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Take a look at your right-hand. Which of your fingers is longer: your ring finger, or your index finger? Surprisingly, a passing stranger who noticed a difference in length between these two fingers might infer some very personal characteristics about you. With no more data than that gleaned from a passing glance at your hands, a stranger might infer whether you are likely to have homosexual inclinations, are highly fertile, may eventually suffer from a heart attack or breast cancer, have musical aptitude or sporting prowess, and a surprisingly long list of other characteristics.
Why do the fingers reveal such a wide spectrum of information (albeit very probabilistic)? Scientists reviews evidence to suggest that the ratio of the length between the ring and index finger is somewhat sexually dimorphic, that this ratio is determined during early fetal development, and that it is influenced by sex hormones, particularly testosterone. If this is true, the fingers may provide a permanent, and easily visible, historic marker of important hormonal events that occurred during a critical time of fetal development, the latter part of the first trimester. This is a critical time of sexual differentiation of both the brain and body.
Specifically, it is the ratio of the length of the index finger (digit 2, or "2D") and the ring finger (digit 4, or "4D") that is sexually dimorphic. Generally, males have a ring finger that is longer than their index finger. Females typically have index and ring fingers of about the same length. The ratio of index finger length to ring finger length is called the “2D:4D digit ratio,” or more simply, the “digit ratio.” Scientists reports that, for males, the index finger is generally about 96 percent of the length of the ring finger, which gives an average digit ratio for males of .96. The digit ratio would be 1.00 if the ring and index fingers were the same length, and greater than 1.00 if the index finger was longer than the ring finger. Males generally have a digit ratio below 1.00 -- they have what is termed a "low digit ratio." Women generally have a digit ratio of about 1.00 (the index and ring fingers are of about equal length), or a "high digit ratio."
Scientists links the proximate causes of digit ratio sexual dimorphism to the effects of sex hormones during early fetal development. He believes the evidence is persuasive, but not yet definitive, that higher levels of testosterone during this critical developmental stage facilitates the growth of the ring finger, while higher levels of estrogen facilitates the growth of the index finger. He states: “In general, it seems that 2D:4D is the most reliable of the predictors of hypermasculinization…” (p. 139). One of the consequences of hypermasculinization, as reflected by the digit ratio, may be higher levels of fertility in men and lower levels of fertility in women. He also suggests that hypermasculinization increases the likelihood of homosexuality or bisexuality, in both males and females.
Scientists devotes separate chapters to explore the relationship between digit ratio and a variety of characteristics, including assertiveness and attractiveness , reproductive success, hand preference, verbal fluency, autism, and depression (chapter 5), health and disease , homosexuality, musical aptitude and sports aptitude . A brief summary Scientist's findings (some of which are quite preliminary) is presented below.
Why do the fingers reveal such a wide spectrum of information (albeit very probabilistic)? Scientists reviews evidence to suggest that the ratio of the length between the ring and index finger is somewhat sexually dimorphic, that this ratio is determined during early fetal development, and that it is influenced by sex hormones, particularly testosterone. If this is true, the fingers may provide a permanent, and easily visible, historic marker of important hormonal events that occurred during a critical time of fetal development, the latter part of the first trimester. This is a critical time of sexual differentiation of both the brain and body.
Specifically, it is the ratio of the length of the index finger (digit 2, or "2D") and the ring finger (digit 4, or "4D") that is sexually dimorphic. Generally, males have a ring finger that is longer than their index finger. Females typically have index and ring fingers of about the same length. The ratio of index finger length to ring finger length is called the “2D:4D digit ratio,” or more simply, the “digit ratio.” Scientists reports that, for males, the index finger is generally about 96 percent of the length of the ring finger, which gives an average digit ratio for males of .96. The digit ratio would be 1.00 if the ring and index fingers were the same length, and greater than 1.00 if the index finger was longer than the ring finger. Males generally have a digit ratio below 1.00 -- they have what is termed a "low digit ratio." Women generally have a digit ratio of about 1.00 (the index and ring fingers are of about equal length), or a "high digit ratio."
Scientists links the proximate causes of digit ratio sexual dimorphism to the effects of sex hormones during early fetal development. He believes the evidence is persuasive, but not yet definitive, that higher levels of testosterone during this critical developmental stage facilitates the growth of the ring finger, while higher levels of estrogen facilitates the growth of the index finger. He states: “In general, it seems that 2D:4D is the most reliable of the predictors of hypermasculinization…” (p. 139). One of the consequences of hypermasculinization, as reflected by the digit ratio, may be higher levels of fertility in men and lower levels of fertility in women. He also suggests that hypermasculinization increases the likelihood of homosexuality or bisexuality, in both males and females.
Scientists devotes separate chapters to explore the relationship between digit ratio and a variety of characteristics, including assertiveness and attractiveness , reproductive success, hand preference, verbal fluency, autism, and depression (chapter 5), health and disease , homosexuality, musical aptitude and sports aptitude . A brief summary Scientist's findings (some of which are quite preliminary) is presented below.
