descent with modification

[pfeaster]

It would require a lot of reordering in Currier A to follow the trajectory: maybe there is no trajectory and the ratio varies randomly both in Currier A and Currier B? I don't know.

Nor do I -- I'm just suggesting that the evidence for a gradual [Ey] to [Eo] shift in Currier A is comparable to the evidence for a gradual shift towards [Ed] in Currier B.  In both cases, we can arrange pages along a continuous spectrum, but what that means isn't necessarily clear.

I just modified my "Voynich Imager" script so that instead of analyzing paragraphs separately, it can now instead track the positions of features within whole pages (to test hypotheses about self-citation).

If [Ed] became more frequent over time because of the cumulative effects of asymmetrical changes made in its favor during copying, and if a significant number of words were typically sourced from earlier positions on the same page (as needed to explain the co-occurrence of similar words nearby each other), I believe we should expect to see the relative frequency of [Ed] increasing on average from the top of each page to the bottom of each page.  At the top of the page, we should expect more words to be "first generation" copies from some earlier source which should (because earlier) have contained a smaller proportion of [Ed]; each will have had perhaps one opportunity to undergo a change.  At the bottom of the page, we should instead expect a higher proportion of words to be "second generation" or later copies of recently re-copied words, and hence more likely to contain the favored change because they've had more opportunities to undergo it. 

However, the relative frequency of [Ed] doesn't perceptibly increase, on average, as we move down a page (brighter = more prevalent):

   

Within Currier B, if we plot [Ed] in red, [Ey] in blue, and [Eo] in green, we get this:

   

The proportion of [Ed] relative to [Ey] and [Eo] doesn't increase, on average, as we move down the page.