Witness, therefore, how numerous and far-reaching have been the changes in language, speech, and writing since the days of Adam. How much greater must have been the changes before Him!
Baha'is believe that Earth coalesced from cosmic material billions of years ago as willed by a Creator we call God (In Arabic, Allah; in Spanish, Dios; etc.). While our ancestors surely didn't look like us, they were always human, albeit unevolved physically and lacking intellectual developement and spiritual awareness. Our progress from our primitive origins was incremental. We evolved from an embryonic condition to our current state of relative perfection.
"(A)t one time man was an inmate of the sea, at another period an invertebrate, then a vertebrate and finally a human being standing erect. Though we admit these changes, we cannot say man is an animal. In each one of these stages are signs and evidences of his human existence and destination." --Abdu'l-Baha
I believe Adam was the first human given the knowledge that our nature is essentially spiritual. As such, he became "The First Man". Adam proclaimed the knowledge of God to his contemporaries, and the truth he told eventually was recorded in the written word. Genesis conveyed our relationship with the Creator in a manner comprehensible to our ancestors. Scientific inquiry and discovery have given us a clearer idea of our physical origins, and the Manifestations of God provide us with an understanding of our spiritual reality which transcends time and space.