One of the topics making the rounds today is the connection between Plio-Pleistocene hominins and their carnivorous contemporaries. Ann Gibbons gets the ball rolling by reporting on recent research by Lars Werdelin and colleagues on the apparent extinction of carnivores, particularly the omnivorous variety, between 3.5 – 1.5 million years ago.
Werdelin found that all but six of 29 species of large carnivores (animals that weighed more than 21.5 kilos) had gone extinct in that time. Moreover, the mass extinction began just before H. erectus appeared in the fossil record 1.9 million years ago. He also found that the community of carnivores alive 2.5 million to 2 million years ago ate a much broader range of food—with species within a community filling a wider range of dietary niches. By 1.5 million years ago, just hypercarnivores that ate only meat, such as lions and leopards, had survived while omnivores that scavenged and ate a wider range of foods, like civets, had disappeared. “Even I was surprised by the dramatic drop,” Werdelin says
John Hawks picks up the story and comments on the possibility of Malapa, positioned provisionally at a hair less than 2 million years of age, to add to this story.
On that note, there are some incredible carnivore materials from Malapa that may really add to the picture of carnivore-hominin relations. The first of these were published last fall by Brian Kuhn and colleagues, including Werdelin [3]. It will be exciting to see more of this work come out, as I’m sure that the preservation of a wide array of carnivore materials is really shifting how we can think about the relative diets and ecological roles of these species. It’s another case where paleontologists can now leverage the vast record of time covered in East Africa by applying the detailed information from the exceptionally preserved Malapa deposit.
I will just add that Dmanisi, situated in Georgia between about 1.81 – 1.75 million years is even better positioned to enter into these discussions. Dmanisi has an extremely abundant and well-preserved assemblage of carnivores that address the potential large-scale issues of continental dispersal and potential co-dispersal of carnivores and other taxa (including meat-eating, omnivorous early Homo). Here is a recent paper by H.J. O’Regan and colleagues, for example, on the topic:
Overall we conclude that there is now little evidence for major waves of dispersal between the Pliocene and Pleistocene mammal faunas of Africa and Eurasia. Instead the pattern seems to be highly complex, with few species moving in concert. Previously identified faunal ‘events’ such as the Elephant-Equus event and the dispersal of African bovids into Asia at 2.5 Ma have also been discounted, and it may be that talking in terms of events is too simplistic. It makes for a useful shorthand but can end up trapping things in its own logic, so that the appearance of a true Canis in Europe would have to be later than 1.7 Ma on the basis of earlier ideas about a ‘wolf event’. We therefore need to be clear about what we can say
The Dmanisi fauna in general, including the carnivores, are only just beginning to be more widely published. A 2011 paper by Hemmer and colleagues discusses a possible large cheetah-like carnivore found at the site. This 2010 paper by Sotnikova and Rook looks at Canid evolution in Eurasia more broadly, but discusses the abundant Canid material from Dmanisi in some depth.
In addition to these broad questions, the extent of the exposures and abundance of both fossil and archaeological material at Dmanisi raise the possibility of addressing specific questions about early Homo-carnivore interactions. Excavations over the past several seasons (since the construction of a roof structure) at Dmanisi have yielded increasing evidence, most notably in the form of large numbers of coprolites, that some of the accumulations at the site are the likely product of carnivore denning and that the hominins present would have had a potentially high degree of both temporal and spatial overlap with these groups.
UPDATE: Kate Wong, writing for Scientific American, chimes in with her own thoughts on the research:
That the loss of top predators can transform an ecosystem is well known. In the simplest arrangement, the disappearance of the predator allows populations of their prey species to expand, which alters the plants those prey species eat. Biologists call the domino-like chain of events a trophic cascade. The reintroduction of wolves into Yellowstone National Park in the mid-1990s nearly a century after they were exterminated provides a striking example of the far-reaching effects of top predators: not only did the resident elk population shrink back down to a more manageable size, but the aspen and cottonwood trees began to recover, as did the willows, which brought back the beavers whose dams create ponds. How East African ecosystems were affected by the loss of large carnivores two million years ago remains to be determined, however.
…
Yet even if humans were responsible for the demise of those animals, we can still blame climate change. Shifting conditions between three million and two million years ago fueled the spread of grasslands in Africa, forcing our earliest ancestors out of the trees and onto the open savanna, which is how they ended up facing off against the large carnivores in the first place.
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1. Hemmer, H., R.-D. Kahlke, et al. (2011). “The cheetah Acinonyx pardinensis (Croizet et Jobert, 1828) s.l. at the hominin site of Dmanisi (Georgia) ‚Äì A potential prime meat supplier in Early Pleistocene ecosystems.” Quaternary Science Reviews 30(19‚Äì20): 2703-2714. DOI: 10.1016/j.bbr.2011.03.031
2. O’Regan HJ, Turner A, Bishop LC, Elton S, and Lamb AL. 2011. Hominins without fellow travellers? First appearances and inferred dispersals of Afro-Eurasian large-mammals in the Plio-Pleistocene. Quaternary Science Reviews 30:1343 – 1352. DOI: 10.1016/j.quascirev.2009.11.028
3. Sotnikova, M. and L. Rook (2010). “Dispersal of the Canini (Mammalia, Canidae: Caninae) across Eurasia during the Late Miocene to Early Pleistocene.” Quaternary International 212(2): 86-97. DOI: 10.1016/j.quaint.2009.06.008
