Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



Methane Rich Greenhouse Boosted Evolutionary Process

cyanobacterial remains in rock
Denver - Oct 28, 2002
What constrained the evolution of life during the very hot early Earth? Was a simple drop in temperature largely responsible for the emergence of cyanobacteria, a large and varied group of bacteria with chlorophyll that carry out photosynthesis in the presence of light and air with concomitant production of oxygen? Was it a reduction in carbon-dioxide levels?

Geochemist David Schwartzman of Howard University and Ken Caldeira of the Climate and Carbon Cycle Group at Lawrence Livermore National Laboratory have a different view. Looking at how feedback operates in Earth systems, they propose that the transition from a carbon-dioxide dominated greenhouse world to one dominated by methane actually did the trick.

Schwartzman and Caldeira will present findings of their research on Monday, October 28, at the annual meeting of the Geological Society of America in Denver, CO.

It's been argued that surface temperatures of 80-60 degrees centigrade kept the lid on evolution during the carbon-dioxide dominated greenhouse world of 3.8 to 2.5 billion years ago.

Dominant forms of life were very simple, consisting of prokaryotes (cells without nuclei that reproduce asexually) and eucaryotes (more advanced cells with nuclei). Metazoa, the animal kingdom, did not emerge until 0.7 to 1.5 billion year ago, when temperatures apparently dropped below their upper limit.

"I have argued that primitive organisms emerged once their upper temperature limit was reached as the relatively high climatic temperatures of the Archean declined," says Schwartzman.

"It appeared likely that methane replaced carbon dioxide as the dominant gas in the greenhouse atmosphere of early Earth by about 2.8 billion years ago. So we began to look at the dynamics of methane dominance, reduced levels of CO2, reduced surface temperatures, and the appearance of cyanobacteria.

"The question that arose for me is, "Is it a coincidence that the first good evidence for methane as a significant component of Earth's atmosphere occurred at the same time as analogous evidence for the first cyanobacteria?"

Schwartzman and Caldeira followed up the proposal of Charles Dismukes and coworkers that now extinct bacteria were performing oxygen-based photosynthesis before cyanobacteria came onto the scene.

In a CO2 dominated world, these early oxygenic photosynthesizers split bicarbonate instead of water as the source of oxygen. They apparently boosted organic productivity and caused greater methane production by methanogens living in the ocean.

"It takes far less methane to maintain climatic temperatures than it does carbon dioxide," says Schwartzman.

As methane became dominant, CO2 levels dropped dramatically. Cyanobacteria then emerged and began oxygenic photosynthesis by splitting water as the source of oxygen. According to Schwartzman, only when atmospheric oxygen levels began to rise some 2.2 billion years ago did a CO2-concentrating mechanism emerge, an adaptation to declining CO2/02 ratios in the external environment.

Thus, global constraints on evolution appeared to have included carbon dioxide as well as oxygen levels in the atmosphere along with surface temperature. All the former have been strongly influenced by biological evolution in a complex set of feedbacks, an essential aspect of biospheric evolution.

"The classical paradigm of evolution, that changes in the local environment lead to natural selection, should be rethought to include these feedbacks on a global scale.

"We hope that our hypothesis will be tested by looking more closely at the extant geologic record of the proposed transition as well as the insights from the study of photosynthesis and molecular biology of modern organisms," says Schwartzman.

Related Links
Howard University
Geological Society of America
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Methane Explosion Warmed The Prehistoric Earth, Possible Again
Greenbelt - Dec 10, 2001
A tremendous release of methane gas frozen beneath the sea floor heated the Earth by up to 13 degrees Fahrenheit (7 degrees Celsius) 55 million years ago, a new NASA study confirms. NASA scientists used data from a computer simulation of the paleo-climate to better understand the role of methane in climate change. While most greenhouse gas studies focus on carbon dioxide, methane is 20 times more potent as a heat-trapping gas in the atmosphere.



Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only






Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.