Sunday, November 9, 2014

Fossils falling like rain revolutionize our understanding of the deep past

New findings accumulate like Olympic records. Here we are, in the age of the microchip and the Mars explorer, and yet some of our most exciting and extraordinary scientific discoveries are extinct species in Earth’s fossil record.

These species reveal fundamental facts about our evolutionary past that cannot be derived by studying living organisms. Recently discovered 385-million-year-old fish fossils preserved with flexible limbs explicitly document the transition from life in the water to life on land. Diverse fossils of animals and plants show that some 100 million years ago, Antarctica was a greenhouse, with lush forests bathed in warmth.

This rapidly accumulating evidence also gives us a much clearer sense of what happened during the great mass extinction events of the past that wiped out between 50 and 90 percent of all species. Without a fossil record, our recognition that extinction is both an integral part of the evolution of life and a material reality — at this moment in human history, a far from academic concern — would not be possible.

The 1.8 million species of living organisms so far identified and named are but a fraction of the totality of life on Earth. Thanks to the fossil record, incomplete though it is, we can estimate that more than 99 percent of all species that ever lived are extinct. In a deep sense, our understanding of the future of evolution is rooted in the past.
And what we know of the past can inform our thinking about the present, and the future:
Scientists estimate that because of the current destruction of natural habitats and the disruptive power of climate change, we may lose anywhere between 20 and 50 percent of all living species by the end of this century.

The fossil record tells us that mass extinction events were so devastating that it took hundreds of thousands, even millions, of years for the few species that survived to once again diversify and flourish and for ecosystems to recover. In other words, what we know about the past signals that we are in a truly traumatic phase of the planet’s history that could affect much of life on Earth, including our species.
Who killed them off, those other hominin species?
Just 50,000 years ago — a blink of an eye in the deep time of paleontology — there were at least three, and maybe four, species of the human lineages cohabiting on this planet. Yet within that span of time, only our own species made it through the evolutionary sieve.

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