- Ape's nest controversy -


Yes, probably,
but their terrestric nests were much more important! <1>

Critical notes on how the Yerkesian term "constructivity" became lost in primatology!

A reply to 'Current Anthropology'

by Nold Egenter

February 1998

References are given only if necessary in the present context. For references given by the report of Sabater Pi et al. the original should be consulted.


The above main title is the header of a recent, fairly sensational report in Current Anthropology submitted by Jordi Sabater Pi et al. (1997). It starts fairly innocently with the generally accepted 'credo' "that primatology can offer valid information regarding the behaviour of fossil hominids" and then, introduces the particular topic:"Nesting is one fossil hominid behaviour on which the behaviour of modern apes may shed light." Evidently, the emphatic style of the report is based on new research results! Contrary to conventional ideas that early hominids moved exclusively in upright posture ("terrestric bipedalism"), recent studies indicate the persistence of arboreal anatomical characteristics of the earliest hominids. Consequently, the core of the report maintains a five-point program in support of the claim that "Australopithecus and even H. habilis ... should have nested in the trees as do modern apes." The points are:(1) recent 'mosaic theses' of Miocene and early Pliocene biotopes, (2) postulates that 'due to"deficient nocturnal ... vision" diurnal primates are at "considerable disadvantage" with carnivores, therefore "apes seek safety at night in relatively inaccessible refuges, individual nests which they build in the branches of trees." Point (3) gives a quantitative comparison of mammal populations in savanna and forest ecosystems in regard to herbivores and carnivores suggesting that in open spaces "trophic pressure is high", whereas"in dense forest, trophic pressure is low" (leopard only). Point (4) then refers to fire as "absolutely essential to ward off possible attacks by carnivores" and adhering to currently accepted data relating controlled fire to final Homo erectus and archaic H. sapiens. "Australopithecines, H. habilis and Paranthropus had no knowledge of fire...". Consequently "as they moved through a mosaic of biotopes with an abundance of forest areas and a high presence of predators, it is highly likely that they built nests in trees in which to sleep." Point (5) then - we have mentioned it already - gives the conclusion:"Without fire, with practically no nocturnal and crepuscular vision and a type of sleep that requires a recumbent position, and given the danger represented by the large carnivores, Australopithecus and even H. habilis.... should have nested in the trees as do modern apes."


For those who know the history of observation and research into the great apesÕ nest building behaviour, this sudden emphasis on the tree-nest and its anthropological implications is puzzling. Evidently it is dramatically triggered by recent finds of "arboreal anatomical characteristics in Australpithecus and Homo habilis". But, what happened to the apeÕs nest in general and its high complexity (Yerkes/ Yerkes 1929, Groves/ Sabater Pi 1985)? What happened to the terrestric ground nest? What shall we do with the most important characteristic of hominids and humans, bipedic posture and free handedness, if Homo habilis still nested in trees like chimpanzees?

But, let us first see how this recent report looks at nesting behaviour in general. "Nesting unites members of social units during sleep and the long periods before and after sleep." In the process of hominisation, this "may well have had an active socialising function, culminating in home bases ... or fixpoints (Groves and Sabater Pi 1985)." Surprise! Cultural evolution through collective sleep? Is the nest of the great apes only part of a social pattern?

Evidently, the structural elements of nest-building have moved into the background. Sabater Pi et. al.'s evaluation of nest building in general adheres to the recent 'evolution theory' of the apeÕs nest (Fruth and Hohmann, 1996:from 'feeding nest' on the ground to sleeping nest in trees) and the resulting new interpretation of the nest in the framework of sleep. Sleep is considered positive for socialisation.

In spite of these substantial structural losses Sabater Pi et. al. still cling to their former extrapolation of the apesÕ nests in direct line to hunter-gatherersÕ camps as 'fixpoints'. But, how do they now trace this line from nests high up in trees, located in dense forest-refuges, down to the terrestric campsites of gatherer / hunter societies with their shelters and huts? Note that already the discussion in Groves/Sabater Pi (1985) was fairly naive in view of the nest's cultural extrapolation. Camps of hunter-gatherers were simply called "nests" in several cases and the question "Why did nests become reusable and long lasting?" [in view of gatherer / hunter's camps] demonstrates a complete ignorance of the structural complexity of the nest and its evolution.<2>

Further, Sabater Pi's theory based on trophic pressure is highly questionable, particularly if the night camp of the great apes is not just described in the schematisms of Hediger's terms, but is looked at structurally and spatially and in view of the individuals topologically engaged. Kawai and Mizuhara (1962) were - if I am right - the only ones who drew maps of such night camps (mountain gorilla). Interpreting this plan we become aware that the night camp of gorillas is socially and spatially arranged in order to keep the environment under control. <3> Any predator would risk being attacked by the group. These 'defensive' or 'strategic' characteristics of the night camp of higher apes might have provided a much wider spectrum of choice than Sabater Pi assumes.

