Chimpanzees are our closest relatives in the animal kingdom, genetically speaking. We share between 95 and 98 percent of DNA with them. Like us, they use tools to achieve their goals, laugh with one another and form social groups. Even though we've been studying them for decades, we're constantly learning new things about them, much in the same way we learn new things about ourselves.
Here are several things we've recently learned about chimpanzees that reinforce just how similar we are.
1. Chimps and humans may share an ancient body language. A 2018 PLOS Biology study analyzed gestures made by both chimpanzees and bonobos — closely related members of the great ape family — and found a 90 percent overlap, far more than would have been possible by chance. These gestures included flinging hands to shoo another ape away or stroking the mouth of another ape to indicate the ape wanted the other animal's food. Interestingly, humans are able to understand what many of these gestures mean as well, indicating that perhaps the gestures were used by our last common ancestor. Another study supported this finding and showed that toddlers between the ages of 12 months and 24 months share nearly 90 percent of gestures such as jumping, hugging, stomping and throwing objects.
Additionally, chimpanzees have been observed using 58 different gestures to communicate with each other. A team of international researchers studied video footage of wild chimpanzees at Uganda's Budongo Forest Reserve and recorded 2,000 examples of these gestures. Commonly-used gestures represented short phrases and meanings, while longer gestures were broken up into smaller gestures similar to how the human language has longer words that are comprised of multiple syllables.
2. Chimps warn their friends of danger. Chimps live in dangerous spaces, but fortunately they have each other's backs. Warning of danger isn't uncommon within chimp groups, but a 2014 Science Advances study found that chimps will adjust their warnings based on the information they perceive other chimps have about the threat. Chimps will make alarming vocalizations and gaze at a threat and then back at their group until other chimps see the threat. If they believe another chimp is unaware, their vocalizations and gestures become more urgent. Additionally, the study found that chimps will give more warnings about threats to chimps who are relatives or friends.
3. Chimps will wage war. In 1974, Jane Goodall observed a splintering between a group of apes in Tanzania's Gombe Stream National Park. Once a unified group, they split into northern and southern subgroups, and friendliness turned to violence. (Later research indicated that the split actually started in 1971 but came to a head in '74.) Over the next four years, the chimps fought over territory and deliberately killed one another, including an ambush of six chimps against one. While one group ended up victorious, their expanded territory pushed against the range of a third chimp group, prolonging the conflict. Goodall was shocked by the violence, and her reports were initially dismissed by some.
4. Chimps follow fashion trends. Social learning is common in chimps. They learn to make tools from one another, for instance, but they also pick up fashion tips. In 2010, a Zambian chimpanzee named Julie stuck a stalk of grass in her ear for reasons that no one has been able to ascertain. The rest of her group followed suit. This behavior was reported in a 2014 study published in Animal Cognition, but the researchers still couldn't figure out the purpose of the ear grass accessory beyond that it just looked cool.
5. Chimps can catch the common cold. In 2013, an outbreak of some kind of respiratory disease occurred in a group of chimps in Uganda's Kibale National Park. Five of the 56 chimps died due the disease. When the body of a 2-year-old chimp was recovered and autopsied, researchers discovered the cause: rhinovirus C, one of the primary causes of the common cold in humans. "Chimps seem to be genetically predisposed to have problems with this virus," James Gern, a coauthor of the study and a professor of allergy and immunology at the University of Wisconsin-Madison School, said in a 2017 statement. "The virus found in Betty was one that looked like it came from a human, and the level of virus in the lung was comparable to what we see in children."
6. Chimp will eat just about anything. For a long time we assumed chimps were herbivores, but it turns out that chimps are omnivores, meaning they eat both meat and plants. They use sticks to extract termites, which was when Goodall first observed the creatures eating something other than plants. Over half their diet, however, is comprised of figs, which can be filled with wasps. Chimps will also eat the meat of monkeys, in particular the red colobus monkey. They are willing to avoid gross things, however, according to a 2017 study published in Royal Society Open Science, including food with smells associated with biological contaminants.
In the video below, you can see chimpanzees at the Project Chimps sanctuary in Blue Ridge, Georgia eating a variety of vegetables, fruit, nuts and seeds.
7. Chimps have demonstrated signs of Alzheimer's. A team of researchers analyzed the preserved brains of 20 chimps that died between the ages of 37 and 62. They specifically looked at the regions that are damaged by Alzheimer's. They found that four of the 20 brains contained plaque made of a protein called amyloid-β and tangles of a protein called tau. Both of these are signs of Alzheimer's in humans. All 20 brains showed signs of "pre-tangles." Researchers didn't have records of changes in the chimps' behaviors, including severe dementia, but the presence of the proteins and the plaque suggest that it would have been possible for the chimps to experience such changes.
8. Chimp have stable personality types. In 1973, a group of researchers described the personalities of 24 chimps in Gombe National Park using the Emotions Profile Index (EPI), which assigns scores based on eight major personalities: trustful, distrustful, controlled, dyscontrolled, aggressive, timid, depressed and gregarious. Generally, females demonstrated more trusting natures, while males were more gregarious. Outliers, existed, however, including one female chimp named Passion who rated very high as distrustful, aggressive and depressed. (She and her daughter killed four infants belonging to another female.) In 2010, researchers returned to the park to gauge the personalities of 128 chimps using 24 different metrics, and found that personalities remained stable among chimps regardless of if they had been in the wild or in captivity.
9. Chimps may have rituals. A 2016 Scientific Reports study outlined the curious case of four groups of chimpanzees in West Africa that would throw stones at or into certain trees and then leave the rocks so they could repeat the process. The practice had nothing to do with foraging or with tool use. The authors suggest that the activity may be ritualistic in nature, while acknowledging that the very definition of "ritual" in this case is contested. The significance of the practice itself remains unclear but it opens up another avenue for understanding chimpanzees.
10. Chimps make a new nest everyday. Did you know that chimpanzee nests are cleaner than our beds? According to a 2018 North Carolina State University study, their nests are less likely to harbor fecal, skin or oral bacteria compared to human beds because they build a new nest daily — preventing bacteria from accumulating. Researchers also noted that they only discovered four individual parasites among a total of 41 nests they analyzed. So, chimps are sleeping peacefully in a nearly bug-free, bacteria-free nest.
Editor's note: This article has been updated since it was originally published in September 2018.