Going Back in Time
By Shanuka Kadupitiyage Ceylon Today Features
If you’ve been reading Scribbler for the past few weeks, you would already know a lot about Dinosaurs –how they might have gone extinct and also what led them to become the rulers of the ancient Earth, hundreds of millions of years ago. All this time, we were discussing only the Mesozoic era. We have many more years’ worth of interesting things to talk about the history of the Earth.
That’s why instead of talking about all that happened after the K-T extinction and the dinosaurs going extinct, let’s go back in time and talk about a special moment of time for all life on Earth; the Paleozoic Era (pronounced Pay-Lee-oh-zoic). This is the era before the great dying; or the biggest mass extinction event which you read about last week.
That was what marked the end of this era. To learn more about the Paleozoic era, we have to travel more than 200 million years before the great dying; nearly 500 million years ago, to one of the most interesting time periods of all Earth’s history; the Cambrian period.
A huge chunk of the Earth’s history was there before the Cambrian period, which we now call the PreCambrian era. It was during this time that the Earth became a planet, cooled down and early signs of life started to appear. Until this point, the only way you could have seen life on Earth was through a microscope. Bacteria and other cellular organisms (or-gan-isms) were all that there was. But all of that changed during the Cambrian period.
We learnt about the time when almost all life on Earth was wiped out. Now we are going to discover the period when life exploded. Scientists aren’t completely sure how, but after millions of years of only single celled organisms, fossils that dated back to around 500 million years ago show that life exploded on Earth, with new species being found. Scientists call this time period the ‘Cambrian explosion,’ and it was during this period that arthropods, molluscs, fish and other types of animals we see on Earth started to appear in fossils. However, these creatures were very different from the creatures we see on Earth today.
Some of the creatures that lived during the Cambrian explosion and afterwards were so bizarre that even the scientists had a hard time believing it all. One such creature was Hallucigenia, who looks nothing like any animal we see in the world today, with its seven or eight pairs of legs and equal number of spikes protruding out of its back. It was in this period that we start seeing Trilobytes, one of the most iconic creatures of the Cambrian period as well. Anomalocaris was a more familiar creature, being an early version of shrimp we see today.
The difference was that unlike the shrimp we see today, that we can probably see grow to about three inches in size, Anomalocaris was three feet long; that’s as wide as your arms stretched out wide. There were plenty of other creatures as well that are hard to believe to have ever existed such as the creepy Wiwaxia and the creepy Marella. Of course there are a few familiar creatures to the world today, such as the ancient ancestor to starfish and sea urchins, Helicocystis.
A new age
There are plenty of mysteries that we still don’t know about the Cambrian period. What sparked this sudden appearance of all these creatures? How did life that was limited to a handful of cells suddenly appear as complex, multicellular beings? Were there other creatures that we don’t know about? These are questions we still don’t know the answers to.
Of course all these mysteries have to be answered with more studies and research by scientists. Even though we don’t know everything about the Cambrian period, there is a lot we do know about. Of course, you’ll have to find all about that on your own.