Phelps (1952) first proposed the sex-influenced mode of inheritance. Note that there is not a bimodal distribution of long and short. All ratios are less than 1, presumably because finger length was measured using X-rays. In reality, there is a continuous distribution of relative finger lengths: Histogram of index:ring ratios data extracted from Fig. The myth divides hands into two categories, those with index fingers longer than ring fingers, and those with index fingers shorter. The person on the left has an index finger longer than the ring finger (L), while the person on the right has a shorter index finger (S). Each technique measures from a different place on the finger and therefore would give different results on the same hands. The most precise measurements come from X-rays, but this is obviously impractical for classroom use. Measuring from the knuckle to the fingertip, or from the crease between finger and palm to the fingertip, is imprecise because skin moves around. Placing the hand palm-down and seeing which finger extends further is a problem, because a slight shift in the angle of the fingers dramatically changes the relative position of the fingertips. It is difficult to measure finger length accurately. Here are a few examples of web pages that perpetuate this myth: Thus SS and SL males will have short index fingers and only LL males will have long index fingers, while SS females have short index fingers and SL and LL females have long index fingers. In males, the allele for S is said to be dominant, while the allele for L is said to be dominant in females. This is said to be a sex-influenced trait. Others have an index finger that is shorter than their ring finger (S). Some people have an index finger that is longer than their ring finger we'll call this long index finger, or L. Myths of Human Genetics: Finger Length Myths of Human Genetics: Finger Length
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