On average, girls begin puberty at ages 10–11; boys at ages 11–12. Girls usually complete puberty by ages 15–17, while boys usually complete puberty by ages 16–17. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average between ages 12–13; for males, it is the first ejaculation, which occurs on average at age 15.In the 21st century, the average age at which children, especially girls, reach puberty is lower compared to the 19th century, when it was 15 for girls and 16 for boys. This can be due to improved nutrition resulting in rapid body growth, increased weight and fat deposition, or eating meat from animals which have been dosed up with estrogen. Sexual attraction to tweenagers or people going through puberty is called hebephilia.