Deathclaws are large, mutant versions of Jackson's Chameleons. The ones on the East Coast in Shy-Town are hairy, a trait they evolved to cope with the colder temperatures. I forget if the Deathclaws were a natural mutation or the result of a government experiment in the interest of using them as weapons. The fact that they are so tough, adapt to their environment so quickly, have evolved much faster and to a near-human level of intelligence than their surrounding fellow mutants, (mole rats, ants, etc.), and that they are a creature seemingly designed for killing would indicate the former.