How do we know humans and other apes share an ancestor?

Several independent lines of evidence agree. DNA comparisons show that humans are most similar to chimpanzees and bonobos, then gorillas, then orangutans, then monkeys. Older protein tests gave the same ordering, and shared anatomy fits it too. Together they indicate that humans and the other apes descend from common ancestors. Humans did not descend from any living ape or monkey. [1] [2]

The Smithsonian's Human Origins Program reports that the DNA difference between humans and chimpanzees is about 1.2 percent, counting substitutions in shared genes. Bonobos differ from humans to the same degree. Gorillas differ by about 1.6 percent, orangutans by about 3.1 percent, and rhesus monkeys by about 7 percent. Chimpanzees, bonobos and humans each show the same amount of difference from gorillas, which places the three on one branch of the family tree. See [humanorigins.si.edu](https://humanorigins.si.edu/evidence/genetics). [1]

The figure depends on the method. If deleted, duplicated and inserted stretches of DNA are counted as well, the same source adds another 4 to 5 percent of difference between the human and chimpanzee genomes. The American Museum of Natural History cites 98.8 percent shared DNA. Whichever way it is calculated, humans, chimpanzees and bonobos remain closer to one another than to gorillas or other primates. See [amnh.org](https://www.amnh.org/exhibitions/permanent/human-origins/understanding-our-past/dna-comparing-humans-and-chimps). [1] [3]

Before genomes could be read, researchers compared proteins using antibodies. A rabbit's antibodies against a human protein react more strongly to a similar chimpanzee protein than to a less similar one. In the 1960s, Vincent Sarich and Allan Wilson used such tests, assuming fewer differences meant a more recent split, and estimated that humans, chimpanzees and gorillas shared an ancestor only about 5 million years ago, much more recently than was commonly accepted then. Later, Charles Sibley and Jon Ahlquist used DNA-DNA hybridization, in which more similar DNA binds more tightly. It suggested that human and chimpanzee DNA was more alike than either was to gorilla or orangutan DNA. See [evolution.berkeley.edu](https://evolution.berkeley.edu/the-history-of-evolutionary-thought/1900-to-present/genetic-similarities-wilson-sarich-sibley-and-ahlquist/). [4]

DNA is one line of evidence among several. Berkeley's Understanding Evolution site notes that anatomical, behavioral and developmental studies are also crucial. Biologists build family trees from homologous traits, which are features inherited from a shared ancestor. Human, chimpanzee and gorilla thumbs are homologous, whereas the panda's thumb evolved independently, so it says nothing about close kinship. OpenStax adds that fossils and DNA comparisons together indicate humans and chimpanzees diverged from a common ancestor about six million years ago. See [openstax.org](https://openstax.org/books/biology-2e/pages/29-7-the-evolution-of-primates). [5] [4] [6]

The sources give slightly different dates. The Smithsonian places the last common ancestor of humans and chimpanzees between 8 and 6 million years ago, OpenStax gives 5 to 7 million, and the AMNH says six or seven million. Monkeys and apes share an older ancestor from about 25 million years ago. A common misconception is that humans came from chimpanzees. Instead, both lineages evolved separately from a shared ancestor species. [1] [6] [3] [2]