A lot of things changed with the Great Flood and all of them a degradation. For examples:
1. Yeasts, molds, and bacteria were introduced, shortening the lifespan of men. (Gen 6:3)
2. Fruits that once yielded juice that could be kept in carafe for weeks at room temperature began to quickly spoil and ferment, causing grape juice to turn into intoxicating wine. (Gen 9:21)
3. Edible plant life no longer contained all the nutrients needed for man's nutritional needs, so people were forced to eat meat to supplement their diet. (Gen 9:3)
It's why there were really 2 great falls of man, not just one. The very laws of physics were changed and death gained an even tighter grip on people after the flood.