I found this:
Now, God had set Adam to name every beast, bird and other living thing. When they passed before him in pairs, male and female, Adam-being already like a twenty-year-old man-felt jealous of their loves, and though , he tried coupling with each female in turn act but found no satisfaction in the act. He therefore cried: 'Every creature but I has a proper mate ! ', and prayed God would remedy this injustice.
The tradition that man's first sexual intercourse was with animals, not women, may be due to the widely spread practice of bestiality among herdsmen of the Middle East, which is still condoned by custom, although figuring three times in the Pentateuch as a capital crime. In the Akkadian Gilgamesh Epic, Enkidu is said to have lived with gazelles and jostled other wild beasts at the watering place, until civilized by Aruru's priestess. Having enjoyed her embraces for six days and seven nights, he wished to rejoin the wild beasts but, to his surprise, they fled from him. Enkidu then knew that he had gained understanding, and the priestess said: 'Thou art wise, Enkidu, like unto a godl'