The story of Noah’s flood leaves a lot of people- believers and skeptics alike- with a lot of questions. Where did all the water come from? Did the flood really cover the whole world? What did Noah and his family do in the ark for an entire year? How did Noah fit all the animals onto the ark? The last question presents a particular challenge to many people. The Bible says God commanded Noah to take two of every kind of animal on the ark. Since there are millions of different kinds of animals in the world today Noah could not possibly fit two of every animal on the ark. But did God command Noah to transport millions of animals?
Noah’s ark was over 450 feet long and 75 feet wide with three decks that each had approximately 35,000 square feet of floor space. The total floor space of the ark was over 105,000 square feet. This is roughly equivalent to the floor space of 260 semi-trailers (but with a lot more head room). To understand how much room there was on the ark, consider that a modern semi-trailer can haul over 30 full grown cows on 400 square feet of floor space. That means the ark had enough space on each deck to haul over 2,500 cows.
7,500 cows is a lot of beef, but that does not seem like big enough to haul two of every kind of animal in the world. Would Noah have taken on the ark a pair from every species and sub-species of air breathing animals? Would he have had two lions, two tigers, two cheetahs, two leopards, two panthers, two mountain lions and two of every variety of house cat? The Bible’s use of the word “kind” in Genesis 1 helps us understand God’s command to Noah in Genesis 6. God created the animals after their kind and told them to be fruitful and multiply. “Kind” seems directly related to the ability to interbreed.
The modern taxonomic system was invented hundreds of years after the Bible was written. The ideas of genus and species are foreign to the Bible. Modern taxonomy is one way of classifying life in the world, but not the only way. We have no reason to think the Biblical authors categorized animals in the same way we do today. God could have brought to Noah one pair of animals out of a larger set of multiple species that were able to interbreed. Instead of bringing two lions, tigers, etc., God may have brought to Noah two of the cat “kind.” This ability to interbreed is not just true of cats. Most species in the world can interbreed with other species of the same genus. If Noah took one pair from each group of animals that were able to produce fertile offspring, then the number of animals Noah had to bring on the ark would be much smaller than originally thought.
Reducing the number of animals to a reasonable estimate of the breeding kinds of non-aquatic, air breathing animals makes the number much more manageable. Biblical scholars who have done significant work in this area have concluded Noah probably had to bring ten to fifteen thousand animals on board the ark. Still sound like too many animals? If we can only get 7,500 cows on board, what about dinosaurs? Dinosaurs take up a lot more room than cows. Though there are many large animals in the world, there are many, many more small animals. The average animal size, including dinosaurs, is about the size of a sheep. At a very conservative estimate, the ark could have carried at least four times more sheep than cows. That means the ark had room for 30,000 sheep. Consider Noah was transporting these animals, not providing them a zoo like habitat. He needed space to stable them, but not room to let them run free. When you also consider the likelihood that Noah would not have brought full sized animals onto the ark, we can see how the ark had ample space for all the animals and plenty of room for Noah’s family.
Answers in Genesis has done a lot of work in this area. You can read some of their answers here and here and here.