Tinbergen's four questions

Darwin's theory of evolution by natural selection is the only scientific explanation for why an animal's behaviour is usually well adapted for survival and reproduction in its environment. However, claiming that a particular mechanism is well suited to the present environment is different from claiming that this mechanism was selected for in the past due to its history of being adaptive.[4]

The literature conceptualizes the relationship between function and evolution in two ways. On the one hand, function and evolution are often presented as separate and distinct explanations of behaviour.[5] On the other hand, the common definition of adaptation is a central concept in evolution: a trait that was functional to the reproductive success of the organism and that is thus now present due to being selected for; that is, function and evolution are inseparable. However, a trait can have a current function that is adaptive without being an adaptation in this sense, if for instance the environment has changed. Imagine an environment in which having a small body suddenly conferred benefit on an organism when previously body size had had no effect on survival.[4] A small body's function in the environment would then be adaptive, but it would not become an adaptation until enough generations had passed in which small bodies were advantageous to reproduction for small bodies to be selected for. Given this, it is best to understand that presently functional traits might not all have been produced by natural selection.[4] The term "function" is preferable to "adaptation", because adaptation is often construed as implying that it was selected for due to past function. This corresponds to Aristotle's final cause.[6]

Evolution captures both the history of an organism via its phylogeny, and the history of natural selection working on function to produce adaptations.[7] There are several reasons why natural selection may fail to achieve optimal design (Mayr 2001:140–143; Buss et al. 1998). One entails random processes such as mutation and environmental events acting on small populations. Another entails the constraints resulting from early evolutionary development. Each organism harbors traits, both anatomical and behavioural, of previous phylogenetic stages, since many traits are retained as species evolve.

Reconstructing the phylogeny of a species often makes it possible to understand the "uniqueness" of recent characteristics: Earlier phylogenetic stages and (pre-) conditions which persist often also determine the form of more modern characteristics. For instance, the vertebrate eye (including the human eye) has a blind spot, whereas octopus eyes do not. In those two lineages, the eye was originally constructed one way or the other. Once the vertebrate eye was constructed, there were no intermediate forms that were both adaptive and would have enabled it to evolve without a blind spot.

It corresponds to Aristotle's formal cause.[6]

Some prominent classes of Proximate causal mechanisms include:

• The brain: For example, Broca's area, a small section of the human brain, has a critical role in linguistic capability.
• Hormones: Chemicals used to communicate among cells of an individual organism. Testosterone, for instance, stimulates aggressive behaviour in a number of species.
• Pheromones: Chemicals used to communicate among members of the same species. Some species (e.g., dogs and some moths) use pheromones to attract mates.

In examining living organisms, biologists are confronted with diverse levels of complexity (e.g. chemical, physiological, psychological, social). They therefore investigate causal and functional relations within and between these levels. A biochemist might examine, for instance, the influence of social and ecological conditions on the release of certain neurotransmitters and hormones, and the effects of such releases on behaviour, e.g. stress during birth has a tocolytic (contraction-suppressing) effect.

However, awareness of neurotransmitters and the structure of neurons is not by itself enough to understand higher levels of neuroanatomic structure or behaviour: "The whole is more than the sum of its parts." All levels must be considered as being equally important: cf. transdisciplinarity, Nicolai Hartmann's "Laws about the Levels of Complexity."

It corresponds to Aristotle's efficient cause.[6]

Ontogeny is the process of development of an individual organism from the zygote through the embryo to the adult form.

In the latter half of the twentieth century, social scientists debated whether human behaviour was the product of nature (genes) or nurture (environment in the developmental period, including culture).

An example of interaction (as distinct from the sum of the components) involves familiarity from childhood. In a number of species, individuals prefer to associate with familiar individuals but prefer to mate with unfamiliar ones (Alcock 2001:85–89, Incest taboo, Incest). By inference, genes affecting living together interact with the environment differently from genes affecting mating behaviour. A simple example of interaction involves plants: Some plants grow toward the light (phototropism) and some away from gravity (gravitropism).

Many forms of developmental learning have a critical period, for instance, for imprinting among geese and language acquisition among humans. In such cases, genes determine the timing of the environmental impact.

A related concept is labeled "biased learning" (Alcock 2001:101–103) and "prepared learning" (Wilson, 1998:86–87). For instance, after eating food that subsequently made them sick, rats are predisposed to associate that food with smell, not sound (Alcock 2001:101–103). Many primate species learn to fear snakes with little experience (Wilson, 1998:86–87).[8]

See developmental biology and developmental psychology.

Explanations of Animal Behaviour: Causal Relationships; Adopted from Tinbergen (1963).

