Human behavior is a highly debated topic in the scientific community. While geneticists argue that an individual's innate qualities and genetic makeup cause individual differences in human behavior, psychologists believe that an individual's personal experiences or their environment causes those differences. This debate is known as “nature versus nurture,” and the two sides have evolved as more information has been found in genetic research. While there are still different ideas about how much effect genes and environment have on human behavior, there is a consensus that the two factors work together to influence or predict how a person is most likely to act. But these predictions are not absolute or deterministic, and the factors are not necessarily deterministic.
Humans are genetically predisposed to behave a certain way, and certain genes can “trigger” certain behaviors. Many studies have been conducted on animals, which can be considered in the debate about human behavior because animals have molecules that are also present in humans (Robinson 2004; Bettelheim 1998). For example, in one study, a gene that is responsible for preparing a mother mouse to care for her young – by triggering maternal instincts and behavior – was inactivated in pregnant mice, which resulted in three out of four pups dying from neglect. When the surviving pups were put into the care of foster mothers with the activated genes, 85% of them survived (Bettelheim 1998). This is significant because the absence of one gene affected mouse behavior in an observable way, which shows that genes affect behavior. Another study transplanted Japanese quail brain cells that control quail sounds and head movement into chicken embryos. As a result, the chickens did not act like chickens; their head movements and sounds were like quails, and they responded to quail sounds rather than chicken sounds (Bettelheim 1998).
Such drastic manipulation of genes cannot be ethically conducted in humans, but some human behaviors have been linked to human genes. One such project is The Human Genome Project, which sought to map all of the human genes to understand how they work together (Bettelheim 1998; Plomin et al. 2000). Genes began to be linked with behaviors. For example, the sevenfold repetition of the dopamine code in DNA is linked to quick tempers, thrill-seekers, and drug addiction, although addiction also depends on the sequence of ten other genes (Bettelheim 1998). A shorter version of the serotonin transporter gene was also found linked to impulsive and aggressive behavior, anxiety and negative thoughts, and autism (Bettelheim 1998; Ferguson et al. 2010). Unlike how disorders can caused by a single gene (such as in Huntington's Disease or Anemia), a single, isolated gene cannot explain human behavior.
Although some genes have been linked to certain behaviors, most behaviors or disorders are predicted by a combination of many genes (Begley 2009; Manuck et al. 2014; Bettelheim 1998). A...