[Final, summary post.]

I thought I should post some notes about the responses to Andrea’s recent 
postings. Several people seem to have extrapolated beyond what Andrea said.

After a few months of the Cardini, O’Higgins, Rohlf, and Bookstein 
collaboration (Polly was CC:ed on the very early emails but I do not 
remember him engaging), I suggested to Andrea that there should be two 
publications not one. I could see that while writing about the same flaws 
in the same method the approaches Fred and I were taking would be difficult 
to combine in the same paper. Andrea and Paul agreed and Andrea then 
suggested to Fred that he write a paper separate from ours.  Thus, Fred did 
not unilaterally jump ahead and just write his own paper as some seem to 
have assumed. The understanding was that we expected the two papers to be 
published together as “companion papers” in some journal yet to be 

I know that Fred was concerned about the ethics of waiting a long time to 
warn people that they were using a severely flawed (I would say strongly 
biased) method.  The usage of BG-PCA seems to have increased lately and it 
did not seem fair to let people continue to write papers and dissertations 
based on this method once we knew how bad it was. His biorxiv upload and 
his announcement of it on morphmet were not a surprise to us. There were 
emails exchanged about the need to warn users. At the time, Fred told me 
that he needed to go ahead with the biorxiv upload as it was unclear how 
long it would take our ms. to be completed due to other demands on our time.

Reading Fred’s papers can take time but if one just looks at his Fig. 1 
(Google "biorxiv 627448" if you lost the link that Fred posted) you will 
see the magnitude of the problem. It is not subtle! Incidentally, the 
Cardini et al. draft also has a more extensive Figure illustrating the same 
problem as a function of n but the rest of the paper is very different. In 
fact, I found it interesting how two papers about the same defect in the 
same method and reaching the same conclusion could have so little overlap. 
Thus, Fred’s paper does not infringe on the content of the Cardini et al. 
manuscript or interfere with its publication – in fact I think it makes it 
more important as it will show the problem does not require an 
understanding of an abstract theorem. I believe the Cardini et al. paper 
will show that the defects in the method are very easy to understand and 
obvious once you think about it in the right way.

F. James Rohlf, Distinguished Professor, Emeritus. Ecology & Evolution
Research Professor, Anthropology
Stony Brook University

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