No doubt, the recent report owes its basic motive to the attempt to find datable support by fossile records. Everyone knows, the nest is directly not provable (its durability is about 2 months!). But, indirectly 'arboreality of early hominids' points to nest building in trees if one follows the 'credo'. In other words, the report is adapting to fossile records and other 'current' microtheories supporting the otherwise purely speculative postulate of nests among the earliest hominids.

The scientific policy of Current Anthropology favours such quick adaptions to new research results. But, in this particular case it may be rewarding to go back in time and to place such 'current' microtheories into a quite different and theoretically more fertile circle.


Doubtless, the Yerkes (1929) were the first to take the phenomenon of nest building among the great apes really seriously. They concluded their extensive survey of accumulated literature like the following:"The observed range of variation is from almost complete lack of tendency and capacity for construction of nest or bed to their definite presence in the anthropoid apes and their relatively high development in man. This comparison is peculiarly significant because nesting behaviour illustrates the appearance and phylogenetic development of constructivity, and, coincidentally, the transition from complete dependence on self-adjustment to increasing dependence on manipulation or modification of environment as a method of behavioural adaptation." (Yerkes/Yerkes 1929, :564).

It should be noted here that this was a tremendous statement, a masterpiece of scientific formulation! It clearly combines a microtheoretical position with a macrotheoretical outlook! <4>

Paradoxically post-Yerkesian primatology was not aware of the Yerkes' macrotheoretical implications. Research mentioned the nest, described it from various viewpoints, but left it essentially where it had been before the Yerkes:in the framework of social behavior. In short, a microtheoretical seclusion which - in spite of recent ecological extensions - continues up to recent research (Fruth and Hohmann, 1996).

In several papers and publications (Egenter 1982, 1983, 1987, 1990a, b, 1992) the present author, coming from the cultural side, had strongly focussed on the macrotheoretical implications suggested by the Yerkes (1929), considering the nest of the great apes definitely as a building and using it as the basic support of an architectural evolution (architectural anthropology).

In 1985 Sabater Pi published his 'Etologia de la vivienda humana' in Spanish (Sabater Pi 1985) and in the same year, together with Groves, their 'From Ape's Nest to human Fix-point' in 'Man' (Groves/ Sabater Pi 1985). The first and larger part of the latter gives very detailed descriptions of gorilla and chimpanzee nests from various points of view. Data are based on literature and on the authors' independent field research in Equatorial Guinea and Rwanda. Orangutan nests are mentioned at the end for completeness. A short second part then compares the data gained from ape nest camps to three types of hunter-gatherer camps, more or less on the level of Hediger's fairly abstract biological definition of 'fixpoint'.

I was very happy with these publications, since they confirmed my own research into nest building behaviour of the great apes. In addition, Groves/ Sabater Pi brought interesting new aspects, for instance the detailed lists on fairly differentiated uses of materials (grasses).

However there were also strong points in which views differed. Groves/ Sabater Pi (1985) did not mention the Yerkes (1929) in their study, thus implying that they were the first to give such broad concern to this topic. Their only reference to the history of nest building research is Du Chaillu 1861! To be frank, to someone who knows the history of research, this isolated reference is very misleading!

Consequently, Groves/Sabater Pi did not pay much attention to the difference between tree- and ground nests. On purely quantitative grounds they attribute the former to chimpanzees, the latter to gorillas in spite of the fact that both (all) species practise both types of nests. This negligent classification is also at the basis of the recent report. It stipulates the chimpanzees as the model of the 'first Hominids', as nest builders in trees. In view of 'constructivity' however, the difference between tree nests and ground nests is fundamental. Only the ground nest can be considered as a valid prototype of hominid and human constructions.

