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Palaeontology

Mass extinctions follow 27-million-year cycle

December 14, 2020 | Comment icon 16 comments



Are we overdue a mass extinction event ? Image Credit: NASA
Scientists have determined that mass extinctions have occurred throughout history with striking regularity.
Multiple times throughout history, combinations of catastrophic events have resulted in the mass extinction of countless plant and animal species, both on land and in the oceans.

It is these events that brought about the evolution (and demise) of the dinosaurs, as well as the ultimate emergence of our ancestors and all of the animals that we see today.

Exactly what caused these mass extinction events however - and whether or not we are overdue for another one - has long remained a topic of heated debate among scientists.
Now a new study based on a new analysis of the dates of mass extinctions, as well as on the ages of major asteroid impact craters and other physical traces of catastrophic events, has revealed that mass extinctions occur approximately once every 27.5 million years.

The discovery lends credence to the idea that some sort of cyclical system may be at work, however it remains unclear exactly what process might be responsible for this.

Some scientists have speculated that major volcanic eruptions might occur due to long-term periodic cycles deep within the Earth, while others have suggested that an undiscovered body in the outer solar system with an extremely wide orbit could be periodically flinging space rocks in our direction every few million years when it passes closest to Earth.

It is worth noting of course that if the 27.5 million year figure is accurate - and given that the last mass extinction event happened 66 million years ago - we may be long overdue another one.

Source: Slashgear | Comments (16)



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Recent comments on this story
Comment icon #7 Posted by Myles 12 months ago
I thought the same thing.  They proved their own idea was wrong.
Comment icon #8 Posted by pbarosso 12 months ago
well, ill go with: most of the asteroids that were in a position to be flung about have already done so and theres just not much out there (or far less) to cause any major damage. the solar system is settling down.
Comment icon #9 Posted by Tom1200 12 months ago
Agree 100%.  A quick search of extinction events throws up lots of graphics like this one:  I know those labelled are just the major ones, but I can't see any clear 27-million-year cycle here.  Next consider what we (think we) know about these particular extinction events: end-Ordovician: continental drift ? Gondwanaland drifted across the South Pole ? ice cap grew ? sea levels fell ? habitat loss late Devonian: lasted up to 25 million years, so extremely difficult to pinpoint one cause end-Permian: Siberian Traps volcanic activity ? dust clouds ? blocked sunlight ? disrupt photosynthesis ? co... [More]
Comment icon #10 Posted by quillius 12 months ago
agreed, then throw in the simple fact its been 66m years since last 'suspected' extinction event.....proves there is no cycle.. Do people not bother to think before they type these days?
Comment icon #11 Posted by Tom1200 12 months ago
That would take effort, and leave me no time for sitting on my fat **** watching telly.   Damn my failing eyesight - which emoji is that?
Comment icon #12 Posted by quillius 12 months ago
sorry just in case my post was lost in translation, I mean the journalist not you
Comment icon #13 Posted by kartikg 12 months ago
Yeah that actually makes sense. Most of the bombardment is over. 
Comment icon #14 Posted by Abramelin 12 months ago
I think there may be a cycle of impact events of around 27 million of years, but that 'only' a few of those impact events actually resulted in an extinction event. Saying, these extinction events are points on the graph, but don't form a graph. Edit: The impact cycle, in its most simplistic form, can be displayed as a sinusoid:   The crests are the impact events. And what I meant was that only a few of those crests are extinction events. So, the extinction events are part of a cycle  but don't form a cycle just by themselves.  
Comment icon #15 Posted by Carnoferox 12 months ago
There is no 27 or 26 million year cycle of mass extinctions. This is a claim that has been recycled for the past 30 or so years, and somehow still gets published. This particular study has selectively sampled mass extinctions in order to force this result. They only included extinctions that affected terrestrial tetrapods, so all mass extinctions from the Ediacaran-Devonian are excluded. They included at least one "mass extinction" (end Jurassic) that is no longer even thought to have been a significant extinction event. For some reason they also excluded the end Pleistocene extinction event. ... [More]
Comment icon #16 Posted by Carnoferox 12 months ago
I would also like to note that, as is typical for these studies, none of the authors are paleontologists. Understanding the different faunas of each time period is crucial to quantifying mass extinctions, so if there are no paleontologists on the team it should automatically ring alarm bells. The lead author Michael Rampino has been pushing this pet hypothesis since the 90's about how mass extinctions are on a 26-27 million year cycle and how it is all somehow related to dark matter. No real data to back this hypothesis of course, but it makes for a good story to keep selling to magazines and ... [More]


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