November 7, 1996: Life Before 3850 Million Years Ago? What'sNEW

A report in Nature pushes back the date of the earliest evidence for the life on Earth. Based on the isotope ratios in carbon inclusions in apatite grains in a "banded iron" formation in Greenland, the date is now estimated as 3850 million years ago (2). This evidence squeezes the time available for life to originate from nonliving chemicals to "vanishingly short" (3):

Many scientists believe that the chemical processes that gave rise to life must have taken hundreds of millions of years to develop the essential enzymes, proteins and genetic codes. Evidence of a very quick beginning might mean that there was too little time to complete the job on Earth, and that life therefore must have originated elsewhere, drifting through space to Earth in the form of spores or by some other means. This is known as the "panspermia" theory.

Earth's 'Time Capsules' May Be Flawed by Sid Perkins, ScienceNow, 17 Nov 2011.
23 Aug 2011: Fossilized microorganisms that are 3.4 billion years old have been found in in Western Australian sandstone.
Young graphite, old rocks: looking for evidence of earliest life, Carnegie Institution for Science, 16 May 2011.
A New Picture of the Early Earth by Kenneth Chang, The New York Times, 1 Dec 2008.
1 Aug 2006: The case for life on Earth 3.8 billion years ago has been reinforced.
13 Jun 2006: Early life on Earth was already diverse, Australian and Canadian biologists conclude.
Robert S. Boyd, "Stage set earlier for life on Earth" [text], The Seattle Times, 7 May 2005.
Was Early Earth a Cool World?, ScienceNow, 6 May 2005.
New Thermometer Confirms Wet Conditions on Earliest Earth, National Science Foundation, 5 May 2005.
Frances Westall, "Life on the Early Earth: A Sedimentary View" [summary], doi: 10.1126/science.1107227, p 366-367 v 308, Science, 15 Apr 2005.
24 Mar 2005: Evidence for very old life is questioned.
Study resolves doubt about origin of Earth’s oldest rocks, possibility of finding traces of ancient life, University of Chicago, 16 Dec 2004.
Michael M. Tice and Donald R. Lowe, "Photosynthetic microbial mats in the 3,416-Myr-old ocean" [abstract], p 549-552 v 431, Nature, 30 Sep 2004.
Mark A. Van Zuilen, Aivo Lepland and Gustaf Arrhenius, "Reassessing the evidence for the earliest traces of life" [abstract], p 627-630 v 418, Nature, 8 Aug 2002.
Rex Dalton, "Squaring up over ancient life" [text], p 782-784 v 417, Nature, 20 June 2002.
Kenneth Chang, "Dusted for Life's Fingerprints, Rocks Fail" [text],The New York Times, 4 June 2002.
Earliest life or rare dirt? — fossil bacteria 3.5 bya? — by Tom Clark, Nature Science Update, 7 Mar 2002.
The First Sulfur Eaters, "3.47 billion years ago," by Leslie Mullen for NASA Astrobiology Institute, on SpaceDaily, 19 Dec 2001.
2001, January 17: Earth had liquid water 4.3 to 4.4 billion years ago.
Australia fossil... A 1.25 meter, "egg carton" shaped rock contains fossilized stromatolites. At 3.46 billion years old, "this is the oldest solid evidence of biogenic structures in the world." CNN.com, 3 September 1999.
Yuji Sano, Kentaro Terada, Yoshio Takahashi and Allen P Nutman. "Origin of life from apatite dating?" and reply by S. J. Mojzsis, T. M. Harrison, G. Arrhenius, K. D. McKeegan and M. Grove, p 127-128 v 400, Nature, 8 July 1999. Lead isotopes might indicate a younger age for the sediments, but Mojzsis et al. do not retreat.
1999, February 10: New evidence for old life.
Hints of life from 3.7 billion years ago: Scientists find signature of plankton in tiny specks of graphite within rock. MSNBC, 28 January 1999.
Life on Earth Began at Least 3.85 Billion Years Ago, 400 Million Years Earlier than Previously Thought, Scientists Say, NASA News Release 96-230, November 6, 1996.
Science News Online - This Week - News Feature - 11/9/96
Earliest Known Life on Earth. News Release from Oxford Brookes University, December 8, 1996.

Arrhenius and Mojzsis

References