The worst mistake in the history of the human race, according to Jared Diamond, is our allowing the extinction of dozens (perhaps even hundreds) of plant and animal species on the world's islands by introducing predators and competitors to previously predator-free islands. On continental land masses many plant and animal species have coevolved over millions of years with predators so that neither group can eliminate the other. By contrast island species have often evolved in absence of predators and competitors and thus lack appropriate defenses to combat these 'new' species humans introduced. While island species evolved to fill specific niches in their ecosystem, once humans introduced invasive species to these ecosystems the indigenous island organisms were unable to compete and were wiped out. Examples of human-introduced predators and species that have caused catastrophic extinctions include the introduction of dogs and rats to the Galapagos; European pigs and cats to the Caribbean; stoats and rats to New Zealand; and boa constrictors and mongooses to Hawaii. Diamond estimates that over tens of thousands of years humans wiped out over 500 bird species and 100 mammal species from islands all around the world. Diamond cites this as our greatest mistake because the extinctions were a human error easily avoided if only humans had thought out the consequences of their actions.