Regular readers may already know that I have an interest in the natural world and how living things interact with each other ecologically, both now and in the past. Because of this, I was keen to join the Extinctions: Past and Present course offered through FutureLearn. The next run of this course will start on April 30, 2018. Like most other FutureLearn courses, access for a limited period of time is free.
You can earn a certificate after paying and gaining a pass mark in the assessment. The assessment is only available to paying students, although some free practice quiz questions are found at various stages in the course. Paying students are also able to access all the course resources for as long as it is available on the FutureLearn site.
Presented by Dr Anusuya Chinsamy-Turan, a paleobiologist from the University of Cape Town, this five-week course looks at the five known mass extinctions in Earth’s history and asks if we are in the throes of a sixth extinction triggered by humans.
I really enjoyed this course. Many people know about the end-Cretaceous extinction that ended the dinosaurs’ dominance, but fewer have heard of the four other earlier mass extinctions.
What is a mass extinction?
Most paleontologists define a mass extinction as an event when more than 50% to 75% of the earth’s species become extinct in a relatively short geological time frame.
The largest mass extinction was the end-Permian, which resulted in the loss of about 90% of life on Earth around 252 million years ago.
The course explains what we know about the major extinctions, plus one or two of the smaller extinction events that have occurred at other times. It ends on a positive note, with Dr Chinsamy-Turan explaining her belief that there is still time for humankind to change its ways and save some of the species that are currently threatened.
Fossils from Africa
Having been brought up hearing about famous European, American and Chinese fossils, I was intrigued to learn about many fossils from Africa. During the course, Dr Chinsamy-Turan interviewed experts in a number of fields at the University of Cape Town. Specialists included ecologists, plant biologists, and anthropologists among others. For example, it was interesting to learn about the evolution of the relationship between plants and insects.
There were even videos recorded at Cape Town’s Botanical Gardens and South Africa’s West Coast Fossil Park, which is about 125 km north of Cape Town.
Time Commitment
Information about the course estimates that students will take about three hours per week to work through the videos, readings, and discussions. I found this quite realistic. Look out for the supplementary materials in the “See also” section at the bottom of many pages. Some of these were very recent.
Week by Week
Week one discusses the origin of life on Earth and introduces what happens after mass extinctions. “After each extinction event, there appears to have been a distinct adaptive radiation of organisms to occupy the vacated habitats.”
Week two teaches us about life before and after the first two major extinctions: the end-Ordovician around 443 million years ago and the end-Devonian about 373 million years ago. The Devonian period is known as the “Age of Fishes”. Early fish did not have jaws, and the development of jaws during this period allowed them to proliferate because they could eat a wider variety of food.
Week three discusses the end-Permian extinction around 250 million years ago, which was the most catastrophic event known. More than 90% of species were wiped out, paving the way for both dinosaurs and mammals. It is astounding to learn that mammals co-existed with dinosaurs for over 165 million years. During all this time the mammals were small, rat-sized creatures who survived by being inconspicuous.
Week four covers the ages of the Dinosaurs and the end-Triassic and end-Cretaceous extinctions that wiped most of them out. The Triassic time period saw major geological changes associated with increased plate tectonic activity and the movement of landmasses. By the end of the Triassic, around 208 million years ago, Pangaea was the dominant land form. The forces at play in the breaking up of the supercontinent were associated with massive volcanic eruptions from rifts opening up as the tectonic plates split apart. These volcanic eruptions caused atmospheric changes and in particular, global warming and changes to ocean chemistry. Thus, while volcanism seems to be the most plausible cause of the end-Triassic extinction event, the impact on life came from factors such as global warming, ocean acidification and sea level rise. And, as many people know, there is evidence that a catastrophic meteor strike may have triggered the end of the dinosaur age at the close of the Cretaceous period around 65 million years ago.
Week five addresses a possible sixth extinction. Dr Chinsamy-Turan provides evidence that this event may already be underway due to human-caused climate change, habitat destruction, and pollution. Many scientists agree. Can we stop the sixth mass extinction? The course ends on an optimistic note by explaining how we can prevent it.
A Final Thought
Whether or not the current extinction rates continue to create a sixth mass extinction, it’s almost certain that life will continue in some form.
By Pat Bowden, published April 24, 2018.
