American Journal of Nasal Anatomy  (1987),  17: 230-239.

Nose-Picking in the Pongidae and Its
Implication for Human Evolution

By Dr. Thomas L. Harrison
Primate Behavior Research Group
Harvard University

Introduction

      Nose-picking and subsequent consumption of nasal detritus are activities that have been widely observed among extant species of pongids, and that appear to be almost instinctive behavior patterns in most, if not all, human groups (Barnesdale, 1975; Glicks, 1978; Bidwell and MacCown, 1979; Stevens, 1981; Marshall et. al., 1983; and Harrison, 1986).  Since it has not been recorded in the Cercopithecoidea (James, 1982), it is suggested that it represents a behavioral adaptation that arose some time after the hominoids diverged from the Old World monkeys approximately 20 million years ago.
      We are interested in nose picking variations (I shall refer to both nose-picking and detritus-eating by the collective term "nose-picking") among extant pongids with particular respect to variability in environmental resources. We are also interested in how old this behavior is.  It is suggested that the more protohominids picked their noses, and the more dependent they might have become on such nutritious (Yarnell, 1985) albeit meager supplemental fare, the larger their noses became, the more acute their sense of smell became, and the more proficient as hunters they became.  Thus a behavior pattern that evolved for a completely different function fueled the transformation of the hominid lifestyle.  If we can demonstrate that nose-picking varies with resource levels, we will have shown a possible mechanism whereby such behavior could have been selected for.  There are two questions that we will address:  (1) what does the fossil record tell us about the possible evolution of this behavior, and  (2) does nose-picking increase or decrease as a correlate of any natural cycle of food availability?

 

The fossil record

      To begin with, the fossil record is amply illustrative of several things.  First, homo sapiens is almost certainly derived from the general sivapithecine complex that was widespread from 15 to 8 mya.  So also are Pan, Gorilla and Pongo.  The phyletic position of the hylobatids with respect to the sivapithecine-dryopithecine split is uncertain at this time.  The orangutan is the only definite remaining descendent of the Asian sivapithecines that inhabited an area from the Siwaliks to China.  Pan, gorilla and homo are the likely descendents of the sivapithecines that occupied East Africa and the Middle East and spread to North Africa and central Europe.  We share with the sivapithecines the large nasal orbit size and distended index phalanges that so clearly differentiate us from the small-nostrilled dryopithecines that went extinct.  The report in 1967 of the discovery of the late Miocene hominid skeleton with the large-nosed cranium by Sir Arthur Baslington Chillingford Streebs-Watley, and attributed by him to Dryopithecus nasalia, has since been proven to be a hoax thus far surpassed only by Piltdown.
      Although there was a range of nasal orbit size among the dryopithecines that did overlap to a small degree with that of the ramapithecine-sivapithecine complex, this should not obscure the fact that, even taking allometry into account, this little forest creature had an extremely small nose.  It has often been pointed out that the sense of smell is less important than that of vision (Bidwell and MacCown, 1979), and so a forest-adapted animal would be expected to have a reduced nasal capacity.  The sivapithecines presumably needed a more acute sense of smell in the expanding open woodlands of the middle Miocene to which they were adapting, and Table 1 well reflects this size differential:

Table 1

Species

Sivapithecus indicus
S. meteai
Gigantopithecus blackii
Ramapithecus punjabii
Dryopithecus fontanii
Proconsul nyanzae
Pliopithecus ssp.
Propliopithecus

A

1.7
1.9
3.1
1.5
1.1
0.9
1.3
 0.8
B

4.3
4.0
6.2
3.9
3.2
2.7
3.6
 2.1
C

2.0
2.3
4.4
1.8
1.5
1.2
1.9
 1.0
 

A.   Dimension of Nares, anteroposteriorly, in cm.
B.   Dimension of Nares, transversely, in cm.
C.   Sphenoidal process of palatine bone, anterior to posterior length

