More than 99 percent all species that have ever lived on Earth have become extinct. For many people, when they think about extinction, they think about dinosaurs. The dinosaurs were huge terrestrial animals that lived during the period about 240 to 66 million years ago (called the Mesozoic Era). They had rich varieties in body size, shape and way of life. They ruled the Earth for more than 100 million years, till somehow they suddenly vanished on the Earth more than 65 million years ago.
The mystery of the extinction of the Dinosaurs has been the focus of research and debate for long. Many different theories have been put forth as explanations. Some of the well-known ones include invoking climate change to which the dinosaurs could not adapt; continental drift causing climate change; flipping of earth’s magnetic poles leading to the dramatic changes of natural environment; acid rain leaching away important micronutrients; rodents eating dinosaur eggs as food; etc.
The most commonly accepted explanation is that a meteor struck the earth 66 million years ago leading to a nuclear winter that led to the extinction of the non-avian dinosaurs (birds are accepted as having evolved from a branch of the dinosaurs). The rock slammed into the Yucatán Peninsula moving at something like forty-five thousand miles per hour. The asteroid blasted into the air more than fifty times its own mass in pulverized rock.
The resulting huge cloud of very hot vapor and debris raced over the North American continent incinerating anything in its path. Owing to the composition of the Yucatán Peninsula, the dust thrown up was rich in sulfur and particularly effective at blocking sunlight. After the initial heat pulse, the world experienced a multi-season “impact winter.” Forests were decimated. Marine ecosystems collapsed. And the non-avian dinosaurs died out.
The interesting question is: how did scientists find out about a meteor-strike that happened all that long ago? Before that story, one needs to know about a clash between two schools of thought in evolutionary biology: uniformitarianism and catastrophism.
In the opinion of uniformitarians like Darwin, the emergence and disappearance of species are the outcomes of natural evolution. When there is change in natural environment, the species is no longer able to adapt to the new environment and if there are no other proper places for migration, the population of the species will diminish till it becomes extinct. They believe that the emergence and disappearance of species is the effect of slow natural selection. The uniformitarian view denied sudden or sweeping change of any kind.
On the other hand, catastrophists believe that sudden, short-lived, and violent events lead to the extinction of many organisms. The leading scientific proponent of catastrophism in the early nineteenth century was the French anatomist and paleontologist Georges Cuvier. He believed that the history of life on earth indicated that there had been several of these revolutions, like earthquakes and floods, which he viewed as recurring natural events, amid long intervals of stability.
The more that was learned about the fossil record, the more difficult it was to explain the sudden disappearance and appearance of large numbers of species, which, according to Uniformitarians, should take millions of years. The Uniformitarians said that maybe the losses shown in the fossil record did constitute a “mass extinction.” But mass extinctions were not to be confused with “catastrophes.” They maintained that the fossil record was incomplete and the missing spans of time would eventually be found.
In the war of words between the two groups, Uniformitarians held the upper hand for many decades. The feeling between the two groups was so bitter that Uniformitarians described catastrophism as 'evolution by jerks'. In retaliation, Catastrophists described Uniformitarianism as 'evolution by creeps'. Who said academics don’t have a sense of humour?
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