General overview The evidence for evolution Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms. The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources. The following sections identify the most productive of these sources and illustrate the types of information they have provided.
Organismic trait designed to solve an ancestral problem s. Shows complexity, special "design", functionality Adaptation that has been "re-purposed" to solve a different adaptive problem.
Williams suggested that an "adaptation is a special and onerous concept that should only be used where it is really necessary. Obligate and facultative adaptations[ edit ] A question that may be asked about an adaptation is whether it is generally obligate relatively robust in the face of typical environmental variation or facultative sensitive to typical environmental variation.
By contrast, facultative adaptations are somewhat like "if-then" statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, the propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers could be trusted to provide reliable assistance and attention.
The adaptation for skin to tan is conditional to exposure to sunlight; this is an example of another facultative adaptation.
When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence the expression of the adaptation. Cultural universal Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations.
Basic gender differences, such as greater eagerness for sex among men and greater coyness among women,  are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females.
Human evolution Evolutionary psychology argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the "environment of evolutionary adaptedness".
More specifically, the environment of evolutionary adaptedness is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation. Humans, comprising the genus Homoappeared between 1.
Because the Pleistocene ended a mere 12, years ago, most human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection during the Pleistocene.
Evolutionary psychology therefore proposes that the majority of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments.
The environment of evolutionary adaptedness is significantly different from modern society. Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit "mismatches" to the modern environment.
One example is the fact that although about 10, people are killed with guns in the US annually,  whereas spiders and snakes kill only a handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits or flowers.
There is thus a mismatch between humans' evolved fear-learning psychology and the modern environment. The term was coined by Niko Tinbergen to refer to non-human animal behavior, but psychologist Deirdre Barrett said that supernormal stimulation governs the behavior of humans as powerfully as that of other animals.
She explained junk food as an exaggerated stimulus to cravings for salt, sugar, and fats,  and she says that television is an exaggeration of social cues of laughter, smiling faces and attention-grabbing action.
The human mind still responds to personalized, charismatic leadership primarily in the context of informal, egalitarian settings.
Hence the dissatisfaction and alienation that many employees experience. Salaries, bonuses and other privileges exploit instincts for relative status, which attract particularly males to senior executive positions.
One of the major goals of adaptationist research is to identify which organismic traits are likely to be adaptations, and which are byproducts or random variations. As noted earlier, adaptations are expected to show evidence of complexity, functionality, and species universality, while byproducts or random variation will not.
In addition, adaptations are expected to manifest as proximate mechanisms that interact with the environment in either a generally obligate or facultative fashion see above.
Evolutionary psychologists are also interested in identifying these proximate mechanisms sometimes termed "mental mechanisms" or "psychological adaptations" and what type of information they take as input, how they process that information, and their outputs. Evolutionary psychologists use several strategies to develop and test hypotheses about whether a psychological trait is likely to be an evolved adaptation.
Buss  notes that these methods include: Characteristics that have been demonstrated to be cross cultural human universals such as smiling, crying, facial expressions are presumed to be evolved psychological adaptations.
Several evolutionary psychologists have collected massive datasets from cultures around the world to assess cross-cultural universality. Function to Form or "problem to solution". The fact that males, but not females, risk potential misidentification of genetic offspring referred to as "paternity insecurity" led evolutionary psychologists to hypothesize that, compared to females, male jealousy would be more focused on sexual, rather than emotional, infidelity.
Form to Function reverse-engineering — or "solution to problem". Morning sicknessand associated aversions to certain types of food, during pregnancy seemed to have the characteristics of an evolved adaptation complexity and universality.The theory of evolution by natural selection, first formulated in Darwin's book "On the Origin of Species" in , is the process by which organisms change over time as a result of changes in.
The neutral theory of molecular evolution proposed that most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. Hence, in this model, most genetic changes in a population are the result of constant mutation pressure and genetic drift.
. Using the History of Evolutionary Theory student esheet, students should visit Pre-Darwinian Theories for an explanation of the development of modern evolutionary thinking. Students should read the page on Pre-Darwinian Theories and then move on to Darwin and Natural Selection by clicking on "Next Topic" at the bottom of the page.
To introduce the concept of evolution by natural selection from a historical standpoint and to examine the evidence and arguments that support this theory. Science never takes places in a void and evolutionary thought is no exception.
Although Charles Darwin is considered to be by many the "father. Evolution: Evolution, theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations.
It is one of the keystones of modern biological theory. Evolutionary theory has many applications in medicine. Many human diseases are not static phenomena, but capable of evolution.
Viruses, bacteria, fungi and cancers evolve to be resistant to host immune defences, as well as pharmaceutical drugs.