When the ancient fossils of a primitive land mammal were unearthed in New Zealand, they provided the first concrete evidence that the island country had once had indigenous land mammals. Until that discovery, New Zealand had no known native land mammals. The discovery thus falsifies the theory that New Zealand' s rich and varied native bird population owes its existence to the lack of competition from mammals.
The statement 'The recently discovered land mammal became extinct long before the native bird population was established' most seriously weakens the argument.