Of Mice, Mastodons and Men: human- mediated extinction on four continents (Lyons et al. 2004)
This article covered a wide range of topics and causes for the extinction of mega fauna. The most centered reason being how humans had a huge impact on the surrounding mega fauna.
During the Pleistocene extinction, mega fauna liked mammoths and saber tooth cats roamed the globe. There are many theories as to the cause of this large extinction including over hunting by humans and rapid climate and vegetation change. This article focuses on mammalian faunas of Africa, North and South America in the late Pleistocene, 12-15 thousand years ago, and 50 thousand years ago for Australia. Body size distributions were calculated to compare body size distributions before and after human colonization. Extinction patterns were also examined to determine ecological conditions of the environment.
Historical and modern patterns both show a very similar size selection bias. Not only were patterns skewed more for large bodied organisms, the biggest organisms were completely eliminated in all of the continents mentioned. Human hunting of these animals may not have been the only cause, other factors such as the introduction of exotic predators or competitors, agriculture and grazing by domestic livestock causing fractures natural habitats could also be part of this situation. We lean towards these causes because during the time of the aboriginals because it was not a time of significant climate change. Climatic factors of course still have an effect on the ecosystems but it is only secondary in comparison to the anthropogenic factors, plus only in the last glacial-inter glacial period were there climatic changes fully responsible for the extinctions of large mammals on these continents.
Q’s: Why would the aborigines hunt the largest prey? What data or hypothesis supports this?
Why aren’t we be able to see mass hunting efforts in the fossil record as new hunting technologies developed?
Aborigines hunted the largest prey because it provided the most materials used for food, clothing, and hardware. This is supported by the size bias seen in these extinctions, with the larger mammals going extinct and the smaller ones living on. Simulations of these time periods show the opposite, where the large mammals expand ranges and the small ones die off. But once humans are introduced to these simulations, they show the same outcome as what is seen.
ReplyDeleteAs for the mass hunting efforts: I would say that humans hunted the largest animals at a rate consistent with the size of their population. This would show up in the record as a continually increasing death rate in the species rather than a drop in population size.
I would have to agree with Nathan that one of the main reasons why large prey is hunted more is because it has a great deal of resources to offer. There's more food available to take as well as the larger body parts such as pelts and bones can be used for clothes and tools. The data from the paper shows that just a little after humans were introduced we see changes in number of mega fauna on different continents, rather than big changes in smaller genera.
ReplyDeleteI would also like to agree with Nathan and Kayleigh that the large prey is hunted more because its economically more cost effective for the humans to collectively go after a large food source instead of spending time and energy developing strategies for smaller food sources. Along with that the large animal would also be able to provide other necessities as previously stated. This has evidence that no only happened in the mega-extinction but other times and areas where humans were introduced to an envirement causing extinction to the larger animals living in the area.
ReplyDeleteTo add on about the mass hunting, i believe that once humans were able to harness more of an agriculture approach for food necessity,they were able to wean off the need to hunt to extinction with comes with the global weather change.
Aboriginal man found that it was most effective to spend his efforts in hunting one large animal, rather than many smaller ones because of the higher food returns per unit of effort. Mixed-model hypotheses support this thought, as they indicate that both climate and man had a hand in the extinction of these larger species. There are a lot of other factors, such as the fact that the introduction of man weakened the population of larger beasts and the larger carnivores then finished them off. This, it is also thought, was also because the larger beasts(such as elephants and rhinos) can change a forested area into a savannah, making a huge impact on their environments, so that they may not be able to survive. But there is no real substance to this as there was no widespread in marine species at the same time, which would have pointed to a climatic change.
ReplyDeleteThe results of this study indicate that these extinctions were caused by man and the timing of them coincided with a mildly changing climate between glaciers. The facts point to direction that populations of the large herbivores, such as horses, camels and water buffalo, would have dominated the planet if not for the hunting of man. On each continent studied, extinctions happened after the introduction of man, but not all at the same time, which would point to a major climate change.
While correlation may not equate causation, enough correlation begins to induce suspicion. The abrupt extinction of large mammals on each continent immediately following the arrival of humans paints a fairly obvious picture. ~ that large mammals should survive climactic shifts and fifty or so ice ages only to get knocked out by the Younger Dryas, and the Younger Dryas alone, seems somewhat unlikely.
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ReplyDeleteI would have to agree with some of the people above as to why larger animals are prey, it is definitely more food and not only food but it can provide a larger amount of fur and that can be used for different things. I would also like to comment on Derek's point, that the time spent killing one large animal is more time efficient than hunting and killing multiple small animals. This explains the extinctions of certain animals and not others, men were able to influence which animals continued in life and which ones did not without even realizing it at the time.
ReplyDeleteI have to agree that the major reason for hunting larger game seems to be that more resources can be gained from it with less energy expended than can be gained from hunting smaller game more frequently. Good evidence of this is given by the extinctions of the animals with the largest body sizes on each continent. No other extinction events have been so selective based on size.
