V.1.-8 This is not Christianity, remember, but what Solomon sees as going on in every day life.
V.9-15 Everything keeps going on, man cannot really change anything, nor can he tell the future. All is in God’s hands, but even the knowledge of this does not bring contentment.
V.16-22 Without the revelation of God’s truth, these verses are the only conclusion a man can make — no real difference between man and animal. That is where the teaching of evolution comes from, for evolution denies the truth of God’s Word that He created the world.