For some of the people responsible for deciding
which animals deserve protection, so that poor welfare
is prevented, the key issue is whether or not those animals are useful. Other arguments about which animals
to protect have involved analogy with humans in that if
the animals seem to be more like us, they are considered to be more worthy of protection. The argument
advocated here and by D. M. Broom & K. E. Littin views the qualities of the animal on an
absolute scale that includes known animals, but would
also be relevant to unknown living beings such as
those that might be found on another planet. Such
arguments can be supported by scientific evidence, which has increased more and more in
recent years.