What caused this comp shingle damage?

[Kenton H. Shepard, CMI]

Home at about 9000 ft. in the Rockies
Poorly insulated roof with an overhang to the right, vaulted ceiling under the peak at the left. Almost identical shingle damage at the peak and above the overhang.
The interior shot of the peak was taken looking the other direction, so the pitches are reversed.

I know what I think, but I'd like to hear some other theories.

[Peter C. Russell]

Little or no ventilation??

[Kenton H. Shepard, CMI]

Why wouldn't it be uniform across the roof? Why is it only at a narrow band along the peak and at the overhang?

[Peter C. Russell]

Because the cathedral ceiling helps disperse the heat and it's more consintrated at the ridge and eave?

[Kenton H. Shepard, CMI]

Damage was limited to one side even though shingles on both sides appeared to be the same age.

[Peter C. Russell]

Compounded by a southwest exposure?

[Jeffrey Moore]

Retained heat from logs and exposure?