The Earth has lost approximately half of its large mammal species (≥45 kg, one-third of species ≥9 kg) over the past 120,000 years, resulting in depauperate megafauna communities worldwide. Despite substantial interest and debate for over a century, the reasons for these exceptionally high extinction rates and major transformation of the biosphere remain contested. The predominant explanations are climate change, hunting by modern humans (Homo sapiens), or a combination of both. To evaluate the evidence for each hypothesis, statistical models were constructed to test the predictive power of prehistoric human and hominin presence and migration on megafauna extinction severity and on extinction bias toward larger species. Models with anthropic predictors were compared to models that considered late-Quaternary (120–0 kya) climate change and it was found that models including human factors outperformed all purely climatic models. These results thus support an overriding impact of Homo sapiens on megafauna extinctions. Given the disproportionate impact of large-bodied animals on vegetation structure, plant dispersal, nutrient cycling and co-dependent biota, this simplification and downsizing of mammal faunas worldwide represents the first planetary-scale, human-driven transformation of the environment.

在过去的 12 万年里，地球已经失去了大约一半的大型哺乳动物物种（≥45 公斤，三分之一的物种≥9 公斤），导致全世界巨型动物群落萎缩。尽管一个多世纪以来引起了人们的极大兴趣和争论，但这些异常高的灭绝率和生物圈重大转变的原因仍然存在争议。主要的解释是气候变化、现代人类（智人）的狩猎)，或两者的组合。为了评估每个假设的证据，构​​建了统计模型来测试史前人类和古人类的存在和迁徙对巨型动物灭绝严重程度以及对较大物种的灭绝偏见的预测能力。将具有人为预测因子的模型与考虑第四纪晚期（120-0 kya）气候变化的模型进行比较，发现包含人为因素的模型优于所有纯粹的气候模型。因此，这些结果支持智人的压倒性影响关于巨型动物的灭绝。鉴于大型动物对植被结构、植物传播、养分循环和相互依赖的生物群的影响不成比例，全球哺乳动物区系的简化和规模缩小代表了人类驱动的第一次全球范围内的环境转变。