There are many reasons people find Gene Roddenberry's vision of the future a little hard to believe. The main one is that humanity transcends its petty bigotries, fears and tribalism to become a united Earth committed to the goal of peaceful exploration and scientific advancement. While humans are integral to the United Federation of Planets, they aren't, technically, the smartest alien species in Star Trek. There are many contenders, but it all depends on how one defines intelligence.
Source：https://www.cbr.com/star-trek-smartest-species/
