When was body parts used to measure length?

Answer 1

Body parts were always used as the first 'weights and measures'.

An example from England is that we still measure horses' height in 'hands', now accepted as four inches (about 10 cm) and defined as the width of a full-grown man's hand.

Examples that we don't use are many, since England changed to the metric system, but include 'inch' (the distance from the knuckle to the tip of the right thumb, 'foot' (self explanatory) 'yard, (the distance from shoulder to tip of the right arm [note that a 'yard' as a sailing term is the bit that goes across the mast for the sail to be suspended from])

Therre are similar examples from cultures across the world.

English weights and measures were eventualy standardised because, naturaly, these 'measures' varied just as much as people do, so buying from a 'big' man was likely to be more advantageous to the buyer than a similar purchase from a 'small' man, and vice-versa.

In England, further references can be obtained through the history of the Weights and Measures Office, as well as many other sources. Try your local library!