Over 80% of prehistoric megaherbivores went extinct due to human activity and not climate change: Study

Today, it's undeniable that humanity holds a profound influence over Earth's climate and its biodiversity. However, contrary to modern media sensationalism, this relationship is not a recent revelation but a saga as ancient as time itself. Human impact on our planet's intricate web of life stretches back tens of thousands of years — possibly even since they first sauntered into the picture.

Recent studies have spotlighted the extinction or rapid decline of large mammals over the past 50,000 years. While climate change was once a convenient scapegoat, it has proven insufficient to explain these phenomena. Instead, mounting evidence implicates human activity as the primary driver.

This phenomenon, known as the late-Quaternary megafauna extinction, marks a significant departure from previous extinction events in Earth's history, with distinct characteristics that set it apart. Unlike earlier extinction events that were often localised, the late-Quaternary extinctions were global in scope and severe in impact. They disproportionately affected larger-bodied species, with megaherbivores weighing over 1,000 kg particularly vulnerable. Shockingly, of the 57 known megaherbivore species from this period, only 11 survived beyond 1,000 AD, highlighting the scale of loss.

Tale as old as time

The narrative begins roughly 100,000 years ago, a time when mammoths roamed icy plains, sabre-toothed tigers prowled lush jungles, and giant ground sloths navigated primaeval forests. Despite the formidable odds, Homo sapiens, armed with finely crafted spears, ascended to the top of the food chain. However, their ascent left behind a trail of dwindling populations and silent extinctions.

Previous periods of dramatic climate shifts, like ice ages, didn't cause such widespread extinction of large animals. New research highlights key points that point towards human intervention:

• Timing: Megafauna extinctions coincided with the arrival of modern humans in different regions around the globe.
• Targeted hunting: Evidence from archaeological digs, like traps and spear points, suggests humans actively hunted these large animals. Isotope analysis even reveals that these giants were a major food source for our ancestors.
• Vulnerability of megafauna: Large animals with slow reproduction rates were particularly susceptible to overhunting by humans.

Yet, the impact wasn't limited to extinctions. Even species that survived, like elephants, bears, kangaroos, and antelopes, bore lasting scars from humanity's rise. A 2023 study analysing the DNA of 139 surviving megafauna species reveals a troubling decline in their populations over the last 50,000 years.

Further, challenging prevailing theories that blame climate change for extinctions, study author Jens-Christian Svenning emphasised that many extinct megafauna inhabited temperate or tropical climates, undermining climate as the sole explanation.

Looking ahead

The loss of so many large animal species has had profound ecological consequences worldwide. These include disruptions to trophic processes, alterations in physical environmental engineering such as landscape modification, and changes in the transport of energy and matter within ecosystems. The repercussions of these extinctions continue to reverberate through modern ecosystems.

In response to these ecological shifts, efforts in megafauna-based trophic rewilding have gained traction as a potential strategy for ecosystem restoration under current global change scenarios. By reintroducing large herbivores into landscapes, researchers and conservationists aim to re-establish ecological processes and enhance biodiversity.

Furthermore, the interplay between megafauna and human-driven biotic globalisation underscores the complex relationships between species and ecosystems. Domesticated megafauna, such as livestock, present both ecological challenges and opportunities in managing modern landscapes.

As debates continue among scholars — whether to blame climate change or human migration — the echoes of history resound clearly. Standing on the brink of a new era where our technological prowess imperils ecosystems and countless species, the story of these giants serves as a stark warning. What remains to be seen is if we heed the lessons from their decline and the enduring impact humanity has etched into the fabric of evolution, or if we will repeat the errors of our ancestors, leaving only silence in our wake?