If Noah and his family were the only people to have survived the worldwide flood, how did giants come to dwell in the land of Canaan when God commanded the Israelites to destroy them?
The Bible talks about giants with several words. If we accept the general understanding of most scholars concerning the Nephilim in Genesis 6:1-4 to be giants, this is one of the words used by the Bible to describe them.
Later on in the book of Numbers, another word that is used for giants is the Anakim, the children of Anak, who are considered giants in the land of Canaan. The Anakim are mentioned nine times in Scripture.
The Anakim live in the land of Canaan (Joshua 11:21) and are reported as taller than the Israelites by the twelve spies (Deuteronomy 1:28). Other groups who are considered tall are compared to the Anakim (Deuteronomy 2:10-11, 21; 9:2).
Is because of the fear of these giants in the land of Canaan that the first generation of Israelites coming out of Egypt end up spending 40 years in the wilderness and dont possess the Promised Land. They die in the wilderness because of their unbelief that God can fight their battles for them. Because of their fear of the giants they dont possess the land.
Its up to Joshua and the second generation of free Israelites to conquer the land of Canaan and either destroy or dispossess the Anakim in the land (Joshua 11:21-22).
Once living in the land, Caleb, the other of the twelve spies to believe they could take the land but was overruled, asks for the land the giants used to live in (Joshua 14:12). In referring to the city of Hebron Joshua clarifies its former name before it was conquered (Joshua 14:15), named after the man who was very tall.
The other word used for giants, Nephilim, is used three times in the Bible to describe very tall people (Genesis 6:1-4; Numbers 13:33). In Genesis 6:1-4, the most common understanding of the Nephilim is that they are the offspring of the unholy marriage between the sons of God (understood to be angels) and the daughters of men.
The Israelites understand these Nephilim (the Hebrew word meaning Fallen ones) to be giants. We know this because the later reference in Numbers is describing a people of great height in the Promised Land of Canaan (Numbers 13:32-33).
A parenthetical statement in Numbers describes the Nephilim as the sons of Anak, related to the Anakim, the other explanation of giants discussed above. So the Israelites use the word Nephilim to describe giants, or at least people who are taller than them.
The reason its important to understand that the Israelites use Nephilim to describe giants, based on their interpretation of the Nephilim in Genesis 6:1-4 as the offspring of angels and the daughters of men to be giants is that they believe all giants in the land of Canaan to be related to these Nephilim.
One possible theory of how there could be giants in the land of Canaan after the flood of Noah is that Noah and his family carried the gene for larger human beings with them from the old world to the new.
The table of nations in Genesis 10 mentions that the Philistines came from the line of Ham (Genesis 10:14). Goliath is a giant killed by David among the Philistines. Some scholars believe the Philistines were a very tall race of humans.
If nothing else, the Israelites associate tall giants with the word Nephilim from their tradition and interpretation of Genesis 6:1-4 and call the tall people in the land of Canaan giants. The Bible does not clarify how much taller than the Israelites these giants are.
It is from their perspective that they are giants. By estimates from scholars and archaeologists the Israelites were not a very tall people, averaging around five and a half feet tall. It didnt take a whole lot for them to look up to another people and call them giants. The only time we get a height for a giant is with Goliath who was nine and a half feet tall.