Image: Kamilah
San Diego Zoo via AP
Scientists deciphered the draft genetic code for a female western lowland gorilla named Kamilah at the San Diego Zoo, and compared it with the genetic blueprints of humans and chimpanzees to better understand how humans evolved.
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updated 3/7/2012 3:18:06 PM ET 2012-03-07T20:18:06

Adding to the already-sequenced genomes of humans, chimpanzees and orangutans, researchers have completed the set of the great apes by sequencing the genes of a western lowland gorilla.

The complete genome comes from a female western lowland gorilla named Kamilah, who was born in captivity and now lives at the San Diego Zoo Safari Park. The researchers also sequenced parts of the genomes for two other western lowland gorillas and one eastern lowland gorilla. The results reveal more than ever about how the evolutionary tree connecting humans, chimps and gorillas was shaped.

"The gorilla genome is particularly important for our understanding of human evolution, because it tells us about this crucial time when we were diverging from our closest living relatives, the chimpanzees," study researcher Aylwyn Scally of the Wellcome Trust Sanger Institute said in a news conference about the findings.

Family ties
The results show that humans are closer to gorillas than we'd realized. The human-chimp part of the great ape lineage split off from the gorilla line about 10 million years ago, study leader Richard Durbin, also of the Wellcome Trust Sanger Institute, told reporters. Humans and chimps then diverged from each other about 6 million years ago. Evolutionarily speaking, that's fast.

"The interesting consequence of that is actually that the pattern of ancestry across the three genomes changes from position to position (in the genome)," Scally said. "So although most of the human genome is indeed closest to the chimpanzee genome on average, a sizeable minority, 15 percent, is in fact closer to the gorilla, and another 15 percent is where gorilla and chimpanzee are closer."

Genetic differences
In fact, the new data confirm that humans and gorillas are about 98 percent identical on a genetic level, said Wellcome Trust researcher and study co-author Chris Tyler-Smith.

But the differences are illuminating. For example, the researchers found that certain genes involved in sperm formation have become inactive or have been reduced in the gorilla genome compared with the human genome. That may be because gorillas live in harems with one male to many females, Tyler-Smith said, so there is little competition between different males' sperm.

The researchers also found rapid evolution in a single gorilla gene called EVPL, which contributes to keratin formation on the skin. Keratin is the tough protein found in hair and nails. For gorillas, the activity of this gene may be related to the tough knuckle pads that enable gorillas to walk on their fists.

Another interesting nugget of information in the gorilla genome had to do with a passel of genes related to hearing. Researchers already knew that humans had accelerated activity in these genes, meaning evolution was acting on them and suggesting some adaptive benefit to the resulting genetic changes. Now, researchers can see that this accelerated activity stretches back into the gorilla years, too.

"The implication of that is this is not because of human language ability," Tyler-Smith said. "It must be for some broader role."

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Finally, the researchers found certain genes shared by gorillas and humans that cause disease in our species, but not in our ape cousins. One of these variants is linked to dementia in humans, and another to heart disease.

"If we could understand more about why those variants are so harmful in humans but not in gorillas, that would have important useful medical implications," Tyler-Smith said.

The researchers reported their results Wednesday in the journal Nature.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Explainer: The world’s 10 smartest animals

  • EBU

    We humans have the ability to learn, to reason and solve problems. We're self-aware, and we're also conscious of the presence, thoughts and feelings of others. We make tools and practice the art of deception. We're creative. We think abstractly. We have language and use it to express complex ideas. All of these are arguably signs of intelligence. Scientists may not agree on the best and fullest definition of intelligence — but they generally agree that humans are highly intelligent.

    Other members of the animal kingdom exhibit signs of intelligence as well, and some scientists might say the definition of animal vs. human intelligence is merely a matter of degree - a point that was brought home in 2005 when the London Zoo put "Homo sapiens" on display in the exhibit pictured here. Click ahead to learn about nine other species that stand out for their smarts.

  • Chimps are almost like us

    Tetsuro Matsuzawa  /  AP

    If we humans possess intelligence, chimpanzees must have some as well: Our genomes are at least 98 percent identical. Chimps make and use tools, hunt in organized groups and engage in acts of violence. Wild troops have distinct behaviors and customs. Field observations and lab experiments show chimps are capable of empathy, altruism and self-awareness. In the experiment pictured here, chimps performed better than humans on a number memory test.

