The power of microbes

The popular theory about the extinction of dinosaurs 65 million years ago is that they died off after the Earth was hit by a huge meteorite. There are, however, several other theories that try to explain what happened to the dinosaurs. Despite its popularity even among the ordinary public, this is not the only ‘extinction event’ in the history of Life on Earth. There have been several such instances.

Apart from the dinosaur event, another well known extinction event took place 252 million years ago when many species were wiped out. Various theories were put forward to explain this event as well. However, scientists at the Massachusetts Institute of Technology (MIT) have forwarded an intriguing new theory.

The mass extinction 252 million years ago may have been the work of a tiny microbe, according to new research from the MIT. Daniel Rothman and Gregory Fournier of MIT lead research into the role the microbe may have played in the Great Dying. This study of the “root causes of the Permian-Triassic extinction” was published in the Proceedings of the National Academy of Sciences of the United States of America.

Extinction

The Permian-Triassic extinction event caused 90 percent of all species living on Earth to die off in a short period of time. The ‘Great Dying’ was the worst of five great extinctions in the history of our planet. Marine invertebrates were particularly affected, especially species with shells.

Scientists have argued for decades over the cause of this global Extinction Level Event (ELE). Scientists earlier thought that volcanoes could have been responsible for the extinction.

According to the latest theory, the culprit may have been a microbe called Methanosarcina. Research has found that these microscopic life forms saw a population explosion and emitted tremendous quantities of methane into the waters and atmosphere of the Earth. This radically changed the chemistry of the air and oceans to the point where most life could not continue in the new environment. Indeed, the methane theory has been enunciated to explain the vanishing of the dinosaurs as well, by other scientists.

But before you count out the volcanoes altogether, there is an interesting link: Volcanoes erupted more often around the time of the Permian-Triassic extinction event and this volcanism may have introduced more nickel to the oceans. Nickel is essential for the growth of Methanosarcina.

The researchers knew there was a build-up of carbon dioxide in the oceans, which formed the carbon needed for the microbe to grow and multiply. Carbon dioxide was shown to build up over time, which disproves the idea that volcanoes were responsible. In that case, it should have been a sudden build-up. 

Unfortunately for the other living beings, Methanosarcina developed the ability to turn carbon into methane in large quantities. Nickel released from volcanoes acted as a catalyst, aiding even greater proliferation of the gas. Moreover, the tiny organism carried out a gene transfer with a type of Clostridia bacteria, speeding the process. 

The most interesting part is that as methane levels rose in the air, so did the concentration of carbon dioxide in the ocean. This led to an increase in the concentration of carbon dioxide, which wasn’t good news for most marine and land species.

Earth and its flora and fauna apparently took more than 10 million years to recover from this disastrous event. The scary part is that this organism is still alive and well everywhere on Earth - even in our intestines. Thus there is a distinct possibility that such an event could occur again. The only difference this time is that there are people - or more precisely, humans, on the planet who may be able to stem the tide in their favour.

There are many other ways in which Man and other creatures could be wiped out from the Earth. An asteroid/planetary body impact is still one of the most feared possibilities.

Scientists are tracking such objects 24/7 to avert just such a disaster. From time to time, some celestial objects manage to come very close to Earth (in cosmic terms). Scientists are devising various high-tech means and ways of deflecting such objects, including nuclear strikes, to avoid a massive and disastrous collision with Earth - Armageddon or Deep Impact style.

Epidemic

Another possibility is a disease which turns into a virulent epidemic, killing off most of the world’s population. Yes, the Earth itself would not be affected, but the human population and/or some other animal populations would be effectively wiped out.

We have seen several close calls in recent times - SARS, bird flu, H1N1 - which can all potentially turn deadly on a massive scale. Scientists are racing to find cures and vaccinations to these afflictions before they can cause harm on such a global scale.

Many movies depict a post-apocalypse Earth with little or no human presence - it is an eerie thought, albeit a probable one.

Mankind may also be eventually responsible for its own downfall and the destruction of the Earth. Our activities have caused climatic changes which led to a rise in Carbon Dioxide levels, just as in the extinction event outlined earlier. Nuclear war among even just two States can destroy much of the world.

The resulting radioactive ash cloud will prevent the sun’s rays from penetrating to the ground which will hasten the demise of plants and animals in that order. (Without ample sunshine, plants will not be able to engage in photosynthesis, their preferred method of energy generation.)

We are still learning about our planet. The Earth has survived so far for nearly 4.5 billion years and can go on at least for another 4.5 billion years (as long as the Sun lasts). The only exception will be an event, natural or man-made, that fundamentally alters it.

However, long before that, intrepid humans will have explored other worlds beyond our Solar System and established colonies that will also be inhabited by selected flora and fauna. The Earth will live on by other means, even if it is destroyed physically.