Scientists believe that if you were able to add up all the species of life that have inhabited the Earth that it would be around five billion! Today, there are an estimated 10 million species alive on the planet. That means that 99% of animals that ever lived on the Earth are extinct.
Many species were victims of mass extinction events in history like the meteorite that is believed to have killed the dinosaurs. Oddly enough, scientists believe we are currently living through a mass extinction event. Species are disappearing at rapid rates that have only been observed five times in the last half a billion years.
This time period is being referred to as the sixth mass extinction. Generally, scientists agree that humans are to blame for this extinction event due to overhunting, overfishing, and habit loss due to human-driven land development.
In fact, humans have altered the Earth so much they have coined this epoch the “Anthropocene.” Humans are on track to eradicate as much as half of all current living beings by 2100.
Living currently in this mass extinction helps scientists to be able to explain it and offers some insight into what may have contributed to other mass extinctions too. But since scientists are able to directly observe those events, there is some disagreement in the scientific community on what may have killed off certain animals in the past.
Pleistocene mini-extinction event
In addition to the six mass extinction events, there have been periods in history where the rates of extinction were elevated on a smaller scale. One example is the Pleistocene era right around the end of the long Ice Age. Many of the victims of this event were larger animals over 97 lbs like mammoths.
Scientists differ on what they believe is the main cause of the species dying out during this time period. Plausibly it was a combination of factors. A lack of evidence contributes to the disagreements among experts. Rates of extinction varied according to geographical areas and human populations, further complicating the issue.
A big contributor, many scientists believe, is climate change. During these years, the planet was emerging from a long Ice Age. The global temperatures elevated quickly by a massive six degrees Celsius. Many animals, it is believed, died out because they were unable to adjust to the heat. One theory is that larger animals were more severely affected by the heat because it is more difficult to release heat from their bigger mass. The thick coats that had served these massive mammals well in the Ice Age became a liability with new weather that changed quickly from hot to cold. In hotter temps, the coat made hairy creatures too hot.
Could humans be the cause?
Another school of thought leans towards blaming the rise of humanity for the demise of the mammoth and other creatures during this period. The overhunting theory was formed in 1870 when it was discovered that humans and mammoths walked the Earth at the same time.
While hunting could be a contributor, many debunk this theory with evidence that the extinction of mammals was spread out across too long of a time for overhunting to be the cause.
But could humans still be to blame? Another theory suggests that humans nomadic hunting habits spread the disease to mammals across the planet.
Most scientists now believe the wipeout of large mammals on Earth was likely a combination of the above-mentioned factors. Overhunting killing many on some continents, disease on others, and climate change across the globe.
