God called Abraham (then Abram) to forsake all that was familiar to him and be ready to establish a great nation (Genesis 12:1 & 2). Joshua 24:2 tells us that Abraham's father Terah worshiped other gods. Perhaps this was true of Abraham as well before he was chosen and called? Abraham made that fateful decision to relinquish the familiarities...which paved the way for his descendants' new form of religious fervent.
Genesis 11:27 gives us a brief description of Abraham's lineage.
This is the account of Terah’s family line.
Terah became the father of Abram, Nahor and Haran.
And Haran became the father of Lot.
Haran was born in UR of the Chaldeans; where he later died (Genesis 11:28).. After his death; His father Terah decided he wanted to relocate to Canaan. Nahor remained in UR, while Abraham (Abram) and his wife Sarah (Sarai at the time), and Lot accompanied Terah. But when they came to Haran they settled there (Genesis 11:31). It was at Haran, Terah ultimately dies (Genesis 11:32)
The Sumerian civilization invented writing, composed dictionaries, and had superior knowledge of astronomy and arithmetic. Astrology as a form of religion was common practice. Ur was accustomed to polytheistic worship...the god of fire, moon, sun, and stars, were among their traditional entities of homage. Ur (which is modern day Iraq) was prosperous during this era.
As Abram was migrating; the Lord appeared to him and made a promise concerning Abram progeny. It was there that Abram built an altar unto God (Genesis 12: 6&7). The Holy Bible tells us that Abram (as a monotheist) went to Egypt to live for a while because of severe famine (Genesis 12:10).
This area is known as "The Fertile Crescent".
The region was occasionally watered by the rainfall. When the quantity of rain was low; drought obviously occurred. It was under these circumstances that brought many foreigners to Egypt. Egypt was typically well saturated due to the seasonal inundation of the Nile.....causing it to often withstand the surrounding droughts. It left Egypt to play host for its neighbors. Ancient Egyptian records tells of a drought that lasted from 2150 BC to 2000 BC. This fits into the time-frame of Genesis 12:10 involving Abram.
What is most interesting is the finding of a cuneiform by the ancient Sumerians (Keep in mind that Ur was an important Sumerian city) that dates to the same period (2050-2000 BC)...speaking on a great drought... the document is titled: Ur III cuneiform.
The Sumerian civilization gradual demise is linked by archaeological and geological evidence to a 200 year long drought that occurred around the same time in question. Shortly after, the Sumerian culture began to go extinct. More than 70 percent of ancient Mesopotamian colonies was deserted. Almost 100 percent of the occupied sector dwindled. Ur felled
around that time (about 2000 BC). It is within this backdrop that Abraham would come to understand how obeying the voice of God preserves.