Inspiration (Ilham) on Hassania AlGohar from Imam Mehdi Gohar Shahi

It means people were one nation in the time of Adam and they shall become one again in the time of Mehdi. This is why adam was the first khalifa and Mehdi is the last khalifa.

Explanation by His Holiness Younus AlGohar

Humanity was but one nation in Adam's Era, because He was the first caliph from God. Imam Mehdi is the Last and final Caliph from God, hence, Humanity will become One Nation again. All previously established religions will perish. Adam established Hubb-e-Ilahi as the primary religion. Mehdi will establish Ishq-e-Ilahi as the culminatory religion. All Nations will merge into One United Nation and all religions will merge into One God One Religion for all, the Religion of God.