Cool little website here titled The Aryan Trail (3500 - 1500 BC). A lot of the stuff will look very familiar to those who've been following this blog and the latest ancient DNA results, which, among other things, include the discovery of Y-chromosome haplogroup R1a-Z94 in a sample from a Kurgan burial at Potapovka, near the Volga River, Russia, dated to 2925-2536 cal BCE (see Poltavka_outlier, ID I0432, Mathieson et al. 2015). Of course, R1a-Z94 is one of the most common Y-chromosome haplogroups amongst present-day Indo-Aryans.
Excavations conducted from 1985-1988 in Potapovka exposed four burial mounds, or kurgans, dated between 2200-2000 BC. Beneath kurgan 3 the central grave pit had remains of a man buried with at least two horse heads and the head of a sheep, in addition to pottery vessels and weapons. After the grave pit was filled, a human male was decapitated, his head was replaced with the head of a horse, and he was laid down over the filled grave shaft. This unique ritual provides a convincing antecedent for the Rig Vedic myth of Dadhyac Atharvan who knows the secret of making Soma juice, the nectar of immortality. The Asvins insists that Dadhyac tell them the secret. He refuses. They cut off his head and replaces it with the head of a horse, through which he becomes an oracle and tells them the secret.
Source: The Aryan Trail (3500 - 1500 BC)