Science today isn't the same as the science 2000 years ago was but some principles remain the same. The human knowledge constantly grows but with more knowledge there comes even more mysteries and unsolved questions, so science is always going forward.
Causes. The most common cause of a cervical herniated nucleus pulposus is gradual degeneration of the disc, attenuation (weakening) of the posterior annulus fibrosis, and subsequent protrusion of the nucleus pulposus into the spinal canal causing compression of the nerve root.
Aging and the Nucleus Pulposus. In young people, the nucleus pulposus is made mostly of water (which makes the risk of a disc herniation higher in this age group). As we get older, the disc, but especially the nucleus pulposus dries out. This dehydration results in a significant loss of disc height, so by the age of 60 to 70, the disc is composed entirely of fiber, and shock absorption for the spine is for the most part, lost.