What do you think of this fact?
How many bones would you need for a neck that’s more than two meters long? You’d probably guess a few dozen. The answer is 7, exactly as many as you have.
Same number, very different size
According to the San Diego Zoo, the neck of an adult male giraffe is about eight feet long, roughly 2.4 meters. No other living animal has a neck even half that long. Still, it is made of just 7 neck vertebrae.
The trick is size. According to an EarthDate fact sheet, each of these vertebrae is about 25 centimeters long in a giraffe. Yours are only a few centimeters. Same blueprint, completely different scale.
Almost all mammals stick to 7
It gets stranger when you look beyond giraffes. The Natural History Museum in London says that almost all mammals have 7 neck vertebrae. That goes for you, for the giraffe and for the house mouse, whose neck bones are tiny. A giraffe towers more than five meters over a mouse, yet when it comes to necks, both count to 7.
Other animal groups are very different. According to ScienceDaily, the number varies a lot in birds, reptiles and amphibians. Swans, for example, have 22 to 25 neck vertebrae.
The rare exceptions
Only a few mammals break the rule, mainly sloths and manatees. A research group led by biologist Frietson Galis looked into why. According to ScienceDaily, unusual neck vertebrae in mammals are linked to higher risks of stillbirth, childhood cancer and neurological problems. Galis suggests that sloths are spared these effects thanks to their slow lifestyle and low metabolism.
Bonus fact: According to ScienceDaily, about half of the dugongs studied had fewer neck vertebrae than usual, and all of those also showed other skeletal abnormalities.
Evolution could have simply given the giraffe more vertebrae. Instead, it stretched the 7 it already had until they were long enough.
The tallest neck in the world is basically your neck, just in XXL.