The apostle Paul describes the fallen condition of humanity in Romans 1:21-23, writing, "For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their speculations, and their foolish heart was darkened. Professing to be wise, they became fools, and exchanged the glory of the incorruptible God for an image in the form of corruptible man and of birds and four-footed animals and crawling creatures." Jonathan Parnell, in his post "When People Look Like Satan", provides a powerful description of humanity's fallen condition, highlighting Greg Beale's explanation, Parnell writes the following;
"God made humans to reflect his image and advance the display of his glory over the created world (Genesis 1:26–28). But Adam failed in this commission. Rather than have dominion over the serpent he succombed to its craftiness. As Greg Beale explains, 'Instead of wanting to be near God to reflect him, Adam and his wife hid themselves from the presence of the Lord God among the trees of the garden' (Genesis 3:8 [so also 3:10])" (NTBT, 359).
Sin brought chaos and disorder. Things got all messed up. In fact, things became so backwards that Adam could be seen as actually supressing the image of God to reflect the image of the serpent, like a back-story to Romans 1:18–25.
Adam was the first human idolator who became something he was not supposed to become, looking more like the snake than he did his Creator. Beale explains how:
'Idol worship' should be defined as revering anything other than God. At the least, Adam's allegiance had shifted from God to himself and probably to Satan, since he came to resemble the serpent's character in some ways.
The serpent was a liar (Genesis 3:4) and a deceiver (Genesis 3:1, 13). Likewise Adam, when asked by God, "Have you eaten from the tree of the which I commanded you not to eat?" (Genesis 3:11), does not answer forthrightly. Adam replies, "The woman whom you gave me to be with me, she gave me from the tree, and I ate" (Genesis 3:12). Adam was deceptively blaming Eve for his sin, which shifted accountability from him to his wife, in contrast to the biblical testimony that Adam, not Eve, was accountable for the fall (e.g., see Romans 5:12–19).
[He Didn't Trust God's Word]
In addition, Adam, like the serpent, did not trust the word of God (with respect to Adam, see Genesis 2:16–17; 3:6; with respect to the serpent, Genesis 3:1, 4–5). Adam's shift from trusting God to trusting the serpent meant that he no longer reflected God's image but rather the serpent's image. . . .
[He Exalted Himself]
[Adam] not only stood by while his covenantal ally, Eve, was deceived by the serpent, but also decided for himself that God's word was wrong and the devil's word was right. In so doing, perhaps Adam was reflecting another feature of the serpent, who has exalted his code of behavior over and against the dictates of God's righteous standard. But, if not, certainly Adam was deciding for himself that God's word was wrong. This is precisely the point where Adam placed himself in God's place — this is worship of the self.
G. K. Beale, A New Testament Biblical Theology, (Grand Rapids: Baker, 2011), 359f., headings and full biblical citations added.
Adam was a deceiver. He didn't trust God's word. He exalted his standard above's God's in the worship of himself. Humans, created to image the majesty of God, rebelled and imaged the character of the serpent. This was the fall. And it's not just Adam's story, it's our story, too."
The result of this fall is death. Death is the penalty for sin (Romans 6:23) and sin is the condition of all humanity (Romans 3:23). But praise be to God, the story does not end here! Through His predetermined plan of redemption, God would restore His glory by reconciling His people through the sacrifice of "His only begotten Son, that whoever believes in Him shall not perish, but have eternal life" (John 3:16) Paul further explains, "But now Christ has been raised from the dead, the first fruits of those who are asleep. For since by a man came death, by a man also came the resurrection of the dead. For as in Adam all die, so also in Christ all will be made alive" (1 Corinthians 15:21-22.)