Wednesday, December 14, 2011

Extraterrestial cause for Cambrian explosion of life?

Our planet, the sole known habitat of homo sapiens sapiens in the entire Universe, is estimated to be about 4500 million human years old. Very first signs of life have been detected in 3500 million years old rocks. But that is more or less where things remained for a long period of time in human years - rare signs of life here and there in pre-Cambrian rocks.

About 650 million years ago something begins to happen. There are the sessile organisms of the Ediacaran period, unable to move and truly enigmatic as far as their position is considered in the tree of life upon Earth.

Then something happens!

The Cambrian explosion or Cambrian radiation was the relatively rapid (over a period of many millions of years) appearance, around 530 million years ago, of most major phyla, as demonstrated in the fossil record, accompanied by major diversification of other organisms, including animals, phytoplankton, and calcimicrobes.

Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 or 80 million years the rate of evolution accelerated by an order of magnitude (as defined in terms of the extinction and origination rate of species) and the diversity of life began to resemble that of today.

No matter whether we call it explosion to emphasize the Big Bang like change in the history of life on our planet or use the subtler term radiation which has little to do with enriched uranium radiation; something extraordinary happened and so we humans are here, writing blogs and reading and commenting them on myriads of subjects over a global network of electronic wires.

Early ET visitors empty handed
So let me repeat... 4500 - 580 ... planet Earth orbits the Sun but is a very quiet place as far as life is concerned. It all changes in the Cambrian period.

Extraterrestrial visitors would have been rather disappointed some two three billion years ago - so much water but so few living organisms and none of them even able to translate Hello world! into Martian or ask Ah'chu apenkee? in Huttu. Not much higher intelligence here for most of the time this planet has existed in the universe.

Of course, even the rise of higher more complex life forms in and after Cambrian did not yet create human languages but those magnificent animals did know how to communicate each in the given speech consisting of sounds and expressions and other signals God has given them. Speech as we use it developed only very recently on the planet, possibly only some two million years ago judging from the making of standardized stone tools by early man (if the tools are valid criteria).

Second start?
As noted in the Dr Watson column there is no simple logic that can deduce early Cambrian life forms logically from Ediacaran microbial mats and other enigmatic things just before the explosion of life.

This break, possibly hiatus on life, could suggest that maybe there is not a single line of ONE life from its early origins but rather several starts. The pansperma theory of life containing meteorites flying around and impregnating planets does not necessarily require a single point of origins for all life on Earth.

We need to remember two things, though:

  • our very limited knowledge of earliest life forms on Earth
  • our total lack of knowledge of what is life in the first place
By pushing origins of life, or the origins of water on Earth, to some space agent science takes certainly a step forward. But at the same time, such evidence of extraterrestrial origins of life would only push the question of origins of life further away into the deep space and the realm of astrobiology.

Maybe that is how it is. We will know sooner or later.

No comments:

Post a Comment