Genesis 14:14 describes Abram’s rescue of Lot as follows: “When Abram heard that his kinsman had been taken captive, he led forth his trained men, born in his house, 318 of them, and went in pursuit as far as Dan.”
Dan was the name given to a city in the northern-most territory in Canaan, occupied by the descendents of Dan, the son of Jakob. Given the fact that the descendents of Dan did not occupy this area until after the Conquest of Canaan, this could be pointed to as evidence that Genesis (or at least this periscope within Genesis) was not written until some time after the conquest of Canaan. Seeing that Moses died before the Israelites entered Canaan, he could not have written this account.
There are at least two possible rebuttals. One would be to suggest that the identification of this area as “Dan” was due to a later updating of the text. On this view, Moses wrote this periscope and used the name of the city/region as it was called in his day. Later scribes, however, updated the text to reflect the modern names of the cities and regions Moses spoke of since modern readers would not be familiar with the ancient names.