Stage 5 (final stage) sexual traits are obtained on average at age 14.6 http://www.patient.co.uk/doctor/Puberty-Normal-and-Abnormal.htm as for the fertility claim, I am having trouble to find *any* studies that show fertility information for those below the age of 20. In the studies done, fertility is at its peak in the 20's , but none of the studies I can find even observe teenage years. I believe in the past I have read that peak fertility is from the start of reaching full sexual maturity (14.5 about) to sometime in the 20's. I will continue looking for a citation, but please find me a citation that people in their 20's are actually more fertile than teenagers, rather than a citation that people are at peak fertility in their 20's (because I can find that citation all over the place as well, but the studies don't have information for people below their 20's so it doesn't disprove what I said).