A Type D personality is distressed, Type D's have a negative outlook towards life and are pessimistic. A small event that is not even noticed by type B can ruin type D's day. Type D personalities are more subject to depression than other personality types.
For most of human history, horses were seen as prey to be hunted for sustenance. During the late Pleistocene, around 55,000 years ago, Neanderthals scavenged off of horse carcasses and made occasional kills of their own.
It is supposed that the horse was first used by a tribe of Indo-European origin that lived in the steppes north of the chain of mountains adjacent to the Black and Caspian seas. Influenced by climate, food, and humans, the horse rapidly acquired its present form.