Asked by: Jacob Hackett, Swadlincote
Males have slightly higher mortality rates for subtle genetic reasons as well as war and occupational hazards. To offset this, we have evolved a slight male bias of 110 boys born for every 100 girls. This gap gradually narrows as you move up through the age groups to reach a 1:1 ratio around reproductive age. The ratio of men then continues to fall to around 79:100 after age 65.
Read more:
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
Authors
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.
