Were there humans before Adam?
Some people think “Adam” was not the first man, but was a name for the first group of humans God created. They usually point to Genesis 5:2, which says in the King James Version:
“Male and female created he them; and blessed them, and called their name Adam, in the day when they were created.”
This problem arises when people don't realize that there are two slightly different Hebrew words translated into English as Adam. You could think of the difference as being roughly equivalent to spelling Adam with a capital “A” (Adam) and a lower case “a” (adam).
The equivalent of adam (lower case) can mean either an individual human or a group of humans. This is the word used in Genesis 5:2.
The other word (Adam) is used only in reference to the first man, and to a city on the River Jordan that later was given the same name.
Knowing this difference solves all the problems that come about if people try to use the English word always to mean the same thing.
Verses such as Genesis 5:3 make sense only when you realize that it refers to an individual.
“And Adam lived an hundred and thirty years, and begat a son in his own likeness …”
This could not mean that the whole human race lived 130 years and gave birth to a son. Other verses also make sense only if they apply to an individual.
First Adam, last Adam
In fact, in 1 Corinthians 15:45 the Apostle Paul tells us that the first man was Adam, and he compares the first man Adam with Jesus Christ, whom he calls the “last Adam”.
As Christ was an individual, this comparison makes sense only if the first Adam was also an individual.