  In this article, we study complete Type I ancient Ricci flows with positive
sectional curvature. Our main results are as follows: in the complete and
noncompact case, all such ancient solutions must be noncollapsed on all scales;
in the closed case, if the dimension is even, then all such ancient solutions
must be noncollapsed on all scales. This furthermore gives a complete
classification for three-dimensional noncompact Type I ancient solutions
without assuming the noncollapsing condition.
