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Why Do Humans and Giraffes Have Same Number of Neck Vertebrae?

John M Jun 17, 2019
The world's tallest land mammal- the giraffe, known for its long neck, has the same number of neck bones as you and me.

Tallest Land Mammal in the World

Giraffe is a fascinating species, known for its long legs, distinctive coat pattern, and of course, its extremely long neck.
Native to several African countries, the giraffe is a herbivore and the largest land mammal on earth.

How Big is a Giraffe?

A fully grown adult giraffe will typically stand at between 14 to 19 feet tall, with tallest ever on record being a male giraffe at 19.3 feet.

In terms of weight, male giraffes can weigh around 1,200 kg compared to an average weight of 830 kg for female giraffes.

The Giraffe's Neck

The giraffe's elongated neck is arguably its most unique feature and contributes significantly to its overall vertical height.

Despite being so long, the giraffe has the same number of neck vertebrae as a human.

The Human Neck

Comparing the anatomy of the human spine with that of a giraffe, it's evident that both species have 7 cervical (or neck) vertebrae, despite there being such noticeable difference in the overall visible neck length of both species.

Why same number of neck vertebrae

The answer to why giraffes have same number of vertebrae as mammals, is that they are both mammals - and all mammals (with the exception of only a few) have 7 cervical (neck) vertebrae. So not only does a giraffe have the same number of neck vertebrae as a human, it also has the same number of vertebrae as a mouse.
In other animal groups, such as birds and reptiles, there is much more variance when it comes to the number of neck vertebrae in individual species. So almost all mammals having 7 neck vertebrae, is a fairly unique characteristic.

Bigger Bones

The reason why a giraffe has a longer neck than humans and all other mammals with 7 vertebrae is due to the fact that their neck bones are larger.

Each neck bone can be over 25 cm in length - which explains why the total neck length of a giraffe is so significant.

Exceptions

Sloths and manatees are both, examples of mammals which don't have 7 cervical vertebrae. Two-toed sloths can have between 5 and 7 cervical vertebrae, whereas three-toed sloths can have 8 or 9.
It's thought that the slow lifestyle of the sloth is the main reason why it has evolved to have an abnormal number of neck vertebrae compared to most other mammals.
Having 7 neck vertebrae is the general rule for mammals. Thus, giraffes and humans share this anatomical characteristic, although the size of vertebrae will vary significantly among species.
So, a giraffe's neck is much larger than the neck of any land mammal, despite having same number of bones.