I found this the other day in my RSS inbox - interesting read:

The UNIX shell has been around for more than 35 years now—through evolution and enhancements—and is still going strong! It all began in 1971, when Ken Thompson of AT&T Bell Laboratories created the first UNIX shell named (appropriately) the Thompson shell. Fundamentals of the Thompson shell, such as redirection of data, exists in shells used today, although the shell lacked some important built-in functions that UNIX users use every day, such as pipes (|), the ability to write shell scripts, and if conditional statements.

As a result, the Thompson shell was replaced with the Bourne shell, or sh, in 1977. The Bourne shell, created by Stephen Bourne of AT&T Bell Laboratories, became the default shell for UNIX version 7 (V7). The shell took a huge leap into the future for UNIX. Now, users could write shell scripts; store and export information in variables; control file descriptors; control signal handling, for loops, and case statements; and so much more. Even though the Bourne shell was created more than 30 years ago, it is still widely used by many current UNIX systems and is the default shell for the superuser—root—on many UNIX systems today.

Over the past three decades, there have been changes and improvements to the UNIX shell. As a result, several different shells have been created. Figure 1 illustrates the family tree of a few of the UNIX shells. This figure is by no means complete, but it shows the major shells from which other, minor shells have been derived.




Read more here