Grey aliens are time-traveling genetically modified humans

Grey aliens [1] are the most commonly encountered type of space alien by humans, accounting for 43% of reported alien encounters in the US [2]. The similarity in the configuration of their bodies to that of ours and the observed variation in their bodies have been difficult to explain, and have led many to believe that the reported encounters did not actually occur. [1§Evolutionary feasibility debate]

In the context of human colonization beyond our solar system, it has been proposed that we send humans who are genetically modified to be better adapted to the environments they will find on the planets they are to colonize. [3][4][5][6]

Time travel may exist in the future, especially with the explosion of technology that is just starting these days and will likely be enhanced a great deal by having many more billions of humans on several planets developing technology.

Therefore, I propose a theory to explain Greys: They are distant-future genetically modified descendants of humans who come back in time to visit us, possibly even to plant the seeds of their own existence.

This is effectively the inverse of another theory that has been proposed and declared nonsensical: They visited Earth throughout our evolutionary history and guided our evolution to produce beings similar to themselves. [1§Evolutionary feasibility debate][7]