The
new article asking a professor about how Fusion may work is pretty interesting.
"Dragon Ball’s Fusion involves a process where each person touches the other’s fingers after doing a unique movement, and then there’s a burst of light. In that instant, the two trying to fuse each returned to their single-celled zygote (or fertilized egg) state, and then the two zygotes fuse to become one fused cell, which then grows rapidly, becoming a single individual.
This seems ridiculous for humans, but it seems possible that a single individual with the genetic information of two people could exist. The three processes "return to the zygote", "fusion", and "growing into a human form" all occur instantly."