From the moment a baby is born, the adults around the infant often speculate as to what its personality will be like. “Maybe it will be smart like its father,” its grandmother may remark. The mother of the child may think that it will have her own cheerful demeanor, or at least, she probably hopes it does.

All of the speculation begs an important question: how much of our personality do we have at birth? What are we born with, and what is shaped by the world around us? Does that newborn already have a cheerful personality? Is it smarter than the average newborn? Could it have a social disability, like autism?

How much of its personality is actually due to genetics? The answer to those pressing questions begins at the moment of conception, but in order to understand the answer, one must first know what genetics are.

Every human is composed of 23 sets of unique chromosomes. These chromosomes are composed of huge strands of DNA (deoxyribonucleic acid). Specific sections of DNA are called our genes, and our genes are responsible for a number of things, including hair color, eye color, how we respond to diseases, and possibly even part of our personalities.

For the most part, our genes come directly from our parents. We get half of our DNA from our mother and half of our DNA from our father. This simple transition is only sometimes interrupted by mutations, but this is extremely rare. It is important to understand simple heredity in order to understand why some scientists speculate that a large part of our personality is something that we are born with. It is also important to understand the other side of understanding of where personality comes from -- the nurture side of the nature vs. nurture debate.

It is often argued that a baby is a blank slate. It is born with no understanding of anything and no personality. The infant supposedly begins to develop a personality as it grows and experiences things, and therefore, the environment the infant is raised in is a huge factor in how the infant’s personality develops, rather than its parent’s genes.

To some, this outlook makes more sense than the personality through genetics, and it suggests that individuals are not doomed to act a certain way due to their genetics. However, it also suggests that those raised in harsh conditions are doomed to fail and those lucky enough to be born into a relatively good environment will be more positive people overall. Overwhelmingly, modern research shows that the “blank-slate baby” theory is incorrect.

In the past, research has been mostly inconclusive in the nature vs. nurture debate. It is a sensitive topic and hard to study. The best way to truly see the results of nature vs. nurture is to study identical twins separated at birth raised in completely different environments. Identical twins have identical DNA, meaning that they share the same genes.

Any difference in the personality, preferences, or mannerisms of identical twins separated at birth has to be purely from the environment. Interestingly enough, most twins who were brought up in different homes do not end up being very different at all.

One of the most interesting cases of identical twins being apart but growing up to be eerily similar is the case of Jim Lewis and Jim Springer. The men were separated at four weeks old and reunited at age 39. After being reunited, the men realized they drove the same model of car, smoked the same brand of cigarettes, had the same headaches and vacationed at the same beach. Even though they had grown up in different households with different parents and environments influencing them, they still grew up to be extremely similar.

The Jim twins were not alone, either. Other pairs of twins studied show the same results. Identical twins were seen standing the same way in family pictures, whereas separated fraternal twins (twins without the same DNA) were seen with completely different postures. The only explanation for such astounding parallels is a very simple one: genetics.

One of the most interesting correlations between genetics and personality is the link between genetics and autism. Autism is a disorder that affects many social aspects of an affected individual’s life, including speech and behavior. It is sometimes argued that autism is caused by environment, or even by vaccination, but research strongly suggests that genetics are the culprit. In a study of British twins, it was found that 60% of identical twins where at least one of the twins had autism, they both had autism, whereas 0% of non-identical twins both had autism.

Furthermore, in 92% of identical twins where one twin suffered from a social disorder, it was found that both twins were affected, whereas in non-identical twins the percentage of linked social disorders was much lower at only 10%. Once again, the fact that identical twins have identical DNA supports the fact that much of one’s personality comes from genetics.

These compelling statistics still leave some questions about how much of one’s personality comes from nature, however. What about the 40% of identical twins where only one twin has autism? Did something from the environment have to spark the other’s twin gene that makes them more susceptible to autism?

The truth is, environment also plays a huge role in how personality is developed. While genes make one more likely to behave a certain way, upbringing can either trigger or suppress certain genes. A good example of environment playing a large role in personality is the theory of “relagraphics” -- the idea that others have an effect on one’s personal views and decisions, despite whether they are one’s relative or not.

A national Penn, Schoen and Berland Associates survey of 1,000 Americans observed that those who were brought up in certain types of households or who shared other relationship characteristics were also more likely to share various ideologies, a sign that the environment that they were brought up in shaped their personality and viewpoints, or at least did have some influence on it.

For example, 64% of people raised in religious homes grew up to identify as a Republican. Furthermore, 47% of those raised in liberal households claim to be satisfied with their sex lives while only 43% of those raised in conservative households claim the same. These statistics seem to suggest that the environment these adults were exposed to as children shaped their adult lives.

The political party one chooses to identify with doesn’t seem to be all environmental, however. There is evidence that even an individual’s political views can come from genetics. In another study on twins, identical twins were found to have much more similar political views than their non-identical counterparts.

Furthermore, high correlations between things that seem otherwise unrelated, such as having a low-disgusting images tolerance and being opposed to gay marriage or tasting bitterness in certain foods and voting democrat add to the evidence that political views are very genetically influenced alongside environmental influences.

Much like politics, it is commonly assumed that negative personality traits and disorders like depression and addiction are strictly environmentally influenced, however, these traits strongly parallel disorders such as autism. In a study conducted on a group of 60 women, the results showed that the link between DNA and addiction is very intense.

The study included a group of 30 women addicted to alcohol or opiates and a control group of 30 women with no psychiatric diagnosis. In the set of opiate addicts, the heredity factor was an astonishing 62.5%. In the set of alcohol addicts, the heredity factor was 50%.

In the control group, there was only a heredity factor of 13.3%. While this evidence does not explicitly reveal that all addiction is caused purely by genetics, it is very compelling evidence that specific genes to make certain individuals more likely to become addicts themselves.

Depression, likewise, has a specific gene associated with it. In a recent study, it was discovered that those suffering from major depression have a specific gene that makes the processing of hormones associated with feelings of joy impossible. While it may often be assumed that people are depressed due to their environment, the truth lies in the very DNA of those suffering from major depression.

Other cases of depression may be caused in part by environment, however, and it is true that the environment does have a large influence on an individual’s mood.

While the blank-slate baby theory made have held some merit in the past, with new research showing that there is a definitive link between genes and personality today, it is easy to conclude that that theory no longer holds relevance in any conversations anywhere, from the scientific community to the delivery room. When a grandmother assumes a baby will inherit one of its parent’s demeanors, it is more factual than one might think!

Genetics play a huge role in one’s personality, from whom they select on a ballot to if they are more likely to become addicted to substances. This isn’t to say that environment plays no role in the development of a child as it clearly does, this is simple to say that perhaps the “nature vs. nurture” debate is outdated. Instead of focusing on one or another, one should realize that personality is developed by “nature through nurture”.

In most cases, one’s genes are expressed a certain way because of the environment around them. This creates the billions of personalities that are enjoyed by all of mankind today, regardless of differences in DNA.