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In our
attempts to view the human situation in meaningful perspective, it is
essential that we take account not only of our cultural background,
but also of our biological history. For the human species evolved in
an environment very different from that to which most of us are exposed
today, and it was this evolutionary environment which determined, through
natural selection, the innate characteristics of the species. While
this fact has important implications for many of the major problems
facing human societies today, this paper concentrates for the most part
on a single aspect, namely, the biological history of Homo sapiens
as it relates to problems of human health and well-being in the modern
world. It concludes, however, by suggesting that this evolutionary approach
to the health requirements of the human organism can lead to insights
of relevance not only to public health, but also to the major social
problems of our times, including the ecological predicament.
For the
purposes of this article, I define "biological determinants of
optimal health" as those various conditions which tend to promote
or permit optimal physiological, mental, and social performance in an
animal in its "natural" or evolutionary environment. They
may also be defined as those various conditions which tend to promote
the kind of functioning of mental and physiological processes most likely
to ensure the survival and successful reproduction of the individual
in the natural environment. Whereas, in the case of human beings, this
degree of health is certainly not necessary for survival and reproduction
under modern urban conditions, I contend that it is nevertheless a most
desirable objective in terms of life enjoyment.
The Darwinian
theory of evolution through natural selection assumes that populations
of animals are heterogeneous, in the sense that there are inheritable
differences between individuals, and that, because of these differences,
in any given set of circumstances certain individuals are more likely
than others to survive, reproduce, and successfully rear young. The
individuals which are better suited to the prevailing conditions tend
to contribute more to the genetic constitution of subsequent generations
than do those which are less well suited, so that eventually the population
as a whole tends to become better suited to these conditions. From time
to time, changes spontaneously occur in the genetic material (due to
recombination, mutation, etc.). If an individual carrying such new genetic
characteristics is, as a result of the change, less well suited to the
prevailing conditions and consequently less likely to survive and reproduce,
then the new genetic material will, before long, be eliminated from
the population. If, on the other hand, the individual with the new genetic
characteristics turns out to be better suited than its fellow to prevailing
conditions, it will tend to contribute more offspring to the next generation,
so that eventually the new characteristics will spread in the population,
ultimately replacing the less advantageous characteristics. Thus, over
many generations, populations tend to become better and better suited
to the environment in which they live.
Phylogenetic
maladjustment
The important
corollary to Darwinian theory that I wish to stress has not been given
a name, but I shall refer to it here as the "principle of phylogenetic
maladjustment". According to this principle, if the conditions
of life of an animal deviate from those which prevailed in the environment
in which the species evolved, the likelihood is that the animal will
be less well suited to the new conditions than to those to which it
has become genetically adapted through natural selection and consequently
some signs of maladjustment may be anticipated. Obvious though this
principle is, and obvious though it's importance, it is seldom referred
to in the literature, and consequently its significance seems to have
been largely overlooked. Although highly pertinent to the study of health
and disease in mankind, I have not seen the principle mentioned in any
of the standard textbooks of medicine. I have come across only two clear
statements of the principle in the medical literature-one in the introduction
to The Saccharine Disease by Cleave and Campbell (1966) and the
other in Man's Presumptuous Brain by Simeons (1960).
The term
"phylogenetic maladjustment",(note-The maladjustment is phylogenetic
because it represents a characteristic response of the species to the
changed environmental circumstances.) then, specifically refers to disorders
which represent the reactions of organisms to conditions of life which
differ from those to which the species has become genetically adapted
in evolution through the processes of natural selection. This principle
relates not only to environmental changes of a physiochemical or material
nature, such as changes in the quality of food or air, but also to various
non-material environmental influences, such as certain social pressures
which may affect behaviour. Furthermore, signs of phylogenetic maladjustment
may be physiological, behavioural, or both.
We can
easily think of countless examples of the principles of phylogenetic
maladjustment operating in Homo sapiens . The traditional "scourges"
of mankind such as plague and typhus and the great deficiency diseases
such as scurvy, beriberi, pellagra, and kwashiorkor are all straightforward
examples of the principle. An examination of reports on the reasons
why patients visit their physicians in the most developed countries
in Western society today (e.g. Logan and Cushion, 1958) shows clearly
that the majority of the disorders of which they complain fit into this
category, and are "diseases of civilization", in the sense
that they would have been rare or non-existent in primeval society (e.g.
virus infections of the respiratory and alimentary tracts, peptic ulcer,
cardiovascular diseases, obesity, diabetes, and probably much psycho-neurosis).
