as far as it goes. But for the logic to be valid in making inferences about the human diet based on ape diet, it must be based on accurate observations of the actual food intake of apes. Idealists such as we Hygienists don't often appreciate just how difficult it is to make these observations, and do it thoroughly enough to be able to claim you have really seen everything the apes are doing, or capable of doing. You have to go clear back to field observations in the 1960s and earlier to support the contention that apes are vegetarians. That doesn't wash nowadays with the far more detailed field observations and studies of the '70s, '80s, and '90s. Chimp and gorilla behavior is diverse, and it is difficult to observe and draw reliable conclusions without spending many months and/or years of observation. And as the studies of Jane Goodall and others since have repeatedly shown, the early studies were simply not extensive enough to be reliable.[73]
Citing of outdated science an earmark of idealism out of touch with reality. Science is a process of repeated observation and progressively better approximations of the "real world," whatever that is. It is critical then, that we look at recent evidence, which has elaborated on, refined, and extended earlier work. When you see anybody--such as apologists for "comparative anatomy" vegetarian idealism (or in fact anybody doing this on any topic)--harking back to outdated science that has since been eclipsed in order to bolster their views, you should immediately suspect something.
Accumulation of modern post-1960s research shows apes are not actually vegetarians. The main problem with the comparative anatomy argument, then--at least when used to support vegetarianism--is that scientists now know that apes are not vegetarians after all, as was once thought. The comparative anatomy argument actually argues for at least modest amounts of animal flesh in the diet, based on the now much-more-complete observations of chimpanzees, our closest animal relatives with whom we share somewhere around 98 to 98.6% of our genes.[74] (We'll also look briefly at the diets of other apes, but the chimpanzee data will be focused on here since it has the most relevance for humans.)
Diet of chimpanzees. Though the chimp research is rarely oriented to the specific types of percentage numerical figures we Hygienists would want to see classified, from what I have seen, it would probably be fair to estimate that most populations of chimpanzees are getting somewhere in the neighborhood of 5%* of their diet on average in most cases (as a baseline) to perhaps 8-10%* as a high depending on the season, as animal food--which in their case includes bird's eggs and insects in addition to flesh--particularly insects, which are much more heavily consumed than is flesh.[75]
- Meat consumption by chimps. There is considerable variation across different chimp populations in flesh consumption, which also fluctuates up and down considerably within populations on a seasonal basis as well. (And behavior sometimes differs as well: Chimps in the Tai population, in 26 of 28 mammal kills, were observed to break open the bones with their teeth and use tools to extract the marrow for consumption,[76] reminiscent of early Homo habilis.) One population has been observed to eat as much as 4 oz. of flesh per day during the peak hunting season, dwindling to virtually nothing much of the rest of the time, but researchers note that when it is available, it is highly anticipated and prized.[77] It's hard to say exactly, but a reasonable estimate might be that on average flesh may account for about 1-3% of the chimp diet.[78]
- The more significant role of social-insect/termite/ant consumption. Now of course, meat consumption among chimps is what gets the headlines these days,[79] but the bulk of chimpanzees' animal food consumption actually comes in the form of social insects[80] (termites, ants, and bees), which constitute a much higher payoff for the labor invested to obtain them[81] than catching the colobus monkeys that are often the featured flesh item for chimps. However, insect consumption has often been virtually ignored[82] since it constitutes a severe blind spot for the Western world due to our cultural aversions and biases about it. And by no means is insect consumption an isolated occurrence among just some chimp populations. With very few exceptions, termites and/or ants are eaten about half the days out of a year on average, and during peak seasons are an almost daily item, constituting a significant staple food in the diet (in terms of regularity), the remains of which show up in a minimum of approximately 25% of all chimpanzee stool samples.[83]
- Breakdown of chimpanzee food intake by dietary category. Again, while chimp researchers normally don't classify food intake by the types of volume or caloric percentages that we Hygienists would prefer to see it broken down for comparison purposes (the rigors of observing these creatures in the wild make it difficult), what they do record is illustrative. A chart for the chimps of Lope in Gabon classified by numbers of different species of food eaten (caveat: this does not equate to volume), shows the fruit species eaten comprising approx. 68% of the total range of species eaten in their diets, leaves 11%, seeds 7%, flowers 2%, bark 1%, pith 2%, insects 6%, and mammals 2%.[84]
A breakdown by feeding time for the chimps of Gombe showed their intake of foods to be (very roughly) 60% of feeding time for fruit, 20% for leaves, with the other items in the diet varying greatly on a seasonal basis depending on availability. Seasonal highs could range as high as (approx.) 17% of feeding time for blossoms, 22-30% for seeds, 10-17% for insects, 2-6% for meat, with other miscellaneous items coming in at perhaps 4% through most months of the year.[85]
Miscellaneous items eaten by chimps include a few eggs,[86] plus the rare honey that chimps are known to rob from beehives (as well as the embedded bees themselves), which is perhaps the most highly prized single item in their diet,[87] but which they are limited from eating much of by circumstances. Soil is also occasionally eaten--presumably for the mineral content according to researchers.[88]
- Fluid intake in chimps not restricted to fruit, and includes water separately. For those who suppose that drinking is unnatural and that we should be able to get all the fluid we need from "high-water-content" foods, I have some more unfortunate news: chimps drink water too. Even the largely frugivorous chimp may stop 2-3 times per day during the dry season to stoop and drink water directly from a stream (but perhaps not at all on some days during the wet season), or from hollows in trees, using a leaf sponge if the water cannot be reached with their lips.[89] (Or maybe that should be good news: If you've been feeling guilty or substandard for having to drink water in the summer months, you can now rest easy knowing your chimp brothers and sisters are no different!)