      Secondly, although postcranial material is sparse for many of these taxa, there is sufficient data to confirm a relative increase in the length of the first and second phalanges of the index finger in sivapithecines as compared to the dryopithecines and their allies.  When we compare nasal orbit size to phalanx length, allometry being adjusted for, we find that in every case an increase in one is matched by an increase in the other.  The enlargement of the phalanges was a trend that reached its peak in the genus Gigantopithecus, and is reflected today in the orangutan.
In the case of Gigantopithecus, the so-called "giant-nosed ape," it was the very size of its nose, and not just the size but its peculiarly bulbous morphology, that was responsible for its downfall.  This large-snouted anthropoid actually attempted bipedalism, but its nasal orbit size had expanded to such a degree that it was subject to things flying into its nose, like the small Miocene lake birds that were as common as fleas.  Every time it tried to stand up, something would fly into its nose, and so it went extinct.
      Third, the fossil record demonstrates adequately, I believe, a continuing expansion of the nasal cavity in general, and of the sphenoethmoidal recess, the pharyngeal recess, and the sphenoidal sinus in particular (see Table 2).  It is clear that for the last 15 million years, our noses have been getting bigger, and we have apparently been taking full advantage of it.  Were we to continue to evolve for another 15 million years, our noses would probably be as large as coffee cups.
Table 2

Species

Aegyptopithecus zeuxis
Pliopithecus vindobonensis
Sivapithecus indicus
A. africanus
Pongo pygmaeus
Pan troglodytes
Homo erectus 1
Homo erectus 2
Homo sapiens

A

5.3
5.9
6.7
7.5
8.4
8.2
7.9
9.2
 9.5
B

1.1
1.5
3.2
4.1
4.7
4.4
4.2
5.6
 5.9
C

0.4
0.8
1.5
1.9
2.4
2.2
2.2
3.2
 3.6
D

0.3
0.6
1.1
1.6
2.0
1.8
1.7
2.9
 3.2
A.   Nasal cavity volume in cubic cm.
B.   Volume of sphenoethmoidal recess.
C.   Volume of pharyngeal recess.
D.   Volume of sphenoidal sinus.
1.   Homo erectus before nasal cavity expansion.
2.   Homo erectus after nasal cavity expansion.

      Fourth, the fossil record is quite clear that there was a large-scale expansion of the nasal cavity about one million years ago.  In many respects, this blossoming of the central portion of the hominid face was the last major factor that propelled Homo erectus into truly modern morphologies and behavior patterns, and the transformation was driven in large part by nose-picking.  The recent tabulation of the phalanx length-nasal orbit size ratio (McCully-Anderson, 1987) demonstrates conclusively the corresponding expansion of the digit, which could only have arisen from its utilization as the first tool.
      There is general agreement that bipedalism arose approximately 3 mya and there are those who contend that it was the freeing of the hands to pick the nose that drove man into a hunting posture.  There is much agreement too that tools began to be manufactured about 2 mya, but the earliest evidence of organized hunting is from about 1 mya. Why did it take a million years after the development of tools for early man to begin using them for hunting purposes? Paleo-scientists have been puzzling about this for years, and especially since the spectacular find of the fossil somewhat curiously named "Millicent" in the back of a petrol station in Addis Ababa.
      The suggestion is, and the evidence for it is mounting, that the increase in hominid smelling abilities bestowed upon them a tremendous advantage over all those others who really couldn't smell at all well, and that the gene controlling the morphology of the face that produced the largest nose was adaptively selected for, and at the same time the increase in nasal dimensions and the probable concurrent behavior pattern of nose-picking caused their owners to be even more successful, and thus for the activity to be carried on.
      Whether Miocene sivapithecine apes picked their noses and consumed the detritus thereof as a dietary supplement during times of resource scarcity (Barnesdale, 1975; Stevens, 1981; and Marshall et. al., 1983), thereby expanding their noses and allowing them to better adapt to the conveniently spreading open woodland environments, or whether they adapted to the savannah first, discovered that their noses were getting bigger, and only then began to utilize them as food, are questions that are difficult to answer at this point.  The crucial early phalange material that might reveal when the digits began lengthening is unfortunately missing.

