Anthro

Anthro, the First Boy, was the first boy to exist in the timeline.

Biography
Anthro was the first boy in the timeline of Earth-1. As of 2049 Eobard Thawne had recorded the entire timeline from him to Kamandi, the last boy on Earth.

Behind the Scenes

 * In the comics Anthro is the first Cro-Magnon, the predecessor of humanity.