Comment by Lord Weeblee on Sekigan, Sekiwan, Sekkyaku no Majutsushi ~Mori no Koya ni Komotteitara Haya 2000-nen. Kizukeba Majin to Yobareteita. Boku wa Tada Majutsu no Tankyuu wo Shitai Dake na no ni~ - Chapter 13

@Lord Weeblee Not only that, but also that they are dead in the first place, as was under the assumption it had only been just a few years, or at least well within human's lifetime anyway.