Thankfulness and worship are inseparable. Romans, chapter one shows us the road away from God into sin. The word "knew" in our text above shows it is a path that has a certain knowledge of God but fails in its inherent obligation to thankful worship. This behaviour is without excuse.
It will not do to plead belief in atheism or evolution while we indulge ourselves in the gifts God has given. Earlier verses in Romans 1 show that the very things God has created and supplied to us are evidences of Himself and His goodness. "Because that which may be known of God is manifest in them; for God hath shewed it unto them" (Romans 1:19). When we take in the beauty of the autumn leaves we are witnessing the proof of God's creative power and workmanship. He is showing us "Exhibit A".
"For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse" (Romans 1:20). God Himself, and His almighty power are invisible but we learn of Him from the things that He made. And according to this verse it is "understood" by us all. An intuitive cause-and-effect consciousness leads us to certain necessary conclusions. Evolutionary theory is speculative and requires a suppression of the evidence and a suppression of our rational natures.
When a crime is committed and a suspect is found to be in possession of a large quantity of stolen goods he may not simply plead that the material appeared on its own, or evolved. No judge would accept this defence. Neither would God. One may not push away from another fabulous Thanksgiving dinner of turkey and dressing, fresh vegetables, pumpkin pie and all the rest of the fixings (compliments of God), and offer the opinion that God does not exist. Unbelief with a full stomach is unthankfulness for God's goodness and suppression of plain evidence. God's goodness should lead us to repentance of sin and acceptance of His Son, Jesus Christ.