Genesis 5:1-3 This is the book of the generations of Adam. When God created man, he made him in the likeness of God. 2 Male and female he created them, and he blessed them and named them Man when they were created. 3 When Adam had lived 130 years, he fathered a son in his own likeness, after his
image, and named him Seth.
Read the entire chapter from your Bible and begin to ask questions. It is by asking questions that we gain understanding. The Lord, who is our Teacher (John 14:26; 2 Corinthians 3:18) is very able to answer the questions we ask. Give Him time to answer.
The God who created the heavens and the earth and all that is in them has given us the age of the earth by giving us the generations from Adam to Abram complete with ages in chapters 5,6,9-11 of Genesis. Genesis chapter 5 takes us within at the most 97 years of the flood. How do we know that? In Genesis 7:11 we are given down to the day how old Noah was when the flood began, "In the six hundredth year of Noah's life, in the second month, on the seventeenth day, on that day all the fountains of the deep burst forth, and the windows of heaven were opened." Noah was six hundred years old when the flood began and his three sons were born after he was 500 years old (Genesis 5:32).
Please note that the text begins the generations of Adam with Seth, not with the first born children of Adam and Eve. Why is this? If we look at what God said to the serpent (Satan) in Genesis 3:15, we find that God was going to give the woman an offspring, a son, to defeat Satan. Satan would wound the son's heal and the son would wound Satan's head. The "heal" wound is not fatal; the "head" wound is. This is a picture of Christ being put on the cross, yet rising from the dead and Satan being destroyed on the cross (John 2:18-22;Hebrews 2:14-15). Seth began the genealogy that led to the Christ, the fulfillment of Genesis 3:15 (see Luke 3:38 for the line of Christ through Seth). Please notice also that Jesus called the scribes and the Pharisees, who called for the death of Jesus, children of devil, who is Satan (John 8:44).
We know from Genesis 4 that Cain and Abel were children of Adam and Eve, but they are not placed in the genealogy. We know that Adam and Eve lived on a sin free earth when they were commanded to be fruitful and multiply. We know that they had multiplied to the extent that the earth was peopled enough to make Cain afraid to leave the protection of Adam and Eve's household, enough for Cain to have a wife. We don't know when Satan tempted Eve, and Adam and Eve sinned by eating of the tree of the knowledge of good and evil. Between the time of Adam and Eve beginning to populate the earth and the time of sin entering the earth could easily have been 100 years. Cain and Abel were born just prior to Seth. Abel was a prophet instructing the people to make blood sacrifices because of sin. The population could have easily been 4000 plus people by the time sin entered the world and infected the entire creation, which remains infected right up to this present day (Romans 5:12; 8:20-22).
What we are to do with the Scripture we have before us today. We are to trust God's word over historical hypotheses concerning the beginning of the heavens and earth. We do not know what changes took place when sin entered the world or after the world wide flood. Observable science of how things work today fit better with a young earth than with an old earth. Evolution is a way for mankind to remove itself from being accountable to God and live in sinful ways that seem right to man but end in death. The environment pre-flood could obviously sustain a longer life span. Jesus confirmed the truth of the Bible by rising from the dead (John 2:18-22). Live by God's word. If man's word differs from God's word, then live by God's word. Jesus created us, died for us and rose from the dead to prove He can do what He says. Learn and live His word and you will live an abundant life even with afflictions and trials of many kinds now and a sin free eternal life when your body dies.
See answersingenesis.org for solid science information that backs a young earth.