http://www.gty.org/blog/B150217/evangel ... sis-crisis
Some people like to dismiss this debate as a secondary issue, not directly related to the gospel. But it is clearly an issue that goes to the authority of Scripture. And furthermore, as MacArthur rightly points out, it has massive repercussions for the gospel:
If Adam was not the literal ancestor of the entire human race, then the Bible’s explanation of how sin entered the world makes no sense. Moreover, if we didn’t fall in Adam, we cannot be redeemed in Christ, because Christ’s position as the Head of the redeemed race exactly parallels Adam’s position as the head of the fallen race: “For as in Adam all die, even so in Christ all shall be made alive” (1 Corinthians 15:22). “Therefore, as through one man’s offense judgment came to all men, resulting in condemnation, even so through one Man’s righteous act the free gift came to all men, resulting in justification of life. For as by one man’s disobedience many were made sinners, so also by one Man’s obedience many will be made righteous” (Romans 5:18–19). “And so it is written, ‘The first man Adam became a living being.’ The last Adam became a life–giving spirit” (1 Corinthians 15:45; cf. 1 Timothy 2:13–14; Jude 14).
So in an important sense, everything Scripture says about our salvation through Jesus Christ hinges on the literal truth of what Genesis 1–3 teaches about Adam’s creation and fall. There is no more pivotal passage of Scripture.
The opening chapters of Genesis are not up for debate, nor are they negotiable. The academic credibility of our faith is meaningless if we’re so quick to sacrifice the meaning of Scripture at the altar of public opinion. Better to be counted a fool for the sake of God’s Word than to be embraced for our willingness to compromise it.
It's basically saying that if you're not a YEC then you're not really a true Christian at all.