Most of these theories are rooted on the natural instinct that leads to commitment of crime or forces that compel individual to develop crime traits. There have been studies that have been carried out suggesting that genetic factors and other biological harming aspects like head injury and exposure to toxic substances, and others may increase the chances of someone becoming a criminal by developing some criminal traits like impulsitivity and sensations seeking. This effect of biological harms on individual traits has been explained to be the effect on the central nervous system including sympathetic and parasympathetic system. Many of the researches that have been carried out in this area focuses on chemical messenger which is the neurotransmitters which relays signals between neurons and the brain, and the hormones regulating body urges like sex drives and response to stressors like testosterones. Other factors like skin conductiveness, level of brain activities, and others which affects functioning of nervous system may lead to a dysfunction of the nervous system leading to development of crime traits.
The general expression of these studies is that there are some natural factors that determine individual vulnerability to committing a crime. This means that some factors in the body and others in the environment that affects the biological status of the body can be responsible for criminal activities since they induce the development of criminal behaviors. Hence, there may be likelihood that criminals may be having a particular crime inducement gene that is not found in other people. Let us look at the postulation of the gene-based evolutionary theory.
Gene-based evolutionary theory is supported by studies which suggested that crime is inherited in some genes. Although there has been no prove on crime genes as such, there is a likelihood that some individual traits like 'pushiness' or 'deception' may have some effect on development of crime traits. Studies have suggested that individuals with such traits can reproduce and pass on the traits to the next generation which may develop the same crime traits. However there has been much acrimony about the postulation of these genetic based crime theories with some arguing that they have not been able to explain some aspects of crime. It has also been argued that these theories give a postulation that we cannot control crime by the fact that we cannot change criminal behavior in the population since it is genetic. The theory wipes away the effects of the social environment on crime and supports the postulation that races and ethnic groups' view of crime may have biological backing.
The two theories above can be explained by their postulation that there is crime traits in the individual is a functions of the biology of the body. This means that criminal traits in the individual can be inherited in the genes or it can result from change in the biological make up of the body as a result of exposure to harmful activities. They can be explained in a simple fact as their postulation that crime traits are determined by some factors beyond individual control.
Determinism is supported by the earlier theories of crime which tried to explain the individual do not choose to engage in crimes