Pongid behavior studies

      The literature is replete with reports of various types of nose-picking activities in several extant species of pongids in at least two widely-separated regions of the world, subtropical East Africa and tropical Southeast Asia. The species that have been covered the most extensively are the western lowland and mountain gorillas, the Bornean orangutan, and Pan troglodytes and paniscus, the common and pygmy chimpanzee.  The eastern lowland gorilla is extremely nasty, and has not been researched much for that reason, while the Sumatran orangutan was the subject of a ten-year project which unfortunately came to a bad end when the Danish researcher who was studying them was overcome with exhaustion and was unable to fight off pirates while crossing the Sulu Sea and unhappily lost all his data overboard.
      Glicks spent two years at the Kutai Nature Reserve in East Kalimantan.  The avowed purpose of his study was specifically to collect data on orangutan nose-picking activities.  He was interested in diurnal-nocturnal and seasonal variations, and infraspecific differences in orangutan dietary patterns and preferences.  If only he could have collected some data, it would have made his project all the more worthwhile and exceedingly germane to the topic of this paper, but he was ill for the first twenty-two months, being too weak to do much more than call for an occasional cup of tea.  By the time he had recovered, his grant had run out and he was forced to seek other employment.
      Bidwell and MacCown on the other hand met with a great deal of success in their far-reaching study of orangutans and gibbons.  Their study area was the northern half of Sumatra, all of Borneo, and certain areas in Malaysia and Thailand.  Although the winds were variable and it was frequently difficult to see down from the balloon, they managed to compile life histories including dietary preferences and activities for 127 individuals, logging 12,372 balloon hours in the process.  Their correlation of periods of resource scarcity and nose-picking frequency demonstrated quite clearly the fact that there are fluctuations in food availability and that orangutans are not above doing a little nasal prospecting when the hunger bug bites.
      It is to be expected that a food resource item might be competed for during a time of scarcity, and this is precisely what Bidwell and MacCown's data shows (Bidwell and MacCown, 1979).  Although orangutans are primarily solitary animals, they do sometimes congregate around an individual who either has a large nasal capacity or else is too weak to defend its own nose.  In these associations, it is invariably the largest adult male with the fully-developed cheek pads that is in the best position to take advantage of someone else's nose.  In three recorded instances, they observed adult females moving toward an actively-picking male, although they couldn't be sure and admit that they could have been moving away.  The use of infrared detectors to track wild orangutans has since been discontinued.
      Over the four-year study, a fairly good idea was gained of the seasonal pattern of Sumatran and Bornean vegetation.  All trees over 10 m. in height were mapped, roughly measured, and identified as well as possible from the balloon.  A total of 495 new species of dipterocarps was recorded, along with 1,376 new fruiting shrubs and 2,632 new species of flowering vines.  Although the orangutan is an opportunistic eater and will readily adapt to a new food source, it has approximately a dozen favorite food species.  It is in areas where or at times when there is not at least one of these species available that the orangutan turns to its nose.  Table 3 shows the relationship between the fruiting of sven major food species and the frequency of nose-picking:

Table 3

Species

Dracontomelon mangiferum
Koordersiodendron pinnatum
Pandanus epiphyticus
Kompassia excelsa
Dillenia borneensis
Jarandersonia sp.
Ficus albipila

1974

90.8
94.1
84.9
89.0
92.8
93.6
 92.5
1975

92.3
89.6
88.0
92.1
90.0
94.1
 91.8
1976

86.5
92.6
95.2
94.9
88.7
90.5
 93.6
1977

90.6
93.1
94.5
97.4
92.6
89.2
 94.3
Figures are a function of 100% as a perfect correlation between food scarcity and nose-picking frequency.
      In marked contrast to the orangutan, the gorilla lives in a group environment that makes it possible to collect much more data in a shorter period of time, which is convenient for the researcher, although when there are six to eight individuals all within sight and all actively picking their noses, it is sometimes difficult to maintain one's composure. And whereas the orangutan has completely returned to the forest*, the gorilla and chimpanzee occupy varied habitats more similar to those to which the African sivapithecines adapted


