getting bitten by some red ants or knocked down by another monkey.
This excitement for novel things extends to adult primates too, who show significant interest and a desire to explore when shown something new from the human world, such as a television or a cool gadget. They will diligently try to figure out its use. This often comes back to the love of learning and the desire for social advantage that primates have.
They Use Important Learnings
An experiment in the 1960s showed that primates learn cause-and-effect concepts. In the trial, a group of rhesus monkeys learned that if they pulled a chain, they would get a serving of food. However, once a new monkey was introduced to the group, he started getting an electrical shock whenever the lever was pulled.
In true learning fashion, some monkeys discovered a separate chain that administered less food when pulled, but it never delivered an electric shock. Others stopped eating so they didn't risk shocking the new guy.
Are There More Studies on the Similarities?
Researchers are keen to learn more about the finer points of primates' emotional and social behaviors to see just how similar they are to humans. A study published in Science Daily last year looked at how monkeys communicate threats.
It described how wild sooty mangabeys made a certain vocalization when in danger from a snake attack. Initially, it was thought this was simply to warn family members, but when it was more closely investigated, the noise was different and was intended to inform wider group members about a potential threat, proving that primates express selflessness as well as self-preservation.
Can Humans and Primates Be Friends?
Human children tend to have the best success in befriending primates, indicating they can see the vulnerability and innocence of younger humans. National Geographic, for example, reported on a young boy in India, who was accepted into a group of gray langur monkeys.
Initially, it was thought the boy was teasing the monkeys, but, in fact, lightly tugging their tails and chasing them showed a similarity to the rough play of monkeys. This didn't harm either the monkey or the boy, as they sweetly leapt around, chasing each other and jumping on the boy's back.