During the crossing of the great Land Bridge from modern-day Siberia to Canada, man's brain was relatively undeveloped; as a result, his nerves were also undeveloped, especially involving sexual titillation. Getting a man to climax took extreme feats.
Fossils have been found of a grown man having entered a woman from the vagina with most of his lower body, having pierced her left and right armpits with mammoth tusks and using that, it seems, as leverage to move in every direction inside of her. Judging by the proximity to where the fossils were found, it seems that the woman was ritualistically waterboarded as well, perhaps to make her body convulse and writhe in order to arouse the male.
There is also evidence of using some sort of sticky substance, perhaps syrup, instead of lubrication, in order to add friction to the penetration.
Most intriguing, however, is the recent find of what appears to be a sacrificial bowl on top of a pillar, which closely resembles the modern day Stanley Cup. Judging by the premature bones found in the bowl, it appears that, in cases of extreme inability to reach climax, the male would perform the above sexual act on an infant so that there was more control over movement. When the act was finished, the semen was harvested and implanted into a mature female using moose antlers, and the infant was nursed back to health using syrup, which was the ancient's version of Advil, KY, and Elmer's.