The 4 biggest milestones in the history of life on Earth
   3.7-billion-year-old rocks in Greenland. That suggests life popped up
   Years ago, the study of life beyond Earth was called “exobiology” or
   extrapolation. The one data point we have about life is what we see
   milestones in the history of life on Earth. It’s an incredible tale.
   details of that remain murky. Since life began, Earth has been
   Confounding matters further, life may not have had a singular origin.
   became life. Kate Adamala, who studies the origin of life and now
   from no life to life. There was likely a very gradual and slow
   a precursor. Life is a process of modification and descent, rather than
   Once life got rolling, the Next Big Thing was photosynthesis, says J.
   emergence of life that could use oxygen metabolically, which
   reproduction roughly a billion years ago. Until then, life merely
   After that, life was off to the races, doing all kinds of crazy stuff,
   (end-Permian, end-Creteacous, etc.), but life always found a way to
   “There are only a few things in the history of life that matter. The
   mats, then life was fairly complex early in the planet’s history and
   interpreted as a sign that life emerges quickly in general under the
   observer looking for the origin of life will likely be one in which
   life began early – because on such planets life has had a very long
   With only one example of life – the stuff we see on Earth – we don’t
   years ago defined life as “a self-sustaining chemical system capable of
   “I don’t think anyone has a definition of life that is universally
   agreed upon. The best we can do is describe some attributes of life –