Dec. 09, 2003

French student looks for lefties among earliest cave painters

The Dallas Morning News

Prehistoric shamans used to mark the transition from the real world to the spirit world, anthropologists think, by blowing pigments around their hands onto cave walls. These ghostly hand prints, which still dot European caves more than 10,000 years later, now serve a less ethereal purpose — telling scientists how many of those shamans were left-handed.

New research shows that the frequency of left-handed painters — 23 percent — is the same today as it was back then.

The work is a rare look at how left-handedness has persisted for millennia, says Charlotte Faurie, the French graduate student who performed the research. It suggests no evolutionary disadvantage to being a lefty, as some scientists had thought.

There’s older evidence that lefties were at work almost as soon as Homo sapiens arose: Wear marks on stone artifacts may signify the presence of southpaws 200,000 years ago. Neanderthals also had their share of lefties; some of their fossilized teeth carry telltale marks that indicate left-handed eating practices, Faurie says.

Such evidence is rare and doesn’t allow scientists to estimate the frequency of left-handedness. That’s why Faurie turned to a database, compiled by Marc Groenen of the Free University of Brussels, of prehistoric hand prints.

In caves stretching across France and Spain, Groenen identified 507 “negative hands,” in which pigment was splattered around a hand by blowing through a tube, spitting, or daubing the paint. Oddly, such negative prints are much more common than positive hand prints in which the palm was painted and pressed against a surface, Groenen says.

By taking careful measurements, Groenen often could identify the age and gender of the person who made the negative hand. In 343 cases, he could determine the handedness of the artist; somebody holding the pigment tube in his or her left hand presumably would have made the imprint of a right hand. Groenen found that 79 prints were of right negative hands, suggesting that 23 percent of the cave artists were left-handed.

Faurie thinks the European caves represent a fair sampling of the number of lefties back then. Some of the hand prints are large and some are small; others are higher or lower on the wall.

“Maybe some hands are from the same artist,” she said. “But we are sure that it is at least many artists.”

She decided to test the cave-painting numbers against the experience of students at her university, France’s University of Montpellier II.

First, she gave students an ink-blowing pen and asked them to outline one hand on a piece of paper taped to a wall. Next, she had them pick up a ball from a table and throw it at a target across the room. Finally, she asked them to identify with which hands they normally wrote.

Just as in the cave paintings, 23 percent of the students held the ink-blowing pens with their left hands and created right negative hands, Faurie and her adviser, Michel Raymond, report in an upcoming issue of Biology Letters.

After that, things become murkier. Only 9 percent of the students wrote with their left hands, and 8 percent threw as lefties.

The findings show how difficult it is to quantify left-handedness, Faurie says. Many people are southpaws for certain tasks but not for others.

Estimates of left-handedness range from 3 percent to 30percent of the population, depending on how and where questions are asked. Studies of tool use show that the northern Inuit people are just 3 percent lefties, while the Yanomami tribe of the Amazon are 23 percent left-handed, Faurie says. About 10percent of Americans write left-handed.

Negative hands appear in caves in other countries, including Australia, South America and Indonesia. Faurie wants to extend her study to those areas, if they have enough well-catalogued hand prints to make the findings statistically significant