Brain expansion in early hominins predicts carnivore extinctions in East Africa

Abstract

While the anthropogenic impact on ecosystems today is evident, it remains unclear if the detrimental effect of hominins on co-occurring biodiversity is a recent phenomenon or has also been the pattern for earlier hominin species. We test this using the East African carnivore fossil record. We analyse the diversity of carnivores over the last four million years and investigate whether any decline is related to an increase in hominin cognitive capacity, vegetation changes or climatic changes. We find that extinction rates in large carnivores correlate with increased hominin brain size and with vegetation changes, but not with precipitation or temperature changes. While temporal analyses cannot distinguish between the effects of vegetation changes and hominins, we show through spatial analyses of contemporary carnivores in Africa that only hominin causation is plausible. Our results suggest that substantial anthropogenic influence on biodiversity started millions of years earlier than currently assumed.These authors contributed equally to this work.

The past and future human impact on mammalian diversity

“…Similar patterns have been found in previous studies ( 6 , 11 , 13 ), which argue that humans have had a large impact on the faunas of particularly Australia and the Americas, since mammals on these continents were behaviorally naïve to the presence of hominins and thus vulnerable to the appearance of H. sapiens as an efficient new predator. Similarly, these studies argue that mammals in Africa and Eurasia were ecologically adapted to predation by hominins through co-evolution, possibly dating back as far as several million years ago ( 26 ), and were thus more resilient to human hunting pressure in the late Quaternary, leading to fewer extinctions, consistent with our findings ( Fig. 1 ).…”

“…Global 1 Eurasia were ecologically adapted to predation by hominins through co-evolution, possibly dating back as far as several million years ago (26), and were thus more resilient to human hunting pressure in the late Quaternary, leading to fewer extinctions, consistent with our findings (Fig. 1).…”

Iterative evolution of large-bodied hypercarnivory in canids benefits species but not clades

“…Moreover, this bias toward the removal of the largest species is unprecedented over the past 65 Ma of mammalian extinction events 51 . While these biodiversity changes began to take place relatively recently in North America, large carnivores started to decline millions of years earlier in Africa, where humans and their hominin ancestors have lived for much longer 52 . This temporal incongruity implicates anthropogenic impacts-as opposed to factors concurrent between the two continents (e.g., changing forest cover)-in the long-term extinction of large carnivores 52 .…”

“…While these biodiversity changes began to take place relatively recently in North America, large carnivores started to decline millions of years earlier in Africa, where humans and their hominin ancestors have lived for much longer 52 . This temporal incongruity implicates anthropogenic impacts-as opposed to factors concurrent between the two continents (e.g., changing forest cover)-in the long-term extinction of large carnivores 52 . While our data are restricted to a single diverse carnivoran family, our finding of minimal ecomorphological selectivity until the end-Pleistocene supports the idea that modern ecosystems are the product of, and continue to be subject to, trophic downgrading, a process that appears to be largely human-driven with negative effects on biodiversity and ecosystem resilience 1,53 .…”

Changes in the large carnivore community structure of the Judean Desert in connection to Holocene human settlement dynamics

“…Disentangling this anthropogenic effect on past ecosystems remains, however, a complex problem 4 . Current research suggests the negative impact of non-industrial and even hunter-gatherer societies on continental-scale trends of biodiversity loss, vegetation change, and megafaunal extinction [5][6][7][8][9][10] . The pace and scale of Holocene faunal extinctions have increased in connection to local cultural changes, human population growth, political instability, and environmental deterioration (e.g., aridification) [11][12][13] .…”