Article curated by Ginny Smith
Extinctions are important events in the history of the earth. By studying fossils, scientists are trying to answer questions about how past species died out, with the long term hope of preventing us from coming to a similar fate. Understanding the causes of extinction can also help conservation efforts, aiming to preserve as many of the incredible diversity of species currently on the planet as possible.
What causes extinctions?
There are some cases where it is clear why a certain animal became extinct. Dodos, for example, were hunted to extinction by humans because of their large size, tasty meat, and inability to fly. In other cases, however, it is less clear why an animal didn't survive.
Woolly Mammoths lived on an Arctic island until as recently 1700BC, but it isn't clear what killed off this last group of survivors. It could have been human hunting, although there is little evidence of it left behind. A virus might have led to their demise, or it could have been a change in the habitat, or a large weather event. Alternatively, it could be that the island habitat just couldn’t support them, so as the ice bridge to the mainland melted they became stranded and could no longer survive. It remains to be discovered which of these theories best fits with the pattern of extinction seen.
We also don't know what wiped out the Neanderthals- a species of human that developed in Europe and Asia while the ancestors of modern humans were evolving in Africa. It is likely they encountered modern humans, as remains dating from similar periods in the same location. However no Neanderthal remains have been found more recent than 30,000 years ago.
So what happened to this robust and successful species? Some people argue that modern human's increased intelligence meant they could out-compete the Neanderthals. Others argue that they were absorbed into our species as Neanderthals and modern humans met and inter-bred. People in Europe, Asia and New Guinea have 2.5% Neanderthal DNA, supporting this theory, although it isn't clear that this amount of breeding would be enough to wipe out the species entirely. Climate could have played an important role, as it was very unstable at the time they died out. What is certain is that more research is needed to find out exactly what happened to the Neanderthals.
What will cause humans to go extinct?
It may be scary to think about, but the liklihood is that one day, humans will no longer exist here on earth. What it is that leads to our downfall, however, is not clear. While there is a chance that it will be something we have done that causes our demise, there are also natural events that could mark the end.
One thing that could wipe us out would be a meteor strike. Millions of meteors appear in Earth’s atmosphere every day, but only a few over the course of a whole year are large enough to be potentially dangerous. NASA should be able to spot the risk early, giving us a significant warning of the danger. But if we did spot a potentially life threatening asteroid hurtling towards the earth, is there actually anything we could be do to divert it? There are many scientists who are currently working on methods for deflecting asteroids, but whether they would work in practice still remains a mystery.
Another natural event which could be disastrous for humans is the eruption of a super volcano. Volcanoes have erupted with devastating effects to local areas during human history, but if a super volcano erupted, it could wipe out our entire species. We know that there was a lot of volcanic activity around the time that most dinosaurs went extinct, and it is thought the volcanoes played a role in that extinction. But could the same happen to us? So far, scientists haven’t been able to find any large magma chambers that would suggest the site of a future super volcano. But why this is is unclear. Maybe there really aren't any looming eruptions, but it could also be that we just haven’t managed to find them yet. Or, more worryingly, maybe a recent suggestion that these chambers develop rapidly and erupt quickly is correct. For the moment, however, geophysicists continue the search for these potentially disastrous magma chambers.
Protecting our planet's diversity
By understanding how and why species go extinct, we can better attempt to conserve those animals and plants currently sharing our planet. One area of study is how diversity differs in different regions of the earth. We know that some areas are home to a multitude of different species, while others can only support a few, but the time and resources required to fully explore these differences mean there is still much work to be done.
This article was written by the Things We Don’t Know editorial team, with contributions from Cait Percy, and Johanna Blee.