And of every living thing of all flesh you shall bring two of every sort into the ark, to keep them alive with you; they shall be male and female. Genesis 6:19"In the book Noah’s Ark: A Feasibility Study, researcher John Woodmorappe suggests that, at most, 16,000 animals were all that were needed to preserve the created kinds that God brought into the Ark. Woodmorappe used a “worst case” scenario of the Biblical “kind” being equated to the genus level of classification.
The Ark did not need to carry every kind of animal—nor did God command it. It carried only air-breathing, land-dwelling animals, creeping things, and winged animals such as birds. Aquatic life
(fish, whales, etc.) and many amphibious creatures could have survived in sufficient numbers outside the Ark. This cuts down significantly the total number of animals that needed to be on board. Woodmorappe used a “worst case” scenario of the Biblical “kind” being equated to the genus level of classification.
Using a short cubit of 18 inches (46 cm) for the Ark to be conservative, Woodmorappe’s conclusion is that “less than half of the cumulative area of the Ark’s three decks need to have been occupied by the animals and their enclosures.” This meant there was plenty of room for fresh food, water, and even many other people. Noah’s cubit was probably longer, like the royal cubits used in the pyramids of Egypt and elsewhere. For the Ark Encounter, we have used a royal cubit of 20.4 inches (51.8 cm) as a typical benchmark for ancient construction.
Another factor which greatly reduces the space requirements is the fact that the tremendous variety in species we see today did not exist in the days of Noah. Only the parent “kinds” of these species were required to be on board in order to repopulate the earth. For example, only two dogs were needed to give rise to all the dog species that exist today.
Creationist estimates for the maximum number of animals that would have been necessary to come on board the Ark have ranged from a few thousand to 35,000, but they may be as few as 7,000 if the biblical kind is approximately the same as the modern family classification. Researchers for the Ark Encounter have determined that there would have been approximately 1,400 kinds of animals on the Ark. Taking into account that God brought pairs of the unclean animals, seven pairs of clean animals, and seven pairs of the flying creatures (including birds, bats, and pterosaurs), there would have been about 7,000 individual animals on the Ark.
Noah wouldn’t have ted before, taken the largest animals onto the Ark; it is more likely he took juveniles aboard the Ark to repopulate the earth after the Flood was over. These younger animals also require less space, less food, and have less waste." AIG