What is the natural history of the straight edge?

Various forms of razors were used throughout history, which are different in appearance but similar in use to modern straight razors. In prehistoric times clam shells, shark’s teeth, and flint were sharpened and used to shave with. Drawings of such blades were found in prehistoric caves. Some tribes still use blades made of flint to this day. Excavations in Egypt have unearthed solid gold and copper razors in tombs dating back to the 4th millennium BCE. The Roman historian Livy reported that the razor was introduced in ancient Rome in the 6th century BCE. by legendary king Lucius Tarquinius Priscus. Priscus was ahead of his time because razors did not come to general use until a century later.[6]...there’s much more http://en.wikipedia.org/wiki/Straight_razor

The only thing coming to mind would be a string (rope or cord) attached to a weight and used as a plumb line.

It’s not quite the same as a ruler but would definitely produce a straight line.

I knew the answer to this, dammit. It had something to do with, um,

rats

I think maybe rubbing two surfaces, like lengths of metal or stone or some other abradable surface, against one another so that eventually the high points would be ground away on each one and what remained would be straight? Something like that. I read it in passing a while back and thought it was interesting, but I didn’t know there was going to be a quiz.

@Jeruba

As I was reading your answer, I actually got a mental picture of rats in my brain and had trouble imagining what on earth they could possibly have to do with straight lines…

…but then I read through to the end.

:D

When asked and without prompting, my husband remembers this same thing about rubbing two flat surfaces together until they abrade away each other’s high points. He thinks it was stone too. (We’re staying strictly away from the metaphorical here and just speaking literally.) The number of things we both read is fairly narrow, mainly books we read aloud together. However, we’re not recalling the source.

Chances are also good that if this information was correct, it can be found elsewhere.

Sorry, @Buttonstc, a little mad stream-of-consciousness there as I banged on a stuck file drawer in my increasingly creaky memory.

Wouldn’t it be kind of difficult to shave with a stone, no matter how straight or sharp ?

Sure—but the question wasn’t about shaving. It was about drawing a straight line.

In reading back I just realized that it was not the OP who was referencing razors. It was in the first answer rather than the original Q.

Sorry about that; I goofed. I need to read a little more slowly next time.

String/twine/thread fills the bill.

Wikipedia says, “The discovery of dyed flax fibres in a cave in the Republic of Georgia dated to 34,000 BCE suggests textile-like materials were made even in prehistoric times.”

String or twine definitely fills the bill, especially if attached to a weight to create a plumb line.

Voilà. A straight line :)