How closely related are gorillas and humans? Closer than you might think.

A new effort to sequence the gorilla genome has filled in many of the gaps from the first attempt to map the primate’s DNA while revealing that they may be more closely related to humans than previously believed, according to research published Friday in the journal Science.

University of Washington professor of genome sciences Evan Eichler and his colleagues used an 11-year-old Western lowland gorilla named Susie as the subject for their sequencing efforts, and found that human and gorilla genomes diverge by just 1.6 percent, Reuters reported on Thursday. Only bonobos and chimpanzees are more closely related to humans, they added.

Among the area of genetic divergence are the immune and reproductive systems, the areas that control sensory perception, those governing the production of the protein keratin (which is used by the body to build hair, skin and fingernails) and those that regulate insulin. Their research has also resulted in the discovery of thousands of new protein and peptide-encoding segments.

The differences between the species “may aid researchers in identifying regions of the human genome that are associated with higher cognition, complex language, behavior and neurological diseases,” study author Christopher Hill, a genetic researcher at UW, told the news agency.

Study could shed new light on evolutionary history of gorillas, humans

The sequencing effort is part of the university’s efforts to compile a comprehensive catalog of genetic differences between humans and all of the great apes, including gorillas, orangutans and chimpanzees, Reuters said. A blood sample from Susie, who now lives at the Columbus Zoo and Aquarium in Ohio, was taken when she was at Chicago’s Lincoln Park Zoo.

Eichler, Hill and their fellow researchers used Single Molecule, Real-Time (SMRT) technology and the assembly tools Falcon and QUIVER as part of their sequencing attempts. In a statement, they explained that these methods allowed them to generate long sequence reads more than 100 times the length of many other, commonly used technologies.

By doing so, they were able to reduce the number of fragments from 400,000 to just 1,800 and increasing the size of those pieces by 800 times. Furthermore, they were able to close 90 percent of all the gaps in the original sequencing effort, discovering several segments and regulatory elements that had been missed as part of the earlier attempt. The goal, they said, is to learn how humans evolved to be so vastly different than their great ape relatives.

“My motivation in studying human and great ape genomes is to try to learn what makes us tick as a species,” Eichler explained. “I’d like to see a re-doing of all the great ape genomes, including chimpanzee and orangutan, to get a comprehensive view of the genetic variants that distinguish humans from the great apes. I believe there is far more genetic variation than we had previously thought. The first step is finding it.”

In addition to providing new insights about humans, the improved genome assembly provides an enhanced look at the evolutionary history of the lowland gorilla, the authors said. Earlier studies revealed that the gorilla population experienced a bottleneck in the relatively recent past, but this new effort shows that this event was more severe than previously thought. Genetic patterns in the creatures could also show how the gorilla population was effected by pathogens, climate change, and human activity, they concluded.


Image credit: Higashiyama Zoo and Botanical Gardens