Chapter 14 455 geo-racial groups, we would expect it to be about five years later for Asians and 10 years later for Africans. (The term geo-racial is used instead of ethnic in this chapter because the genetic traits of these three groups was very much influenced by geography as two of the three names indicate.) The age that graying begins: Keogh and Walsh pointed out that the perception of graying for the percentage of “any gray” hair is higher for those with darkest hair and lowest for those with the lightest colored hair, as shown in Table 1. Chi Square analysis shows significant differences between fair and medium-to-dark haired groups. To test at what ages the detection of graying begins, we examined the Keogh and Walsh data for the three classes of hair color because the data collection started at age 25, making the data acceptable for study. The models summarized in Table 1 were mathematically extrapolated to % “any gray” to determine the age at which graying begins for the three different hair color groups. This analysis suggests that the detection of any gray hair for the dark-haired persons begins at about age 21–22 for medium-color-haired persons it begins at about age 25 and for the fair-haired persons it begins at about age 26. There is also evidence in the literature that graying occurs at ages earlier than those suggested.7 This “premature graying” has been defined in Caucasians as the onset of graying before 20 years of age,7 before 30 years of age in people of African descent,2,8 and before 25 years of age in Asians.2,7 This definition agrees well with our statistical models for the beginning of graying in Caucasians. The conditions of premature graying are generally related to diseases such as pernicious anemia, hyperthyroidism, and certain autoimmune diseases or even premature cardiovascular disease.8 In contrast to slight or moderate graying, complete graying appears to occur earlier in the fair-haired group than in the other two groups, especially after age 40. The question then becomes, does this effect arise because light hair will appear to be more completely gray before dark hair, because dark hairs will stand out more readily