The adolescent growth spurt and the evolution of “adolescence”

When, after a considerable period of time, the human brain reaches adult size, energy intake can finally be used to nourish body growth. At this stage, a rapid increase in height and weight occurs in the human body following sexual maturation, and secondary sexual characteristics appear. This is called the “adolescent growth spurt.”* The delayed development of the body due to early brain development resulted in the second unique stage of the human life cycle: “adolescence.”

■References (Books, papers, Web articles, etc.)
サルの生涯、ヒトの生涯——人生設計の生物学』  デビッド・S・スプレイグ (京都大学学術出版会、2004)
家族進化論』 第4章・第10節 脳の大きさと生活史の変化  山極寿一 (東京大学出版会、2012)

*Adolescent growth spurts occur in males at around twelve to twenty-one years old, and in women at around ten to eighteen years old. At the beginning of the adolescent growth spurt, the production of sperm and the menstrual cycle have already begun, and breeding is possible, but it is not until later that reproduction actually starts.

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