Removal
of "optimum health"
It is worth
emphasising that one of the most significant influences of civilisation
on the biology of mankind has been the removal of "optimal health"
as a prerequisite for individual survival and reproductive success.
In the evolutionary environment, survival and reproductive success were
dependent on superb physical fitness, acuity of vision and hearing,
absence of debilitating or painful illness, mental alertness, a good
memory, and a state of mind which permitted, when necessary, concentration,
patience, and a willingness to co-operate with others. None of these
attributes is necessary for the individual's survival and reproduction
in the protective environment of modern society, although, clearly,
many of them are important in relation to life enjoyment. This molly-coddling
influence of civilisation has been referred to as "pseudoadaptation"
(Boyden, 1970; 1972a. & b.) because, while it mimics true adaptation
by allowing the survival and multiplication of human populations under
changed environmental conditions, it differs from true adaptation in
that it does not involve any active response on the part of the individual
or of society, and consequently the forms of maladjustment are permitted
to persist indefinitely.
Before
proceeding further, it may be as well to refresh our memories on a few
aspects of human evolution. It appears now that there were already beings
on earth at least two million years ago conforming to Leakey's (1961)
definition of "man" (i.e. an animal that makes tools to a
set and regular pattern). These people were, of course, rather different
from ourselves in that their cranial capacity was about half that of
modern man and there were other morphological, and no doubt behavioural
differences.
By 300,000
years ago, however, human culture was perpetuated by beings who differed
only slightly from modern mankind in their physical characteristics,
although the average size of their brains was still somewhat less than
the modern average. But our ancestors of 60,000 years ago had a cranial
capacity at least as big as ours, and they are classified as belonging
not only to the same species as ourselves, but also to the same subspecies,
namely Homo sapiens sapiens.
That was
some 2,400 generations ago. It was not until about 400 generations ago
that, in certain regions of the world some of our ancestors, for reasons
unknown to us now, gave up the nomadic hunter-gatherer way of life for
a new kind of economy based on the domestication of plants and animals
for food production and on a lot of hard work. This domestic transition
was thus a very recent even in the biological history of mankind. Accordingly,
we can safely infer that the innate phylogenetic or species characteristics
of mankind were determined by the selection pressures operating in the
primeval environment and were already established by the time of the
advent of civilisation. (note-"Primeval" in this paper refers
to the long hunter-gatherer period of human existence before domestic
transition.) In the context of the present paper, the important point
is that the innate biological determinants of human health were established
under primeval conditions, and any innate needs that mankind may have
for survival or well-being could be satisfied under those considerations.
It follows from these considerations, and from the fact that Homo
sapiens is no exception to the principle of phylogenetic maladjustment,
that any deviation that can be recognised from the primeval conditions
of life must be suspect as a possible cause of physiological or behavioural
disorder. For this reason, knowledge of the biological conditions of
life of primeval mankind is distinctly relevant to our concern for the
health and well-being of mankind now and in the future.
Let us
attempt, therefore, a very brief description of the biology of human
beings in typical primeval society in much the same way as we might
describe the biology of the jack rabbit, the mountain gorilla, or any
other animal species (except that, in the case of Homo sapiens,
we do not have to make a special effort to resist the temptation to
anthropomorphise).
The following
description is written in the past tense, although many of the data
on which it is based are derived from the work of anthropologists on
existing (or until recently existing) hunter-gatherer societies. (note-The
description is based partly on justifiable inferences derived from general
biological principles and partly on data reported in the anthropological
literature which was reviewed by Frances Barnes in her article "The
Biology of Pre-Neolithic Man" (1970).)
The
biology of primeval mankind
Nutrition
and feeding habits:
The energy
required for growth, muscular work and basal metabolism was obtained
from food of both animal and plant origin. The relative proportions
of meat and vegetable matter varied according to circumstances, but
usually the greater part of the diet was, by weight, of plant origin.
Most of the food was brought back to the camp for eating.
Under favourable
or typical conditions, activities aimed at the collection of food probably
lasted for an average of two to three hours per day.
