Esearchers dissent with a popular hypothesis behind the evolution of early life on Earth

Updated on: Wednesday, December 26, 2012

esearchers have debunked a popular hypothesis behind the evolution of early life on Earth.
 
Scientists led by biogeochemists at the University of California, Riverside tested a popular hypothesis in paleo-ocean chemistry, and proved it false.
 
The fossil record indicates that eukaryotes - single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes, such as bacteria - show limited morphological and functional diversity before 800-600 million years ago.
 
Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the trace metal zinc in seawater.
 
As it is for humans, zinc is essential for a wide range of basic cellular processes. Zinc-binding proteins, primarily located in the cell nucleus, are involved in the regulation of gene transcription.
 
Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures.
 
Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.
 
After analysing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic era were similar to modern concentrations. Zinc, the researchers said, was never bio-limiting.
 
"We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth's history," said Clint Scott, the first author of the study, adding "we found no evidence for zinc biolimitation in seawater".
 
Scott said that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic.
 
Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he said.

More Education news

• Karnataka department of higher education to further strengthen protection to women students and employees
• Heads of government and private schools directed to keep a close watch on the behaviour of teachers
• Chairman of the National Commission for Minority Educational Institutions submits his report
• Everyone will be given due representation says Goa CM
• Pune Education Department to hold meetings with schools to ensure a smooth RTE implementation
• Health and Medical Education, Forest and Home departments within the ambit of Public Services Guarantee Act
• 'value education' courses in engineering colleges to inculcate better values and character building
• students challenge new NET gidelines
• Proposed multi crore edu city project nearing completion
• 21 engineering colleges affiliated to the Dr Babasaheb Ambedkar Marathwada University to seek accreditation
• MBBS and PG medical seats to be increased by 50% and 100% respectively from academic year 2013-14
• M S University's faculty of fine arts mired in controversy over a painting hurting religious sentiment
• IICA inks MoU with Bangalore-based National Law School of India University for forging academic partnership
• President asks private players to contribute in improving the standards of higher education
• First technical and medical university at picturesque Apatani Plateau in lower Subansiri district
• Prayas scheme to be extended to 4 more districts
• Jamia Millia Islamia Professor gets Japan Society for the Promotion of Science Fellowship
• Japans new government will not waive tution fee to pro-Pyongyang high schools
• Most Israeli high school students found accessing Mobile phone during class hours
• UGC notifies the procedure and criteria for declaration of result for NET to be conducted on 30.12.12