Chimpanzees, along with bonobos, are the closest living relatives of humans. In fact, you may have heard that humans and chimpanzees share 98.8% of their DNA.
But is this actually true? And what does “similar DNA” mean?
The truth is that 98.8% similarity between chimpanzee (pantrogloycetes) and human (homo sapiens) DNA overlooks important differences in species genomes, experts told Live Science.
Human and chimpanic DNA is made up of four basic building blocks, or nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T). David Haussler, director of science at the UC Santa Cruz Genomics Institute, said that the genomes of both species can be thought of as “strings of letters A, C, G, and T.”
When scientists compare human and chimpanic DNA, they identify letter (nucleotide) sequences in both genomes and look for DNA stretches with many overlaps between the two genomes. Next, count the number of matching characters in these regions.
“It’s like comparing one version of a very long novel to another.
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Early studies suggested that the human and chimpanzee genomes are more than 98% identical. “What that means is that for each part of the human genome where chimpanzees have the corresponding DNA sequence, one of the average 100 nucleotides (single A, C, T, or G bases) is different,” explained Katie Pollard, director of Gladstone Data Science and Biotechnology at the University of California, San Francisco.
For context, humans share about 99.9% of their DNA with each other, Haussler said.
However, the 99% figure is misleading because it directly aligns human and chimpanzee genomes and focuses on stretching DNA that can neglect sections of the genome that are difficult to compare.
The human DNA sections without a distinct counterpart of Chimp DNA account for about 15% to 20% of the genome, Marques-Bonet said. For example, certain types of DNA exist in one species, but others lack it. These are known as “insertions and deletions.” During the evolution from a common ancestor, some DNA of some species were broken and reattached elsewhere along the chromosome.
Thus, while previous studies suggested similarity between 98% and 99%, Marques-Bonet says that comparisons involving areas where ariin is difficult brings that difference closer to 5% and 10%. “And if the region that can’t be properly coordinated with current technology is still too complicated, the true overall difference is likely to be over 10%,” he said.
In fact, a 2025 study found that the genomes of humans and chimpanzees differ by about 15% when compared directly and completely. However, when this direct method is used, there is a lot of variation in the species themselves. Up to 9% of chimpanzees were found in a 2025 study.
“Contrary to this background, the close genetic relationship between humans and chimpanzees has not changed,” wrote Martin Neucum, a chemist at the Institute of Technology Munich, who was not involved in the 2025 study, in a translated article.
According to Pollard, the difference between the human and chimpan genomes is primarily in the non-coding DNA, which does not encode specific proteins and is a segment that accounts for about 98% of the genome.
Differences in non-coding DNA have a major impact. DNA coding includes instructions for building proteins, but “regulatory regions” in non-coding DNA controls control how, when, and where these proteins are produced, explained Marques-Bonet. They act like switches and control whether genes are on or off.
Therefore, small adjustments in the genome, especially in these regulatory regions, can ripple over large differences in properties. “Small changes in DNA can have great consequences for how that DNA is expressed,” Haussler said. “And change in expression can lead to even greater changes in phenotypes.
Therefore, chimpanzees and humans share the same genetic toolkit, but how these tools are used makes a big difference. “Humans and chimpanzees are essentially made up of the same building blocks (proteins), but these are used in slightly different ways to make humans and chimpanzees,” Pollard said.
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