...mountain gorillas mentioned above that did practice geophagia only did so c. 5 or 5 times a year makes it clear there were other reasons associated with its consumption than the claim re dealing with antinutrients.
I think the use of the term geophagia by that 1990 article is a bit out of date. Geophagia is sometimes used to describe an eating disorder, whereas I am more specifically discussing the natural practice of animals and people in the wild who eat clays and soils for beneficial purposes, rather than out of a pica disorder. Scientists now generally use the term geophagy for the latter.
I provide more up-to-date sources below that better reveal the importance of clay consumption among primates and other animals, but 5 to 6 times a year sounds reasonable to me for some mountain gorillas, especially when combined with the clay-containing termites that mountain gorillas feed on and other detoxicant sources (and the groups that don't eat clay directly may eat more of the clay-eating termites or other detoxifying and/or mineral-rich foods/materials). The tiny levels of toxins take a while to accumulate to toxic levels in the massive bodies of gorillas. I don't find anything I disagree with in that source--though I can only access the first page. On the contrary, it appears to support what I have been trying to say:
"Clay particles in ingested soil can absorb dietary toxins and aid in their excretion and can have an effect on gut pH that is favourable to symbiotic bacteria (Oates, 1978), although they can also chelate metal ions and prevent their adsorption (Robbins, 1983). ....
Mountain gorillas (Gorilla gorilla beringei) studied at the Karisoke Research Centre in Rwanda's Parc National des Volcans have been observed to eat sediment that they dig from slightly weathered regolith (mass wasted deposits) (Fossey & Harcourt, 1977; Fossey, 1983; Watts, 1984). Not all study groups or individuals have been seen to eat such sediment. Those groups that eat sediment do so only five to six times per year, so that geophagia accounts for only a tiny fraction of dietary intake (Watts, 1984). Karisoke Group 5, however...."There is also this:
"Chimpanzees select fungus-growing termites high in protein, energy and manganese, while gorillas select soil-feeding termites high in iron and ash with possible anti-diarrhoeal characteristics. Termite eating in western lowland gorillas might therefore be a high quality alternative for geophagy." How Insectivorous are Gorillas? Gorilla Journal 33, December 2006, http://www.berggorilla.org/english/gjournal/texte/33insect.htmlChimps also ingest clay:
More on medical geophagy in chimps: montmorillonite clay and the origins of life
http://scienceblogs.com/terrasig/2008/02/more_on_medical_geophagy_in_ch.php
French research group's studies on the rationale underlying Ugandan chimpanzee behavior of eating clay soils prior to their favorite plant. The researchers found [http://www.springerlink.com/content/c75t402487h68126/?p=01a5f0d6094d485aae42440e42f82d48&pi=0] that the combination of soil and the plant, Trichilia rubescens, led to activation of the plant's antimalarial compoundsprimates are definitely not like that parrot species Attenborough described which primarily eat only highly toxic plants and HAVE to eat clay immediately afterwards.
Yes, and I would not dream of equating the level of clay consumption of primates with that of parrots, so we agree on that. I think the much smaller bodies of birds is another likely factor in toxicity level.
Here is more on the subject of geophagy from
Wild Health by Cindy Engel, 2003, pp. 64-69...
"High in the Virunga Mountains of Rwanda, the last few hundred mountain gorillas continue to mine yellow volcanic rock from the slopes of Mount Visoke, as they have done for generations. From the size of the caverns they have carved out under the roots of trees, it is evident that these vegetarian [sic] apes treasure this dirt. After loosening small pieces of rock with their teeth, they take small lumps of their powerful leathery hands and grind them into a fine powder before eating.
Since George Schaller first documented gorillas mining volcanic rock on nearby Mount Mikeno in 1963, several other field workers have observed similar behavior. Diane Fosse reported that gorillas were far more likely to rock in the dry season when their diet changed dramatically to bamboo, Lobelia, and Secio plants--all containing more toxic plant secondary compounds than their usual diet. Along with this change in diet came a synchronous increase in diarrhea (a natural response to rid the body of toxins). This extra loss of fluid, in the dry season, the tensely be a serious health problem for the gorillas. Fossey suggested that the mining and processing of the fine volcanic dust was a response to the seasonal change in diet.29
....
