You talk about the fruit, that is after its root. The natural man has the capacity to understand or comprehend upon the conviction of the Holy Spirit. By believing/ responding to the word, the gospel, or of Christ, he would be born again. Ever notice that even the words of Christ is spirit. in line with this to be born again is to be regenerated by the word. Note, the word of God is inseparable with the Holy Spirit and that is what scripture is given by inspiration i.e. in-spirit...the act of the Holy Spirit through the agency of the word thus responding it by faith is to be born of the Spirit.
John 6:63 King James Version (KJV)
63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
1 Peter 1:23 King James Version (KJV)
23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.