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Biology 103
2003 Third Paper
On Serendip

Put Your Dukes Up; Nature and Nurture Go at it Again

Megan Williams

The Judd family is blessed with vocal and dramatic talent, as the James family was cursed with a lust for crime and the fast life, as the Bush family exudes, well, a good hair line. But is that truly the case? Can Ashley and Wynonna hit that high C simply because Naomi Judd, their mother, could? Did Frank and Jesse James both have the same gene that gave them their love of robbing banks and aggressive nature, passed on from a great-grandfather somewhere down the line? Or were these characteristics groomed by experiences and environment? What gives humans their traits and behavior?

The case of human traits and behavior is yet another battle in the on-going war of nature versus nurture. As in all prize fights, the challengers must be introduced. Nature versus nurture is a popular phrase used in most contemporary debates over what degrees genetic makeup, or "nature", and life experiences, or "nurture", influence traits or behaviors. Nature can encompass genetic makeup, as well as human nature, or instincts. Nurture has historically referred to care given to an individual by their parents, but can also include experiences in the womb, childhood friends, and one's early experiences with the television (1),as well as environment in which one lives.

In specific regards to human characteristics, there is a strong case for at least partial biological predetermination. On the obvious level, humans "breathe, sneeze, laugh, cry, sleep, and otherwise engage in a variety of activities which need not be learned" (2).From this we can derive that there are human activities or behaviors that need not be learned from experience. There are some proven cases in which it makes sense to say that a particular trait is due entirely to nature. Huntington's disease is a highly penetrant genetic disease, and one will only contract Huntington's if they have the corresponding gene variant.
Scientists are sure of the fact that genes do code for things such as eye and hair color. However, whether or not genes determine common human traits is still based all on theory. One such theory is the Nature Theory (3). The Nature Theory hypothesizes that abstract human traits such as intelligence, sexual orientation, and aggression are decided by DNA. For example, in the case of human aggression, the fact that our early human ancestors, as well as species closely linked to humans, display aggression also merits that the behavior is at least partially predetermined by genes. Unearthed Australopithecus skulls have indications of wounds caused by tools, among which some are considered to have been mortal. In some digs, remnants of cannibalistic meals have been discovered (7). Genes do not directly determine traits, in simplicity, genes code for protein. Yet genes do influence the developmental expression of traits, which "...represent the expression of the interaction of genes with environments." (6). And humans do obviously share genes with their ancestors. Sociobiologists use man's descent from hunters to support a genetic basis for human behaviors like aggression; we carry genes from a hunter/gatherer society, therefore it is embedded in our brains. Human aggression has been thought to be "an innate, unlearned behavior pattern" (4).

Research also shows that behavior could be mediated by the brain, the amygdala in particular. Texas sniper Charles Whitman begged for an autopsy after his execution because he believed that his actions were a result of his brain's inner-workings. The autopsy revealed he had a tumor pressing into his amygdale (4). Studies have also been done involving identical twins. The twins are separated at birth and have totally different lives and experiences, yet test back to have similar personalities and levels of intelligence. The only shared experience of these twins was that in the womb (1).

The other side of the argument is obviously the Nurture Theory. Psychologist John Watson experimented with environmental learning, and in doing so, demonstrated that the acquisition of a phobia could be explained by classical conditioning. Watson claimed: "Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select...regardless of his talents, penchants, tendencies, abilities, vocations and race of his ancestors." (3)

Another development in the nature versus nurture controversy was the Human Genome Project. Set to determine exactly how many genes a human has, it was discovered that humans possess 30,000 genes, which is barely twice that of a fruit fly (3). "We simply do not have enough genes for this idea of biological determinism to be right," concluded Craig Venter, president of Celera Genomics.

Back to our human aggression model, the fact that modern humans are much more aggressive than their ancestors shows that environment and upbringing definitely effect levels of human aggression. In the modern world, factors such as "influence of media, smoke, noise pollution, air pollution, abusive parenting, overcrowding, heat, and even atmospheric electricity" can lend a hand in aggravating the aggressiveness in humans (6). Behaviorists generally view aggression as a set of acquired behaviors and attach less emphasis on biological determinants. These scientists commonly apply the "principles of social learning theory" when addressing aggression.

The public view on the nature versus nurture argument tends to sway to both sides. People are ready to accept that it is genes that cause diseases and cancer, even obesity and homosexuality. Of course, this takes the blame off of human lifestyle. If it is written into their genes, there is nothing they can do about it. However, the public tends to favor the nurture side of the argument when it breaches sensitive topics such as aggression or intelligence. If people truly believed that intelligence was totally dependent upon genes, there would be no waiting lists to get into the best private schools, no SAT tutors, and no French lessons for three year olds. When the Columbine school shootings went on, it was the angry music, the video games, and the parents that were blamed. No one even brought up the fact that the two shooters genetic makeup could have had anything to do with it. Eminem and Double Dragon took the rap, and the parents were questioned as why they hadn't known about it or prevented it.

Today's biologists tend to agree that traits and behaviors are dependent upon not only nature, but also nurture. Particular genes can influence the development of a specific trait, or can agitate a specific behavior. Rather, the question is not whether it is nature or nurture, the question becomes how the two interact to produce human traits and behaviors. The University of California did a study on perfect pitch. Perfect pitch is the "ability to recognize the absolute pitch of a musical tone without any reference note". (5). People with perfect pitch often have relatives with the same quality, and recent studies show that perfect pitch is possibly the result of a single gene. But the studies also demonstrate a requirement for early musical training, before age six, in order to manifest perfect pitch (5). Therefore, even if the perfect pitch "gene" is inherited, if it is not exercised at an early age, it will go wasted and undetected.

The lessons learned from this? Don't believe those headlines that say that scientists found the cancer-causing genes. Don't blame your mother for your inability to cook or poor handwriting. The nature versus nurture argument will go on forever, as people look for scapegoats to blame for their misfortunes and factors to praise for their luck. There will never be enough evidence to prove whether it is one or the other, people just need to add space in the pot for both theories. Mix in a little free will and you've got yourself a real party. Ashley Judd should thank her mother, not only for giving her the building blocks to a stellar voice, but also for putting her in those acting and singing classes and exposing her to the music world at an early age.


1)Wikipedia, online Encylclopedia site

2) Montagu, Ashley. The Nature of Human Aggression. London: Oxford University Press. 1976.

3)Genetics, discussion of Nature versus Nurture argument

4)Human Evolution, essay on Human Evolution and Behavior

5)Human Genome Project,findings from Human Genome Project

6)Human Aggression, discussion of Nature versus Nurture in human aggression

7) Heller, Agnes. On Instincts. Netherlands: Van Gorcum. 1979

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