Tinbergen's four questions
Tinbergen's four questions are a general schemea used by biologist to classify the different causes of animal behavior and morphology. They were spelled out in the 1960s by Nikolaas Tinbergen who says he was inspired by Aristotle's four types of causes. The four causes that Tinbergen delineated have received wide usage to frame papers and concepts in the fields of ethology, behavioral ecology, sociobiology, and evolutionary psychology.
The four causes
The four causes can be divided into two major categories. The first two are deep time causes that relate to the evolutionary explanations for behavior. The second two are based on causes that occur in the life time of the organism.
Deep time or Ultimate causes
Evolutionary, and Functional Causes:
The ultimate or functional cause is selection. These are explanations that attempt to describe the causes of behavior or morphology based on function or selective advantage. In science these are called adaptations.
These are deep time causes that are anything other than selection and adaptation. This can take the form of drift, phylogenetic constraint, or homology. Essentially any evolutionary expiation that is not linked to a selective advantage.
These are causes that are related to the development of the organism. This can include the unfolding of hox genes or learning or anything in between. These causes address only those elements of development that work with in the life time of the organism. For example, explaining the order of development by the alignment of hox genes is a proximate developmental causative explanation. But the explanation for the reason why the hox genes are aligned in a particular fashion would be an ultimate causative explanation. See developmental biology and developmental psychology.
Other proximate mechanisms:
These include such things as hormones, brain areas, and nutrition. These are anything working with in the lifetime of the organism that is not related to development.
Separate but Equal
One of Tinbergen's major points is that all of these explanations are complementary to each other. Two researchers addressing two different areas of causation will explain the same behavior in a different way but these are not conflicting explanations. The human eye can be explained at all four levels: the functional argument would look at the benefits of having eyes such as finding food or avoiding predators, a phylogenetic argument might explain the structure of the eye such as the blind spot as a factor of constraint and homology, the developmental argument might describe the stage at which the eye develops and the genes involved in it development, while other proxmiate explanations might examine how different receptors encode different color of light. All of these explanations are separate but equal in Tinbergen's paradigm.
Alcock, John (2001) Animal Behavior: 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 Behavior, MIT Press, ISBN 0-262-53170-4.