*  The orangutan as has been mentioned is almost certainly descended from the Asian sivapithecines.  Cheek tooth enamel, nasal orbit size, and a suite of shared derived characters show this clearly.  The sivapithecines were adapted to more open svannah-type woodlands, although the Siwaliks and China retained a more laurophyllous vegetation until the late Miocene, and so it is no surprise that middle Pleistocene fossils of the extinct orangutan Pongo pygmaeus weidenreichi show marked skeletal adaptations characteristic of more terrestrial locomotor patterns, indicating that their arboreal existence is a relatively recent development.


      Chesley Wottenham spent his entire life attempting to study gorillas.  He shuttled back and forth between Zaire and Gabon every few weeks, back and forth, observing first Gorilla gorilla graueri, the eastern lowland gorilla, and then G. g. gorilla, the western lowland gorilla.  He amassed a mountain of behavioral research data that was the envy of every worker in the field, despite the general nastiness of the eastern sub-species.  The trouble was that bus service was very bad between Zaire and Gabon.  The roads were not good, and neither were the facilities for obtaining drinking water, or for eating a meal, or for staying the night, or for buying groceries, or pharmaceuticals, or clothing, or lamp fuel, or reading and writing materials.  Twenty years of that was all he could take and then he died.  (See Table 4 for a breakdown of his various activities.)

Table 4

Activity

(% of time spent)
Observing G. g. graueri
Observing G. g. gorilla
Riding on the bus
Receiving therapy for injuries    sustained while riding on the bus

1915-
 1920

7.5
20.2
62.3
 10.0
1920-
 1925

7.0
24.3
58.7
 10.0
1925-
 1930

7.9
22.8
59.3
 10.0
1930-
 1935

5.3
10.1
70.6
 14.0
      Oxford University, for which he had been conducting the research as a doctoral thesis, unfortunately rejected his work and said that he had been a dyslexic and that for all those years he had been confused about east and west, thereby hopelessly muddying his data.  Still, his conclusions were interesting, but we don't have time to go into that here.
      The question of resource variability and its effect on pongid nose-picking was one that had fascinated Dr. Patricia Emory ever since she was a child.  Sponsored by the L.S.B. Leakey Foundation, she set off for Rwanda in 1980 to see for herself just what the noses of mountain gorillas were really like.  Having studied nasal structure at Princeton, she received her doctorate in paleonasology at the Charles DeGaulle Institute of the Sarbonne.  Like Bidwell and MacCown in Southeast Asia, she was scrupulous in recording the seasonal fruiting and flowering of each of the two dozen or so food species most utilized by the mountain gorillas.  Recognizing that gorillas are basically foliverous, she also recorded twelve of the non-fruit species favored by them, and Table 5 is a compilation of their nine most utilized food sources, tabulated similarly to Table 3.
Table 5

Species

Hagenia abyssinica
Hypericum lanceolatum
Senecio erici-rosenii
Pygeum africanum
Arundinaria alpina
Peucedanum linderi
Galium spurium
Rubus runssorensis
Helichrysum formosissimum

1981

95.8
92.1
82.4
84.2
88.2
94.2
91.3
85.1
 98.6

1982

96.2
89.4
86.1
78.5
89.2
96.1
92.8
89.6
 93.9

1983

92.9
90.0
80.2
77.5
88.2
95.6
95.4
72.8
 97.8

 
 

