A (Very) Short History of Life On Earth

To paraphrase what somebody once said in another context, the careers of all living things end in extinction. Even life itself will not endure, Homo sapience will be no exceptionto this.
Not an exception, perhaps – but exceptional, nonetheless. Although most mammal species last for around a million years, and Homo sapience even its broader sense has existed for less than half that time, humanity is an exceptional species. It could last for millions of years more – or suddenly drop dead next Tuesday.
The reason why Homo sapience is exceptional is that it is the only species which, as far as is known, has become conscious of its place in the scheme of things. It has become aware of the damage it is doing to the world, and, therefore, has begun to take steps to limit it.
There is much current concern that Homo sapiens has precipitated what has been called the ‘sixth’ mass extinction, an event of similar magnitude to the ‘Big Five’, the extinctions at the end of the Permian, Cretaceous, Ordovician, Triassic, and Devonian periods – events detectable in the geological record hundreds of millions of years later.
Whereas it is true that the ‘background’ rate of extinction – the meat-and-potatoes business in which species evolve and become extinct, each for its own reasons – has risen since the evolution of humans, and is especially high at present, human beings will need to carry on what they are doing for another 500 years for the current extinction rate to signify among the Big Five. This is almost twice as long as the interval between the Industrial Revolution and the present day. Much damage has been done, but there is still time to prevent it becoming as bad as it might be, were humanity to do nothing. It is not the sixth extinction. At least, not yet.
Humanity has also precipitated an episode of global warming due, largely, to the sudden emission of carbon dioxide in the atmosphere. The effects of global warming are already being felt, and are causing significant disruption to human health and security, as well as to the lives of many different species.

2 thoughts on “A (Very) Short History of Life On Earth

  1. shinichi Post author

    超圧縮 地球生物全史

    by ヘンリー・ジー


     ある人が別の文脈で語った言葉を借りれば、すべての生き物のキャリアは絶滅で終わる。 生命そのものも永遠にはつづかない。ホモ・サピエンスも例外ではない。
     例外ではないかもしれないが、それでも特別ではある。ほとんどのほ乳類は100万年程度で絶滅する。ホモ サピエンスは、まだその半分以下しか経過していないが、人類は特別な種だ。人類は、あと何百万年も生きつづけるかもしれないし、来週の火曜日に絶滅してしまうかもしれない。


     背後絶滅(種が進化し、それぞれの理由で絶滅すること。大量絶滅に対して、通常の絶滅を指す)の割合は、人間が進化して以来上昇し、現在特に高いことは事実だが、ビッグ ファイブと比べて、現在の絶滅率が意味を持つようになるには、人類があと五〇〇年はいまの状態をつづける必要がある。これは産業革命から今日までの期間のほぼ二倍に相当する。多くの被害が出ているが、(このまま人類が手をこまねいて、)事態が深刻になるのを防ぐ時間的な猶予はまだある。少なくとも、いまはまだ、第六の絶滅ではない。


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