Evolution: Massive Extinction

Gradual changes and the progressive transformations of our world, allow evolution time for its species to adapt to the new conditions.

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The sifakas, like all the group of the lemurs to which they belong, arose in the evolutionary isolation of Madagascar. There are no lemurs in any other part of the world and there never have been. And the same is true of over 150,000 plant and animal species that are exclusive to this African island. 
The lemurs appeared after Madagascar separated from the African continent. They are therefore a group that has developed without the evolutionary pressure of competition with continental species. 
But this absence of competition brings acute risks. All the species that developed in these evolutionary islands closely depend on their equally exclusive ecosystems. Lemurs, chameleons, fossas and insects, geckos, iguanas and the over 7,300 endemic plant species are the cells of the organism which is Madagascar, pieces in a living whole who could not survive without each other.  
And this affects both animals and plants, large and small, hunters and prey.
The travellers of these islands of independent evolution can teach us much not only about how life diversifies but also about the fragility of life on earth. They are small scale worlds, examples reflecting the destiny of the entire planet in a much shorter period of time.

On the other side of the Indian Ocean, a much larger island conserves species which show us what the world might have been like without the placentary mammals.
The interior of the prehistoric jungles of Australia is still home to the descendents of the distant Gondwana, the southern super-continent that split apart fifty million years ago.
This echidna is a representative of a lineage that became obsolete when the mammals acquired the ability to develop their young inside them, thus freeing themselves from the older formula, which was to lay eggs.
Along with the monotremes – the name given to this group of egg-laying mammals, Australia also has another type of mammal: the marsupials, who complete the development of their young inside pouches or marsupia.
The marsupials, and the majority of the species originating in the distant Gondwana, had left behind the continental competition faced by the plants and animals in the rest of the world. But Australia would also subject them to harsh tests.

When Australia became an independent island, it began a slow journey northwards. Over thousands of years, the island approached warmer latitudes and that brought progressive but important climatic changes in its interior. 
The warming of that young Australia might well have led to a massive, localised extinction. But the process was so slow that the Australian animals had time to adapt and evolve. 

The case of Australia is a perfect example demonstrating how, in the massive extinctions that have ravaged our planet, there is one factor that determines the ability of the earth, and life, to resist – and that factor is time.
The impact of a meteorite is an aggression of such speed and magnitude that it unleashes the destruction of millions of species. But gradual changes, the progressive transformations of our world, allow evolution time for its species to adapt to the new conditions. And it is that ability that has permitted, despite the great extinctions, life to recover time and time again.
 If life is given time, it demonstrates that it can be adaptable and flexible.

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