system
Given the following post, respond as if you're commenting on Reddit:
human
[Futurama] Since Fry went back in time and became his own grandfather, why does he bear such a striking resemblance to Enos?

Since Fry has now become a closed loop of genetics, why does he look almost exactly like his "grandfather" Enos?  And for that matter, how can they be descended from David Farnsworth? Unless I have my family tree wrong, aren't both the professor and Fry the progeny of Enos and his wife?  Wouldn't that make it so the Professor *also* lacks the brain wave that the giant brains use against the planet?
gpt
It's possible that the rules of time travel in Futurama aren't like other things, that Enos was supposed to survive to an old age and when Fry accidentally killed him, he simply 'patched' the timeline by inserting himself in his grandfather's place. He was related to Enos in the original timeline, explaining his resemblance to him, but that got shunted aside/merged when he became his own grandfather. He still holds Enos' genes, however. (This would also mean that Fry's father was sleeping with his own grandmother in the 'new' timeline, making it two generations of incest to remove that specific brain wave.)

The reason the Professor still has the brain wave is that a thousand years have passed since then and he's had enough genetic material from different sources to regain that specific brain pattern. There are at least ten generations between them, meaning ten different pairs of fathers/mothers equalizing Fry and his father's acts of incest with new genetic material.