Biology 202, Spring 2005
Third Web Papers
On Serendip

A recent study on water-fleas shows that genetically identical crustaceans can adopt completely different physical make-ups depending on the environment in which they were raised. These animals glide over water, and can be an easy target for fish and other predators. Some have, however, developed a "helmet," or hard shell around their heads, making it more difficult or fish to eat them. While one could simply attribute this to survival of the fittest, those with the helmet and those without are exact DNA clones of one another, making this conclusion false.

This variation between the same species suggests that environment plays just as strong a role as genetics. While these fleas come from the same parents, those raised in an aquarium with no predators did not develop the helmet amour. By injecting the smell of fish into a separate aquarium, the fleas grew the helmet. This emphasizes the role of nurture, not simply nature, as "it can elicit markedly different traits from the same DNA. (1) "

The argument in favor of nurture is by no means limited to water-fleas, and has surfaced in several other recent studies. Another example is found in the oak-tree caterpillar. Depending on what time of year the caterpillar hatches, it will take on a different physical look. Those who hatch in the spring eat the flowers of the tree and take on the appearance of oak blossoms, while those who are born in the summer eat leaves and resemble twigs. This physical distinction is a result of their environment and diet, not of a genetic disparity (2) . Does this mean that if given a third or fourth environment they would again change? This distinction is not one which evolves over hundreds of generations, but arises in a single lifetime. Eric Turkheimer explains that "Once a new environment comes along it can change everything, so what you though was a fixed effect of a gene isn't (3) "

In a study examining neuroticism in mice similar results were found. Scientists assumed that neuroticism was a result of DNA because a gene had been located for it. Nevertheless, the behavior patterns associated with neuroticism, anxiety, fear, and agitation, were all reversible if raised in a more loving environment. Regardless of what gene the mice possessed, their level of neuroses was directly proportional to the amount of maternal care (grooming, physical contact, etc.) the mouse received as an infant (4) .

These findings are not reserved for mice alone, but have been examined in human beings as well. Certain traits which used to be considered innate are now being attributed to life experiences. The gene MAOA, monoamine oxidase-A (5) , has frequently been associated with violence, especially in men (as it is sex linked). Those who produce inadequate amounts of MAOA were thought to be more violent than those who produced a normal amount. In a study tracking 442 men, researchers found that weather or not there was a scarcity of MAOA in the brain did not matter, so long as the men had been raised in loving and supportive families. Those who lacked the MAOA enzyme in conjunction with being raised in an unstable and violent households were twice as likely to commit crimes, be antisocial, and physically abusive (6) . Again one sees that genetically comparable individuals can display polar traits when raised in contradictory environments.

What then of the countless stories of identical twins raised appart from each other and having similar traits later in life? They are genetic clones of one another and may display certain similarities regardless of their respective environments. Perhaps it is that their environments were analogous in certain key factors. If one had been raised in an abusive household, while the other was exposed to a nurturing and loving family, conceivably they would no longer exhibit identical behavior. Small personal habits, such as nail biting or reading a magazine from end to beginning may be associated with identical twins, but larger life patterns like violence verses passivity are shown to be a result of environment, in spite of genetic make-up. Science historian Evelyn Fox Keller states that "what our biology really gives us is our plasticity, our ability to respond to our experiences. That's what's innate. (7) " If we are all born with the potential to be one of two, or three, or possibly more individuals, regardless of our genetic make-up, how do we know who we really are?

Does this mean that I can really be whoever I want to be? Is my life destiny truly in my hands? Yes, I have been dealt a set hand of genetic cards with which to play, but perhaps each one of those cards holds multiple outcomes depending upon how I elect to use them. I can no longer change weather or not I received affection and love as a child, so perhaps that strain of my personality is already determined, but there must be other roads which are still open to interpretation. Or is there an age at which one's personality is, for the most part, fixed? The oak caterpillars do not have the ability to chance from looking like blossoms to looking like twigs after they have chosen one form, so how much room for change do I have this late in life? Do we stop developing as individuals and simply act in accordance with the way our genes have been raised thus far at a certain period? If so, when? Early childhood is when we are most impressionable, but we defiantly change tremendously in all aspects of ourselves at puberty, and many people continue to pursue their academic education long after puberty ends. If I change my environment now will I be a different person, or is it too late? My DNA will remain the same, but will my personality be affected?

