One story stands out to me in particular. Erlik, a deity in Mongol mythology, was either the brother of or created as the first human by the supreme god Ülgen. I read that Erlik wanted to become equal to Ülgen and supposedly tried to seduce humans to take the forbidden fruit from the first tree, and as a result, Erlik was banished to rule over the lower world and assume a position akin to the Christian devil. Was this myth around before Christian influence? In what ways did Mongol mythology change after coming into contact with Christianity?
This "falling from grace" story did not originate with Christianity. Take Tantalos for example, or Zeus banishing Hades to the underworld.
As for earlier "fruit-picking" mythology, there's the story of the Monkey King stealing the peaches of eternal life from the Jade Palace in Chinese mythology.