Occasionally it's good to review what you believe and why you believe it. For those who adhere to a literal interpretation of Genesis and believe in a young earth, scripture is the first, final and unrivaled authority on the questions of the origin of the universe, the origin of life, the origin of man, and the age of the earth. Young Earth Creationists (sometimes referred to as "YECs") believe that the Bible is the inerrant Word of God to which the ever-changing theories of fallible man cannot hold a candle. We know that the observable facts of science are consistent with the YEC view even when the "facts" and theories of materialistic scientism are not.
There were no human eyewitnesses to the creation of the universe, the earth, and life. It is for this reason man on his own can never really know what happened. But there were eyewitnesses. The triune God was there and has communicated his observations to us via Moses in scripture. God's Word is as true as any observable fact of science. For this reason, one must take both the facts of scripture and science into account when considering origins. Scientific theories (e.g., macroevolution) which are not in agreement with the clear teachings of scripture are wrong by definition; science is always subordinate to scripture, never vice-versa, nor should they be given equal weight. When science and scripture seem at odds, scripture is given the benefit of the doubt; science usually catches up to scripture—eventually.