"Boys’ voices are breaking earlier; girls are developing breasts as young as six. But why?" Danish researchers began investigating when a church choir could not find enough pre-pubescent boys. "Most paediatric endocrinologists now agree that the age of puberty is falling fast in developed nations. But there is no consensus on why. The changes are happening too fast to be genetic, so the focus is on environmental factors. Obesity, chemicals and even absentee fathers have all been investigated (a girl who lives apart from her father tends to get her period earlier)."