Working out past relative plate positions

Question 1

How can you construct global APW curves?

Answer 1

By applying the magnetic reconstruction technique to as many rock samples as many continents and the seafloor as possible, we can construct global APW curves and thus reconstruct the locations of the plates relative to each other in geological time

Question 2

There is a big problem with this however. How would you decide whether to shift the Eurasian APW onto the North American APW or vice versa, or in fact whether both need moved?

Answer 2

We need additional evidence.
For example there are only certain climatic zones in which ice sheets can form or different life forms can live, which restricts the positions the continents and oceans could have had at the time
As always with scientific arguments, every little helps and we should consider all this evidence, but on the whole there are still too many uncertainties and circular arguments associated with this
The best thing to do is to look for an absolute reference frame for plate motion