Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mass Extinctions Reset the Long-Term Pace of Evolution

03.07.2012
A new study indicates that mass extinctions affect the pace of evolution, not just in the immediate aftermath of catastrophe, but for millions of years to follow. The study’s authors, University of Chicago’s Andrew Z. Krug and David Jablonski, will publish their findings in the August issue of the journal Geology.

Scientists expected to see an evolutionary explosion immediately following a mass extinction, but Krug and Jablonski’s findings go far beyond that.

“There’s some general sense that the event happens, there’s some aftermath and then things return to normal,” said Krug, a research scientist in geophysical sciences at UChicago. But in reality, Krug said, “Things don’t return to what they were before. They operate at a different pace, sometimes more rapidly, other times more slowly. Evolutionary rates shift, and that shift is permanent until the next mass extinction.”

Krug and Jablonski’s suggestion that the potential for rapid speciation and expansion of survivors and new groups of organisms in the “emptier” world following a mass extinction “is a reasonable possibility as one source of rate change,” said paleontologist Richard Bambach of the Smithsonian Museum of Natural History, who was not directly involved in the UChicago study.

The long-term evolutionary patterns of species diversification following mass extinctions are poorly understood. Paleontologists have extensively debated whether diversity has increased over the last 251 million years, which followed the most devastating mass extinction in Earth history, Bambach said

Inconsistent classifications

Scientists have been putting Latin names on fossils since 1758, often inconsistently. Methods and tools have changed with the times, but old names often remain. The UChicago paleontologists have combed through seemingly endless volumes of research papers and countless museum drawers in an ongoing attempt to standardize these classifications.

For their Geology study, Krug and Jablonski analyzed contemporary groups of organisms from the end of the Pleistocene Epoch, which ended approximately 10,000 years ago, to the Jurassic Period, which began approximately 200 million years ago. The availability of globally abundant data on bivalves, a group that includes clams, oysters and scallops, set the study’s time boundaries.

“With some groups, like sea urchins or corals, you just couldn’t do it because the numbers aren’t big enough,” said Jablonski, the William R. Kenan Jr. Distinguished Service Professor in Geophysical Sciences.

When he and Krug statistically plotted the origination rate of new bivalve species at 50 million-year intervals, they found that all the species evolved at a fairly steady rate for millions of years. Then the bivalve groups show a sudden increase or decrease in the rates at which new species evolved. These sudden shifts marked the occurrence of a mass extinction. “They settle back down to a different rate from what was before, and they do it multiple times, corresponding to each mass extinction,” Jablonski said.

Theoretically, the origination rates of the organisms might have “been all over the map,” with evolutionary rates varying in a random or chaotic style, but they didn’t. “It’s surprising how organized the pattern is,” he said.

Krug and Jablonski’s perspective of the data is somewhat different from Bambach’s. These perspectives are “not contradictory, but complementary, ways of looking at the data,” Bambach said. “One of the valuable things about their work is that they record the pattern and pattern change during intervals that I lump together.”

Bambach bases his work on older data compilations that include the animal kingdom as a whole, while Krug and Jablonski use their new, carefully vetted data from bivalve mollusks.

Setting a new pace

“There’s been a lot of talk about the evolutionary role of mass extinctions, but it’s like the weather. Everyone talks about it, but no one does much about it,” Jablonski joked.

“No one has really thought about it in terms of these downstream dynamics, once the smoke has cleared and ecosystems have found a new equilibrium, for want of a better word. But the wonderful thing is that when they find a new equilibrium, it’s a different evolutionary pace from the one that prevailed for the preceding 50 million years. The survivors of the mass extinction, or the world they inherited, is so different from what went before that the rate of evolution is permanently changed.”

Krug and Jablonski’s research builds upon the work of UChicago’s David Raup, the Sewell L. Avery Distinguished Service Professor Emeritus in Geophysical Sciences, and Michael Foote, professor in Geophysical Sciences.

In 1978, Raup published a method for determining the extinction rate of organisms. His method involved monitoring the survivorship of a group of organisms that had all originated during a specific time period and quantifying when they disappeared. It would be like collecting census data for all individuals born on Jan. 1, 1899, tracking their longevity, then finding that the 1918 influenza epidemic had produced a spike in this group’s mortality.

Foote followed up in 2001, showing that Raup’s method worked equally well for determining origination rates as it did for extinction rates. One simply needed to use the method in reverse, tracking the time since origination of a group of co-occurring lineages as opposed to the time until extinction. Now comes Krug and Jablonski’s latest study, finding that the evolutionary “birth rate” was also reset at major catastrophes. “It’s very Chicago-esque,” Jablonski said.

Citation: Andrew Z. Krug and David Jablonski, “Long-term origination rates are re-set only at mass extinctions,” Geology, posted online June 29, 2012.

Funding: National Aeronautics and Space Administration Exobiology Program and the National Science Foundation.

Steve Koppes | Newswise Science News
Further information:
http://www.uchicago.edu

More articles from Earth Sciences:

nachricht 'Quartz' crystals at the Earth's core power its magnetic field
23.02.2017 | Tokyo Institute of Technology

nachricht NASA spies Tropical Cyclone 08P's formation
23.02.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>