On the phylogenetic tree of life on earth, the oldest of the three main branches is that of the Archaea
, a class of prokaryote including extremophiles
, organisms that inhabit environments far outside the range which is comfortable for humans. For example, in the submarine volcanic environment of Loihi
, which erupted violently in 1996, microbial mats have since been found (see picture).
The evidence for life on earth dates back to the oldest rocks on earth, namely the Akilia island
sediments of West Greenland. Although the evidence in carbon isotopes for life in these particular sediments has been open to question, there is plenty of evidence in other ancient rock sediments which typically date life back 3.55 billion years.
The theory that life originated in space, and was transported to the Earth's surface from space, is known as panspermia
. But if the oldest life on Earth, perhaps as old as Earth, likes hot
environments, is there perhaps a different explanation? Astrobiologists such as Lawrence Krauss
think that extremophiles will radically alter our understanding of the origins of life.
If there was a Black Hole at the centre of the Earth, would it have anything to tell us about the evolution of life?