It’s awesome to see this OS post OS9 and how far it’s come! We “should” be able to add the Lion chapter tomorrow. This only begs the question, “What comes after the Big Cats?”. Only time will tell…

From Cult of Mac:

The release of Mac OS X Lion culminates a decade-long software development process. Back in 2001 Apple introduced a new (and long awaited) replacement to the Classic Macintosh System Software, Mac OS X. How far we’ve come in ten years. As Lion goes on the prowl, we present a brief look back at Apple’s Big Cats over the years and review the Evolution of Mac OS X.

See the evolution here:
Cats on the Prowl: The Evolution of Mac OS X [Gallery] | Cult of Mac.