Faces and hearts occur regularly in rocks and stones.
This rock was found by my son next to a Sweet Chestnut tree that must be at least five hundred years old. Amongst the images and art in this rock you can see a few different faces front facing and in profile, animals, hearts and an Owl.
The half face seen on the far left of the image above has the same stripe markings as the side profile of the face in the image below.
The image below shows the first pictured rock rotated and tilted slightly. You can now see a prehistoric woman and man with large headdress caressing each other.
I see what you mean about the wolf across the top of the stone Colin. I hadn't noticed that.
If you follow the bottom tip of the stone in the first photo up the curved line, the heart is located just to the left of where the line stops 2/3 of the way upwards. Just above that line to the right at the top of the stone I also see an Owl crouching on the shoulders of someone.
The subjective nature of this art never ceases to amaze me.
The simple lines creating detailed animal depictions never ceases to amaze me.