Your review of recent research into the origin of spear-throwers is an engaging read (“Girls on Top,” April 12, 2008). The tool serves to amplify the hurler’s arm movement, so that the spear can be propelled at greater speed and distance. As you report, John Whittaker, an anthropologist at Grinnell College in Iowa, believes that they were social equalizers. A simple spear is a man’s weapon requiring strength and body mass. Using the spear-thrower requires skill, though. As women were the prize of warfare in hunter-gatherer societies, dexterous women could defend themselves with spear-throwers even against men. Splendid. The only missing bit in this theory is why the men did not take up spear-throwers, as well, and so regain their previous advantage. Two possibilities suggest themselves: either men are less dexterous than women, or they are less intelligent. Tertium non datur. Further research by Dr. Whittaker will resolve this trifling conundrum, I am quite sure.