While if a cow is killed at thirty months, it is no more tragic than being killed at forty, fifty or sixty months, no one will say anything. This prime example of humans being deemed more superior, they think nothing of the cow and how she suffers. Then Singer reformulates his argument to compare a human with low cognitive abilities and a cow, both of which have no plans for the future, so the new argument would be about the difference between killing a human and a human with severe mental retardation. This, although it may raise much controversy, applies to humans and non-humans. Singer also says that the capacity to grieve is an important aspect of life. Every living animal has the capacity to suffer, which means that humans and non-humans are very similar. Whether it's a human or a non-human, when they lose someone close to them, you see a change in them