The first piece of wooden "furniture" was undoubtedly a fallen tree trunk, with some Homo Erectus using it to take a load off. Ergonomically speaking, it wouldn't have been a bad choice, as Dutch industrial designer Ruud-Jan Kokke learned. While speaking with orthopedic surgeon Piet van Loon, "Van Loon gave me the example of a tree trunk on which you can sit upright without effort," Kokke explains.

Kokke and van Loon, whose mission is to correct people's poor posture and subsequent back pain, collaborated on the design of this unusual-looking Zami Ergo stool:

"The sitting posture on Zami Ergo does not cause any skew on the back," writes Zami Ergo, the company formed to commercialize the design. "This ergonomically correct posture ensures good and active sitting."

The company offers a range of stools in wood and metal, including a rather ungainly-looking model with a back (which seems to contradict the design, no?).

You can see their full line-up here.