Origin of Life: Massive Extinctions

Massive extinctions took place millions of years ago, so long ago that life had time to start again from zero, leaving behind creatures that were lost forever in the transformations suffered by a young, inexpert and changing. 

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We are the most efficient agent of a phenomenon which is as old as life itself: the extinction of species. But we are becoming so efficient in our role as destroyers that, as we begin to understand the interdependent mechanisms of life on earth, we are realising that perhaps our own activities could end up leading our species along the road to extinction.
Life is, above all, a mystery. The Earth became a planet of possibilities for life. 
 Each ecosystem, each niche, each space on the earth or beneath the sea, was exploited by biological prototypes that have gradually taken shape as the passage of eras changed the conditions of the natural environment. 
The species changed as the planet matured. 
 The first living beings did not appear until almost four thousand million years after an explosion - for us unimaginable, though small on the scale of the universe – gave rise to the solar system. 
But following the first pulsations of life, it immediately began its relentless mutations. 

The forms of life multiplied, varying their bodies, their capacities  and their requirements for subsistence. The complexity of living beings increased, animals and plants diversified…The new species were more complex and sophisticated; they even became sociable, giving rise to behaviour that favoured the survival of the group above that of the individual. And the Earth was filled with specialists, marvellous biological entities capable of perpetuating themselves.
Life spread to every corner of our small, extraordinary planet.

But in this process of experimentation and change there were failures as well as successes. Terrestrial and extraterrestrial factors marked eras of great changes during which life had to start all over again. From the time the first living being appeared to the present day, these great changes have wiped out 99% of all the species that have ever existed. And they did so in specific periods of time, millennia marked by unusual mortality which we have called massive extinctions.

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