ANSWER: Some people believe Adam and Eve were just two representative people among many, but that is not what the Bible states. Scripture reveals only two people were specially and personally created by the hand of God. Additionally, evidence to support the fact that the Lord created only two original humans, and not a second Adam, can be found in the meaning of Eve's name.
After Eve, the second human, was created she was brought to Adam. Upon meeting his helpmate for the first time he named her in the Hebrew ishshah, or "woman" (Strong's Concordance #H802). This is the generic designation of all females (Genesis 2:23). Interestingly, it was only AFTER they sinned that Adam gave his wife a personal name (Genesis 3:20).
Eve's name in Genesis 3:20 is translated from the Hebrew word chavvah (Strong's #H2332) which literally means "life" or "living." Inserting the actual Hebrew meaning of her name into the verse in question, we get the following, "And Adam called his wife's name Life, because she was the mother of all living."
Eve was named LIFE, or the mother of all living, because out of her would spring the entire (not just some of or most of) human race! Her name does not leave any room for human beings to be created or produced by any other woman or means.
How big was Adam and Eve's immediate family? The Bible only mentions, by name, three children produced by them. Cain was the firstborn child (Genesis 4:1) followed by Abel (verse 2). Seth came into the world sometime after Cain killed Abel, when Adam was one hundred and thirty years old (Genesis 4:25). Genesis 5 tells us that after Seth was born other children were brought into the world (Genesis 5:4).
Adam lived a total of nine hundred and thirty (930) years! It would be safe to assume that Eve lived at least as long, maybe even longer, than her husband. Even if we assume they only had three children in their first 130 years together, they had PLENTY of time after this to take full advantage of God's blessing and obey His command to procreate (Genesis 1:28).
According to William Whiston, who translated the writings of Jewish historian Flavius Josephus, an old tradition states that Adam and Eve ultimately produced thirty-three sons and twenty-one daughters (Antiquities of the Jews, Book 1, Chapter 2)! Some mathematicians have calculated that at the time of Noah's Flood, which was roughly 1,600 years after the creation of man, that the population on earth was easily more than one billion.
Additionally, since Adam and his wife were created perfect, their genetic makeup would be perfect and so would that of their first few children. With no genetic problems to enter the picture, God allowed their offspring (for a time) to marry each other. This meant the world's population could grow quite quickly. As time went by, however, genetic imperfections would make close-kin marriages impractical and risky.
The Bible record leads us to conclude that God personally created only two humans. He only made Adam and Eve and not a second male. He then let the biological processes and urges He placed in the first humans produce the rest of humanity.