Thursday, November 14, 2013

Oldest life found in Australia?

A rock displaying some of the structures that some
scientists think may be the oldest signs of life.
Image source.
According to the evolutionary timeline of history, life began approximately 3.5 billion years ago, 1.1 billion years after the earth formed.  This early life is thought to consist of single-celled organisms that gathered together into large colonies of microbes termed "microbial mats."  These underwater mats influenced sediment deposition, leaving behind microbially induced sedimentary structures (MISS) in the rocks.  Until recently, the oldest MISS were dated to 3.2 billion  years ago, or 300 million years after life was thought to evolve.  Existence of life prior to this was inferred largely from geochemical signatures in the rocks.

Last week, an article appeared in the online version of the scientific journal Astrobiology claiming to have found MISS in rocks dated 3.48 billion years old.  If verified, these structures could be the oldest direct signs of life ever found, according to the evolutionary view.  Does this find prove that life evolved 3.5 billion years ago?  Not necessarily.

First, understand that microbial mats do not indicate some exotic, archaic, primitive form of life.  Microbial mats are still quite common, as the authors of the new study indicate, which is how they are recognized in the rocks.  If one assumes that all life descended from a single cell, then one must infer that early life consisted of these microbial mats.  However, the presence of microbial mats is not indicative of a universal common origin of life.

Second, there is the question of the age of the rocks.  The rocks in question were found in Western Australia in the Dresser Formation, dated at 3481±3.5 million years old.  Interestingly, the formation was originally dated using uranium–lead radioisotope methods at 3525±2 million years old, but that date was changed when other rocks in the formation came up with a slightly younger date.  The dating process was not used on the sedimentary rock itself, but on zircon crystals contained within the rock.  This same method of using uranium–lead dating on zircons was investigated in the RATE (Radioisotopes and the Age of the Earth) project by a group of scientists from the Institute for Creation Research.  One of these scientists, Dr. Russell Humphreys, analyzed the rate at which helium is produced by uranium decay and the rate at which it leaks from zircon crystals.  I will not try to detail his study here, but he claims that these measured rates seem to support the creationist timeline, wherein there was a period of accelerated decay at some point in the past, giving vastly inflated results for any dating methods using radioactive decay.  These results, of course, are disputed by evolutionists, and the debate continues to rage back and forth.  My point, however, is that the given age of these rocks is not final and definitive.

Rocks like those in the Dresser Formation are considered by creationists to be mostly pre-Flood sediments.  It is possible, in the creationist model, that these microbial mats and their associated structures were present on the sea floor, either in the open ocean or in a shallow inland sea, just prior to the great Flood.  They may have been picked up and moved in chunks, but I find it more likely that they were formed in place, because any transportation would probably destroy the structures.  They may also have formed just at the very beginning stages of the Flood, when the ground was moistened and sediment was plentifully provided by waters flowing from the land.  One could speculate endlessly on the exact circumstances in which these structures were formed, so I reiterate that the interpretation put forth by the article authors is not absolute.

2 comments:

  1. Wait, 3.481 billion +/- 3.5 billion years old? So they could be from the FUTURE???

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  2. Ah, good catch. In my defense, that is what the original article said. Looking at other sources, apparently it was a typo. It is now fixed.

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