It corresponds to Aristotle's material cause.[6]

Four ways of explaining visual perception:

• Function: To find food and avoid danger.
• Phylogeny: The vertebrate eye initially developed with a blind spot, but the lack of adaptive intermediate forms prevented the loss of the blind spot.
• Causation: The lens of the eye focuses light on the retina.
• Development: Neurons need the stimulation of light to wire the eye to the brain (Moore, 2001:98–99).

Four ways of explaining the Westermarck effect, the lack of sexual interest in one's siblings (Wilson, 1998:189–196):

• Function: To discourage inbreeding, which decreases the number of viable offspring.
• Phylogeny: Found in a number of mammalian species, suggesting initial evolution tens of millions of years ago.
• Mechanism: Little is known about the neuromechanism.
• Ontogeny: Results from familiarity with another individual early in life, especially in the first 30 months for humans. The effect is manifested in nonrelatives raised together, for instance, in kibbutzs.

Four ways of explaining romantic love have been used to provide a comprehensive biological definition (Bode & Kushnick, 2021):[9]

• Function: Mate choice, courtship, sex, pair-bonding.
• Phylogeny: Evolved by co-opting mother-infant bonding mechanisms sometime in the recent evolutionary history of humans.
• Mechanisms: Social, psychological mate choice, genetic, neurobiological, and endocrinological mechanisms cause romantic love.
• Ontogeny: Romantic love can first manifest in childhood, manifests with all its characteristics following puberty, but can manifest across the lifespan.

Sleep has been described using Tinbergen's four questions as a framework (Bode & Kuula, 2021):[10]

• Function: Energy restoration, metabolic regulation, thermoregulation, boosting immune system, detoxification, brain maturation, circuit reorganization, synaptic optimization, avoiding danger.
• Phylogeny: Sleep exists in invertebrates, lower vertebrates, and higher vertebrates. NREM and REM sleep exist in eutheria, marsupialiformes, and also evolved in birds.
• Mechanisms: Mechanisms regulate wakefulness, sleep onset, and sleep. Specific mechanisms involve neurotransmitters, genes, neural structures, and the circadian rhythm.
• Ontogeny: Sleep manifests differently in babies, infants, children, adolescents, adults, and older adults. Differences include the stages of sleep, sleep duration, and sex differences.

• Alcock, John (2001) Animal Behaviour: An Evolutionary Approach, Sinauer, 7th edition. ISBN 0-87893-011-6.
• Buss, David M., Martie G. Haselton, Todd K. Shackelford, et al. (1998) "Adaptations, Exaptations, and Spandrels," American Psychologist, 53:533–548. http://www.sscnet.ucla.edu/comm/haselton/webdocs/spandrels.html
• Buss, David M. (2004) Evolutionary Psychology: The New Science of the Mind, Pearson Education, 2nd edition. ISBN 0-205-37071-3.
• Cartwright, John (2000) Evolution and Human Behaviour, MIT Press, ISBN 0-262-53170-4.
• Krebs, J.R., Davies N.B. (1993) An Introduction to Behavioural Ecology, Blackwell Publishing, ISBN 0-632-03546-3.
• Lorenz, Konrad (1937) Biologische Fragestellungen in der Tierpsychologie (I.e. Biological Questions in Animal Psychology). Zeitschrift für Tierpsychologie, 1: 24–32.
• Mayr, Ernst (2001) What Evolution Is, Basic Books. ISBN 0-465-04425-5.
• Gerhard Medicus. "Tinbergen's four questions in behavioural Anthropology" (PDF).
• Gerhard Medicus (2017) Being Human – Bridging the Gap between the Sciences of Body and Mind. Berlin: VWB 2015, ISBN 978-3-86135-584-7
• Nesse, Randolph M (2013) "Tinbergen's Four Questions, Organized," Trends in Ecology and Evolution, 28:681-682.
• Moore, David S. (2001) The Dependent Gene: The Fallacy of 'Nature vs. Nurture', Henry Holt. ISBN 0-8050-7280-2.
• Pinker, Steven (1994) The Language Instinct: How the Mind Creates Language, Harper Perennial. ISBN 0-06-097651-9.
• Tinbergen, Niko (1963) "On Aims and Methods of Ethology," Zeitschrift für Tierpsychologie, 20: 410–433.
• Wilson, Edward O. (1998) Consilience: The Unity of Knowledge, Vintage Books. ISBN 0-679-76867-X.

• The Four Areas of Biology pdf
• The Four Areas and Levels of Inquiry pdf
• Tinbergen's four questions within the "Fundamental Theory of Human Sciences" ppt
• Tinbergen's Four Questions, organized pdf

• On aims and methods of cognitive ethology (pdf) by Jamieson and Bekoff.