Hard to read, but I get the drift. Africans were culturally more promiscuous and women had a greater choice of partners than other parts of the world, and this is quite well-known. Therefore, women chose the partners who gave them greatest pleasure. It is also thought that the corona (the ridge that is part of the glans) on the penis actually removes semen deposited by other lovers, and a thicker penis would be more effective in this regard, meaning the man with the thickest penis had a greater chance of producing an offspring. Promiscuity is still a feature of much of Africa, which is why Aids has spread so rapidly through the heterosexual population.
Penis size in Asia is not necessarily that much shorter, but it has been measured as thinner on average. This is Africa in converse, where Asian women were less likely to have sex before marriage due to cultural pressures, and less likely to have other lovers while in marriage.
Europeans are somewhere in the middle in terms of penis thickness, and prior to the sexually repressive Victorian era, were rather flexible about sexual morals. For example, in Britain, marriage vows were suspended for the month of May until the late 18th Century, and any woman could have sex with any man, and the 1st of May was the date for a sexual free-for-all. Farm workers and working class couples didn't often marry, and were flexible about how long they lived with their partners before moving to someone else. We tend to think of European sexuality in terms of upper-class arranged marriages, such as written about by Jane Austin, but the majority of the population were not like that.
