Ice age is defined as 115,000 – c. 11,700 years ago. The current theory is blonde formed in the ice age. Interesting: the small populations of isolated blacks in Oceania with "blond" hair are from a different gene https://www.discovermagazine.com/the-sciences/case-closed-blonde-melanesians-understood TYRP1 is a pigmentation related locus, so it isn’t surprising that the mutation was around that region of the genome. The key though is to note that the specific mutation is not found in Europeans.