Gegan's irrefutable evidence
The Distant Origin Theory was a scientific hypothesis propounded by Voth scientist Forra Gegen in the 24th century, which stated that the Voth originated not in the Delta Quadrant, but on a distant planet.
For ten years, Gegen only had a theory, until 2373, when he found the remains of Voyager crewmember Hogan on Hanon IV. Analyzing his bone structure and DNA structure, Gegen found that Humans and Voth share 47 genetic markers.
After several weeks of investigation, Gegen was able to track down the USS Voyager and analyze its crew. He eventually realized he was correct – Humans had evolved from the same genetic ancestors as the Voth. Having presented his evidence to the Voth Ministry of Elders, they refuted his claims, and threatened to place him and the entire Voyager crew in prison unless he retracted his theory. Gegan sadly agreed, to protect his evolutionary "distant cousins". However, as he said goodbye to Chakotay, with whom he had developed a friendship, Gegan was given a globe of Earth as a parting gift, and expressed a hope that, someday, all Voth would see Earth as home. (VOY: "Distant Origin")