All hunting
(except for small animals, such as lizards) was carried out by men,
while the women, accompanied by some children, collected fruit, nuts,
roots, etc. Men sometimes also took part in the gathering of vegetable
food-stuffs.
Hunting
was an occupation which was almost certainly enjoyed by the men. This
sense of enjoyment in hunting may well be an innate characteristic of
the species, of survival value in the evolutionary environment, and
the product of natural selection. The same may well apply to food-gathering
in women.
In the
evolutionary environment, natural regulatory mechanisms operated to
ensure that, under normal conditions, the intake of energy was directly
related to the energy requirements of the body (Boyden, 1969). Much
of the energy consumed was, in fact, utilised in the various activities
associated with food-gathering itself, which involved periods of quite
vigorous exercise each day.
Hunting
combined the use of knowledge learned by experience and that transmitted
by culture (relating to the environment, animal behaviour, etc.); it
called for maximum use of intelligence; it involved the application
of learned physical skills; it was characterised by co-operation between
individuals; it was goal-directed (i.e. it had a built-in sense of immediate
purpose); when successful it had a built-in sense of immediate reward
- not only in the form of the satisfaction of hunger, but also in the
form of praise and smiles from other members of the group, especially
the women and children; it represented a challenge to the individual's
mental and physical prowess and to his courage; it provided a daily
outlet for aggressive feelings.
Rest
and sleep:
In hunter-gatherer
groups people tended to rest or sleep when they felt like it. Freedom
to respond to feelings of sleepiness by going to sleep resulted in a
polyphasic sleeping pattern, which typically included at least one nap
during the daylight hours, usually around midday or slightly after.
Sexual
behaviour:
Very little
is known of the details of sexual behaviour in primeval societies.
Creative
activity:
(a) Typically,
most individuals in hunter-gatherer groups spent part of each day making
and shaping things. This activity had the following characteristics:
(i) it involved the exercise of learned manual skills; (ii) it was goal-directed,
i.e. it had a built-in sense of purpose, as in the manufacture of weapons
for hunting or defence, or utensils for preparing food or of ornaments
to decorate the individual. It is noteworthy that the finished article
frequently appears to be the product of more workmanship and effort
than was necessary to render it functional, suggesting that some satisfaction
may have been derived from bestowing an extra aesthetic quality on the
object.
(b) Some
individuals in the hunter-gatherer groups specialised in such creative
activities as story-telling or music making.
Social
interaction:
Hunter-gatherer
bands varied in size according to the nature of the terrain, and other
factors. A typical band consisted of 30-40 individuals, including children.
Bands might split up, come together again and exchange numbers according
to circumstances (e.g. distribution of food supply, personality factors,
etc.). Flexibility seems to have been the rule.
Much time
was spent in conversation, discussing matters of mutual interest, exchanging
information on aspects of the environment, sharing problems and anxieties,
joking and story-telling.
Children
were shown much affection by adults, and the attitudes towards them,
especially small children, were generally permissive. While the parents,
especially the mother, were expected to take main responsibility for
their children, there was a good deal of communal co-operation with
respect to the minding of children. For example, small children might
be left with elderly members of the group at the camp when their mothers
went off to gather food, and sometimes one woman would take care of
several children other than her own for a considerable period.
In primeval
societies there was little evidence of sharp "generation gaps",
although the onset of puberty was often recognised as an important event.
Young children tended to learn skills and to acquire knowledge from
their older siblings or friends, who in turn learned from their older
siblings and friends, and so on. Elderly people were, under favourable
environmental conditions, treated with respect.
Strangers
and strange groups were regarded with suspicion. However, open hostility
between groups, involving physical violence, is not a feature of extant
hunter-gatherer societies although this is not to say that such hostility
never occurred in primeval times.
Visual
environment:
It was
an environment full of interest to the observer; it was characterised
by a certain functional harmony, and it was dynamic in the sense that
significant changes were occurring in it from day to day or from season
to season (i.e. it was never completely static - as, for example, a
room in a modern home may be). Another point of relevance is that, if
there are genetically-determined components to a man's aesthetic sense
(and I strongly suspect that there are), then these were determined
through natural selection by pressures associated with the visual environment
of the evolutionary period.
Health:
The mortality
rates in primeval society were much higher than in modern Western society,
and consequently the average age at death was much lower. The main factors
contributing to ill-health and mortality were probably injury sustained
in hunting and food-gathering (with subsequent infection of wounds)
and attack by predators. Neither infectious disease due to bacteria
and viruses nor malnutrition was a common cause of ill-health.
