I'm not really qualified to report a history of office task chairs, but there are some obvious milestones on the way to what is offered today. Among the inexpensive and often inadequate offerings of cheap office supply stores you will see the spawn of past seating breakthroughs now offered as 3rd generation knock-offs of once revolutionary office chair designs. The take away from all this is don't cheat yourself on your office chair. Next to your mattress its probably the place where you will spend the biggest part of your day, and possibly harm yourself the most if you don't have a decent chair.
Things we take for granted today, like a task chair that swivels and rolls on casters, were originally seen as ways to increase the productivity of the office worker. Just about every breakthrough in office seating has had the same motivation. Ergonomics, the study of people's efficiency in their working environment, has lead to the addition of other features and strategies for making productive seating for the office. We'll spend some time over a few posts looking at the emergence of these features before we look at a range of contemporary office chairs.
The first breakthroughs were getting the chairs on castors and swivel + tilting bases. You'll notice that almost all older office chairs had four legs with castors following the four legs of conventional chairs. The convention of a five leg spider base which is much more resistant to tipping over came much later.