I'm afraid this is getting off-topic again ...
One cannot apply statistics in that way.
The more samples one takes, the younger the 'most recent' sample becomes. This is simply a consequence of the fact that the measurement error has some error distribution.
One cannot just take a number of samples, and then concentrate only on the extreme case (either way). This is a selective, or biased approach.
All samples play a role. They are all related to the creation time. Even if it took 10 years to create the MS, and the sheets were bought little by little, the sources that went into the MS contents would not have appeared at the very end of this time frame.
Well, not too far off topic - hopefully. The question is whether the Jonah image in the Ms. germ. text could have influenced the VMs, if that Jonah image is dated after 1450. If all parchment was made before 1438, then there would need to be a decade-plus lag between parchment production and VMs creation. On the other hand, if some of the parchment was made after 1438, that decreases the potential lag time. (Assuming there was a relationship between the two.)
The four parchment sample results occur along a timeline. And there is a fair amount of uncertainty inherent in the C-14 testing process. All the variation in test results could be the result of inaccuracies in the testing process (single source model). Or the variations could be a combination of an actual differences between samples combined with the testing inaccuracies (two source model). How can the investigator tell the difference between one-source and two-source models if the C-14 test can't distinguish between real chronological differences and inherent testing inaccuracies?
Anyway, thanks for your consideration.
The easier solution seems to me to be that this illustration in MS germ. fol. 642 is not unique.
Others may exist, may have been digitised, but not yet found by this group.
Or it may exist, but was not (yet) digitised.
Or it may have been in one of many hundreds of thousands of manuscripts that once existed but simply have been lost.
Well, not too far of topic - hopefully. The question is whether the Jonah image in the MS. germ. could have influenced the image of the VMs mermaid, if the Jonah image is dated after 1450? If all VMs parchment is created before 1438, then there is a decade-plus lag between the production of the parchment and the 'potential borrowing' of the Jonah image. If some of the VMs parchment production was after 1438, that alters the calculation a bit.
The four VMs dates exist along a timeline. The C-14 has a significant margin of error. All variation could be attributed to the inaccuracies of the C-14 testing method, the single source model. Alternatively, some variation could be attributed to an actual, chronological difference combined with inherent testing inaccuracies. If there are chronological differences between samples, then the model is a two source system. Using the most divergent alternative, this model will produce a result somewhat more conducive to 1450 connections. How does an investigator differentiate between a one-source model and a two-source model, if the C-14 test cannot distinguish between actual chronological differences and inherent testing variation? It would require some other method of dating that would be accurate within five years instead of 30 - but we don't have that. Sufficient data and higher accuracy would fill in the time-line and inform a correct decision, but that won't be happening either. So the situation will remain unresolved, perhaps for some.
Anyway, thanks for the consideration.
PS: I've been looking at Jonah illustrations a bit, not much that has the same similarity of style. However, that doesn't require a direct connection, or any connections at all. Still an interesting comparison.
There is a Jonah image that is similar, from approx. the latter 14th century, but they chose to put Jonah reaching for vines (rather than being on grass) to illustrate the land-connection.
It's exactly the same fish-head in terms of style (bump nose, eyes, full coverage of scales.). One thing I noticed when collecting zodiac drawings is that copyists often mirrored figures even when they kept all the features the same. This one isn't an exact copy but the face of the fish definitely puts it in a certain tradition.
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BNF fr. 400 It says it's from England, but I have noticed from articles written about them that a number of the English manuscripts from this time period, that are housed in the French national library, were created by scribes and illustrators with Anglo-Norman backgrounds.
I've tried to keep my eyes open over the years for where this style of fish may have originated.
Here is an early one (9th century) but not necessarily the first (looking for these is a sideline, so there might be earlier ones that I haven't seen).
Note again the "eyelid" line, the bump nose, and the all-over scales. It's not as similar as the two above, but may be in the same general tradition.
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From the Abbey Saint-Pierre de Corbie, Lat. 13025
It's one of my favorites... fish eating lion eating fish
For contrast, here is a very different kind of fish. No eyelid line, a more horse-like nose instead of the bump, the scales are discreet (spaced away from each other) and more pointed (and no teeth showing, but that depends on the pose):
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There's more than one illustrator in this manuscript and some of the noses are the bump style, but the rest of the fish is not like the fol 642 example.
Definitely similar with post #45 - both have three similarly spaced teeth in upper and lower jaws. Other examples lack teeth.
What the illustration in post #45 lacks is the more exaggerated "S" curvature of the fish's body. Other examples are all pretty straight.
And of course this Jonah is 3/4ths of the way out of the fish's mouth at a dead run; he got that leg working. Feet, don't fail me now. While other examples <in the original post & elsewhere> show him standing only half way out.
This one is thematically similar to the one on the grass and is from France:
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BNF Lat 512, possibly mid-1400s
This is not as similar but I decided to post it because it's so easy to miss. It's tucked into the border decorations and is quite small:
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Morgan MS M.1004, c. 1425, Paris, France