- The predilection of chimpanzees toward omnivorous opportunism. An important observation that cannot be overlooked is the wide-ranging omnivorousness and the predilection for tremendous variety in chimpanzees' diet, which can include up to 184 species* of foods, 40-60 of which may comprise the diet in any given month, with 13 different foods per day being one average calculated.[90] Thus, even given the largely frugivorous component of their diets, it would be erroneous to infer from that (as many Hygienists may prefer to believe) that the 5% to possibly 8% or so of their diet that is animal foods (not to mention other foods) is insignificant, or could be thrown out or disregarded without consequence--the extreme variety in their diet being one of its defining features.
Over millions of years of evolution, the wheels grind exceedingly fine, and everything comes out in the wash. Remember that health is dependent on getting not just the right amounts of macro-elements such as carbohydrates, fats, and proteins, but also critical amounts of trace minerals and vitamins for instance. We require, and are evolutionarily adapted to, the behavior that is natural to us. Where chimps are concerned, 5% or 8% animal food--whatever it actually is--is a modest but significant amount, and not something you can just say is incidental or could be thrown out without materially changing the facts.
Other ape diets. In order of how closely related the other great apes are to humans, the gorilla is next after the chimpanzee, then the orangutan, and gibbon in decreasing order.[91] I'll just briefly summarize a few basic facts about the other great apes here, concentrating primarily on the gorilla.
- Diet of gorillas compared with chimps. Interestingly, while the gorilla has often been cited as a model in the modern mythology of "fruitarianism,"[92] on average it is actually the least frugivorous of the apes. Highland gorillas (where less fruit is available in their higher-altitude mountainous habitat) have become primarily folivorous (leaf/vegetative-eaters), while the lowland gorilla is more of a hybrid folivore/frugivore.[93] I might mention in this regard that there is some suggestion chimps seem not to prefer extra-high roughage volumes, at least compared to the gorilla. Certainly they do not seem to be able to physiologically tolerate as much cellulose from vegetative matter in their diet.*[94]
Gorillas can, however, tolerate higher amounts of folivorous matter, due apparently to their more varied and extensive intestinal flora and fauna.[95] Chimps, however, are known to "wadge" some of their foods, which is a form of juicing that has the effect of reducing their fiber intake.[96] Wadging means that they make a wad of leaves which is mixed in with the primary food item (such as a fruit) as a mass, which is then used as a "press" against their teeth and palate to literally "juice" the main food which they may suck on for up to 10 minutes before discarding the wadge of fiber after all the juice has been sucked out. Wadging may also serve as a way to avoid biting into potentially toxic seeds of certain fruits, from which they can then still extract the juices safely, or as a way to handle very soft items such as pulpy or overripe fruits, as well as eggs and meat.[97]
Such behavior ought to debunk the prevalent Hygienic/raw-foods myth that it is always the more natural thing to do to eat "whole" rather than fragmented foods. This is not necessarily true, and again, such a view is based in subjective definitions out of touch with the real world. Another example here is that chimps (and gorillas as well) also eat a fair amount of "pith" in their diet--meaning the insides of stems of various plants--which they first have to process by peeling off the tough outer covering before the pith inside is either eaten or wadged.[98]
- Other apes less closely related to humans. All the great apes, with the exception of the gorilla, are primarily frugivorous, but they do eat some animal products as well, though generally less than the chimp--although lowland gorillas eat insects at a comparable rate to chimps. In decreasing order of animal food consumption in the diet, the orang comes first after the chimp, then the bonobo chimp, the gibbon, the lowland gorilla, and the highland gorilla--the latter eating any animal foods (as insects) incidentally in or on the plants eaten. Again, remember, animal food consumption here does not equate solely with flesh consumption, as that is less prominent than insects in ape diets. The chimp and bonobo chimp are the only ones to eat flesh (other than a rare occurrence of an orang who was observed doing so once). All the apes other than the highland gorilla eat at least some social insects, with the chimp, bonobo chimp, and orang also partaking of bird's eggs.[99]
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