      It is evident that there are greater fluctuations in the data with regard to the mountain gorilla than for the orangutans.  Certain food species, it would appear, are a must for this animal, Helichrysum for example, and Peudedanum, without which they turn to their noses like children to a favored blanket.  Rather than look for some less-favored food, they will sit in a circle, whimpering quietly, and picking their noses.  There are other food species however that do not evoke this kind of behavior, which Dr. Emoryi has termed "nose crying."  On the whole, it is fair to say that despite greater variance in Gorilla than was the case with Pongo, there is still a high degree of correlation between resource levels and nose-picking frequency.
      In February, 1983, Emory's Group 5 occupied a saddle region which was relatively devoid of food sources during a time when the lower altitude Hagenia and bamboo had both suffered a greater than normal die-off, and the amount of time spent during the day picking the nose increased by over 45% over the same period the year before and 40% over the average amount of time for all months over the previous year.  Time spent nose-picking by Group 5's resident silverback, "Wally," increased by 38% over the same period the year before, and by 29% over the average amount of time for all months of the previous year, while juveniles and younger females increased their time spent nose-picking by amounts that varied from 43% to 59%.  (Time spent picking another individual's nose was not included in this figure.)  When Wally led them across a brushy ridge to where there was a thick stand of nettles, they almost immediately reduced their nose-picking time. (Emory, 1984)
      Over the approximately thirty-six months of Emory's study, Groups 6 and 8 were the most consistent nose-pickers, while Group 2 had several individuals who never picked their noses.  Dr. Emory became convinced that nose-picking for the mountain gorillas was not just a dietary phenomenon, but a psychiatric one.  She came to believe that it was therapeutic for the animals to pick their noses, and that certain animals offered their noses up for social picking much as a psychiatrist might offer to absorb the pain and confusion of a sick patient.  The Leakey Foundation suggested that she had gone off the deep end, and withdrew their sponsorship and funding, and she returned crestfallen to her Chair at Princeton with little to show for her three years in the bush.
      Perhaps the best studies of pongid nose-picking have been those of William Barnesdale (1975) and Merton and Nishida (1985), both of which focused on Pan troglodytes, the common chimpanzee.  Badderson, James and Harrison have also conducted field studies.  Despite the number of reports which have been published, little is understood of the role of nose-picking in mediating the relationship between the environment and social structure. Chimpanzee sociality exists within the context of a fusion-fission society, characterized by female exogamy and territorial maintenance by bands of large-nosed males that roam the countryside occasionally engaging in fierce clashes.  Adult females seem to prefer solitary nose-picking, except when mating, but the younger females and adult males pick their noses in groups.  It is unclear at this point whether this activity is a kind of socializing process for chimpanzee infants, but both of the above-mentioned studies record numerous observations of one- and two-year olds playing games that appear to revolve around the nose.
       Whereas adult male orangutans clearly dominate nose-picking activity in Borneo, and adult male gorillas are somewhat less inclined to pick their noses than females and adolescents, adult male chimpanzees within their group are very prone to sharing without regard to the individual's hierarchical position.  Such sharing behavior has been reported by several observers, and seems to occur most often during the first couple of hours after dawn.  It has been suggested that the nasal resources might be more plentiful at that time (Badderson, 1978), but in Uganda, Merton and Nishida (1985) found a morning and afternoon peak.  Barnesdale was the first to report on nocturnal nose-picking.  Having tried Israeli Secret Service infrared binoculars and long-range directional microphones with no success, he took to disguising himself as a very large branch, and on three separate occasions a different chimpanzee male used him as part of its nest.  It was extremely uncomfortable but well worth it, when up close he witnessed for the first time wild animals in their natural habitat, picking their noses at night.
      Solicitation to pick another individual's nose is something that apparently occurs quite frequently.  The one doing the soliciting approaches the other, gives the characteristic hhrrr hhrrr nose bark, and gently rubs the other's nose with his outstretched hand held palm downward.  The other has the choice of moving away or allowing the nose-picking to take place.  There is only rarely an element of force in these encounters (Merton and Nishida, 1985).
      William Barnesdale was the Raymond Dart Visiting Professor of Facial Structure when he took over the Christian Primate Center in Talahassee and immediately left for Tanzania to study the chimpanzees of the Gombe Stream Reserve.  Jane Goodall was unable to prevent him from going there, and he set up a camp about two hundred meters from hers.  He and six native assistants collected data from all-day observations on as many successive days as possible.  Time samples were taken, activities were recorded, and vegetational patterns were noted, all the while ignoring Ms. Goodall's complaints about their presence.  Whereas Ugandan chimps (Merton and Nishida, 1985) preferred various Ficus species and Cordia mellenii, the Tanzanian chimps seemed partial to Parinari curatellifolia and Landolphia lucida.
      The following activity budget was tabulated on the basis of Barnesdale's data, which must nevertheless be looked at with a degree of skepticism since most of the notes written by his assistants were mysteriously damaged in a freak rainstorm and laboriously and only partially reconstructed several months later when the rain stopped.  The percentages are of observational time and they appear to demonstrate a fairly regular inverse relationship between feeding time and nose-picking time.  The reader should also be aware that of his six assistants, five of them were chronic alcoholics and were inebriated much of the time from drinking the potent liquor they distilled from the vine of the Aspilia tree every morning before Barnesdale got up.

