All living organisms depend for their survival on their range of genetic variability.
Early evolution favours increasing complexity but, as a result, the organism becomes progressively more vulnerable to threats. Eventually the genetic variability range is unable to cope, the organism becomes endangered, and finally extinct.
This process has happened many times in geological history. The larger dinosaurs, which existed over a period of over 135 million years from the Jurassic to the Cretaceous, became extinct after they became too large for their territory and for their ability to move – possibly assisted by the arrival of an asteroid. Their smaller cousins who survived were the ancestors of our birds.
Much effort is currently being exerted to prevent or reverse the process of decline of supposedly “endangered species”. One strategy is to provide more living space. This seems to have succeeded, at least for a while, in African wildlife parks where human predators are causing the evolution of elephants without tusks.
The strategy has been less successful in the USA, where the available territory is more limited. A recent article in “Time” magazine shows how many smaller communities in the USA are now threatened with black bears, wolves, cougars. wild pigs, alligators and even bald eagles, who sometimes eat pets and attack children. There are now foxes on the White House lawn. The extra creatures can only find food from human dwellings.
By comparison with the mid 1900s, the population of raccoons has gone up 2.700{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, beaver 2.400{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, cougar 1,600{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} wild turkey 1,500{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, deer 800{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, gray wolf 610{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, alligator 400{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, Canada goose 370{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, black bear 320{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}, wild pig 120{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}.