The most frequent interpretation of Hamas, the reason that G-d declares that the earth must be wiped clean of all living things, aside from Noach and the birds, insects and animals in the ark, is robbery. The famous Gemara says that the verdict was sealed only over Gezel or theft. The question is why was theft such an extraordinary crime that it necessitated wiping out not only mankind, but also all life on the surface, for it's explicitly stated that all life had become corrupted. Animals have no concept or legal standing when it comes to property. Furthermore why is this suddenly an issue that had not been mentioned previously during earlier generations which did not seem to have the same crime problem? To understand that last point, let's go back to the two earlier sins. First Adam and Chava took from the Tree of Knowledge that they had been forbidden to eat from. Second, Kayin, unlike his brother, brought a sacrifice to G-d that was not from the best and resented G-d