Unlike most mammals, mature male orangutans exhibit different facial characteristics: some develop large 'cheek pads' on their faces (as shown above); other males do not. A team of researchers studied the difference in reproductive success between cheek-padded males and males without cheek pads. They found that those with cheek pads are significantly more successful in fathering offspring.
Source: http://link.springer.com/article/10.1007%2Fs00265-015-1991-0
