Climate change, not humans, fueled the decline of prehistoric elephants, mammoths and behemoths


July 1 (UPI) – Sudden and dramatic environmental changes, triggered by climate change, fueled the decline of prehistoric elephants, mammoths and behemoths – and humans likely played only a minor role in their demise – according to a new study.

For decades, hunter-gatherers have been the prime suspect in the world’s extinct megafauna.

After all, their descendants, modern humans, have severely degraded Earth’s ecosystems and destroyed dozens of plant and animal species.

But the latest findings – published Thursday in the journal Nature Ecology and Evolution – suggest that the emergence of small groups of humans wielding spears does not explain the rise and fall of elephants, prehistoric and others.

Yet there were once a lot more large animals than there are today.

Thousands of years ago, a wide variety of large proboscideans – the group of large herbivores that includes mammoths and mastodons – roamed the planet.

Today, only three species remain, all endangered and relegated to the tropics of Asia and Africa.

To better understand the evolutionary history of elephants and their relatives, an international team of paleontologists conducted an exhaustive review of the adaptive characteristics evolved by 185 different species of proboscidians.

The examination included dental and cranial characteristics, chewing methods, size of tusks, body mass and locomotion, among other characteristics.

This analysis has allowed scientists to better appreciate the wide variety of forms and ecologies that proboscidians adopted over millions of years before the arrival of the first humans.

Using sophisticated statistical techniques, the researchers modeled the emergence of these various adaptations in time and space.

“We found that the ecological diversity of proboscidians increased dramatically after they dispersed from Africa to Eurasia about 20 million years ago and to North America about 16 million years ago. ‘years when Earth connections between these continents were formed, ”said Steven Zhang, co-author of the study at UPI. in an email.

“Diversity has also increased in Africa as a result of these events,” said Zhang, associate researcher at the University of Bristol in England.

Before this exodus, the prehistoric proboscidians of ancient Africa evolved quite slowly.

In fact, proboscidians of the Oligocene, the era that began about 33 million years ago, didn’t really look like elephants, and most morphological experiments were evolutionary dead ends.

Once these archaic lineages from North Africa escaped to Europe and Asia, proboscidean evolution accelerated by a factor of 25 as prehistoric elephants quickly adapted to take advantage of a multitude of ecological opportunities.

Unfortunately, boom times don’t last forever. In addition to revealing the timing of proboscidean diversification, the analysis also revealed periodic declines in proboscidean speciation.

“From about 6 million years ago, and especially since 3 million years ago, the ecomorphological diversity of proboscidians began to decrease globally in increments, as a result of climatic cooling and hardening events”, co- author Juha Saarinen, postdoctoral researcher at the University of Helsinki in Finland, told UPI in an email.

Humans fail to explain these periodic declines, according to the authors of the new study.

“For example, in Africa we are witnessing the great extinction of proboscideans around 2.4 million years ago, when members of the evolving hominid lineage were still very bipedal chimpanzees in terms of functional ecology.” Zhang said.

“The latest proboscidian extinction flares that we have detected on various continents do not go hand in hand with improved hunting abilities in archaic hominids or the installation of Homo sapiens on different land masses,” said Zhang.

The latest findings do not rule out human influence on proboscidean extinctions, the researchers said, but they do suggest that an increased risk of proboscidean extinction emerged in Africa, Eurasia and the Americas before the arrival of the human big game hunters.

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