Carnage

Carnage...A fragment of a stone relief depicting a scene of a battle, Discovered in 1983 during excavations of the Yubileinoye I settlement on the Taman Peninsula southern Russia. This relief was made in the 4th century. BC. in the Bosporan Greek workshop...

Now the guys who commissioned this relief were not Greeks or Scythians...They were Maeotians, an ancient people dwelling along the Sea of Azov, which was known in antiquity as the "Maeotian marshes" or "Lake Maeotis"

These guys had a complicated relationship with both Bosporan Greeks and Scythians. Most of the time they were actually enemies of Scythians and the allies of the Bosporan Greeks...Other times...They were in process greatly influenced by both Bosporan Greeks and Scythians...

The scene depicted on the relief is one of utter carnage...Among the chaos, it is easy to miss "the interesting bits". So I have tilted the image slightly and have added some notes to it (based on the translation from "Военное дело синдомеотов"

On the left in the foreground is a man with long hair; he is wearing a large torc around his neck, and a bow and arrow is suspended from the belt on his left side...

In his raised right hand, he holds a small spear, pointed downward, the strange position of which suggests that this warrior is defeated by the enemy or, possibly, doomed to death...

His enemy on the right had grabbed him by the hair, and has a sword raised to strike. Probably, this second warrior is mounted on a horse, whose head, with a wide opened eye, as well as part of the neck and chest, is visible in front of him...

The most interesting bit: Suspended to the horse's bridle are two severed human heads, hanging upside down...

Now remember this: Celts, "When their enemies fall, cut off their heads and fasten them about the necks of their horses...." (Diodorus Siculus). 

I talked about the head cutting Celts in my article "Head cutters"...

Also remember that Scythians also liked cutting their enemies' heads off.

I talked about this in my article "Helmet?"...

So, Celts and Maeotians hanged the severed heads of the dead enemies from their horse's bridles...Celts, Scythians and Maeotians collected human heads as trophies...

Who started it? Where? When?