Why did God tell Adam and Eve to fill the earth—if no one died, wouldn't the earth have become overpopulated?

what does the bible say?

The Bible doesn't say anything about overpopulation. Questions about overpopulation and population control often arise from a deeply entrenched modern mindset. Unfounded fears of overpopulation abound, showing a lack of trust in God. Overpopulation is a possibility in our world only if resources became depleted, no one ever died, and if genes and fertility rates were untainted by sin.

However, the question does not concern Adam and Eve in a fallen world but in a perfect, sinless world—the original creation that was far different from today's world. The question thus becomes hypothetical as we try to speculate about modern concerns of overpopulation in a radically different environment. A creation with sinless man wisely overseeing the earth's resources and living in charitable harmony is completely foreign to us.

This question can also arise from two other factors: not understanding how God rules the universe He created (Colossians 1:16-17) and misreading the text. The word "fill" in Genesis 1:28 means to fill to capacity, not to over-fill beyond capacity. God saw that His creation was very good (Genesis 1:31) including natural limits on the maximum capacity for both animal and human populations.

from the old testament

Genesis 1:20-23 describes God's plan to populate the vast seas and skies. After creating various kinds of animals in verse 21, we read in verse 22 that God blessed them, saying, "Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth." Notice that God commands the birds and fish to multiply and blesses them with the ability to do so. Genesis declares not only is God the creator of life, but He is also the One who enables life to reproduce itself. God and God alone is responsible for the design and existence of life. Unlimited population growth of birds or fish doesn't happen because they compete for finite resources in complex ecosystems, according to God's design.Genesis 1:24-31 describes God's plan to populate the land with animals and humans. After creating livestock, beasts, and creeping things in verses 24-25, God created Adam and Eve (male and female) in His own image in verses 26-27. In verse 28 God blessed them, saying "Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth." Just as with the birds and fish above, God commands Adam and Eve to multiply and blesses them with the ability to do so. Humankind's first responsibilities would be to fill (not overfill) the earth with people and to care for the earth as God's representatives. The word “subdue” speaks of a productive ordering of the earth and its inhabitants to yield its riches and to accomplish God's purposes. Since God saw that His creation was very good (verse 31), He included limits on resources to control population growth.“Be fruitful and multiply, and fill the earth" as God blessed Noah and his sons in Genesis 9:1 (c.f., 8:17; 9:7). God gave Noah the same mandate He gave Adam since humanity essentially began all over again after the flood through Noah.

from the new testament

Colossians 1:16-17 tells us that Jesus – who is God - is responsible for creating and sustaining all things. Jesus cares about His creation and would not allow harmful overpopulation to destroy it.

implications for today

Overpopulation is the idea that humanity may become too numerous to be sustained by their environment or resources in the long term, either globally or locally. The belief that global population levels will become too large to sustain is a point of contentious debate. Human population growth has actually been decreasing since 1968 and it is predicted that the population itself will likely peak, and possibly even begin to decrease, before 2100. Previously predicted "population explosions" have not materialized; instead, population growth has slowed. Further, advancements in technology have greatly increased humanity’s ability to produce food and resources. Due to a lack of evidence, some scholars refer to human overpopulation as a myth.

Population dynamics, a branch of mathematical biology, has determined that no population can increase without limitation. Instead, populations in natural ecosystems increase or decrease in response to changes that restrict growth, such as available food, shelter and population density. Unlimited population growth in the animal kingdom doesn't happen, partly because populations compete for finite resources. Human beings are uniquely equipped to overcome some of those limitations. In an ideal, sinless world, we would always do so in responsible and reasonable ways. But even in our fallen state, the idea of global overpopulation seems unlikely.