(In our case "old" is an unknown quantity; we've only recently learned that the last person to live in our house was a veteran of the Great War who came to live here in 1918 or '19. Apparently he was a bit eccentric, perhaps shell-shocked. To this day the neighbors still refer to him as "le Parisien.")
So these friends are scraping away at a wall one day and come across a small cache of....teeth. Molars. Big adult ones. But it doesn't end there. They keep looking and stuffed in the cracks all over the wall....more teeth. Adult teeth, children's teeth. From several people. This has been going on for some time now and they don't know how many different people these teeth come from.
I've heard that the hills have eyes and the walls have ears, but teeth?
My friend is convinced something dark and sinister occurred here long ago. I proposed that perhaps the earth used in building the wall came from the ancient cemetery nearby at St. Pierre de Merdans (see my post about this St. P de M here). My friend disagrees: it's not the same kind of earth, why only teeth and not other bone fragments and most of all, the teeth aren't mixed into the adobe bricks or mortar, they were most certainly placed there after the wall was built.
Perhaps my friend's imagination is being colored by a more recent tale, which we've already covered, about a severed arm found in the woods, that itself recalling the horrible tale of the local tavern whose owner pretty much imprisoned and abused, physically and sexually, a hapless vagrant for years. And then she killed him. The remains have never been found.
Me, I don't know. Perhaps a dentist lived there. Maybe it was an odd family custom: pop the teeth into the cracks. Maybe they felt it would prevent their own teeth from cracking. Or they simply found it amusing.
I tried Googling it, to see if there was any folklore around putting teeth into mortar or brick for superstitious (or other) reasons, but came up with nothing.
Addition 11/28: From Sir James Frazer's The Golden Bough (XXI. 8.):
The Armenians do not throw away their cut hair and nails and extracted teeth, but hide them in places that are esteemed holy, such as a crack in the church wall, a pillar of the house, or a hollow tree. They think that all these severed portions of themselves will be wanted at the resurrection, and that he who has not stowed them away in a safe place will have to hunt about for them on the great day.
Don't know if this is related....
Back in 2009 Gid posted about someone finding a bunch of teeth in clothes at Wal-Mart, which may be some odd practical joke: http://lawsofsilence.blogspot.com/2009/03/human-teeth.html
More germaine, however, is a blurb my sister in law told me about from a French book of superstitions. In the US we have the Tooth Fairy, you know, where we put a fallen tooth under the pillow and in the morning find a coin or some money in its place. Apparently in Great Britain and Ireland it was customary to bury the teeth.
In France, the Fairy is a little mouse, La Petite Souris. The basic exchange is the same, but the actor is different. According to some French traditions, people put the tooth in mouse holes found in the walls of the home in exchange for even greater wealth down the line, and that the real tooth would be replaced by one made of silver. The blurb on this was rather short and ambiguous. We'll see what we can dig up.
French Wikipedia gives us this info:
Par exemple, aux Philippines, quand un enfant perd une dent, il la jette au-dessus du toit de la maison. De cette manière, une souris lui en rendra une autre qui sera aussi solide et blanche que les dents de cette souris. Au Togo, on dit aux enfants de jeter leurs dents de lait au-dessus du toit de la maison, et surtout de ne pas ouvrir la bouche.
Basically in the Philippines children throw their teeth on the roof of the house; the little mouse will then exchange it for one as solid and white as his own. In Togo, kids throw their teeth on the roof but must keep their mouths closed. The French text is unclear if this means only during the duration of this little ritual or if it means they need to keep it closed for a long time afterwards. I certainly see the practical value of that bit of folklore!
Anyway, all this proves nothing, but lends plausability to my initial reaction that the teeth in the Aucamville house are related to some sort of folk belief, even if only to follow an amusing custom....