Bishop James Ussher was a church leader in Ireland in the 1600's, prolific scholar and author of The Annals of the World. Using Bible genealogies, he calculated that Adam was born in the year 4004 BC. This date has been widely quoted and generally accepted ever since.
Over the last 400 years, hundreds of other historians and theologians have drawn the family tree from their own study of scripture, and most come to the same conclusion, as diagrammed above: Adam lived about 4000 BC.
Many Christians who believe that Adam was the first human on earth know that dating the first human to 4000 BC is out of synch with everything we now know about the world. Usually, they just shrug off the conflict by saying, without evidence, that there are gaps in the Bible genealogy.
But there are big problems with the gap theory:
➤ The consecutive male line from Adam to Jesus is clearly stated in the Bible. If there are major gaps, then the Bible is at least misleading, and the genealogy should be restated. But if the genealogy is restated for convenience because it is incomplete and unbelievable, why not restate other troublesome Bible passages too? Obviously, that would be rewriting scripture and intolerable.
➤ If the Bible genealogy shows more time as gaps than as facts, then a reasonable person would have to conclude that it is not a credible genealogy at all and that the Bible is deceptive or fraudulent.
➤ Just for a margin of safety, let's say that the Bible record is only 50% complete and overall omits as many generations as it includes. That would put Adam's time at approximately 8000 BC., which still would not explain known human activity prior to that time. See Bible study here on people before Adam.
➤ Gaps – even enormous gaps – cannot even come close to reconciling Bible geneologies with the findings of modern science and archeology.
This time period is clearly stated in Genesis 5, when human life was much longer. Each father is not only named but given his age at birth of his son. For each generation, the son is again named and aged at birth of the son, thus preluding the possibility of any gaps without changing the meaning of the words father and son.
In this way, time is calculated from Adam to Noah at precisely 1,056 years.
If there are significan gaps in the genealogies, it is probably in this period of approximately 2,000 years, with 24 named generations. Calculated, that averages to 83 years per generation, which seems too high even in light of longer life spans at that time. It is reasonable to suspect gaps in this segment of the genealogical record.
Assuming a generation to be 26 years rather than 83 years, this would add another 4,000 to the timeline and put Adam's existence at about 8,000 BC.
This period of approximately 1,000 years is documented with two genealogies: Mary (mother of Jesus, Matthew 1) with 28 generations averaging 36 years, and Joseph (adoptive father of Jesus, Luke 2) with 39 generations averaging 26 years. There is not room for significant gaps here.
As shown here, the gap theory in Bible method of dating (genealogies) can reconcile
Acknowledge Adam not first.
Complicated if say Adam create first week of anything.