Your report on recent research showing that physiognomy provides a clue to human aggressiveness offers plenty of food for thought (“Facing the Truth,” August 23, 2008). In particular, Justin Carré and Cheryl McCormick of Brock University in Ontario, Canada, have shown that aggressiveness can be predicted from the ratio between the width of a person’s face and its height: those with wide faces are more aggressive than those with long ones. The cause they propose is the exposure to testosterone, as this hormone is known to make people aggressive, as well as to reshape people’s bodies during puberty. What is surprising, however, is that these findings are discussed only in connection with individuals rather than entire ethnic groups. The distinction between the so-called brachiocephali and dolihocephali, or peoples with wide as opposed to long craniums, used to be popular among anthropologists several generations ago, when craniometry was a respected scientific endeavor, but it has been neglected in recent years. Carré and McCormick’s results point at the possibility that entire ethnic groups are more aggressive than others due to differences in testosterone exposures during puberty. Further research would certainly be warranted to explore this connection.