Nearly all mammals, with the exception of sloths and manatees have 7 cervical (neck) vertebrae and this has remained the norm for 160 million years. The (almost) unchanging nature of the spinal column is called evolutionary stasis and while it remains so consistent with the cervical vertebrae, the rest of the spine has also been very consistent through time. It truly is amazing that giraffes and humans have the same amount of neck vertebrae, seriously, the seven neck vertebrae of a giraffe are about the size of a person.
Photo source: Rockymountainbrainandspineinstitute