Why the long neck, you ask? Several genetic clues from the giraffe and its relative may provide insight on how the animals developed their exceptional height, a new study revealed.
Considered as the world's tallest terrestrial species, giraffes are dominated by their long neck and legs, which contribute to their overall stature. These animals' size can reach up to 5.79 meters (19 feet) tall or nearly the equivalent of a two-storey building.
Additionally, giraffes can sprint at a speed of 37 miles per hour (60 km per hour). The animals' heart can pump blood two meters (6.56 feet) up to its brain, suggesting a powerful cardiovascular function. This is plausible, as its left ventricle has evolved to become unusually large.
Evolutionary Comparisons
So how did these animals stretch to such heights?
To figure out the answer, scientists sequenced the genome of giraffes and the okapi — its reclusive relative living in the African rainforest — and compared them to that of 40 other mammals such as the camel, sheep, goat and even humans.
Professor Douglas Cavener of Pennsylvania State University, lead researcher of the study, says the okapi's genome is very similar to that of giraffes because both animals split from a shared ancestor about 12 million years ago.
Despite this link, however, the okapi resembles a zebra and lacks the towering height of the giraffe, as well as its cardiovascular capabilities. Because of this, the okapi allows for a screen that helps scientists identify the genetic changes among giraffes.
After a series of tests and analyses, researchers from Penn State and their colleagues from the Nelson Mandela African Institution of Science and Technology detected 70 genes that indicate numerous signs of adaptation.
More than 50 percent of these detected genes were known to control the physiology and development of the cardiovascular, skeletal and nervous system.
The Evolution Of The Giraffe's Long Neck
Researchers found that the giraffe's long neck and legs, which possess equal number of bones as that of other mammals, do not grow by adding vertebrae to the cervical spine.
Rather, the long neck extends far beyond the vertebrae of the giraffe. This requires at least two genes, Cavener said. One gene specifies the region where the skeleton would grow, while the second gene stimulates growth.
One particular gene called FGFRL1 has a special role in boosting neck growth. This gene contains adaptations that are unique to giraffes only.
This gene is also actually responsible for regulating the development of giraffe embryo, as well as the development of the skeletal and cardiovascular system.
Additionally, another important set of genes were the "homeobox genes," which influence development from embryo into the animals' adolescence. These genes may have instigated rapid growth in the cervical vertebrae of giraffes.
The team's findings were published in the journal Nature Communications on May 17.
Photo: Maureen Didde | Flickr
