The scientists also found genetic clues to the evolution of its long neck and legs.
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According to a story published on the topic by Gizmodo News, “For the first time ever, scientists have sequenced the genome of the world’s tallest land species, the giraffe”.
From a physiological point of view, Darwin and hundreds of biologists who followed in his footsteps questioned the evolutionary benefit of having a heart that needs to pump blood as high as two metres to the giraffe’s brain.
The scientists sequenced genomes of two Masai giraffe (Giraffa camelopardalis tippelskirchi) from the Masai Mara Game Reserve in Kenya and the Nashville Zoo, and one fetal okapi (Okapia johnstoni), from the White Oak Conservatory in Florida. “The giraffe’s long neck and legs are kind of a good example”.
Along with the giraffe’s closet living relative, the okapi, researchers compared both animal’s gene-coding sequences to over 40 other mammals including sheep, camels and humans.
The giraffe and the okapi’s common ancestor had an intermediate neck length, implying that when they split off about 11.5 millions years ago, the okapi evolved to have shorter necks, Dr. Cavener tells the Monitor.
Despite this link, however, the okapi resembles a zebra and lacks the towering height of the giraffe, as well as its cardiovascular capabilities.
Researchers identified 70 of these genes showing signs of these unique adaptations in the giraffe, where more than half of them are genes that help in regulating skeletal growth along with maintaining cardiovascular systems, playing a very crucial role in these unique features of the giraffe.
On comparison, the researchers found 70 genes that were responsible for some of the giraffe’s most distinctive adaptations.
“There are many theories about how the giraffe’s neck lengthened but it does seem that the development of the cardiovascular system evolved in parallel with the development of the skeletal system”, declared Morris Agaba of the African Institute for Science and Technology in Tanzania, as reported by Reuters. Before going to law school, she raised organic lamb on a ranch in the Sierra Nevada foothills, ran a dairy farm in Muscoda, WI, and then owned a popular live music nightclub in Madison, WI. These genes likely allow giraffes to eat acacia leaves and seed pods, which are toxic to lots of other mammals. One gene specifies the region where the skeleton would grow, while the second gene stimulates growth. “Describing genetic changes along the evolutionary branch leading to the giraffe is relatively straightforward; what is much harder is interpreting those changes”, he said.
This particular gene informs the development of bones at embryo stage and beyond birth.
In humans and also in mice, severe skeletal and cardiovascular defects are associated with debilitating mutations in FGFRL1.
Dissimilar to long-necked winged creatures, which have extra vertebrae, giraffes have the same seven vertebrae found in all warm-blooded animals, despite the fact that theirs are significantly broadened.
Moreover, some of the altered genes affect precisely those body regions where giraffes are unique.
But perhaps an even more important take-away from the four-year study is highlighting the need for giraffe conservation: The giraffe population has fallen 40 percent in just 15 years, making them more endangered than elephants.
“Giraffes have declined precipitously in the wild”, says Lee. This feat is possible because the giraffe’s heart has evolved to have an unusually large left ventricle, and the species also has blood pressure that is twice as high as other mammals.
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“We hope that the publication of the giraffe genome and clues to its unique biology will draw attention to this species in light of the recent precipitous decline in giraffe populations”, Cavener concluded.
