One of the most powerful scripture verses occurs in the first book of Genesis. God said to his newly created humanity, “Be fruitful and multiply and fill the earth and subdue it…” (Gen. 1:28a ESV). Population multiplication has been a source of both blessing and concern for human society ever since man has contemplated the concept of population dynamics and issues related to the increase in human habitation of our planet.
We will discuss the statistical trajectory of historic human population after we briefly review the biblical account of the Israelites, God’s chosen people, in the second millennium before Christ. Joseph was a great-grandson of the patriarch Abraham, the grandson of Isaac, and the eleventh son of Jacob. After Joseph was sold to the Egyptians and carried off to Egypt he became an important ruler in the years to follow. Providentially, Joseph’s brothers traveled to Egypt years later to escape a famine in Canaan. They met the brother they had previously sold into slavery. Eventually, seventy Israelites went down to Egypt on Joseph’s invitation to escape the famine in their homeland. Joseph’s seventy-member family became a nation during their 430-year sojourn in Egypt.
The population growth of the Israelites from seventy souls to more than two million in just over 400 years is a tale of fruitful multiplication almost beyond comprehension. Under the most ideal conditions, the mathematical reality of such growth is astonishing. The original 70 souls could multiply to 17000 after 200 years, given four to five generations per century. In an example of geometric progression, those 17000 could easily become two million (600,000 men) in the ensuing two centuries.
A study of human history reveals few population bursts of this magnitude, even in the short term in a limited area. To be fruitful and multiply does not suggest theoretical population increases on such a scale. Population dynamics is far more interesting and complex than that. For example, when we study human population over recorded history, we discover slow growth best described as more or less linear. Contrastingly, the last 200 years human population sometimes manifested “exponential growth.” This sort of growth becomes ever more rapid in proportion to previous size increases of human population. But it may not hold forever.
Human population held below one billion in the first tens of thousands of years of human habitation. The population of humanity on Earth initially hit one billion in 1804. In only 123 additional years (1927) the population was two billion; in 32 additional years (1959) we reached three billion; in 15 additional years (1974) we reached four billion; in 13 additional years (1987) we reached five billion, and in 12 additional years (1999) we reached six billion. In just 12 more years (2011) Planet Earth was home to seven billion souls!
The rate of increase has been decreasing in recent decades. Population increases have persisted, however, and may increase for some time. The graph of human population prior to 1800 may be described as roughly linear, but increasing. Population increases since then result from changes in fertility, mortality, initial population, and time. Fertility rates are affected by acquisition of knowledge. They increase or decrease. Mortality has been decreasing with the advance of biotechnology. Man’s increased knowledge and advances in biotechnology are some of the multidimensional gifts of the Creator of humanity. He supplies man with the ability to “be fruitful and multiply and subdue the earth” in a manner beneficial to himself and all living things.