(Sketch after Meaden, "Secrets" p 104,
details of right face added by me)
The left profile is definitely human, and I first read about it in Meaden's "Secrets" book. However I have never read of the right profiled face anywhere so I assume I am the first to affirm it. This right profile face is somewhat abstract and animal-like, with a distinctive sloping forehead, small concave eye and open mouth.
My intention here is to show that this pattern or design can be seen at the barrow not only on Stone 21, but also just outside it in the blocking stones 45 and 46 (please see the photographs of these stones below, and click on their respective link buttons to see larger versions).
This is a crucial discovery as it proves that the religious imagery on Stone 21, which records beliefs more than 5500 years old, was still relevant and reproduced in the stones used to block up the barrow far, far later in the neolithic, more than a thousand years later in fact.
The later people's memory of, and respect for, the old ways was astounding when you appreciate the timescale involved and consider that the tribe that built the barrow was not the same tribe that eventually completed Avebury itself [Nature volume 555, pages 190–196 (08 March 2018)]. The barrow had originally been built by the Windmill Hill People, and I believe that their religious imagery incorporated in its interior was taken up in later years by the Beaker People who replaced them. The Beakers incorporated the inherited imagery in the stones they used to block the barrow up, and I believe they also used the imagery in their creation of Avebury henge and the West Kennet Avenue. The old barrow religion was recycled by the later immigrant people, it was not forgotten or distained. Their respect for tradition was profound.