Chimpanzees and You: How Are You Related?

Did you know that when you visit the zoo and see the great apes, you are visiting animals that are related to you? Humans and other great apes have a common ancestor that existed millions of years ago. A common ancestor is an individual that you and one of your relatives are descended from. For example, dinosaurs, which lived in the past, are ancestors to today’s birds (Figure 1). These relationships are explained by evolution, which tells us that all living things developed from other living things, over millions of years.

Humans, chimpanzees, gorillas, and orangutans are all considered great apes. Scientists group them together because all the great apes share similar traits, but each species also has its own unique traits. Two traits shared across great apes and humans are hands that can grasp things and brains that are large relative to body size. There are many more similar traits, too. Humans also differ from other great apes in that we walk on our feet, we possess language, and we are much less hairy, for sure! Another big difference between humans and other great apes is how long we live. The average human lifespan is about 70 years in the USA [1], while many chimpanzees in captivity do not live past 50 years [2]. What does that mean for how humans and other great apes mature and age? Comparing the pace of development and aging in humans and chimpanzees can reveal both how we are similar and how we differ from great apes. This work will help us to better understand how human biology and behavior are different compared with chimpanzees.

There are big differences in the speed of development across species. People often talk about how quickly dogs mature, because many of us grow up with dogs and we see them every day. We can appreciate how fast they grow and age compared with us (Figure 2). If you got a puppy when you were very young, you may have watched your dog develop gray hair and have difficulty moving around, while you were still a child. It is easy to see that animals like dogs develop and age at a different pace than humans do. But, until recently, we knew very little about how the pace of development and aging in humans compared with great apes [3]. Therefore, researchers collected a lot of information to compare the speed of development and aging across humans and chimpanzees, to find out how old humans are in chimpanzee years.

How Old Are You in Chimpanzee Years?

There are many changes in the brain and behavior that are similar in both humans and chimpanzees as they age. Humans and chimpanzees both open their eyes, crawl, walk, and lose their baby teeth. The cells of both species contain proteins, DNA, and RNA that change with age. Let us keep in mind that individuals within each species vary in terms of when age-related biological and behavioral changes occur. Nevertheless, scientists can gather information on the average age at which brain, body, and behavioral changes occur, to find out how old people are in chimpanzee years.

Collecting more than a hundred of these time points reveals how the speed of development and aging compares between humans and chimpanzees (Figure 3) [3]. Around birth, chimpanzees and humans are pretty similar in their maturity. That means that, when you were born, your age basically matched that of a chimpanzee that was also close to birth. A human that is about 12 years old matches a chimpanzee that is about 11 years of age. A human in their 50’s matches a chimpanzee in its 40’s. Overall, the speed of development and aging in humans is surprisingly similar to chimpanzees, although humans take slightly longer to mature and age than chimpanzees do. Another important observation is that chimpanzees rarely live past their 40’s (which corresponds to humans in their 50’s). Humans, in contrast, can live past their 80’s. So, that is a phase of human life with no clear match in chimpanzees. Understanding how long humans and other species live, how quickly they develop, and how they age can teach us important things about human aging [2].

Do Chimpanzees Age Like Kids Do?

As people get older, they can still do many of the things they enjoy, like their favorite hobbies and play with their grandchildren, but their activity levels may decrease, and they are also more likely to get sick. Maybe one of your grandparents has experienced eye, heart, or lung problems; difficulty walking; or problems remembering things. You may know an elderly person with Alzheimer’s disease, which causes people to forget many of the things that are important to them. People in the advanced stages of Alzheimer’s may forget how to do simple things like cook an egg or button a shirt. Alzheimer’s is a devastating disease that affects the ability of older people to care for themselves.

Chimpanzees have shorter lifespans than humans, so many of them miss out on both the fun and the devastating illnesses that humans may experience in old age. We do not quite know what most chimpanzees die of in the wild, but one study found that many chimpanzees die of heart disease in captivity [4]. The short lives of chimpanzees mean they have less opportunity to interact with their grandchildren. This may seem sad, but chimpanzees also have a different family structure than humans do, so the lack of grandparents does not affect their lifestyle. Chimpanzees do show signs of Alzheimer’s disease [5], but few chimpanzees should experience it as severely as humans do. Our study suggests this happens because chimpanzees do not have as long of a lifespan as humans [5, 6].

Do you think that it is good that chimpanzees are less likely to experience age-related diseases? Is it cool that humans can live to such an advanced age? The next time that you visit the zoo, think about the differences and similarities between you and your primate relatives, and how amazing it is that humans can live for such a long time.

Glossary

Great Apes: ↑ A group of animals that includes gorillas, orangutans, chimpanzees, and bonobos—animals known for their big brains, opposable thumbs, intelligence, tool use, and close relationship to humans.

Common Ancestor: ↑ A relative like a great-great grandparent that animals or plants shared many years ago.

Species: ↑ A group of individuals that resemble each other and can make babies together. For example, cats are a different species than dogs because cats cannot make babies with dogs.

Alzheimer’s Disease: ↑ An incurable disease that impacts the brain and behavior, mostly in older people.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

Some of this research was originally funded by COBRE NIGMS (5P20GM103653), DE-INBRE pilot grant (P20GM103446), to CC and NICHD R21 (7R21-HD101964-02) to CC. Some of the figures were made with www.Biorender.com. The authors asked chatgpt how to explain complex concepts to a broad audience. Some images are modified from freepik.