How old was Abram when Ishmael was born?

The Bible says Terah begat Abram at 70 years of age, that Terah lived for 205 years (135 years after he begat Abram), and that Abram left only after his father died.  However, Genesis 12:4 says Abram departed when he was only 75 years old, not 135, and that Abram had Ishmael (after he left) at 86.

Response

This is a variation of the argument, “How old was Abram when he left Haran?”  The Bible never says Terah was 70 when he begat Abram, it says he was 70 when he started having sons, and Abram is listed first.  However, just because he is listed first does not mean he was born first; for instance, Shem, Ham, and Japheth are never listed in the correct birth order when they are listed together.  Abram was listed first because of importance.  For more information, please see the related argument.