Some scientist postulated the theory that alien species are likely to be 600 pounds or more. He came to this conclusion with no evidence of any kind and only some vague notion that "larger animals have a lower population density than smaller animals because of greater energy consumption" and "most inhabited planets will be the size of Mars rather than Earth."
I guess he forgot about the Buffalo, the wilderbeast, crocodile...blah, blah, blah.
But why Mars? Why no Earth? or Pluto?
Oh good grief. Why do I internet.
Clearly he missed this story...