Megafaunal loss Today, it is well known that human activities put larger animals at greater risk of extinction. Such targeting of the largest species is not new, however. Smith et al. show that biased loss of large-bodied mammal species from ecosystems is a signature of human impacts that has been following hominin migrations since the Pleistocene. If the current trend continues, terrestrial mammal body sizes will become smaller than they have been over the past 45 million years. Megafaunal mammals have a major impact on the structure of ecosystems, so their loss could be particularly damaging. Science, this issue p. 310 Hominins have caused size-selective extinctions of large mammals since the Pleistocene. Since the late Pleistocene, large-bodied mammals have been extirpated from much of Earth. Although all habitable continents once harbored giant mammals, the few remaining species are largely confined to Africa. This decline is coincident with the global expansion of hominins over the late Quaternary. Here, we quantify mammalian extinction selectivity, continental body size distributions, and taxonomic diversity over five time periods spanning the past 125,000 years and stretching approximately 200 years into the future. We demonstrate that size-selective extinction was already under way in the oldest interval and occurred on all continents, within all trophic modes, and across all time intervals. Moreover, the degree of selectivity was unprecedented in 65 million years of mammalian evolution. The distinctive selectivity signature implicates hominin activity as a primary driver of taxonomic losses and ecosystem homogenization. Because megafauna have a disproportionate influence on ecosystem structure and function, past and present body size downgrading is reshaping Earth’s biosphere.

中文翻译：

---

第四纪晚期哺乳动物的体型降级

巨型动物灭绝 今天，众所周知，人类活动使大型动物面临更大的灭绝风险。然而，以最大的物种为目标并不是什么新鲜事。史密斯等人。表明大型哺乳动物物种从生态系统中的偏向性丧失是自更新世以来人类迁徙之后的人类影响的标志。如果目前的趋势继续下去，陆生哺乳动物的体型将比过去 4500 万年来更小。巨型哺乳动物对生态系统的结构有重大影响，因此它们的消失可能会造成特别大的破坏。科学，这个问题 p。自更新世以来，有 310 种古人类造成了大型哺乳动物的大小选择性灭绝。自晚更新世以来，大型哺乳动物已从地球上的大部分地区灭绝。尽管所有可居住的大陆都曾经拥有巨型哺乳动物，但仅存的少数物种主要局限于非洲。这种下降与第四纪晚期人类在全球的扩张相吻合。在这里，我们量化了过去 125,000 年到未来大约 200 年的五个时间段内的哺乳动物灭绝选择性、大陆体大小分布和分类多样性。我们证明，尺寸选择性灭绝已经在最古老的时间间隔内进行，并且发生在所有大陆、所有营养模式和所有时间间隔内。此外，选择性的程度在 6500 万年的哺乳动物进化中是前所未有的。独特的选择性特征暗示人类活动是分类学损失和生态系统同质化的主要驱动因素。