Mass Extinctions Made Life On Earth More Diverse – And Might Again

Mass Extinctions Made Life On Earth More Diverse – And Might Again Ton Bangkeaw/Shutterstock

In the past half-billion years, Earth has been hit again and again by mass extinctions, wiping out most species on the planet. And every time, life recovered and ultimately went on to increase in diversity.

Is life just incredibly resilient, or is something else going on? Could mass extinctions actually help life diversify and succeed – and if so, how? Given that we’re currently facing another extinction event, there’s extra urgency in trying to work out how mass extinctions affect diversity.

Mass extinction is probably the most striking pattern in the fossil record. Vast numbers of species – even entire families – disappear rapidly, simultaneously, around the world. Extinction on this scale usually requires some kind of global environmental catastrophe, so severe and so rapid that species can’t evolve, and instead disappear.

Mass Extinctions Made Life On Earth More Diverse – And Might Again Catastrophic eruptions are the main driver of mass extinctions. Wikipedia

Massive volcanic eruptions drove the extinctions at the end of the Devonian, Permian and Triassic periods. Global cooling and intense glaciation drove the Ordivician-Silurian extinctions. An asteroid caused the end-Cretaceous extinction of the dinosaurs. These “Big Five” extinctions get the most attention because, well, they’re the biggest. But lots of lesser yet still civilisation-threatening events occurred as well, like the pulse of extinction before the end-Permian event.

These events were indescribably destructive. The Chicxulub asteroid impact that ended the Cretaceous period shut down photosynthesis for years and caused decades of global cooling. Anything that couldn’t shelter from the cold, or find food in the darkness – which was most species – perished. Perhaps 90% of all species disappeared in just a few years.

But life bounced back and the recovery was rapid. 90% of mammal species were eliminated by the asteroid, but they recovered and then some within 300,000 years, going on to evolve into horses, whales, bats and our primate ancestors. Birds and fish experienced similarly rapid recovery and radiation. And many other organisms – snakes, tuna and swordfish, butterflies and ants, grasses, orchids and asters – evolved or diversified at the same time.

Mass Extinctions Made Life On Earth More Diverse – And Might Again Butterflies and asters both diversified in the wake of the end-mass extinction. wikipedia

This pattern of recovery and diversification happened after every mass extinction. The end-Permian extinction saw mammal-like species take a hit, but reptiles flourished afterward. After the reptiles suffered during the end-Triassic event, the surviving dinosaurs took over the planet and diversified. Although a mass extinction ended the dinosaurs, they only evolved in the first place because of mass extinction.

Despite this chaos, life slowly diversified over the past 500m years. In fact, several things hint that extinction drives this increased diversity. For one, the most rapid periods of diversity increase occur immediately after mass extinctions. But perhaps more striking, recovery isn’t only driven by an increase in species numbers.

In a recovery, animals innovate – finding new ways of making a living. They exploit new habitats, new foods, new means of locomotion. For example, our fish-like forebears first crawled onto land after the end-Devonian extinction.

Evolutionary innovation

Extinction doesn’t only drive this process of speciation. It also drives evolutionary innovation. It’s not a coincidence that the biggest pulse of innovation in life’s history – the evolution of complex animals in the Cambrian Explosion – happened in the wake of the extinction of the Ediacaran animals that went before them.

Innovation may increase the number of species that can coexist because it allows species to move into new niches, instead of fighting over the old ones. Fish crawling onto land didn’t compete with fish in the seas. Bats hunting at night with sonar didn’t compete with birds that were active during the day. Innovation means evolution isn’t a zero-sum game. Species can diversify without driving others extinct. But why does extinction drive innovation?

Mass Extinctions Made Life On Earth More Diverse – And Might Again Over 1,000 bat species have evolved without directly competing with birds. Wikipedia

Stable ecosystems may prevent innovation. A modern wolf is probably a far more dangerous predator than a velociraptor, but a tiny mammal couldn’t evolve into a wolf in the Cretaceous because there were velociraptors. Any experiments in carnivory would have ended badly, with the poorly adapted mammal competing with – or just eaten by – the already well-adapted Velociraptor.

But, in the lulls after an extinction, evolution may be able to experiment with designs that are initially poorly adapted, but with long-term potential. With the show’s stars gone, the evolutionary understudies get their chance to prove themselves.

The extinction of Velociraptor gave mammals the freedom to experiment with new niches. Initially, they were poorly equipped for a predatory lifestyle, but without dinosaurs competing with or eating them, they didn’t need to be terribly good to survive. They only needed to be as good as the other things around at the time. So they flourished in an ecological vacuum, ultimately evolving into big, fast, intelligent pack hunters.

