Jesus has always existed and always been God. He came to earth as a man. Just because He was a man does not mean He is not eternal. He is God and always Has been God.
Eternal means "duration without beginning or end". That being said...Jesus has no beginning and He has no end. None of the cults in the world today believe this or teach this truth.
The Jehovah Witnesses say that Christ was "the Archangel Michael...the highest of all Jehovah's creation...the first, the direct creation of God." Obviously if Christ were created He could not have been eternal. He would have had a beginning.
The fundamental doctrines of Christianity are some of these...the inspiration and authority of Scripture, the virgin birth of Jesus Christ, His eternal Deity, His substitutionary death, His bodily resurrection, His ascension bot to Heaven and His coming again.
Many denominations have rejected some or all of these fundamentals. Those who deny the fundamental doctrines of Christianity reject Biblical doctrine of the Deity of Jesus Christ. They also deny the concept of His eternal existence. If Jesus Christ is not God, He is not an eternal person.
The Word of God proclaims Jesus is eternal. Jesus says it Himself in John 8:58 "Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am." The entire book of John emphasizes the Deity of Christ. The first verse of the first chapter proclaims His eternal existence. Micah 5:2 also expresses His eternal existence. (But thou, Bethlehem Ephratah, though thou be little among the thousands of Judah, yet out of thee shall he come forth unto me that is to be ruler in Israel; whose goings forth have been from of old, from everlasting).
Because Jesus is God and part of the Godhead we can know that He had part in creation. John 1:3 "All things were made by him; and without him was not any thing made that was made." This and other statements in God's Word refute all forms of evolution.
Not only is He the creator of all things but He is also master over all creation. It obeys His command. Luke 8:25 "And he said unto them, Where is your faith? And they being afraid wondered, saying one to another, What manner of man is this! for he commandeth even the winds and water, and they obey him." What a mighty God we serve!!