New Study Reveals the Real Impact of Early Humans on Animal Extinction
It has been told and retold and accepted as an unproven truth that early human beings arrived on uninhabited islands and forced other species to make way for them, eventually driving them to extinction. In fact, human migration has always been linked with a converse effect on existing bio-diversity and natural ecosystems and human impact on animal extinction has always been “assumed.” A new study, however, sheds light on unscientific claims of the early human impact on animal extinction.
The study is published in the prestigious Proceedings of the National Academy of Sciences (PNAS) and led by Julien Louys from Griffith University’s Australian Research Centre for Human Evolution. Professor Louys said that there was little to no evidence that the arrival of humans had caused extinctions on individual islands, according to Brisbane Times,. This claim is based on researching islands in the south Pacific, all the way to Australia, which is where early humans eventually leapfrogged to.
Continental island groups with a documented record of Pleistocene hominins and faunal extinction, which suggests human impact on animal extinction came later rather than earlier. Clockwise from the top are Britain (A); Sri Lanka (B); Taiwan (C); Hokkaido (D); King Island and Tasmania (E); Kangaroo Island (F); New Guinea (G); and Borneo, Java, and Sumatra (H). LP, late Pleistocene. (PNAS)
Human Impact on Animal Extinction and Islands
Early humans have been living on islands since the early Pleistocene epoch, i.e., 2.6 million to 11,700 years ago. The Pleistocene, in colloquial terminology, is what we understand as the Ice Age, the Earth’s most recent period of frequent glaciations.
The research team examined archaeological and paleontological records of more than 30 islands that were inhabited by humans between about 2.6 million and 11,700 years ago. This included what is modern-day Britain, Ireland, Cyprus, Taiwan, Okinawa, and Tasmania. They found very little overlap between human arrival and extinctions.
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“Evidence that these earlier humans caused appreciable losses is mostly poor to nonexistent, which suggests that it was deleterious cultural practices—overhunting, excessive resource exploitation—of modern humans that were behind later insular extinctions. Prior to migration of modern Homo sapiens across the planet, other populations and species of hominins lived on a number of the world’s islands,” says Ross MacPhee, senior curator at the American Museum of Natural History’s Department of Mammalogy, and a co-author on the study.
“In fact, there were only two islands we recorded where all the extinctions which occurred are coincident with human arrival - Kume Island in Japan and Cyprus in the Mediterranean. All the other islands, the records of extinctions don’t seem to line up with human arrivals, they are staggered, with no clear discerning cause,” said Professor Louys.
The reason for studying islands over continents, in this regard, was a deeply scientific one. First, islands are prone to widespread extinctions due to their smaller size, population, and lower genetic diversity. Second, there is a greater propensity to be exposed to natural disaster and random geological events on islands. Third, inbreeding and a higher level of native species are more common on islands when compared to continents.
This dead turtle, killed by fishing nets, clearly conveys the image of human impact on animal extinction since the Industrial Age. (maxoidos / Adobe Stock)
The Anthropocene and Exploding Human Ecological Damage
In an email exchange with Live Science, Ross MacPhee continues by saying that human beings are very much responsible for the devastation caused by more recent migratory practices. Admittedly, the impact of “modern humans has been catastrophic.” This was as the result of overhunting, changing habits and the introduction of invasive species. However, the longer we go back in time, the more we see that this “trail of woe grows very thin,” as Ross MacPhee eloquently puts it.
This is linked to the term Anthropocene, which is used to describe the geological epoch that is dated from the beginning of significant human impact on the Earth’s climate, geology and ecosystems.
While the jury is still out on the exact timeline, the Agricultural Revolution of 12,000-15,000 years ago would be a potential starting point of human impact on animal extinction.
This impact increases rather significantly with the arrival of the Industrial Age and the Industrial Revolution in the 18 th and 19 th centuries, which have forever transformed the pace of human activity.
These woolly mammoths, emerging from the cold Pleistocene mists, didn't get completely wiped out by humans and survived on islands. (Daniel / Adobe Stock)
The Real Truth: Actual Human Impact on Animal Extinction
The study looked at extinction and accounted for natural events that caused extinction. For example, the woolly mammoth existed in the Pleistocene but disappeared in the Holocene. During its existence in the Pleistocene, there was a relationship of co-existence with early humans, who used the bones and tusks for making tools, dwellings, and even art.
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The extinction was gradual, and the mammoth would go onto actually survive on two islands for the longest time, even after the Ice Age ended. These were St. Paul Island in Alaska (5,600 years ago) and Wrangel Island in the Arctic Ocean (4,000 years ago).
The study also found that early hominins did not hunt “creatures into oblivion.” MacPhee was quick to add that there is overwhelming evidence of natural co-existence, and that the earlier humans “did not raise extinction rates on the islands they colonized.”
A huge reason for this deviation with respect to modern humans was access to technology, which allowed for a destructive behavioral change towards the environment.
This also helps challenge the unscientific claim and assumption that says that human beings have always been prone to overexploiting resources, because this evidence indicates the human impact on animal extinction was minimal in the beginning.
Top image: Sunrise at Laomei Green Reef on the coast north of Taipei, Taiwan, where researchers found scant evidence of early human impact on animal extinction. Source: Richie Chan / Adobe Stock
AMNH. 2021. Early Humans did not cause island extinctions, according to new study. Available at: https://www.amnh.org/explore/news-blogs/research-posts/early-human-island-extinction.
Geggel, L. 2021. Hobbits and other early humans not ‘destructive agents’ of extinction, scientists find. Available at: https://www.livescience.com/early-humans-island-extinctions.html.
Layt, S. 2021. Early humans off the hook for many species extinctions, experts say. Available at: https://www.brisbanetimes.com.au/national/queensland/early-humans-off-the-hook-for-many-species-extinctions-experts-say-20210503-p57ohr.html.
Louys, J., Braje, T., et al. No evidence for widespread island extinctions after Pleistocene hominid arrival. Volume 118. Available at: https://doi.org/10.1073/pnas.2023005118. Location: Brisbane, Australia