ReplyDeleteAs indicated by many others, it would seem that the aborigines hunted comparatively larger prey given the inherent efficiency associated with such an approach. Further, such an approach has obvious benefits in terms of the ability to use the killed animals not only for food, but also in the construction of tools, or by utilizing the animal pelts (which, potentially, had many uses to aboriginal man). With respect to efficiency, these larger bodied mammals may have been easier to track and locate, given that their large body mass. (e.g. large foot prints). Conversely, smaller animals would likely be more difficult to track given their size.
ReplyDeleteI agree with the consensus that the larger prey were hunted as they provided more, food, clothing etc. Andrew makes an excellent point of the larger prey being easier to track but one must ask what the abundance of such prey? From the reading it would seem that they were quite abundant to be destined to extinction or as the article seems to imply either the human contact & or population increased or they technological advances improved immensely.
ReplyDeleteI think it is clear in prior comments that it makes more logical sense for larger animals to be prey. It provides more energy to the predator plus a larger animal typically has slower locomotion and is harder to camouflage. It was interesting to see in the paper all of the different ways humans were able to utilize different parts of the animal and little went to waste. It is an interesting theory to consider how humans may have played a part in extinction events selecting for larger animals since those were the most beneficial. It seems to be there is some type of link between dwindling numbers of larger animals and the introduction of humans to certain areas.
ReplyDeleteAs mentioned above, I think it is telling that despite the lack of an environmental change in Australia, megafauna went extinct with the introduction of humans to the continent suggesting an anthropogenic cause for their extinction. However, based on the comments above, I did want to bring up a couple of points. (1) Humans were probably eating not just large prey, but smaller prey as well. Sites in North America have evidence of smaller mammals being recovered from larger kill sites. (2) While larger prey is generally considered to have greater returns calorically, you also have to consider that at a certain size, returns decrease because of risk, search time, and processing of the mammal. (3) One of my main questions has always been why didn't Bison antiquus go extinct during this period and remained until approximately 5,000 years ago despite having evidence for massive killings during the Folsom period? Did they just have a smaller population during the Pleistocene and were just not pursued by humans to the same extent?
ReplyDeleteAs previous comments have mentioned, I agree with the "overkill" hypothesis that hunting the largest mammals would provide the most resources for the aboriginal humans. They may have been easier to track, especially if there were a great abundance. This would mean that they were spending less time and energy to gain the most resources.This would lead to an extinction.
ReplyDeleteI tend to agree with most everyone else here that Aboriginal people tended to hunt the larger prey as it provided much more usable and naturally durable resources. While other extinctions like the K-Pg also preferentially selected against larger taxa, there weren't significant climatic shifts on the continents at the time humans arrived. This, combined with the archaeological evidence that we hunted these beasts and used their bones/skins to our advantage strongly suggests that human activity was the primary driver in many of the extinctions we see during this time.
ReplyDeleteWith reference to not finding more mass-hunting efforts in the fossil record even as technology became more lethal, it may have something to do with a trend towards agricultural methods of procuring food. It might also be caused in part by there being less of a need for mass hunting efforts due to the advancement of technology/hunting strategies.
Larger fauna do make ideal prey for pack/community hunters like humans. A large community has to eat, easier to hunt a larger animal: akin to how wolves hunt. And as mentioned in prior comments... humans use the bones, the hides, etc, for many things. This would make larger fauna the primary targets for predation. Though over time technological and agricultural developments made humans more prone to agriculture than hunting. As populations grew and society developed, I believe LESS hunting occurred.
ReplyDeleteI think it's very interesting that we do not have definitive evidence of why the largest fauna disappeared from all the major continents. I think a lot more work and papers like this need to be done to help us understand our impacts on organisms when man first started major hunting practices. In regards to hunting large fauna I think it would have been ideal to hunt the largest animals and with a pack it would have been easier to target these larger animals similarly to what wolves do.
ReplyDeleteI think it's very interesting that we do not have definitive evidence of why the largest fauna disappeared from all the major continents. I think a lot more work and papers like this need to be done to help us understand our impacts on organisms when man first started major hunting practices. In regards to hunting large fauna I think it would have been ideal to hunt the largest animals and with a pack it would have been easier to target these larger animals similarly to what wolves do.
ReplyDeleteThe optimal foraging theory is basically a model that predicts that an animal is (almost) always going to take the easiest path that is going to allows an animal to gain the most energy while expanding the least amount of energy spent. Considering that humans are animals this theory could be applied to the hunting of large prey by aborigines.
ReplyDeleteIt seems like author had some biased towards the theory of human hunting causing extinctions and didn't do much to emphasize the mixed hypothesis approach aside from the disease hypothesis.Humans could have selected for larger prey items as they worked in groups and yielded the most calories for energy spent. But that doesn't mean that humans where always the major driving force for extinction on all continents. Humans could decrease genetic diversity and push them to less desirable habitat, or could introduce invasive plant species that affected plant communities. While there may be some correlation, there may not be causation between the arrival of humans and extinctions. Larger animals could be impacted more by changes in climate because animals of larger sizes are generally less able to cope with higher temperatures without prior adaptations.
ReplyDeletethe large species had too long of a mating cylce to support the rate of hunting. the large animals such as mammals offered many useful reasorces to early settlers that they where a popular hunting option. because mammoths have such long lifetimes, have only a single offspring at a time and take a long time to reach maturity, they did not produce at the rate at which they where hunted.
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