Extinction of Dinosaurs

It would be very unusual if one event or one problem wiped the dinosaurs off the face of the earth.  The dinosaurs were scattered around the world, so typically one activity would not completely annihilate a species that had adapted to multiple threats over millions of years.

Many scientists point to one event as causing the Cretaceous mass extinction about 65 million years ago, killing off all the non-avian dinosaurs.   That event was the resulting death from the impact of a meteorite about six miles wide, forming the Chicxalub crater in the Yucatan Peninsula in Mexico.  About half of the crater is on land and the other half is in the ocean with the center located near the town of Chicxulub.  The crater is more than 110 miles in diameter and 12 miles in depth, making the feature one of the largest confirmed impact structures on earth.

As detectives who are investigating murders will tell you, time lines are critical to establish in determining cause of death.  Clearly, the timing of the death of the dinosaurs and the meteorite’s impact was more than a coincidence.  The impact occurred about 66 million years ago, just about the time of the end of the Cretaceous period when the dinosaurs expired.  Geologists have even found a thin layer separating the Cretaceous and Tertiary (K-T) boundary, which evidenced an impact that would have distributed a layer of debris around the world that could have blocked out the sun for years, creating an impact winter.

This evidence is sufficient to prove that it was not just the impact of the meteor that killed off the dinosaurs.  The climate change, which killed off plants and some animals, would have also contributed to the mass extinction.

However, there may have been other factors that came into play.  On the other side of the world, the Deccan Plateau in India are one of the largest volcanic features on earth.  The Deccan Traps, a large igneous province about the size of Texas, is located in the Deccan Plateau.  These Traps were formed about 60 to 68 million years ago in pulses.  However, the largest eruption occurred about 66 million years ago.  Another coincidence?

Probably not.  The eruptions of the Deccan Traps had started millions of years before the meteorite crashed into earth, but the largest eruptions, which may have lasted about 30,000 years, may have been triggered by the impact of the meteorite on the opposite side of the earth.  But whether the meteorite caused the horrific eruptions in India or not, these two events occurred simultaneously, which would have caused an exponentially deadly environment for the dinosaurs.

Volcanic gases, especially sulfur dioxide, from the volcanic eruptions added to the debris kicked up by the meteorite would have caused a climate change.   Because of its magnitude, scientists have speculated that the gases released during the formation of the Deccan Traps played a role in the extinction.

This impact winter could have caused a sudden tipping point, so that the land-bound dinosaurs, perhaps already on the ropes from some other cause, could not recover as they normally would do.  For example if the creation of Pangea and land bridges allowed migrating dinosaurs to travel into areas where new pathogens and diseases would have weakened them, this may have set them up for the final kill.  Typically, when we stay in the same area for millions of years, our bodies build up immune systems that can survive well in those areas, but when we move into foreign areas with new pathogens, our immune systems may not be able to do as well.  An example is when Europeans brought diseases to natives in the Americas.

Even though it is not probable that one incident destroyed all land-based dinosaurs, it does seem likely that the dinosaurs were not doing very well when they got hammered with two major events, a meteorite impact and a super-volcanic eruption, that created the final, fatal turn of events for them.

Mass Extinction is Our Future

There have been numerous mass extinctions on earth, but the most significant was the Permian extinction, “The Great Dying,” which occurred about 250 million years ago.  What caused this mass extinction? 

There are several theories, most of which center around climatic disturbances.  There were glaciations in the pole regions and desertification in temperate zones.  Severe weather fluctuations on earth occurred when the Permian mass extinction occurred.  But why did these climatic conditions kill off so many species?  We have seen ice ages and other weather patterns that haven’t wiped out so many creatures.  What was different about the Permian extinction?

One difference was there was primarily one giant land mass, Pangea, which was formed during the middle of the Permian era.  By the end of the Permian, the variety of species was on the downswing.  As a general rule, it takes isolated conditions to trigger evolution of new species.

Pangea was not conducive to creating new species that adapted to isolated environments.  We have seen extinctions when the continents were separated that did not have the same devastating effect as when there was only one continent.  Once the Permian extinction started, there were no new species that were available that could adapt to the weather changes.  Only a handful of species survived the Permian extinction to repopulate the world.  When the continents split breaking up Pangea, this triggered the development of new species.  For example, South America became the birthplace for the first dinosaurs in the Triassic, which did not exist in the Permian.

Even though the continents are separated today, our species, which is almost genetically identical worldwide, is overpopulating and is setting itself up for a mass extinction just as if we were on Pangea.  This is because Homo sapiens is homogeneous and exists as if we were all connected.  About 28,000 years ago, the Neanderthals, either a separate species from or subspecies of Homo sapiens, died off in Europe.  About 10,000 years ago, Homo erectus was last found in Java.  Neanderthals and Homo erectus went extinct, leaving Homo sapiens to stand alone as the last hominids on earth. 

There will be no additional hominids created as long as our species is globally connected and lives on the blue planet like it were Pangea.  Homo sapiens beat out the other hominids, surviving the last ice age.  Of the three hominids, the strongest survived.  There was true separation on Java, allowing Homo erectus to live on an island, separated from the mainland.  Today, there is global movement among ethnic groups, so there are few areas that are isolated.    

A genetic bottleneck in our species occurred about 71,000 years ago when a mega-volcano, Mt. Toba, erupted, creating a nuclear winter which killed all but a few thousand Homo sapiens on the earth.  Two points may be made from this event:  (1) this mass killing of our species is why our genetic makeup has very little variety today and (2) this shows how hominids prevailed by having multiple species to compete for survival.  But today’s lack of variety could lead to a mass extinction of hominids because there is only one point of failure.  The survival of the fittest only works when there are multiple species competing.  In our case, Homo sapiens, the last hominid, is vulnerable to weather changes.  Homo sapiens could be completely wiped out just like the animals who died on Pangea 250 million years ago.