This then poses the question of who I am outside of my genetics. I am a person who goes to Bryn Mawr College, and I would still be a physical clone of that person if I had attended school in another country. If those two people were to meet, however, no one could claim that they were the same, after having had such differing experiences. If I do not like who I currently am, have I been given the choice to change me, if not genetically then on another level? On a less philosophical level I have the capability to change some aspects of a supposedly predetermined fate. If I have a gene for high cholesterol, I can resist those effects by controlling my dietary fat intake (8) . Am I like the water-fleas? If I am thrown into a hazardous environment will I find previously untapped resources within myself to help me cope with those new challenges? Who knows what I am capable of, if necessary? I think I know myself, but I have no idea, and can have no idea of my full potential until it is tested.

The bottom line seems to be that "different environments can produce different [traits] from the same genotype (9) ." This makes me believe that I only know a very small part of myself, as I have really only been exposed to one life, and one series of events. To better understand every aspect of me and every facet of my personality I would have to experience a multitude of environments. To discover every side of my being I would have to try everything in every single combination in the world. This is, of course, impossible, as there are an infinite number of possible ways in which to live one's life, experiences to have, places to see, people to meet, and ideas to explore. If there are an infinite number of ways to live, then there must also be an infinite number of people I could become, despite my one set of genes. My DNA is fixed, and has been since I was conceived, but my life is flexible, and those genes could lead me down many different roads.

If water-fleas can change their physical bodies, and mice and humans can have different levels of anxiety and aggression depending on how they were nurtured, I would hope that I can alter some of my less favorable qualities. I do believe, however, that some of traits become less malleable after a defined age. I wonder what this age is, but I imagine that it must vary from person to person, and depend on what trait it is. For example, convicted sex offenders are fairly likely to commit a sex-crime again, but are significantly less likely to do so if they receive treatment. This shows that they have a predisposition to assault, but with an environmental intervention, they have the potential to change (10) . Is there a point at which one can't teach an old dog new tricks? Is the learning dependant upon the trick or the age? Are these altercations possible due to many open gateways in a defined number of genes?

After learning about the possibility for change, in spite of my predetermined DNA, I feel as though I must examine more closely my own actions and the effects they have on my life and those around me. This same question has plagued the minds of people for centuries. In mythology there is the recurring theme of whether we are masters of our own destiny or merely playthings of the Gods. If we consider our genes to be akin to the Gods of that time, in that we are, to a certain extent, at their mercy, we are still asking ourselves this same question. Now that we have scientific evidence to support our potential for mastery of our fates we must, as a society, make a more concentrated effort to use this ability to our advantage. We can not alter the way in which we ourselves were raised, but we can try harder to raise future generations in a certain manner. If creatures as simple as water-fleas can change due to their environment, so too can people. This is a huge discovery, and therefore an immense burden and responsibility for us. We can be masters, to a degree, of our brains, and those of others, and as such we must assume this power with seriousness and care in order to get things "less wrong (11) ."

References

1) Water-Fleas Case Shows that Ability to Adapt is What's Really Innate, The Wall Street Journal, Sharon Begley. April 22, 2005

2) Professor Eric Turkheimer, University of Virginia

3) Professor Eric Turkheimer, University of Virginia

4) Michael Meaney, McGill University

5) Genes Explain Why Some Kids Grow Up to be Violent, Abusive. The Wall Street Journal, Sharon Begley. September 20, 2002

6) Water-Fleas Case Shows that Ability to Adapt is What's Really Innate, The Wall Street Journal, Sharon Begley. April 22, 2005

7) Evelyn Fox Keller, Massachusetts Institute of Technology

8) Terrie Moffitt, University of Wisconsin, Madison and King's College, London.

9) Terrie Moffitt, University of Wisconsin, Madison and King's College, London.

10) ) The Kid Safe Network

11) Professor Grobstien


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