The Origin of the Species
by Al Feldstein
Weird Fantasy #8 (1951)
Two brothers, scientists in the far-off future where scientists wear tight shirts and shorts, disagree about where the "missing link" between men and apes will be found. One thinks it'll be in space, the other thinks on Earth. The first goes off to space, but his ship hits a time-warp and the crew find themselves a million years in the past, when the moon had an earth-like atmosphere and strange animals, including the "missing link".
Returning to Earth, with samples of the creatures, they hope to hit the time-warp again, but fail to, and are stranded in the past. The scientist leaves a journal, and in the present his brother digs up the space-ship and finds they were both right, the evidence of the "missing link" would be found on Earth and in space.
I like the story in this one, but I found the artwork a bit stiff. It's one of the last stories that Feldstein would draw, concentrating on writing, editing and covers after this (his cover for this issue is much better drawn), so maybe he was just rushed by the needs of this other jobs.