"Evidence that forest elephants are using the clay to self medicate against gastrointestinal upset is circumstantial but fascinating. These elephants feed primarily on these all year long except for the month September, when ripe fruit is so abundant that they changed eating mainly fruits. Leaves (as opposed to ripe fruits) generally contain many secondary compounds designed to deter herbivores from feeding on them. A shift from eating leaves to eating fruits would therefore dramatically reduce consumption of toxic secondary compounds -- a natural experiment to see if toxin consumption equates with clay consumption. The only month in which elephants reduce their visits the clay licks is during the fruit eating month, September!
In Africa, then, mountain gorillas, chimpanzees, monkeys, and forest elephants appear to be eating clay to deal with toxins (or their effects) in their tropical forest diet. ....
"After studying geophagy in the Amazon Forest of Peru for many years, Charles Munn has concluded that nearly all vertebrates that feed on fruits, seeds, and leaves also eat clay. ...."33
In 1999 the hypothesis that macaws eat clay in order to deactivate plant toxins was tested experimentally by James Gilardi and a team of scientists at Davis, California. - p. 68 - [They found] that clay can indeed prevent the movement of plant alkaloids into the blood."
...meat eaters do occasionally eat dirt.... Tigers occasionally ingest [black micaceous] soil deliberately ... during November and December. ...the primary benefit of clay consumption is in countering dietary toxins. In essence, eating earth allows animals to deal with the effects of unavoidable toxins.
References:
29. G. B. Schaller, The Year of the Gorilla (Chicago: University of Chicago Press, 1964); D. Fossey, Gorillas in the Mist (London: Hodder & Stoughton, 1983)
30. W. C. Mahaney, S. Aufreiter, and R. G. V. Hancock, "Mountain Gorilla Geophagy: A Possible Seasonal Behavior for Dealing with the Effects of Dietary Changes," International Journal of Primatology, 16(3) (1995):475-488.
31. W. C. Mahaney, R. G. V. Hancock, et al., "Geochemistry and Clay Mineralogy of Termite Mound Soils and the Role of Geophagy in Chimpanzees of Mahale Mountains, Tanzania," Primates, 37(2) (1996):121-134. For a review of geophagy in primates, see R. Krishnamani and W.C. Mahaney, "Geophagy Among Primates: Adaptive Significance and Ecological Consequences," Animal Behavior, 59 (2000):899-915.
33. Discussed in W. Mayer, "Feat of Clay," Wildlife Conservation (June 1999).
Maybe dental caries is something to expect for any frugivore with teeth, eventually.
Indeed, sites such as this one appear to indicate that dental caries is a standard for natural frugivores:-
http://linkinghub.elsevier.com/retrieve/pii/S0003996904002031
Precisely what I have been thinking, but I haven't investigated fruit-caused caries beyond humans and other primates and didn't have references to back it up, so I had thought it might be too upsetting to you to mention my speculation on that without supporting sources. I'm surprised to find that you apparently agree with me on this as well. Thanks for trying to provide a link--unfortunately, I don't have membership to access the one you provided.
It was pointed out that the other primates simply used different, perhaps more effective methods to counter the dental caries(re mention of cashew antibacterial agents).
Yes, antibacterial foods can apparently help offset ingestion of fruit, as I reported (did you think I disagreed with what I reported?), but there would be no necessity for their dental benefits if the fruit in the diet did not contribute at all to caries in the first place. Glander points to BOTH fruit and cashew pedicels as being factors in the low caries rate among howlers--not just one or the other. AFAIK, the connection between fruit sugars and caries is not controversial (except among extreme vegans/vegetarians/fruitarians). I know of no credible scientist who claims there is no link. Do you know of one? One only has to read a fruitarian-oriented forum (or the accounts of former fruitarian-oriented people here) to find plenty of examples of fruit-heavy dieters reporting dental health problems. Even SuperInfinity, who remained unrepentently pro-fruitarianesque to the end, reported dental health problems.
I think that all of this (albeit much of it indirectly) lends credence to your hypothesis that humans are not fully adapted to cooking. It is because of these dental and other health issues of wild primates, giant pandas, etc., in addition to my own experience and yours and others here, that I have been increasingly leaning more strongly to your view that humans are much less adapted to cooking (at least high-heat cooking) than the "experts" believe. If chimps can eat lots of fruit for 6 million years and still get cavities from it, then it is no great surprise that humans might develop some health issues from eating cooked foods 250,000 or more years after they started doing so. In other words, humans can survive on a cooked-food diet, just as chimps can survive on mostly fruit, but that doesn't mean that an all-cooked diet is optimal for humans. I don't think I see it as severely deleterious a practice as you do, and we may focus on different evidence, but I think we basically agree on the main point.