Pre-Flood Longevity

Before the flood Genesis 5 says people regularly lived over 900 years. Methuselah was the oldest and lived 969 years. Some creationists have suggested this is due to a vapor canopy creating a greenhouse effect ideal for long life.

Interestingly, we have discovered ancient Earth's atmosphere was in fact thicker resulting in fainter rays from the sun. We've also discovered oxygen levels were at least 50% higher than today's level of 20%, measuring around 30-35% oxygen, and that this high degree of oxygen was what led to the gigantism of ancient insects seen from the fossil record.

Genealogies
Much of this is similar to Ussher's chronology. It appears Ussher probably used the date Abraham entered Egypt as the starting point for the 430 years to the Exodus referenced in Exodus 12:40-41, which is probably why his early dates vary from my own by 200 years. After the Exodus his dates vary from my own by only 1-6 years. For a comparison between the dates I have reached and those reached by Ussher, see Ussher Comparison. Three dating methods are used below:
 * GC: Gregorian Calendar, the common method used today in which all years are in relation to the death/resurrection of Jesus.
 * YAC: Years After Creation, a total count of years since creation.
 * YAF: Years After the Flood, or the total number of years since the Noahic Flood.

The Patriarchs
S&d is shorthand for "sons & daughters" meaning that the Bible specifically says they had "sons and daughters" but does not give names.

Kings of Judah
The main difference between the Kings and Patriarchs tables is that the Kings table below does not show children and instead shows the start and end ages for when kings reigned, as well as total length of their reign. With almost no exceptions, a king reigned until they died. Those exceptions include Uzziah, who defied God by going into the temple despite not being a priest. Uzziah became instantly leprous and resigned the kingship, living isolated and alone with his disease, and his son Jotham took over rule of the kingdom. (2 Chronicles 26:21) The last three kings of Israel, Jehoiakim, Jehoiachin, and Zedekiah, were carried away in slavery to Babylon (2 Chronicles 36, 2 Kings 24-25).

Population Growth

 * See also Genesis 9

First of all, population growth can be considerably faster when there is more room for expansion. That's why early Americans had such huge families in colonial America with approximately 9 children per family, and few had less than 6. Population growth spiked even higher during America's westward expansion. Furthermore, even today less-developed countries have very high birth rates: Niger's is 7.03, Mali's 6.25, and Somalia's 6.17 as compared to 2.06 for the United States, 1.90 for the United Kingdom, and 1.59 for Canada.

However, to go by what the Bible says, that human lifespans exceeded 400 years on average after the Flood, you would logically see even higher birth rates since fertility would last longer and people would be able to keep bearing children much longer without any time lapse for age development. So instead of a birth rate of 10 or 15 in today's equivalent, we might even be talking as much as 15. When you realize that not only was the birth rate much higher, but the death rate much lower (given average lifespan roughly 6 times that of today's) it quickly becomes evident how population growth could skyrocket in such a short amount of time.

But just for curiosity's sake, lets do the math. Shem was Noah's son. Say Shem's wife lived about the same age as he did, or 600 years. (Genesis 11) We'll assume she could bear children from her teens until about 60% of her life was over, similar to today. So suppose she bore children from age 18 to age 360, or about 342 years, bearing 12 or 15 children every 60 years or so. By the end of her life, she alone will have born around 48-60 children by herself, right? That's a conservative minimum. And they'll each have had children of their own, who'll have had children of their own. And they won't die of natural causes for many centuries.

Critics only see a contradiction here because they try applying modern standards to the Bible without considering the scenario the Bible itself claims of vast lifespans, and because they ignore evidence showing the birth rate can drastically differ based on circumstantial factors.