Dear Yousuf Khan:

On Saturday, January 30, 2016 at 5:55:31 PM UTC-7, Yousuf Khan wrote:
....
My question is, if the isotopic evidence which
was used to create the Theia Hypothesis in the
first place, due to a previously perceived
difference in isotopic abundances, so now that
that isotopic evidence has disappeared, why keep
the Theia Hypothesis? There were other theories
prior to that, which were discarded due to the
isotopic evidence.

How many of them involved collision-and-mergence of two bodies? The only variant I am aware of that is significantly different, is gravitational capture, and that took a third body.

Still have an initial Theia...

David A. Smith