  • Dolphins get creative

    Janet Mann  /  Georgetown University

    This dolphin in Australia uses a sponge to protect her snout when foraging on the seafloor, a tool use behavior that is passed on from mother to daughter. Scientists say that's just one sign of dolphin smarts. Other signs include distinct whistles and clicks that may serve as dolphin names, perhaps used in a type of language. A famous 1960s experiment found that a pair of dolphins entered a tizzy of creativity once they figured out their novel behaviors were rewarded with fish. Frustrated human test subjects just let out a sigh of relief when they caught on to the idea.

  • Elephants exhibit self-awareness

    AP

    The sheer size of their brains suggests that elephants must know a thing or two about the ways of the world. They have been seen consoling family members, helping other species in times of need, playing in water and communicating with one another via vibrations sensed in their feet. A crowning achievement, some researchers say, was when this female Asian elephant named Happy recognized herself in the mirror. The complex behavior is shared only with humans, great apes and dolphins.

  • Cephalopods have big brains

    Binyamin Hochner

    Are octopi, squids and cuttlefish smart? That's a matter of scientific intrigue, but such cephalopods are certainly among the brainiest invertebrates in the sea. The cephalopod brain surrounds the esophagus, but shares with the human brain features of complexity such as folded lobes and distinct regions for processing visual and tactile information. The how-smart debate swirls around deciphering observations that the creatures have a seemingly irrepressible curiosity, a disdain for boredom, an ability to learn and the capacity to use tools. The octopus pictured here exerts precise muscle control to eat.

  • Crows get crafty

    Alex Kacelnik et al.  /  University of Oxford

    Crows are crafty critters: They fashion tools from twigs, feathers and other bits of debris to snare food from hard-to-reach places. A crow named Betty, pictured here, uses a straight wire she bent into a hook to retrieve food from a tube. The birds are born with a tool-making ethic, but they hone their craft by watching their elders, a sign of higher intelligence. Ravens, a type of crow, have even been shown to manipulate the outcomes of their social interactions for added protection and more food.

  • Squirrels can be deceptive

    Gabriel Bouys  /  AFP - Getty Images file

    Is the squirrel pictured here plotting deception? Perhaps. Researchers recently reported that the rodents put on elaborate shows of deceptive caching to thwart would-be thieves. The behavior increased in a lab experiment after squirrels observed humans stealing their peanuts. The researchers called the finding a sign that squirrels can interpret intentions of others, though it could just be a case of learned behavior. Other studies have shown the critters make three-dimensional maps to recall where they cache their nuts. And squirrels in California will cover their fur in the scent of rattlesnakes to mask their own scent from predators.

  • Man's best friend

    University of Vienna

    Are dogs intelligent or just really good at basic obedience? They can learn to sit, lie down and fetch, for example, but can they read their owner's intentions? Research suggests they can at least find food in response to non-verbal cues, a type of understanding that scientists think may be akin to the human ability to understand someone else's point of view. The dog in the experiment pictured here accurately discriminated between photos of dogs and photos of landscapes — an indication the dog was able to form the concept of "dog."

  • Cats are adaptable

    Bob Pennell  /  AP

    Like dog owners, some cat owners have trained their pets to sit down, roll over and jump through hoops. Cats learn the tricks by observation and imitation, egged on with positive reinforcement. But training cats is harder than dogs. Does that mean they are less intelligent? Not necessarily. Cat experts say felines are just different. They are solitary animals, motivated by the need to survive. This has allowed them to adapt to a variety of domestic environments for at least 9,500 years - even the hoods of cars.

  • Pigs are wise ... and clean

    Paulo Whitaker  /  Reuters

    Here's the dirt on pigs: They are perhaps the smartest, cleanest domestic animals known - more so than cats and dogs, according to some experts. But pigs don't have sweat glands, so they roll around in the mud to stay cool. A sign of their cleverness came from experiments in the 1990s. Pigs were trained to move a cursor on a video screen with their snouts and used the cursor to distinguish between scribbles they knew and those they were seeing for the first time. They learned the task as quickly as chimpanzees.

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