This increase in Israelite numbers is depicted in the scripture, showing their transformation from a small clan into a populous nation, akin to a large tree growing from a tiny seedling; they flourished and multiplied like fruitful creatures, such as fish, and spread extensively across the land as water overflowing its banks, gaining strength sufficient to defend themselves in the event of an assault.
To understand the rapid and seemingly exceptional growth of the Hebrews over those 215 years, we must consider several factors. First, the number of those who moved to Egypt was not restricted to 75 individuals, as many members of Jacob's household were not included in that count. Additionally, the group comprised slaves and maidservants, who shared the same religious covenant of circumcision with Jacob's lineage (Genesis 12:13). The sheer number of Jacob's servants is illustrated by his division of them into two groups when he encountered his brother Esau upon returning from Mesopotamia. During their time in Egypt, the Hebrews likely formed familial bonds with their slaves—who were integral to their community—thus blending into a single tribe and fostering their increase.
Secondly, ancient writers widely recognized Egypt as a land particularly conducive to polygamous practices, with Aristotle noting instances of Egyptian women bearing multiple children in rapid succession. This environmental factor may provide an insight into the growth of the Hebrew population, as indicated in the biblical text where it mentions their multiplication upon the earth (with an alternative interpretation in Hebrew suggesting the earth was filled with them).
Most importantly, the remarkable proliferation of the Hebrews in Egypt can be attributed to God's specific blessing, in line with the numerous promises made to Abraham (Genesis 13:16, 15:5) and reiterated to Jacob (Genesis 28:14, 46:47). The very act of relocating the Hebrew tribe to a fertile land for their growth was part of God’s divine blessing. Relying solely on naturalistic explanations for this phenomenon fails to account for the fact that the Egyptians, who existed under similar conditions, did not experience comparable population growth. Although they shared the favorable circumstances, they did not multiply to the vast numbers one would expect over centuries, and Egypt could reasonably sustain a population of only around six million.