New genome sequencing reveals more clues about the genetic changes that led to the evolution of the giraffe's long neck and exceptional height.
How did giraffes get their exceptionally long neck? Many previous researches suggested that it did not happen at once, the transformation took place over time.
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To get the exact answer, scientists have sequenced the genomes of the giraffe and its only closest living relative okapi and found some crucial clues about the genetic changes that evolved giraffe into an exceptionally tall animal.
To support long necks and a massive body, giraffes must have unbelievably strong organs. For instance, giraffe’s heart must pump blood two meters straight up to ensure blood supply to the brain and their blood pressure is twice as high as of other mammals.
“The evolutionary changes required to build the giraffe's imposing structure and to equip it with the necessary modifications for its high-speed sprinting and powerful cardiovascular functions have remained a source of scientific mystery since the 1800s, when Charles Darwin first puzzled over the giraffe’s evolutionary origins.”Lead researcher Douglas Cavener from Penn State University said.
Researchers compared the genomes of giraffe and okapi to 40 other mammals like cows, sheep, goat and even humans. Though, okapi and giraffe share the same ancestry and two diverged around 11 million years ago. Still, their appearances are strikingly different. Okapi looks more like a zebra than a giraffe. Its height is short and also it does not have a characteristic long neck. Due to these differences, researchers believe that okapi could be an ideal candidate to identify genes which led to the extraordinary evolutionary changes in giraffes.
When researchers examined the DNA of both giraffes and okapi, they found no new genes. Instead of it they indentified 70 genes with mutations or adaptations. Most of the genes are known to regulate physical development in mammals. So it adds weight to the theory that manipulations in genes might have turned a small-sized animal into a tallest animal on land.
“These adaptations include unique amino-acid-sequence substitutions that are predicted to alter protein function, protein-sequence divergence, and positive natural selection.” Cavener said.
Researchers also found genetic clues to the evolution of giraffe’s long neck and legs. Giraffes have the same number of bones as humans and other mammals have in the neck and legs but the difference is giraffe’s legs and neck bones are extraordinarily extended due to the mutations in two genes – one that specify the region of the skeleton to grow more and another gene to stimulate increased growth.
Researchers believe that their finding may help scientists understand the unique biology of the animal and also highlight the need of giraffe conservation since the animal has declined by 40 percent over the past 15 years.
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