Biological
determinants of optimal health
We have
already noted that, if the conditions of life of an individual deviate
from those to which the species has become genetically adapted through
evolution, signs of phylogenetic maladjustment (physiological or behavioural)
are likely to arise. With this principle of phylogenetic maladjustment
in mind, I have utilised our knowledge of the conditions of life of
mankind in his evolutionary environment to draw up a tentative list
of some of the biological determinants of health of the human organism.
The list
is not presented in any particular order, although I have tended to
place the more easily definable "physicochemical" or "material"
determinants of health first. There is inevitably overlap between some
of the items on the list, particularly those concerned with behavioural
and social aspects.
(1) An
appropriate intake of calories neither in excess of, nor much less than
the requirements for basal metabolism, growth (in children), and physical
work performed.
(2) A well-balanced
diet of a quality close to that of primeval mankind.
(3) Clean
air. (note-The word "clean" in this list means "free
of noxious agents and harmful products of technology".)
(4) Minimal
contact with pathogenic microorganisms.
(5) Noise
levels not much above or much below the range experienced in the natural
environment.
(6) Minimal
contact with noxious and chemical compounds.
(7) Absence
of accessible physiologically and psychologically harmful drugs.
(8) A visual
environment which is interesting, which has aesthetic integrity, and
in which a certain amount of change meaningful to the observer is taking
place.
(9) Daily
periods of physical exercise, at times vigorous, and with clear goal-direction.
(10) Conditions
which allow natural outlets for the sexual drive, and a reasonable balance
between levels of sexual stimulation and sexual satisfaction.
(11) Opportunities
to rest and sleep in response to the urge to do so (by night or day).
(12) Opportunities
for spontaneous conversation with relatives and friends on matters of
mutual concern and interest.
(13) Freedom
to move at will from one social phase to another (i.e. from one small
group to another or to and from a state of solitude).
(14) Opportunities
for companionship and close friendship with other members of the in-group.
(15) Opportunities
for mothers to leave young children on occasion in the care of others.
(16) Opportunities
for frequent and unimpaired expressions of the universal behavioural
tendencies of the species (e.g. tendency to seek approval, or esteem
within the in-group, and to avoid ridicule, to compete with peers, to
explore the unknown). (note-This whole question of the innate behavioural
characteristics of the species is of critical significance in relation
to the major problems facing human society. It is also a highly controversial
subject [see Boyden, 1973]).
(17) Opportunities
and incentives for personal creative behaviour preferably with clear
goal-direction, involving especially the exercise of learned manual
skills, or in story-telling, music making, etc.
(18) A
considerable degree of emotional involvement and a sense of immediate
purpose in the main activities of the day.
(19) Conditions
which result in full awareness of a role of oneself in the in-group
or community.
(20) A
considerable degree of variety in daily experience and activity.
(21) General
opportunities for self-expression and self-fulfillment.
In essence,
then, this is a list both of the main features of the conditions of
life of Homo sapiens in the evolutionary environment of the species
and of postulated biological determinants of optimal health in modern
society.
Since it
is clear that many of the conditions listed are not features of the
pattern of life of the modern city dweller (note-The range of deviation
in the conditions of life from the primeval pattern is extensive. A
fairly comprehensive list of these deviations has been presented elsewhere
(Boyden, 1972c.)), the question arises, in the case of each deviation
that can be recognised from the evolutionary pattern, whether or not
the change is giving rise to phylogenetic maladjustment in any form,
physiological or behavioural, severe or mild. (note-Lest I be accused
too readily of Rousseauian romanticism, let me hasten to repeat that
neither attack by predators nor serious injury sustained in hunting,
which were common causes of death and suffering in the primeval situation,
are features of life in modern urban communities, and that consequently
the average age at death is much higher now than it was then. Moreover,
infection of the tissues with microorganisms is far less likely to result
in death today than was the case in the primeval environment.)
In some
instances, of course, the connection has already been clearly established
between certain environmental changes associated with civilisation and
certain forms of phylogenetic maladjustment. For example, crowding in
cities, in the absence of appropriate cultural adaptation involving
the introduction of new standards of hygiene to suit the new conditions,
results in alterations in host-parasite* relationships so that item
number four on our list - minimal contact with pathogenic microorganisms
- is not satisfied and severe signs of phylogenetic maladjustment are
manifest in the form of various contagious diseases.