Creative destruction

Life isn’t just resilient, it thrives on adversity. Life will even recover from the current wave of human-induced extinctions. If we disappeared tomorrow, then species would evolve to replace woolly mammoths, dodo birds and the passenger pigeon, and life would likely become even more diverse than before. That’s not to justify complacency. It won’t happen in our lifetime, or even the lifetime of our species, but millions of years from now.

This idea that extinction drives innovation may even apply to human history. The extinction of ice-age megafauna must have decimated hunter-gatherer bands, but it also may have given farming a chance to develop. The Black Death produced untold human suffering, but the shakeup of political and economic systems may have led to the Renaissance.

Economists talk about creative destruction, the idea that creating a new order means destroying the old one. But evolution suggests there’s another kind of creative destruction, where the destruction of the old system creates a vacuum and actually drives the creation of something new and often better. When things are at their worst is precisely when the opportunity is the greatest.The Conversation

About The Author

Nick Longrich, Senior lecturer, palaeontology, Milner Centre for Evolution, University of Bath

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

Life After Carbon: The Next Global Transformation of Cities

by Peter Plastrik , John Cleveland
1610918495The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon

The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert
1250062187Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon

Climate Wars: The Fight for Survival as the World Overheats

by Gwynne Dyer
1851687181Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

LATEST VIDEOS

300 Million Face Severe Risk of Climate-Fueled Coastal Flooding by 2050
by Democracy Now!
As a shocking new report finds that many coastal cities will be flooded by rising sea levels by 2050, Chile’s President…
Climate Warning: California Continues To Burn, Data Estimates Of Global Flooding
by MSNBC
Ben Strauss, CEO and Chief Scientist of Climate Central joins MTP Daily to discuss alarming new information about…
Stanford Climate Solutions
by Stanford
Climate change has brought us to a defining moment in human history.
Buying Renewable Energy From Your Neighbor
by NBC News
Brooklyn Microgrid, a project of parent company LO3 Energy, is looking to disrupt the more than 100-year-old energy…
Debate Over Pipelines Clouds Concern For Climate Change
by Global News
Climate experts are warning that Canada shouldn't ignore the wildfire crisis in California
How Climate Change Affects Wildfires
by NBC News
NYU environmental studies professor David Kanter explains how climate change is creating the perfect conditions for…
Rice Bowl Of Malaysia Threatened By Climate Change
by The Star Online
Kedah is known as the country’s “Rice Bowl,” and it is especially suitable for the growing of the grain.
Maine Cow's Seaweed Diet Research Could Help Climate Change
by News Center Maine
Research in Maine will measure the methane released by cows who have been fed a seaweed diet.

LATEST ARTICLES

Why The Global Climate Treaty Is Not Working
Why The Global Climate Treaty Is Not Working
by Tim Radford
Three out of four nations have yet to start to honour the global climate treaty. The world waits, the seas go on rising…
Why Taxes Are Better Than Bans For Keeping Homeowners From Rebuilding In Fire-plagued Areas
Why Taxes Are Better Than Bans For Keeping Homeowners From Rebuilding In Fire-plagued Areas
by Alexander Smith
Almost 200,000 Californians have been ordered to evacuate as ferocious winds drove several wildfires near Los Angeles,…
How Will 20 Years Of Houston’s Growth Affect Flooding?
How Will 20 Years Of Houston’s Growth Affect Flooding?
by InnerSelf Staff
A new way to show exactly how much the city of Houston has changed in the last two decades gives a dramatic visual…
Why Australia Could Fall Apart Under Climate Change
Why Australia Could Fall Apart Under Climate Change
by Ross Garnaut
Four years ago in December 2015, every member of the United Nations met in Paris and agreed to hold global temperature…
How Greenhouse Gases Drive Australia's Bushfires
How Greenhouse Gases Drive Australia's Bushfires
by Andrew Burgess
Australia’s bushfires are feeding on heat from the climate change happening in the tropics, but its government doesn’t…
How Children Born Now Face Multiple Climate Health Risks
How Children Born Now Face Multiple Climate Health Risks
by Tim Radford
Multiple climate health risks threaten today’s babies. They may grow up hungrier, more diseased and facing more…
This Is What Australia's Growing Cities Need To Do To Avoid Running Dry
This Is What Australia's Growing Cities Need To Do To Avoid Running Dry
by Ian Wright
The increasing thirst of Australia’s biggest cities routinely exceeds our capacity to rely on rainfall for drinking…
Evangelicals In Brazil See Abuse Of God's Earth As A Sin – But Will They Fight To Save The Amazon?
Evangelicals In Brazil See Abuse Of God's Earth As A Sin – But Will They Fight To Save The Amazon?
by Amy Erica Smith
When the Brazilian city of São Paulo abruptly went dark at midday on Aug. 19, there was talk of the Apocalypse – not…