Jesus had red hair, now we have proof of it. Or do we?

In 2017, the authors of the study about the DNA analysis of Napoleon Bonaparte published an analysis of a small fragment of hair found on the Shroud of Turin, a fragment of hair which, apparently, was reddish-blond.
The study is Scanning Electron Microscopic Characterization and Elemental Analysis of One Hair Located on the Face of the Turin Shroud, by Gérard Lucotte e Thierry Thomasset. 
Now, obviously, we all know that debates about the authenticity of the Shroud are still ongoing, and we don’t know who this fragment of hair came from. However, since it is probably reddish, and (as far as I could understand) this is the only human hair found on the Shroud, I thought you might be interested.
Besides, if you follow this blog, you know that there are many paintings depicting Jesus (and often the Virgin Mary as well) with red hair, and you must admit this is quite curious: why choosing the rarest hair colour on earth? Did painters have no trouble finding sitters with this hair colour?

The hair fragment (called b1) is 14 × 9 μ (micrometers) and was found in 1978 between the eyebrows of the face, in a red spot deemed to be a blood spot (although others claim it was found in 1988). 

On the top of the image, the area where the fragment was found

The authors call it “down hair”, that is, a normal body hair, because they found it to be thinnest than a facial hair or a hair from the head or from the eyebrows. They write it is ten times thinner than a beard or an eyebrow hair.
They analysed it with some of techniques we saw in this article, namely the scanning electron microscope (SEM) and the energy-dispersive X-ray spectroscopy (EDX).

Under the electron microscope, the authors observed the cuticle scales, that is, the overlapping structures that form the outer coating of the hair.
In the fragment, the distance between successive rows of scales is approximately 2 μm, but according to the authors' comparison, this characteristic more closely resembles a strand of beard than their sample. However, since the diameter is so thin, they conclude the fragment is a down hair.

Through EDX analysis, carbon, oxygen, a small amount of sulfur and a small amount of calcium were found.
Carbon and oxygen are consistent with the organic component of the hair. Sulfur, on the other hand, is interpreted by the authors as a component of keratin, the primary structural protein in hair. Notably, cysteine molecules can form disulfide bridges with one another and these bonds contribute to the three-dimensional structure and strength of keratin. It is precisely this characteristic that makes hair relatively strong.
The authors note that the sulfur peak in this fragment is quite low (3%) compared to that observed in the modern human hairs used for comparison, therefore they argue the hair's sulfur content may have decreased during the preservation process.
As for the small calcium peak, the authors state that it likely corresponds to a residual calcium deposit on the fragment's surface, rather than the fundamental composition of the hair itself.
They also found copper at both ends of the fragment, attributing this to the fact that the hair was likely cut with a copper or bronze blade.

As for the colour, the authors identify 25 melanosomes on the surface of the fragment: 8 classified as MS1, associated with eumelanin, and 17 as MS2, associated with phaeomelanin. The ratio is therefore approximately 1:2, so they conclude that the fragment was reddish-blond.
According to the studies by Ito and Wakamatsu (like this one), in blond hair the ratio eumelanin/phaeomelanin is 5:1, while for red hair is about 0,8:1, so the colour of the fragment could have really been some sort of reddish-blond, strawberry blond.
If this was a body hair, it is possible the person it belonged to was a redhead, since usually redheads have reddish-blond body hairs. 

 

Schematic representation of the melanosome distributions in the fragment; 1 and 2 numbers concern M1 and M2 melanosome types, respectively