(*The term parasite is used here in the general sense to include bacteria,
fungi, viruses, protozoa, helminths, etc. potentially parasitic in the
human species.)
Implications
for modern society
While the
modern urban environment in the developed countries satisfies the survival
determinants for the average individual, it may not do so well with
respect to the well-being determinants. The average man and woman are
not, for example, involved each day, as were their ancestors, in personal
creative activity; their levels of physical exercise are much diminished;
their opportunities for resolving personal tensions by the reaction
of mutual avoidance are restricted; and society imposes on them a monophasic
sleeping pattern. Even more importantly- the average urban dweller is
little involved emotionally in most of his daily activities. "The
shining eye, ease of movement and quick heart beat which reflect the
adaptation to enjoyable or emotionally inspired activity" (Minc,
1970) are rare sights in the modern city. This culturally-imposed divorce
of the functions of the cerebral cortex and the limbic system deprive
the individual of a sense of immediate purpose and of enjoyment in his
daily routine. Moreover, it has been argued on neurohormonal grounds
that this change may result in various forms of phylogenetic maladjustment,
including cardiovascular disease and "minor morbid conditions which
are so common today: headaches, lassitude, irritability, depression,
and possibly aggression" (Minc, 1970).
The arguments
put forward here represent a development of the idea that an evolutionary
approach to the study of mankind in the modern world can help us to
view the human situation, and both the advantages and disadvantages
of civilisation and technology, in meaningful perspective. By way of
conclusion, it would be useful, I feel, to attempt a brief summary of
the impact of technology on the biology of the human species:
(1) Modern
technological society, by the protection it provides against the primeval
causes of death, by making greatly increased quantities of food available
and, more recently, by the protection it has afforded in more developed
areas against the great lethal diseases of civilisation, has increased
to an extraordinary degree the number of specimens of the human species
that can exist on earth at any given point of time and also their average
life-span.
(2) Technology
has increased to a remarkable degree the impact of the human species
on the biosphere. An idea of the scale of human activity can be gained
from the fact that, as a result both of the massive population increase
and of the even more explosive spread and development of technology,
the human species is now utilising energy at about the same rate as
all the other land animals and plants put together (Boyden, 1972c).
The rate of energy utilisation, which is a fair measure of the impact
of human society on the total environment, is increasing exponentially
at about double the rate of population increase. (note-Part of the dilemma
lies in the fact that ever-expanding industry and advancing technology,
which are supposed to lead to an increased "standard of living",
represent, in effect, a frantic effort on the part of society to continue
to provide very simple and basic human needs (e.g. an adequate and balanced
diet and freedom from pestilence). Ever-accelerating technological advance
seems to be necessary in order to maintain the status quo in terms of
the essential requirements of the human organism. A sophisticated food
technology and an efficient transport and distribution system are essential
if people in the great Western cities are to receive an adequate and
balanced diet. The two automobiles per nuclear family, now common in
some sections of Western society, provide the family with (a) some prestige,
(b) the means by which the adult male can reach his place of work, (c)
the means by which the female can visit relatives and friends and procure
provisions, (d) the means by which the children can participate in group
activities, (e) the means by which they can all visit the natural environment.
It was possible for every one of these human "needs" to be
adequately satisfied in bygone societies, even before the invention
of the wheel, let alone the internal combustion engine.) It is clear
that, if civilisation is to survive, a state of equilibrium must be
restored to the biosphere.
The solution
to the problem, if there is one, must surely lie, not in further mindless
intensification of technological and industrial effort, with increasing
GNP as the sole objective but rather in a re-organisation of society
based on increased emphasis on the quality of individual lives and involving
some fundamental changes in our value systems. The materialistic objectives
of the Western world have been questioned by moralisers and philosophers
for a long while, but the growing awareness of the threats to human
survival in the ecological situation now adds a practical flavour to
the problem. Questions such as "Where are we?", "Where
are we going?", "Where do we want to go?", and "What
is progress?" are taking on a new and urgent significance. It has
been a theme of this paper that human biology can help us see the relevance
of these questions and can also contribute usefully to our attempts
to answer them.
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