guia do novo coronavirus
Imprimir Republish


Darwin, instinct and mind

Geospiza_magnirostris pbwikimedia commonsIn 1837, in Notepad B, where Darwin registered several ideas and comments on evolution, he noted that “ even the mind and the instinct” are influenced by adaptation to new circumstances.  His correspondence at the time and later on also indicates his interest in psychological issues.  In a letter from Edward Blythe to Darwin (1855), we come across a lengthy debate on the issue of instinct and reason in animals and in human beings.  At the end of “ The Origin of the Species” (1859), Darwin predicted that psychology would find “ a solid base […] in the foundation […] of the necessary acquisition of each mental power and of each mental capacity in a gradual manner” (that is, through natural selection). T. H. Huxley, in a lecture given in 1863, stated that the work of Darwin “was destined to be the guide of biological and psychological speculation for the nest three or four generations.” Huxley underestimated the impact of Darwin´s ideas:  they are still relevant nowadays in various fields of the sciences and, especially, in the field of behavioral studies.

An initial and noteworthy contribution by Darwin resides in the generalization of the principles of natural selection to instinctive behavior. The principle is simple:  behavioral traits, like the anatomical and physical traits, vary among individuals, are transmitted through heredity and become more frequent as they provide individuals with a better capacity to deal with environmental challenges and to reproduce. Darwin (1859) applies the idea to impressive instincts, such as the European cuckoo bird´s tendency to place its eggs in other birds´ nests, the behavior of ants that use ants from other species as slaves to carry out the tasks in the anthill, and the hexagonal perfection of the alveoli in bee honeycombs. In each case, individual variants may have been selected throughout the generations, because of reproductive advantages, thus gaining predominance over the given population. Darwin does not eliminate cognition factors from the instinct;  his idea comes quite close to the current view of considering animal behavior as a product of readiness and plasticity factors.

The idea of inserting behavior within an evolutionary framework allows for the comparison and classification of species on the basis of their live interaction with the environment;  it also allows for a better understanding of the functions of behavioral strategies, (a dangerous idea) and that the human being be viewed as one more species, akin, in its way of being, to other animals considered as being inferior.

The theory of evolution began with Darwin, but did not end with him.  Important changes occurred after his time in terms of animal behavior studies.  These studies do not eliminate the general principle: they refine it and unveil new hypotheses.  Darwinian theory presents itself as open-ended and versatile, and it is not possible to predict its development, as it is a step-by-step adaptation to evidences and is refuted by some of the results.

Etiology was an important take-off on Darwin´s ideas.  Etiology was proposed by Konrad Lorenz and his colleague Niko Tinbergen, in the 1930s. They started from the idea that there are inherited behavioral elements automatically unleashed by environmental stimuli. Lorenz, going beyond a line implicit in Darwin, used the behaviors of water bird species, the anatidae, to reconstitute their kinship and phylogenetic development.  Nowadays, evolutionary behavioral analysis is in the spotlight, and has provided important applications for the understanding of the human being´s origin.

Tinbergen started conducting field studies in which he tested the adaptive value of behavioral patterns.  Why does the mother seagull pick up the eggshell and take it far away from the nest right after the egg breaks open? This question has no obvious or anthropomorphic answer and it is clarifying to discover the underlying evolutionary game, comprised of costs and benefits:  by throwing the eggshell away, the adult reduces the probability that the nest will be detected by predators.

The starting point is based on this line of reasoning and leads to a vigorous approach to animal behavior and behavioral ecology.  In addition to promoting the insertion of behavior into the ecological matrix, it formulates hypotheses based on differentiated genetic transmission mechanisms. W.D.Hamilton made important contributions in regard to encompassing aptitudes – which seem to solve the issue of sterile castes in social insects, which was so problematic for Darwin, and provides a basis for the understanding of why cooperation occurs more frequently and in preferential manner among individuals with kinship ties. R. Trivers´ contribution was related to parental investment, which explains why females in general are more selective in relation to their reproductive partners and why males are more promiscuous. The principle in this case is sexual selection, stated by Darwin, and neglected for a very long time.

Darwin´s second contribution to behavioral sciences is related to the understanding of human behavior.   This understanding is essential. This is not a reductionist point of view, as is so often alleged, which refuses to take into account the characteristics of cognition and culture that distinguish the human being. In this respect, Darwin (The descent of man, 1871) writes the following: “If an anthropoid monkey could judge itself impartially, it would admit that […], although it is able to use stones to fight or break nuts, it would not have the conditions to have the idea of transforming the stone into a tool […]. It would also acknowledge that it is not able to follow a metaphysical reasoning until the end or to solve a mathematical problem or to reflect on God or admire a grandiose landscape.” The differences between man and animal, however, would be in terms of degree and not of nature.

In a comparative context, Darwin studied the expression of human emotions. His book (The expression of emotions in man and animals), a bestseller when it was launched in 1872, did not have much impact on research. His proposal was further studied by psychologist P. Ekman, nearly a century later. Like Darwin, Ekman, (with much more sophisticated methods), described how the human face mirrors anger, happiness, fear and other emotions and demonstrated, like Darwin, the transcultural value of expressions. Darwin´s descriptions are outstanding. Even before Desmond Morris, he proves to be a man watcher, a sharp observer of the human being and his details were the legacy of the etiological perspective. Paradoxically, Darwin was not being Darwinian when he leaned towards the “ inheritance of use,”  a version of the hypotheses of the transmission of acquired characteristics to explain the origin of the human expression of emotions.

The recent developments of the evolutionary approach to human behavior go back to the principles of Darwin himself: namely, natural selection and sexual selection.  After the advent of human etiology and sociobiology proposals, we are witnessing the development of evolutionary psychology which boldly seeks to find a synthesis between the Darwinian contributions and the truly psychological ones (Cosmides and Tooby, 1999). This approach joins cognition and pre-programmed processes and describes the human mind, inherited from previous evolutionary contexts, as being comprised of a group of natural competencies, which are the adaptations produced by natural and sexual selection and that result from the interaction between genes and environmental factors. Based on this framework, biological approaches give rise to new hypotheses and non-trivial results on the varied aspects of human behavior, ranging from sexual preferences to competition, altruism and aggressive behavior.

The immediate acceptance of Darwin´s ideas in the field of psychology was not always enthusiastic. “So many obscure ideas, so many false ideas!… such empty and pretentious language!”, wrote J.P. Flourens in 1864 about the Origin of the Species.  J. P. Flourens had written books on animal instincts.  In a comment on The descent of man, published in The Lancet journal (1871), we read: “For those who […] demand more conclusive proof [on] the mental and moral attributes of the human being… the set of facts presented by Mr. Darwin must seem quite inadequate and his reasoning based on them seems to be inconclusive, if not entirely false.” These hurried opinions contrast with the impressive vitality of Darwinian ideas in the fields of psychology and behavioral sciences of contemporary times, not only in the traditional research centers but also in Brazil.  There are many promises related to progress in terms of understanding both the instinct and the mind.

César Ades is a psychologist,  an expert on animal behavior, and a professor at the University of São Paulo.