Nowhere does the Old Testament specifically say that Adam was the first human being. It is silent about people before Adam except for some clues in the first four chapters of Genesis:
Nowhere does the New Testament specifically say that Adam was the first human being.
Neither Jesus nor the Apostles (except Paul) even mention Adam's name. Paul briefly mentions him in I Corinthians 15 and Romans 5 but does not specifically say that he was the first human being, only that he was the first sinner.
When the Bible is silent, we are free to follow historical and scientific evidence wherever it leads.
Archaeologists have unearthed many cities that are much older than Adam. By the time of Adam, some cities already had thousands of inhabitants. The archaeological finds yield not only objects but also rich history and timelines.
There are now many scientific methods for testing age. Confidence is gained when different methods (chemical, radiological, stratigraphical, dendrochronological, DNA, etc.) all converge in the same age range. Human fossils (homo sapiens) have been found which date to thousands of years before AdamThe DNA of hundreds of ancient human skeletons have been sequenced and analyzed, and migration patterns plotted to show beyond doubt that people were traversing the earth prior to 4000 BC (before Adam).
The DNA of hundreds of ancient human skeletons have been sequenced and analyzed, and migration patterns plotted to show beyond doubt that people were traversing the earth prior to 4000 BC (before Adam).