Everyone loves seeing a giraffe in motion. Their supple sinuous bodies seem to glide across the African plains whenever their caught in photos, on film or at the movies. But it’s their long sleek serpentine necks that distinguishes them from just about every other form of wildlife. So different, that one needs to ask how that remarkable attribute came to be?
Darwin might have the answer?
Some would assume it came from years and years of evolutionary change that developed due to their foraging diet of dining off treetop vegetation.
However, recent biological research are indicating something in addition to evolution might be at work here.
Unlike some species of long-necked birds, such as egrets, giraffes didn’t grow their necks by adding vertebrae to their cervical spine. Instead, they just stretched out the seven vertebrae they already had. And the rapid growth that’s required to make this happen must occur while they’re very young.
Now, on the evolutionary side of things, giraffes had to evolve an oversized left ventricle and reinforced circulatory system to handle the stress of pumping blood almost ten feet straight up to their cerebrums.
Additionally, they also have specialized blood vessels in their craniums that regulate blood flow while bending down for their water intake. Otherwise, their blood pressure would dip every time they took a drink.
Interesting to note, that the giraffes' closest cousin is the ‘okapi.’ Looking closer to a cow-and-zebra hybrid, the okapi has a skeletal make-up that is quite similar to the giraffe.
The one differentiator is of course the neck size. Of the 70 genes that researchers have singled out as adaptions between giraffes and okapi, around half likely play a role coding proteins that regulate skeletal, muscular and nervous system development — all important for producing their notable necks.
However, for giraffes’ necks to grow so long, two critical factors need to be at play. First, the genes that tell the neck when to stop growing need to be turned off, and second, genes that promote continued growth need to be upregulated.
The Secret Sauce . . .
Making up the ‘secret gene pool’ sauce are four so-called ‘homeboy genes' that come into play during the giraffe’s developmental maturation from embryo to adolescence. This set of genes also have unique adaptions that the researchers think instigate rapid growth in a giraffe's cervical vertebrae.
However, in addition there is another very important gene that’s integral to neck growth. Labeled FGFRL1, this is the one that possesses adaptions unique to giraffes, and is responsible for regulating embryo development, particularly the skeletal and cardiovascular systems.
Can Mice grow Long Necks?
Is it in the cards to alter the neck size of lab mice? Well, since biologists have been able to single out FGFRL1, they are presently in the process of injecting the gene into mice.
While they caution that creating long-necked mice is probably unlikely, they do hope to observe changes in the development of the spine that could clue them in as to how giraffe necks grow. Interesting proposition, don’t you think?