Professor Christy Turner an anthropologist at the Arizona State University said, “as far as can be empirically documented, the oldest human habit is picking one’s teeth.”

People begun the action of eating, they tried to clean their teeth instinctively. At the same time man devised the axe he may have invented the toothpick. Anthropologists now believe that early men sat around the fire after a hard day’s hunting, picked their teeth after chewing the day’s kill, using the sharp point of the cooking dagger.

The grooves were especially common in the teeth of Neanderthals who lived in Europe and Asia, about 100,000 years ago and similar markings have been found in the fossilized teeth of American Indians and Australian Aborigines.

Toothpicks were introduced into Japan in 6th century after Buddha (500BC) had originally taught his disciples to clean their teeth with tufted toothbrush. In India they used twigs from Neem tree and in Japan hand-crafted quality toothpicks were made from “kuromoji” or spice wood Lindera.

http://en.wikipedia.org/wiki/Lindera_benzoin

Kuromoji is a member of the camphor (linden) family, and besides the inspiring aroma, it is flexible and hard to break, making it an ideal material for toothpicks. If you are searching handmade toothpicks go to Saruya in Tokyo. Founded in 1704, Nihonbashi Saruya is the only shop that specializes in toothpicks made from lindera umbellata.

1-12-5 Nihonbashi-Muromachi Tokyo.
http://www.nihonbashi-saruya.co.jp/

By the way: you can see two toothpicks below, the thinner and the thicker, and the former is the “real deal” and is not made and sold any longer.

source: http://www.nytimes.com/1989/03/07/science/but-did-they-floss.html