The Multics operating system, which was funded by the DARPA at MIT's Project Mac for 10 years, was superior to Unix from a technical standpoint, and it used segmentation.

http://pages.cs.wisc.edu/~solomon/cs537-old/last/segmentatio...

Unix has Paging but not segmentation. Segmentation allows you to grow a memory block without having to copy as it grows, something that just plain paging cannot do.