Digit Ratios

digit ratios

On the second day of our forensics investigation, we took a more detailed look at the hand-print. It turns out that the hands of men and women evolved differently. Scientists think that women evolved to have longer index fingers to be more useful for gripping, while men evolved shorter ones that were better for fighting. After all, when a man throws a punch with a clenched fist, a long index finger is more likely to break.

fingerlength

Because of this difference, investigators can sometimes learn the gender of a suspect simply by looking at the hand print. By dividing the length of our suspect’s index finger (6.9 cm) by the length of the their ring finger (6.8 cm), we can calculate what’s called the “digit ratio.” Our suspect’s digit ratio is about 1.01. Compare that to the average ratios for males and females (see above) and you can be fairly sure that our suspect is, in fact, a girl.

December 10 – Digit Ratios (pg322)

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