I think to some extent that a biblical flood is possible. It’s already established that the theory of Island gigantism occurs with isolated species.
Island gigantism - Wikipedia
Depending on how far back in history you go you had isolated pockets of species that evolved to sizes bigger that they would naturally be. It’s quite possible that they could have been wiped out by a giant flood due to a meteor or natural phenomena.
Island gigantism - Wikipedia
Depending on how far back in history you go you had isolated pockets of species that evolved to sizes bigger that they would naturally be. It’s quite possible that they could have been wiped out by a giant flood due to a meteor or natural phenomena.