Updated
Humans and gorillas share about 98% of their DNA, which makes gorillas our second-closest living relatives after chimpanzees and bonobos. That closeness is visible in a gorilla’s hands, faces and family life, and it has a practical side on every trek: mountain gorillas can catch our diseases. Here is what the figure means, where it comes from, and what the gorilla genome has revealed.
What “98% the same” actually means
The figure compares the sequence of DNA letters in the two genomes. When the gorilla genome was published in 2012, the difference from humans in the parts that can be aligned was about 1.75%, so we share roughly 98.25%. Chimpanzees and bonobos are slightly closer to us, at about 98.8%. The percentage depends on how it is measured; counting insertions, deletions and duplicated stretches gives a lower number. Small differences matter a great deal, because they change when and how genes are switched on.
When our lineages split
Genetic studies estimate that the gorilla lineage split from the line leading to humans and chimpanzees roughly 8 to 10 million years ago, and humans and chimpanzees split later, about 6 to 7 million years ago. One surprise from the gorilla genome was that in around 15% of it, humans are more similar to gorillas than to chimpanzees, because ancestral gene variants were sorted unevenly as the three lineages separated. See gorillas and chimpanzees compared for how the two apes differ in practice.
What the mountain gorilla genome showed
When mountain gorilla genomes were sequenced in 2015, they showed very low genetic diversity and a lot of inbreeding, the result of a small population living in two isolated forests for thousands of years. Researchers also found that some of the most harmful mutations appear to have been purged over time, which may help explain how the population has survived and grown. Read more about what genetics reveals about their survival and the current mountain gorilla population.
Why it matters on a trek
Shared biology means shared illnesses. Mountain gorillas are vulnerable to human respiratory viruses such as colds and flu, which have caused deadly outbreaks in habituated groups. That is why rangers keep groups about seven metres away, may ask you to wear a mask, and turn back visitors who are unwell. Following the trekking rules protects them, and vets from Gorilla Doctors monitor the gorillas for signs of disease.
Seeing the similarity for yourself
During your hour with a family you will notice the resemblance: hands with fingernails and fingerprints, expressive faces, mothers cradling infants, and a rich range of sounds and gestures; read how gorillas communicate. Travelling with children? Our guide to explaining gorilla DNA to children turns the numbers into something they can relate to.
Frequently asked questions
About 98%; the 2012 gorilla genome put the difference at roughly 1.75% in comparable regions.
Chimpanzees and bonobos, at about 98.8%, are slightly closer than gorillas.
Genetic estimates place the split at roughly 8 to 10 million years ago.
Yes. They are vulnerable to human respiratory infections, which is why sick visitors are not allowed to trek.
