Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fossil Records Show Biodiversity Comes and Goes

16.03.2005


A detailed and extensive new analysis of the fossil records of marine animals over the past 542 million years has yielded a stunning surprise. Biodiversity appears to rise and fall in mysterious cycles of 62 million years for which science has no satisfactory explanation. The analysis, performed by researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley, has withstood thorough testing so that confidence in the results is above 99-percent.



“What we’re seeing is a real and very strong signal that the history of life on our planet has been shaped by a 62 million year cycle, but nothing in present evolutionary theory accounts for it,” said Richard Muller, a physicist who holds joint appointments with Berkeley Lab’s Physics Division, and UC Berkeley’s Physics Department. “While this signal has a huge presence in biodiversity, it can also be seen in both extinctions and originations.”

Muller, and his grad student, Robert Rohde, presented their findings in the March 10, 2005 issue of the journal Nature. In a commentary on this research in that same issue of Nature, UC Berkeley professor of earth and planetary sciences, James Kirchner, stated, “It is often said that the best discoveries in science are those that raise more questions than they answer, and that is certainly the case here.”


Muller and Rohde discovered the 62 million year fossil diversity cycle after creating a computerized version of an exhaustive database compiled by the late University of Chicago paleontologist Jack Sepkoski. Entitled Compendium of Fossil Marine Animal Genera, Sepkoski’s posthumously published database is the most complete reference available for the study of biodiversity and extinctions. It covers the Phanerozoic eon, the past half billion years during which multicellular organisms left abundant fossil records in rocks; uses genera, the level above species in taxonomy, because genera classifications are more manageable and less often revised than species classifications; and includes only marine fossils because the records are longer and better preserved than records of land fossils.

For their study, Muller and Rohde defined fossil diversity as the number of distinct genera alive at any given time. This yielded a total of 36,380 genera, whose history the Berkeley scientists tracked over time, using the International Commission on Stratigraphy’s 2004 time scale.

“Putting the timescale in a chronologic format was critical to our findings, because there were no specific years assigned to the geologic timescale used by Sepkoski,” Muller said. “We are the first to reconstruct diversity from the final version of Sepkoski’s Compendium, and the first to use the 2004 geochronology time scale. In a sense, our work has verified the new time scale.”

Muller and Rohde have been working on this study for nearly two years, and first discovered the 62 million year biodiversity cycle in November, 2003. They spent the next year trying to either knock it down or explain it. Despite examining 14 possible geophysical and astronomical causes of the cycles, no clear explanation emerged. Muller and Rohde each has his own favorite guess.

Muller suspects there is an astrophysical driving mechanism behind the 62 million year periodicity.

“Comets could be perturbed from the Oort cloud by the periodic passage of the solar system through molecular clouds, Galactic arms, or some other structure with strong gravitational influence,” Muller said. “But there is no evidence even suggesting that such a structure exists.”

Rohde prefers a geophysical driver, possibly massive volcanic eruptions triggered by the rise of plumes to the earth’s surface. Plumes are upwellings of hot material from near the earth’s core that some scientists believe have the potential to reoccur on a periodic basis.

“My hunch, far from proven,” Rohde said, “is that every 62 million years the earth is releasing a burst of heat in the form of a plume formation event, and that when those plumes reach the surface they result in a major episode of flood volcanism. Such volcanism certainly has the potential to cause extinctions, but, right now there isn’t enough geologic evidence to know whether flood basalts or plumes have been recurring at the right frequency.”

In examining their results, Muller and Rohde found that the fossil diversity cycle is most evident when only short-lived genera (those that survived less than 45 million years) are considered. They also found that some organisms seem to be immune to the cycle, while others are exceptionally sensitive. For example, corals, sponges, arthropods and trilobites follow the cycle, but fish, squid and snails do not. In general, longer-lived genera that are more diverse and widespread stand a better chance of resisting the 62 million year cycle.

Muller and Rohde also found a second, less pronounced diversity cycle of 140 million years. "The 140 million year cycle is also strong, but we see only four oscillations in our 542 million year record,” Muller said. “This means there is some chance that it could be accidental, rather than driven by some external mechanism."

If it is real, the 140 million year fossil diversity cycle could be tied to a reported 140 million year cycle in Ice Ages. Said Rohde, "It is also possible that this 140 million year fossil diversity cycle is driven by passage through the arms of the Milky Way galaxy".

Muller and Rohde are continuing their examination of the data for both cycles, and their search for explanations. This research was supported, in part, by the Ann and Gordon Getty Foundation, the Folger Foundation, and the Larsen Fund.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

Lynn Yarris | EurekAlert!
Further information:
http://www.lbl.gov

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>