When people first arrive in what is now Queensland, they will find land inhabited by large animals including six meters long goannas and kangaroos twice as tall as humans.
We have studied the fossil bones of these animals for the past decade. Our findings, published in scientific journals Natural Communication, shed new light on the mystery of what drove these ancient megafauns to extinction.
The first bones were discovered by the Barada Barna people during a survey of cultural heritage in their traditional land about 100 kilometers west of Mackay, at the South Walker Creek Mine. Our study shares a glimpse of reliable giants who explored tropical Australia between 40,000 and 60,000 years ago.
This megafauna is the largest land animal to live in Australia since the time of the dinosaurs. Understanding the ecological role they play and the environmental impact of their loss remains countless of their most valuable stories.
While megafauna live on South Walker Creek, people have arrived on the continent and spread through it. Our study adds new evidence to the ongoing megafauna extinction debate, but the important thing is to underline how much is left to be learned from the fossil record.
Megafauna welcome party
We excavated fossils from four sites and made detailed studies of the sites themselves to find fossil ages and understand what the environment was like in the past.
Our findings give us an idea of what megafaunal life was like in tropical Australian savanna for about 20,000 years, from around 60,000 to 40,000 years ago. During this time, northern megafaunas differed from southern megafauna.
We have found at least 13 extinct species so far at South Walker Creek, with mega-reptiles as top predators, and mega-mammals for their prey. Many of the species discovered are likely new species or northern variations of their southern counterparts.
Some, like extinct crocodiles, are thought to have gone extinct long before people were in that place. However, we now know they survived in at least one place 60,000-40,000 years ago.
Imagine first seeing a six meter goanna and its relatives the size of a Komodo Dragon, or crashing into a crocodile that lives on land and cousins of armored submarines. Mammals are equally strange, including giant bucktoothed wombats, strange “bear-sloth” marsupials, and large kangaroos and wallabies.
An unnamed giant kangaroo is the largest ever found. With an estimated mass of 274 kg, he defeated his previous opponent, the goliath-faced kangaroo, Goliah Procoptodon.
The largest of all mammals is a three-ton marsupial Diprotodon, and the most deadly is the bag predator Thylacoleo. Living with this giant is another megafauna species that still survives to this day: emus, red kangaroos, and saltwater crocodiles.
Whodunnit? Evidence shows environmental change
However, this theory is not supported by our findings that this diverse collection of ancient giants still survived 40,000 years ago, after humans spread throughout the continent.
The extinction of tropical megafaunas occurred some time after our youngest fossil site was formed, some 40,000 years ago. The time frame of their disappearance coincides with ongoing regional changes in the availability of water and vegetation, as well as an increase in the frequency of fires. This combination of factors might prove fatal to giant land and aquatic species.
The megafauna extinction debate will no doubt continue for years to come. New discoveries will install the key the gap in the notes. With the gap in the north of the largest continent not yet filled.
With the overlap between humans and megafauna around 15,000-20,000 years, new questions arise about shared living. How do people live with this giant during periods of drastic environmental change?
How many more changes can Australia bear?
Major environmental changes and extinctions are not unusual parts of our geological past, but this time are personal; it involves us. Throughout the Pleistocene (time that ended with the most recent ice age), Australia has experienced major climate and environmental changes.
In the same catch from this new megafauna site, one learn shows how the main climate upheaval that began around 280,000 years ago led to the loss of diverse rainforest fauna. This led to a series of changes in the ecosystem that led to the loss of megafauna at South Walker Creek about 40,000 years ago.
It is still unclear what impact these long-term environmental changes and the loss of megafauna will have on survivors.
This long-term extinction trend has now been kicked in by massive changes to the environment created by humans that continue to this day. At the beginning of the 21st century in Australia we have seen an increase in floods, droughts and forest fires, and we hope this increase will continue.
The fossil record gives us a window into our past that can help us understand our past present. As our research shows, dramatic environmental changes have a major impact on the survival of species, especially for those at the top of the food chain. Will we heed warnings from the past or suffer the consequences?
This article was originally published in Conversation by Scott Hocknull at the University of Melbourne, Anthony Dosseto at Wollongong University, Lee Arnold at the University of Adelaide, Renaud Joannes-Boyau at Southern Cross University, Gilbert Price and Patrick Moss at the University of Queensland. Read the original article here.
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