The term Messiah is often used in the Bahai writings, and almost always refers to Jesus, who is also referred to as "the Spirit." The only exception that comes to mind is where Abdu'l-Baha says :
All the peoples of the world are awaiting two Manifestations, Who must be contemporaneous. This is what they all have been promised. In the Torah the Jews are promised the Lord of Hosts and the Messiah. In the Gospel, the return of Christ and Elijah is foretold. In the religion of Muhammad there is the promise of the Mahdi and the Messiah. ...
(Abdu'l-Baha, Some Answered Questions 2014 Translation)
In the 'end times' picture in Shiah Islam there are two figures, the Mahdi and the return of Jesus, and they call the latter the Messiah. But they also believe that Christ was the Messiah when he came in Palestine, before the Islamic age.
As for the theory of evolution, this is endorsed in the Bahai teachings, but that was partly obscured by a bad translation of Some Answered Questions, dating from 1908. That's been sorted out in the 2014 translation. There's no doubt that Abdu'l-Baha knew and understood that life on earth is very old, and that it has changed gradually, and that human beings come out of that same process. I don't know whether he understood the principle of selective survival, which is Darwin's key contribution to explaining why there's gradual change that has a direction, producing new species and whole families of species, such as dinosaurs and primates. He writes :
"... we have no record of twenty thousand years ago, even though we established before through rational arguments that life on this earth is very ancient not one or two hundred thousand, or even one or two million years old: it is ancient indeed, and the records and traces of ancient times have been entirely obliterated.
(Abdu'l-Baha, Some Answered Questions New Translation)
He does however insist that the human spirit has always existed, but not always on this planet. The distinctively human characteristics are not physical but intellectual and spiritual, and the word the translators have chosen - even in the new translation - is "species." But it's not a biological species, homo sapiens or homo neanderthalensis or homo antecessor (look them up, they're fascinating) ... it's a metaphysical category that Abdu'l-Baha is referring to. On the physical plane, human beings come from the same processes as animals: "the animal, as to its body, is made up of the same constituent elements as man." "..the body of man, which is composed of the elements, is ... the most perfect of all existing things. It grows and develops through the animal spirit."
but "Intellect and the faculty of comprehension are God's gifts whereby man is distinguished from other animals."
He's arguing against the idea that humans are just more refined animals, and in favour of the idea that humans are refined animals PLUS a non-physical reality that is a gift of God.
