Human beings have an innate tendency to seek reflections of themselves, from identifying familiar facial features in animals to tracing ephemeral human shapes among the stars. So it’s not surprising then that we stare at gorillas and chimpanzees and see aspects of ourselves: the bestial, the innocent and the adorable.
So, are humans apes?
According to science, the answer is a firm yes. Humans and apes are closely related members of the primate family that share a lineage dating back 5-6 million years, with a genetic overlap of 94 to 99 percent. The connection between us, it seems, is far more profound than mere resemblance. So then why are we the ones standing on the free side of the cage?
Great Apes and Human Origins
Modern biology classifies apes into two major groups: lesser apes and great apes. Humans belong to the latter group, alongside orangutans, gorillas, bonobos and chimpanzees, while gibbons belong to the former.
Around 17 million years ago, the great apes splintered off from their evolutionary kin. Between 200,000 and 300,000 years ago, Homo sapiens emerged on the scene, and the species began its slow ascension toward global domination.
What truly set this particular strain of life apart? Physically, apes are virtually superheroes compared to us. For example, chimpanzees are roughly four times more powerful than the average human [source: ScienceDaily].
While humans lack the sheer power of the mighty chimp, our nervous systems exert much more control over our muscles, enabling us to execute far more subtle movements. Humans possess superior motor control, less body hair and a far more advanced brain.
Neuroscientists have identified substantially more intricate nerve connectivity in the human brain, as well as some things called spindle neurons. Also known as Von Economo neurons (VENs), these cells appear most frequently in areas of the brain associated with social emotions.
Why Did Apes Stop Evolving?
Under “social emotions,” you’ll find a whole Pandora’s box of human characteristics, including empathy, guilt and embarrassment. The consensus is that although humans have evolved socially from our last common ancestor, chimps and other groups of nonhuman primates have remained largely the same.
Our two species still share such bloody traits as male kin bonding and lethal territorial aggression. However, human males and females often share a deeper conjugal bond, creating family-based society. Chimps, on the other hand, have separate male and female hierarchies.
Such differences depend on often slight genetic details. While human and chimps share similar gene sequences, copy number variations can differ greatly, including code repetitions, deletions and backward sequences. Let’s compare it to something as simplistic as human names. On one hand, you have the name “Jim Morrison,” which is different from “Jim Jim Morrison,” “Morrison Jim” or The Doors singer’s anagram pseudonym, “Mr. Mojo Risin.”
Among humans, copy number variation can distinguish one identical twin from another and have also been associated with various diseases, such as AIDS [source: Fox]. In other words, it’s not just what the genes are, but how they’re expressed.
Why Are Humans Classified as Apes?
As researchers continue to delve into human evolution, the undeniable connection between humans and apes remains a fundamental cornerstone. Here are some of the reasons for our shared classification:
- Genetic similarity: Humans share a significant amount of their DNA with other great apes. For instance, we share about 98 to 99 percent of our DNA with chimpanzees, our closest living relatives.
- Evolutionary lineage: Fossil evidence indicates that humans and other great apes share a common ancestor. Over time, evolutionary branches led to the various great apes, including humans.
- Anatomical features: Humans and other great apes have several shared physical traits. For example, we are all tailless and have a similar arrangement of teeth. Our brains are also more developed compared to other primates, allowing for complex thought processes.
- Behavior and cognition: Humans and other apes exhibit advanced cognitive abilities. Tool use, social structures, communication methods and problem-solving capabilities are found in both humans and certain ape species.
- Shared family: The Hominidae family includes orangutans, gorillas, bonobos, chimpanzees and humans. Grouping organisms into families is based on shared characteristics and evolutionary history.
Primate Evolution: Climbing the Tree of Knowledge
Scientists believe that an explosion of genetic changes caused the lineage of the great apes to branch off from the lesser, tailed primates 17 million years ago. Then, between 4 to 7 million years ago, a similar genetic burst splintered humans off from the rest of the apes.
In comparing genetic differences between humans and other apes, scientists at Cornell University reached a theory that the split between humans and chimps might have very well come down to issues of scent and taste [source: Cornell News].
The Cornell team found hundreds of gene sequence changes in areas related to, among other things, smell and digestion. Obviously, humans are the most evolved primate species on the planet, with chimps coming in second.
The hierarchy also exists when you look at meat consumption among primates. Chimps are only surpassed in meat consumption by humans. Researchers suggest that a dietary change brought on by sudden climate change may be the key catalyst behind the explosions in evolution that separated humans and chimps from our most recent common ancestor.
The genes involved also affect long-bone growth, hairiness and hearing — the last of which is closely connected to the development of speech. Increased meat eating also may have lowered the physical playing field between males and females.
Primatologists believe that a new mating system emerged 1.9 million years ago among humans, replacing the dual male-female hierarchy with more of a team effort. As males shared more meat with their females, the latter grew in size and were able to produce bigger children with larger brains.
If these findings are correct, it means that man’s appetite set him on the evolutionary path to global dominance — an insatiable hunger that continues to shape the future for all life on this planet.
Ape Talk: Where Human and Primate Communication Intersect
Great apes use over 80 signals for daily communication, a study published in PLOS Biology reveals. These gestures range from the “big loud scratch,” signaling a request for grooming, to “object shake,” which can mean various things including a request for intimacy or a command to move.
Interestingly, chimpanzees and bonobos, our closest living relatives, share over 90 percent of their gestures, which may have influenced the evolution of human language. Researchers found that human infants use over 50 gestures similar to those of apes.
For the study, over 5,600 participants watched online videos of ape gestures and identified their meanings with more than 50 percent accuracy. This capability suggests a deep-rooted understanding of primate communication, though the exact mechanism behind this comprehension remains a topic of further research.
This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.
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- “DNA analysis for chimpanzees and humans reveals striking differences in genes for smell, metabolism and hearing.” Cornell News. Dec. 18, 2003. (April 24, 2009)http://www.news.cornell.edu/releases/Dec03/chimp.life.hrs.html
- Fox, Maggie. “Gene explosion set humans, great apes apart.” Reuters. Feb. 11, 2009. (April 24, 2009)http://www.reuters.com/article/idUSTRE51A8II20090212
- “Human-chimp Difference May Be Bigger.” ScienceDaily. Dec. 20, 2006. (April 24, 2009)http://www.sciencedaily.com/releases/2006/12/061219201931.htm
- “‘Humans not just “big-brained apes,’ researcher says.” PNAS and World Science. Aug. 22, 2007. (April 27, 2009)http://www.world-science.net/othernews/070821_humans.htm
- Kreger, C. David. “Homo sapiens.” Archeology.info. 2008. (April 24, 2009)http://www.archaeologyinfo.com/homosapiens.htm
- Lovgren, Stefan. “Chimps, Humans 96 Percent the Same, Gene Study Finds.” National Geographic News. Aug. 31, 2005. (April 24, 2009)http://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html
- “The Secret to Chimp Strength.” ScienceDaily. April 8, 2009. (April 24, 2009)http://www.sciencedaily.com/releases/2009/03/090330200829.htm
- Wade, Nicholas. “A Course in Evolution, Taught by Chimps.” New York Times. Nov. 25, 2003. (April 27, 2009)http://www.nytimes.com/2003/11/25/science/a-course-in-evolution-taught-by-chimps.html?sec=&spon=&pagewanted=1