One study analysing the self-reported Kinsey data set found that the average penis of a homosexual man was larger than the average penis of their heterosexual counterparts (6.32 inches [16.05 cm] in length amongst gay men versus 5.99 in [15.21 cm] in heterosexuals, and 4.95 inches [12.57 cm] circumference amongst gay men versus 4.80 in [12.19 cm] in heterosexual men). Evolution
The human penis is thicker than that of any other primate, both in absolute terms and relative to the rest of the body. Early research, based on inaccurate measurements, concluded that the human penis was also longer. In fact, the penis of the common chimpanzee is no shorter than in humans, averaging 14.4 cm (5.7 inches), and some other primates have comparable penis sizes relative to their body weight.The evolutionary reasons for the increased thickness have not been established. One explanation is that thicker penises are an adaptation to a corresponding increase in vaginal size. The vaginal canal is believed to have expanded in humans to accommodate the larger size of a newborns skull. Women may then have sexually selected men with penises large enough to fit their vagina, to provide sexual stimulation and ensure ejaculation.Other evolutionary hypotheses to explain humans relatively large penis length and girth include a sperm competition hypothesis and a mate competition hypothesis. The sperm competition hypothesis does not have much support as in other mammals where sperm competition is present, larger testes evolve, not larger penises.
Sir William Osler was interested in the disorder and chorea in general, and was impressed with Huntingtons paper, stating, "In the history of medicine, there are few instances in which a disease has been more accurately, more graphically or more briefly described." Oslers continued interest in HD, combined with his influence in the field of medicine, helped to rapidly spread awareness and knowledge of the disorder throughout the medical community. Great interest was shown by scientists in Europe, including Louis Théophile Joseph Landouzy, Désiré-Magloire Bourneville, Camillo Golgi, and Joseph Jules Dejerine, and until the end of the century, much of the research into HD was European in origin. By the end of the 19th century, research and reports on HD had been published in many countries and the disease was recognized as a worldwide condition.During the rediscovery of Mendelian inheritance at the turn of the 20th century, HD was used tentatively as an example of autosomal dominant inheritance. English biologist William Bateson used the pedigrees of affected families to establish that HD had an autosomal dominant inheritance pattern. The strong inheritance pattern prompted several researchers, including Smith Ely Jelliffe, to attempt to trace and connect family members of previous studies. Jelliffe collected information from across New York and published several articles regarding the genealogy of HD in New England.