Bible Question:

If there were only Adam, Eve, Cain and Abel in the beginning, how was the world populated?

Bible Answer:

The question we are concerned with is, “How was the world populated before the flood?

How was the world populated before the flood?

First, Genesis 1:24-31 tells us that God created Adam and Eve on the sixth day. After He created them, He commanded them to have children and to populate the world.

And God blessed them; and God said to them, “Be fruitful and multiply, and fill the earth, and subdue it; and rule over the fish of the sea and over the birds of the sky, and over every living thing that moves on the earth.” Genesis 1:28 (NASB)

Adam and Eve were faithful to the Lord’s command and started populating the world. Cain and Abel were the first male children recorded in the Bible (Genesis 4:1-2). Seth came along later (Genesis 4:25). It was common in the Bible to record the birth of only the sons and not the daughters. Also, it was common not to record all of the sons. It was rare that the daughters were named. For example, Genesis 5:4 states,

Then the days of Adam after he became the father of Seth were eight hundred years, and he had other sons and daughters. Genesis 5:4 (NASB)

But we do not know the names of the other sons and no names of any daughters. Nor are we told when they were born or how many. This example is typical of early birth records. Therefore, we do not know how many sons and daughters were born to Adam and Eve and to their descendants by the time of the flood.

How World Populated Before Flood

Estimate of the world’s population before the flood

The world’s population continues to increase today. On May 13, 2023 it was estimated by the that the world population was over 8.03 billion.[1] That is a great number of people but it is not a difficult number to reach. A conservative calculation reveals that the world’s population by the time of the flood would have easily exceeded 8.03 billion.

The calculation is a rough approximation since we do not know the birth rate exactly. The calculation requires several steps.

Step #1 – Determine the time from Adam and Eve to Noah’s Flood. The ancestral line of the early families is given in Genesis 5:1-32 and 11:10-32. From the genealogical listings, we can determine that Noah was born 1,056 years after the creation of Adam and Eve. Noah’s sons were born 500 years later and the flood occurred 100 years after Noah’s sons were born (Genesis 7:11). That means the flood occurred 1,656 years after the creation of Adam and Eve.

Step #2 – Ignore the initial years of population growth. Next, we are told in Genesis 4:16-24 that an initial population of males and females were living on the earth. Since Adam and Eve were the first parents, these humans were their offspring. Abel and Cain were named in scripture because they were involved in the first murder and sacrifice (Gen. 4:1-15).

Scripture reveals that Seth was born to Adam and Eve when they were 130 years old. Genesis 5:6 states that his first son was Enosh. He was born when Seth was 235 years old.

It is clear from Genesis that many children were being born who are not documented in scripture. If the first child of Adam and Eve was born when they were 30 years old, and additional children were being born every three years, the world would have had about 10 children on the earth when Adam and Eve were 60 years old. It is entirely possible for children to have been conceived and born more frequently than every three years. Their first child would be 30 years old, using these assumptions (see “How many children did Adam and Eve have?“). Let us assume that child A married a brother or sister, say child B or C, and then within three years after being married, this couple produced about 10 children by their 60th birthday or when Adam and Eve were 120 years old. If we go back to either child B or C, who did not marry child A, and we assume that child married child D or E, then that child’s marriage would produce about 10 children when Adam and Eve were 124 – 128 years old. If we keep the process going, it is easy to have 100 hundred children, at least, by the time Adam and Eve are 130 years of age, when Seth is born. Scripture typically does not record the birth of females or of all of the males. After 130 years, only 1,526 years remain for children to be born before the flood. The flood started 1,656 years after the creation. Now there is a population giving birth to children. So, that demonstrates the feasibility of rapid population growth.

Step #3 – Next, we must determine a birth rate for each couple. We will assume that each couple is giving birth to six children and then stops. This is unrealistic for parents who are living hundreds of years, but it will make our calculation simpler.

Step #4 – Determine a mathematical equation for population growth. To determine the population growth, we will assume that Enoch had offspring about every 10 years after he married. We will assume that each offspring does not have their first child until they are 117 years old and then they have six children spaced apart every 20 years for 117 years.

The number 117 years is the average age of the patriarchs when they had their first recorded child as given in Genesis 5:1-32 and 11:10-32. Most likely there were other children who were born earlier but not recorded. Yet, we will ignore this factor.

Using these assumptions, Enoch would have had 6 children in 117 years. Now we assume that each of these children had their first child at the age of 117 years and produced children about every 10 years, and their children followed the same pattern.

So if we divide 1,526 years (the number of years from Enoch to the flood), by 117 years (the period of procreation) we obtain 13. Now the formula for computing the world’s population by the time of Noah’s flood is given by the geometric summation of,

Summation of Geometric Series

This summation represents the number of children born to each descendant over 13 periods of 117 years each for a total of 1,526 years, starting from the birth of Seth when Adam and Eve were 130 years of age. The summation can be computed using the following well-known formula,

Exact Equation for the Summation of a Geometric Series

where a = 6, n=13. The result is 15.67 billion people.

Fifteen billion and six hundred thousand people is more than 7.4 billion people. We started the calculation with Seth and ignored all of the other families on the earth at the time of Seth. We ignored the actual death rate but that will not affect the total since we assumed they starting giving birth at 117 years of age and stopped giving birth 117 years after the first child was born.

Here are other estimates.

Many People Could Have Existed Before the Flood


How was the world populated? The answer is simply by Adam and Eve and their children.



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