<P> Premarital sex was not encouraged but was allowed in general, restrictions on adolescent sexuality were incest, exogamy regulations, and firstborn daughters of high - ranking lineage . After their firstborn child, high - ranking women were permitted extramarital affairs . </P> <P> The next day, as soon as it was light, we were surrounded by a still greater multitude of these people . There were now a hundred females at least; and they practised all the arts of lewd expression and gesture, to gain admission on board . It was with difficulty I could get my crew to obey the orders I had given on this subject . Amongst these females were some not more than ten years of age . But youth, it seems, is here no test of innocence; these infants, as I may call them, rivalled their mothers in the wantonness of their motions and the arts of allurement . </P> <P> Adam Johann von Krusenstern in his book about the same expedition as Yuri's, reports that a father brought a 10 - 12 - year - old girl on his ship, and she had sex with the crew . According to the book of Charles Pierre Claret de Fleurieu and Étienne Marchand, 8 - year - old girls had sex and performed other sexual acts in public . </P> <P> The second sexual revolution was a substantial change in sexual morality and sexual behaviour throughout the West in the 1960s and early 1970s . One factor in the change of values pertaining to sexual activities was the invention of new, efficient technologies for the personal control of ability to enter pregnancy . Prime among them, at that time, was the first birth control pill . Liberalized laws on abortion in many countries likewise made it possible to safely and legally break off an unwanted pregnancy without having to invoke a birth posing grave danger to the health of the mother . </P>

Who conducted most sexuality research in the late 19th century ​