If you had to measure the dimensions of a room without using a tape measure, you could walk around the perimeter from heel to toe and count the steps. To estimate the height of the wall, you can count the hand span from the floor to the ceiling. By doing so, you would be joining a long human tradition.
“No one has ever done this kind of systematic, cross-cultural study of body-based measurement before,” says Stephen Chrisomalis, an anthropologist of mathematics at Wayne State University who wrote an editorial accompanying the new paper.
Many past and present standard units of measurement have been inspired by parts of the human body. As early as 2700 BC, the ancient Egyptians used the royal cubit, a unit of length of about 53 centimeters, which was probably derived from the distance from the elbow to the tip of the middle finger. Other units used today, such as the foot and the fathom (originally the span of outstretched arms, now standardized at 1.8 meters) were similarly inspired.
To investigate how widespread such practices have been throughout human history, Kaaronen and his colleagues examined ethnographic data from 186 past and present cultures around the world and searched for descriptions of body measurement units in a database called the Human Relations Area Files.
The team found that these systems were used in every culture they looked at, especially in the construction of clothing and technology. For example, in the early 20th century the Karelian people, a group originating from Northern Europe, traditionally designed skis to be a fathom plus six hand spans long. In the late 19th century, the Yup’ik people of the Alaskan coast recorded builders’ kayaks 2.5 fathoms long plus a cockpit, which was the length of an arm with a closed fist.
Next, the team looked at a subsample of 99 cultures that, by a widely used measure in anthropology, developed relatively independently of each other. Spans, hand spans, and cubits were the most common body measurements, each appearing in about 40% of these cultures.
Kaaronen says. “If you measured it with a meter, it would be quite cumbersome. But measuring loose objects with a fathom is very convenient: Just stretch your arms repeatedly and let the rope pass through your hands. So it is no coincidence that the fathom is used to measure ropes, fishing nets and fabrics all over the world.”
He notes that body-based units also often result in a more ergonomic design because the items are made for the person actually using or wearing them. Kaaronen is a kayaker and woodworker who makes his own paddles – basing their length on the traditional measurements of his reach and cubit. “I personally vouch for traditional paddle design,” he says. “They are very ergonomic and functional.”
Advantages like these could explain why body-based measurements have persisted for so long, the team says. They found that these methods were still in use hundreds or even thousands of years after the introduction of standardized units in each region they examined.
Dor Abrahamson, a cognitive scientist at the University of California, Berkeley, calls the paper’s analysis and conclusions “compelling.” It serves, he adds, as a kind of counterargument to the pressure to standardize tools and objects for more convenient production.
Karen Francois, a philosopher of mathematics at the Free University of Brussels, agrees that the study shows the lasting value of body measurements. “It has value for human problems on human scales,” he says. “It’s local knowledge, it’s ergonomic, it’s technical, and it’s still in use.”
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