Further, Groves' and Sabater Pi's (1985) macrotheoretical connection to more or less temporary 'fixpoints' (Hediger) of modern gatherers and hunters camps and huts ("nests"!) is too narrow and schematic, evidently a biological extrapolation on cultural conditions. The abstract comparisons cover up the factual condition of buildings. Structurally the semi-elliptically interwoven huts of African pygmies are very different from the apes nests which are merely triangularly knotted with rooted plants. Use too among both is very different. The nest is a supporting structure, the animal uses the resulting surface, the nest, as sleeping bed, whereas the Pygmy huts are a fairly evolved architectural type ("domestic architecture") providing protected inside space with an opening for access. (Foy 1984). Consequently, one should remain open for theoretically broad outlooks on the anthropology of constructive behaviour in the macrotheoretical sense of the Yerkes. Doubtless there are common factors in view of environment and territoriality between the night camps of the great apes and human camps and settlements, but they cannot be solved simply by projecting 'biologisms' on cultural conditions.

Parallel to this text the present author also wrote a review of McGrew's recent book "Chimpanzee Material Culture - Implications for Human Evolution". Except some insignificant references to nestbuilding it deals exclusively with tools. In view of the factual quantity of nestbuilding among all great apes (during his average life-time one individual builds a virtual tower of about 11 times the height ot the Eiffel tower in Paris!) and its existential importance (rest and sleep during nightly half of their life), it appears scientifically very misleading to call the highly marginal tool-making and tool-using behavior 'material culture'! The focus on the toolmaking is not only a fixation to the very questionable concepts of the archaeological method, it is primatologically a regress to pre-Yerkian times, where studies were limited on apes in captivity (with practically no nestbuilding) providing a void in which Kšhler's experimental tool-ideology could gain importance.


On the basis of "constructivity" (Yerkes 1929) tree- and ground nests are fundamentally different, not only in view of their locomotory background (arboreal, terrestric), and its evolutionary implications, but in view of the "environmental" conditions, and particularly in regard of material aspects of construction.

The tree nest "borrows" its tectonic qualities from a vertical tree and its branches. Materially there is very limited choice. It is conditioned by the pre-selection of a certain type of tree. However, the adaption of the primary tree nest to terrestric space first led to a definitely proto-human architectural form (static triangular structure generated by interweaving, binding and knotting technology, foundations left naturally) with a potential for physical and cognitive impacts on the builder. And, secondly, with the terrestric nest type the potential choice for 'building materials' increased considerably. This is described in details by Groves/ Sabater Pi (1985).

In view of 'cultural constructivity', however, this was limited on rooted 'building' materials. Very likely, Miocene apes had to build nests and sleep or rest where they found rooted materials fit for their constructional capacities as this is common among all species of great apes today (topological identity of biotope and structurotope). Three things were not yet 'discovered' <5>:1) cutting materials, 2) transportation of materials and 3) artificial fixation of tectonic structures in the ground. Increasing topological divergence between biotope(s) and structurotope(s) may have favoured two important developments:new criteria for the selection of sites and the trend from 'single plant types' (Groves/ Sabater Pi 1985) to 'mixed plant types' of nests or buildings. Anyone familiar with 'architectural anatomy' or, professionally, 'structural systems theory', will be aware that these parameters open up a tremendous potential for a constructive evolution (for archaeological support see below).

A further point is important. If we become aware that ground nests remained rooted 'buildings' in a primary phase, we gain new hypotheses why stone tools might have been important in cultural development. Not primarily because they were good for butchering and slaughtering, but because they triggered the first "architectural revolution". Plant materials of increasing variety and stability could be cut and transported to places selected with new parameters. Different materials could now be combined into the same built form. Very likely this triggered not only a formal, but also a functional diversification of fibroconstructive buildings and objects.

It is historico-methodologically very short-sighted if primatologists operating within a framework focussed on human evolution with its considerable time dimensions, rely on a historistic system (archaeology:man the tool-user) which - as the 'extended arm of written history' - had, in fact, its origins in the Middle Ages. The narrow "beliefs" it produced in its primary phase should still keep scientists skeptical in regard to the historical method and its claims to be an "exact" science. Seemingly reliable microtheories can fairly quickly be superseded and outdated by macrotheories. Darwin was probably most instructive in this respect, using systematic parameters for the 'history' of creation of plants and animals including man! The narrow historical interpretation collapsed.

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