The Lion share of the prey
Modern humans reserved the lion-share of today’s prey animal simply by domestication and agriculture1. But what kind of role did Homo erectus played in the predator guild of Java during the ice age – the hunter or the hunted?
During the ice age, Homo erectus was competing with apex-predators, like tigers, spotted hyenas, wild dogs and saber-toothed cats, for deer, buffalos and pigs in Java. The question, who managed to gain most of the prey in this scenario, is tricky, because palaeoecologists need to rely on a few information derived from fossils rather than population counts, as we have them for ecosystems today.
However, the Pleistocene itself is a geological epoch, also known as the ice-age, covering 2,588,000 to 11,700 years ago. The fauna changed during this epoch, and when Homo erectus has reached the Island by 1.2 million years ago, there was only one large predator present – a Panthera cat2,3. It is not clear if it the bones represent a tiger, but from its shape and size, it must have been at least a 154 – 210 kg4 Panthera cat.
In the next stage, also a dog was present and Homo erectus had to compete for prey with both species. The Tiger was mainly hunting prey of 20 – 200 kg similar as the Trinil-Dog, who was hunting 10 – 200 kg as well, considering this dog as a pack-hunter5.
Prey matching with these prey profiles, were deer, pigs and also buffaloes.
The only phenomenon, that can be observed, is that in the following younger faunal level, the Trinil-dog is extinct3. Here we can find the short-faced hyaena, Pachycrocuta brevirostris, a giant hyaena reaching in Java, body sizes up to 97 kg4,5, while on the mainland this species even reached sizes of 110 kg6. In this fauna we also have slight changes in the composition of prey fauna, e.g. a large buffalo (Epileptobos groenveldt)3,7only known from the Javanese Pleistocene, the Indian tapir (Tapirus indicus)3 and the Indian rhinoceros (Rhinoceros unicornis)3,8. These animals were more in the outer range of the prey spectra of tigers and short-faced hyaenas, and might have been optimal prey for Homo erectus, if he was hunting with weapons.
So far, no hunting weapons were discovered from Pleistocene sites in Java (so far). In Europe, though, oldest complete spears are known from the site of Schöningen in Europe and have an age of 337.000 to 300.0009 and spear point dated to 400,000 years was discovered in Clacton10. These spears are comparable to modern tournament javelins and can be thrown up to 70 m of distance11,12.
Long distance weapons can also be used to hunt larger animals and Homo erectus might have selected larger animals like buffaloes, tapirs, rhinoceros and elephants in Java to avoid competition. This theory is further supported by the results 709,000 years old fossil recently discovered in Kalinga, Northern Luzon13– a butchered rhinoceros.
If the neighbours from the Philippines were hunting on large prey, why not Java-man as well?
Interestingly, Homo erectus is very persistent in Java. Beside the tiger, he occurs continuously from 1.2 million years onwards – something no other mammalian predator made: Merriam’s dog, Trinil-dog, the short-faced hyena, as well as the sabre-toothed cats all became extinct at some point.
Although, it remains an open question if Homo erectus in Java was hunting and how he selected his prey, but one thing we can be sure about is, that focusing on larger prey would have concluded to less competition pressure from the other predators in the guild.
Hominins not only have the advantage to shift to larger or smaller prey sizes, they also had the opportunity to rely on other food resources like fruits, tubers, and nuts. The flexibility in hominin diet was thus a strong advantage and enabled our subsistence.
Homo erectus – Top-predator or scavenger?
Bones of tigers are more numerous than bones of Homo erectus in Trinil.
Top-predators usually gain most of the biomass and thus make also most of the biomass in an ecosystem. But how do we know the biomasses of fossil ecosystems? This is a tricky reconstruction – many so-called taphonomical selection criteria are responsible for the number of fossils in a sample.
Larger animals tend to be more likely to fossilize, because their bones are more robust and thus less likely to be destroyed, decomposed or consumed by predators. Palaeontologists are also dealing with the question if an individual is represented by one or more bones. Usually the geological and geographical history plays a crucial role. All three sites, Trinil, Kedung Brubus and Ngangdong, are typical river sites. That means bones were transported and exposed to water. The fact that tiger bones are more frequent than Homo erectus bones are thus not enough evidences for its role in the predator guild. However, the top role as we have achieved today, is definitely not yet reached by Homo erectus in Java, otherwise we would expect even more numerous fossils from our Pleistocene cousins.
Considering another site, Dmanisi in Georgia, hominins were probably throwing stones to threaten predators away from their kills. This is a theory mentioned by Reid Ferring, might have also applied to the situation in Java, where we found the so-called pebble tools and “bolas”.
As in modern scavenging species, like the spotted hyaena Crocuta crocuta, we can find always a mixture of hunting and scavenging. Living Crocuta crocuta is not a pure scavenger, but also hunting in packs as it can be observed in the Serengti, Ngorongoro, Kruger National Park and the Kalahari desert 14-16. However, the proportion of hunted vs. scavenged prey varies in between several areas, ranging from 17% hunted prey in Kruger 6,16 and up to 99% in Masai Mara 17. The reason for this variation is still unexplained. However, the presence of carcasses and low density of other scavengers might be favouring scavenging by spotted hyaenas in some areas. Hunting on the other hand also comes hand in hand with being vulnerable to kleptoparasitism 18,19. For example in the Ngorongoro crater lions are able to watch spotted hyaenas while they are hunting and due to the physical power of male lions are usually successful in fights over kills as observed in the Etosha park 18. In case males are absent, spotted hyaenas can drive female lions away from their if they outnumber them by the factor of 4 19. Spotted hyaenas hunt on medium to large size ungulates, focusing on wildebeest in the Serengeti, while impala, kudu, and warthog are most frequently hunted in Kruger National Park 16.
The same might also apply to early humans and ancestral hominins: we hunted but might have also drive of predators from their fresh kills, in order to steal them.
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