Table 6

Activity by month as a % of time

Feeding
Resting and grooming
Travelling
Playing
Picking the nose
Digging in the dirt
Attacking others

Jan/Feb

32.1
24.6
15.0
6.9
13.2
3.0
 5.2

Mar/Apr

30.1
22.8
18.2
4.1
16.1
1.3
 7.4

May/Jun

34.6
23.4
15.9
8.2
9.3
2.3
 6.3

Jul/Aug

30.6
20.8
17.9
6.2
17.2
0.0
 7.3

Sep/Oct

32.3
21.7
16.2
6.3
15.6
1.8
 6.1

Nov/Dec

31.5
22.6
17.1
5.6
15.4
0.3
 7.5

      Although he did not specifically correlate nose-picking with resource variation, Barnesdale concluded that the activity did serve a necessary purpose, and had been or still was adaptively advantageous.  In one of his last letters before being arrested, he pointed out with a great deal of satisfaction, I believe, that Tanzanian chimpanzees spent more time picking their noses than did their Ugandan counterparts, and that group size at Gombe was invariably larger.
      Behavior studies of extant pongids over the past fifteen or so years, in addition to those from the earlier part of the 20th century, all agree on two things: great apes pick their noses, and when food resource species decline for any reason, nose-picking frequency increases.  The enlarged nostril volume and lengthened phalanges of Pongo, Pan, and to a lesser extent, Gorilla, are obvious morphological adaptations for nose-picking.  It seems clear that the pongids share with Homo the sivapithecine legacy of picking the nose, and thus when our mothers tell us not to pick our noses, they are denying the logic and rationale of evolutionary biology.  Whether or not the current identification of the KRU-234 fossil from Kenya as Australopithecus nostrilis holds up, the questions remaining to be answered are fascinating ones, and deserving of further study.  Regretfully, this researcher must leave these questions to others.
      I gratefully acknowledge the unstinting support of the Primate Behavior Research Group at Harvard University, the L.S.B. Leakey Foundation, the Ugandan Natural Parks Directorship, the National Wildlife Council of Gabon, Professors Arthur Barber, John Phillip Grant, Maxine Underhill, Lewis Keirfallow and Umbley Nottingham at the Columbia Nasal Research Institute, and the Ford Foundation.  I am indebted to my many colleagues in the fields of primatology and nasal morphology who consented to read this paper and make suggestions.  Additional funding was provided by the Royal Nasal Society of London, the Gorgonzola Monkey Club, and the Association Against the Use of Pongids for Experimental Testing.
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Burrowing Behavior
of Wild Bluetail Monkeys
at the Makokou Study
Area, Gabon
Comparative Plummeting
Rates in Ten Species of
Old and New World
Lesser Primates
Zoological Bromides:
Right or Wrong?
The
Primate
Nooz

 
© M. Charters, Sierra Madre, CA.