Development of the human body used to approximately judge a child's age based on physical development. Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult
Institute for the Study of Human Knowledge web site for a project entitled "The Human Journey". It aims to "follow humanity from our origins in Eastern Africa and the Middle East to the present day, with an eye to what comes next." Institute for the Study of Human Knowledge The Institute for the Study of Human Knowledge (ISHK) is a non-profit educational charity and publisher established in 1969 by the noted and award-winning psychologist and writer Robert E. Ornstein and based in Los Altos, California, in the USA. Its watchword is "public education: health and human nature information." Robert Ornstein, psychologist, writer and professor at Stanford University,