University Of Cincinnati Geologists Analyzes Evolutionary Impact Of Mass Extinctions

August 20, 1998

The dramatic effects of the mass extinctions recorded in Earth's geologic record have led many geologists to view them as a distinct class of events -- so powerful that they swamp out normal evolutionary processes. Others have argued the opposite, that over geologic time, mass extinctions have had little effect on global diversity trends.

University of Cincinnati geologist Arnold Miller argues in a review paper in the August 21 issue of Science that the truth is somewhere in the middle of those extreme views. Miller's evaluation of global marine diversity patterns through the Phanerozoic, in light of recent research, indicates that mass extinctions are simply the most globally extensive of a continuum of abrupt transitions that combine to affect overall global diversity. The Phanerozoic covers the pasts 540 million years.

That view is in contrast to Stephen Jay Gould and others who have viewed mass extinctions as an over-arching tier of evolutionary processes, distinctly different than the processes which occur in the intervening time periods.

"While I agree that mass extinctions are the largest and most important of a class of 'catastrophes,' I would argue that they are not fundamentally different as an evolutionary mechanism from what causes diversity change in the intervals between them," said Miller.

"The so-called background intervals are also built of catastrophes that are more local or regional in scope, but can have the same profound effect on a local biota that a mass extinction has on a global biota."

As an example of an abrupt regional change, Miller discusses the diversification of a group of organisms known as "biological bulldozers," which dig into deposited sediments to find food.

The geologic record includes cases where the bulldozers replaced another group known as ISOSS (immobile suspension feeders on soft substrates). Previously, researchers believed the biological bulldozers out-competed the ISOSS organisms. Miller suggests an alternative explanation.

"Many deposit-feeders favor muddy, nutrient-rich sediments as a substrate to occupy. Just such sediments were provided during key intervals as a consequence of eroding areas uplifted during mountain-building. Quite apart from the action of the bulldozers, many of the incumbent immobile types would not have liked this kind of habitat.

So I am suggesting, as an alternative to the above 'competitive' scenario, that the transition happened because of major, physical changes to habitats."

In fact, previous research reported by Miller and others on the Ordovician Period showed that diversification of certain groups was favored in areas where active mountain-building took place.

As for those who argue that mass extinctions are actually minor contributors to global diversity patterns, Miller has used his database of Ordovician fossil occurrences to demonstrate that regional and local bursts of diversification occur at different times around the world.

Over time, the bursts add up to present what Miller believes is a misleading picture of diversification trends a smooth, gradual change over geologic time.

"The global pattern does not match any localized pattern," said Miller. "The global diversity trend is misleading for what it says about the rates of transition and perhaps even for what causes them."

Miller's research is supported by NASA's Program on Exobiology.

University of Cincinnati

Related Organisms Articles from Brightsurf:

To push or to pull? How many-limbed marine organisms swim
Couinter-intuitively, small marine animals don't use their limbs or propulsors to push themselves through the water while swimming.

Identical evolution of isolated organisms
Palaeontologists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the University of Calgary in Canada have provided new proof of parallel evolution: conodonts, early vertebrates from the Permian period, adapted to new habitats in almost identical ways despite living in different geographical regions.

The EU not ready for the release of Gene drive organisms into the environment
Gene drive organisms (GDOs) have been suggested as an approach to solve some of the most pressing environmental and public health issues.

Tiny marine organisms as the key to global cycles
Marine microorganisms play a very important role in global cycles such as of the uptake of carbon dioxide from the atmosphere.

Why organisms shrink
Everyone is talking about global warming. A team of paleontologists at GeoZentrum Nordbayern at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) has recently investigated how prehistoric organisms reacted to climate change, basing their research on belemnites.

The effects of microplastics on organisms in coastal areas
Microplastics (plastic particles under 5 mm) are an abundant type of debris found in salt and freshwater environments.

Climate change is reshaping communities of ocean organisms
Climate change is reshaping communities of fish and other sea life, according to a pioneering study on how ocean warming is affecting the mix of species.

Fungicides as an underestimated hazard for freshwater organisms
Large amounts of fungicides, used in agriculture, leak into nearby surface waters.

FEFU scientist reported on concentration of pesticides in marine organisms
According to ecotoxicologist from Far Eastern Federal University (FEFU), from the 90s and during 2000s in the tissues of Russian Far Eastern mussels the concentration of organochlorine pesticides (OCPs) that had been globally used in agriculture in the mid-twentieth century has increased about ten times.

How genes interact to build tissues and organisms
A group of scientists at the National Centre for Genomic Analysis (CNAG-CRG) from the Centre for Genomic Regulation (CRG), in Barcelona, Spain, led by Holger Heyn, developed a new computational tool, based on the mathematical Graph theory, to infer global, large-scale regulatory networks, from healthy and pathological organs, such as those affected by diabetes or Alzheimer's disease.

Read More: Organisms News and Organisms Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to