I read/saw in news reports that Notre Dame cathedral housed artifacts such as a crown thought to be part of the crown of thorns Jesus wore on the cross, or a nail and a piece of wood from the cross. As a former Catholic, now atheist, I have always been skeptical of the authenticity of such objects. Is there any effort to make historical documentation of these artifacts? For example, was the crown taken by someone whose name/identity was established and is there a “chain of custody” in any way?
It seems like so many religious artifacts are of dubious authenticity. They always seem to “appear” in the Middle Ages with a vague backstory. But that’s just my amateur opinion.
The chain of provenance is surprisingly detailed for a number of holy relics and artifacts across Europe, but only to a point. They all had to find some point of origin and these origin stories would typically be unsatisfying to the modern historian.
Take, for example, the shards of the True Cross. Looking to hagiography, the true cross was supposedly found by St. Helena, the mother of Emperor Constantine, when she was sent to the Holy Land in search of relics by him in 324 CE. The most common narrative you'll encounter in Western Christianity recounting this story is Jacobus da Varagine's Golden Legend. In the third volume, he states that:
Constantine his son remembered the victory of his father, and sent to Helena his mother for to find the holy cross. Then Helena went in to Jerusalem and did do assemble all the wise men of the country, and when they were assembled they would fain know wherefore they were called. Then one Judas said to them: I wot well that she will know of us where the cross of Jesu Christ was laid, but beware you all that none of you tell her, for I wot well, then shall our law be destroyed...Then Judas made him ready and began to dig, and when he came to twenty paces deep he found three crosses and brought them to the queen, and because he knew not which was the cross of our Lord, he laid them in the middle of the city and abode the demonstrance of God; and about the hour of noon there was the corps of a young man brought to be buried. Judas retained the bier, and laid upon it one of the crosses, and after the second, and when he laid on it the third, anon the body that was dead came again to life.
As you can well imagine this story is likely not quite accurate. It was also written nearly a thousand years after the fact. The earliest historical references to the Helena story are from Socrates Scholasticus, Theodoret, and Sozomen, all writing between 400-450 CE. While some details vary the general nature of the Helena story is consistent. What we know is that a cross was venerated in Jerusalem as far back as the 300s CE and its discovery was attributed to St. Helena.
Now how did some fragments from a cross dug out of the ground in Jerusalem in 324 CE end up at Notre-Dame de Paris in 2019? Like so many other relics found across western Europe today, via Constantinople. The Latin Emperor Baldwin II sent fragments of true cross relic to King Louis IX of France, likely around 1245 CE during his travels in France and Italy. He gave large numbers of relics to Louis IX in exchange for military support and funds--the Latin Empire was essentially bankrupt; Baldwin also rather notably pawned the Crown of Thorns to Venice for a payout of 13,134 hyperpera in 1238 (this later ended up in France after Louis purchased it from the Venetians). The number of relics that arrived in Paris led to the construction of Sainte-Chapelle to house them.
In a sense we are lucky with the Parisian true cross fragments. Unlike many relics, there is a fairly clear chain of custody leading it into the present. The problem, of course, is that we have no idea where this original piece of wood came from, and we can't really compare the Paris fragments to the "original" because the Jerusalem relic was lost to Saladin in the Battle of Hattin and never seen again.
Speaking generally, though, there are countless fake relics across Europe. There are also countless relics with long histories. Generally speaking the strength of the "history" will depend on the prominence of the relic--when such things are exchanged between monarchs or leading prelates, at least some kind of recounting tends to exist. But a huge number of relics flooded into Europe with the loss of the Eastern Roman Empire to Muslim expansion (and, of course, the Latin occupation of Constantinople in the 13th century). For a fairly good popular history coverage of this process, you could check out:
Wells, Colin, Sailing from Byzantium: How a Lost Empire Shaped the World (Delacorte Press, 2007).
For a more academic view on the process of the relics moving to France, I'm afraid I can only recommend some French language titles:
Durand, Jannic. "Les reliques de Constantinople." Dossier d'archéologie 264 (2001).
Durand, Jannic. Le trésor de la Sainte Chapelle (Paris: RMN, 2001).
Le Goff, Jacques. Saint Louis (Paris: Gallimard, 1996).
There's no evidence, to my knowledge, that any relics that claim to be from the time of Jesus of Nazarene are from that period and region. Saintly relics are a much more mixed bag, since some saints are known in historical records to have died and then been interned in a particular place.
It's sort of an answer to a question exactly inverse of yours, but here's an excellent previous answer by /u/ Philip_Schwartzerdt on how you could fake a relic. Naturally, talking about the methodology of passing off counterfeit relics involves talking about the entire trade.