WHAT ARE the origins of modern ideas on animal behaviour?
Embodied in the Greek version of species was the concept of type, or idea (eidos to the Greeks). Underlying this way of thought is the notion that there is a perfect type that underlies each and every species, much in the same way that geometrical shapes have an ideal. An equilateral triangle is the ideal of all three-sided polygons that we call triangles.
By focusing on type, Greeks, subsequent theologians and pre- Darwinian scholars ignored the interesting differences found among the individuals of a single species.
Variation within a single species is what Darwin realised was important for the processes leading to the origin of species. This was Darwin's seminal contribution to scientific thought.
Prior to Darwin's contribution, the paradigm that people operated under was that species arose by special creation and that species were immutable (unchangeable) after this act of special creation. By asserting that organisms were non-changing, the question of the origin of species or the evolution of species was, de facto, a non- question.
The most famous of these evolutionists was Lamarck. In Lamarck's theory, organisms adapt to their environment by acquiring changes in their lifetime and passing on such changes to their offspring. If such a theory operated in practice, Arnold Schwarzenegger would produce offspring with phenomenal or, at least, above average muscle development, largely because of the characteristics that Arnold acquired during his own youth. This is the theory of evolution by the process of the inheritance of acquired characteristics.
Darwin assumed that organisms naturally vary in almost every attribute that they display. Such variation might lead to differences in survival or reproduction. Because an excess number of progeny are produced in all organisms, there is a competition amongst them to produce successful progeny, or what Darwin called a "struggle for existence."
New species arise from old species by the acquisition of slow changes in traits, behavioural traits included, and such changes are driven by the blind force of natural selection. Mutations arise in a probabilistic fashion. Sometimes the mutations are beneficial, but, more often than not, the mutations are detrimental and such detrimental mutations are weeded out by natural selection. …