topum

Men used horses to get girls for centuries and still do sometimes). But apparently horses are just returning the favour from the fifth millennium BCE.

"Horse domestication might have depended on a lucky coincidence: the appearance of a relatively manageable and docile male in a place where humans could use him as a breeder of a domesticated bloodline. From the horse’s perspective, humans were the only way he could get a girl. From the human perspective, he was the only sire they wanted."

The first time I heard about The Horse, the Wheel, and Language by David W. Anthony was in Bruce's blog.
http://underbelly-buce.blogspot.co.uk/2008/08/luckiest-horse-in-fifth-millennium-bce.html