Nature versus nurture: XYY

[Caz]

Discuss.

(Scroll down for the case study.)

[xBlackFlash]

This is a Psych major's wet dream. I'd be interested to see how a poll of this panned out. Or how many people have a stance on this.


I think that nature is relevant in the way a person is and acts, but that the nurture side of things is more powerful. Nurture is not ironclad, but you can see big differences in people who were brought up differently or in different environments.

[Comrade Tortoise]

I am a nature guy. I think that genetics and brain structure largly dictate the sort of people we are, with experience merely hashing out the details.

For example: I am gay. i was born, essentially destined to be gay thanks to a combination of genetics and pre-natal hormone levels which altered my brain structure. What exactly I am attracted to in a man however, is based upon life experience.

On a side note, this does not belont in P&Tit belongs in science and logic. I am therefore moving it. Hope no one minds

[Cynical Cat]

Nurture is important. Since identical twins often (but not always) have the same sexual orientation, more is going on than just genetics or natal hormone levels. Unless we have data on Ben and his mother, we don't even know if this is true, merely that is statistically likely. Early childhood nutrition is tied to brain development, without which Ben (or Caz or whoever) wouldn't be as bright. Education, diet, how lucky you were in the parental lottery, whether or not you are living too close to a toxic spill, all of these things shape you. It isn't a matter of which one is greater, because both of them are extremely important.

[Surlethe]

55%-45%

[xBlackFlash]

In most cases, twins end up being polar opposites as far as personality goes, despite being raised the same way. Though you can credit some of that with twins trying to be different to create their own identity. Now I know this isn't actually possible, but if you had two of the exact same person and put them in different households, they would end up extremely different too.

[Dartzap]

Well, I'd say something real useful in this here thread..if I had not forgotten all my NvN notes at college

In groups discussion, one of my group (who is a mother) said that she generally tried to incorperate a little bit of both "stratagies", because of the fact that someone who is nurtered into being a swot, may not gain the social skills one migh get if they were raised in a natural manner and gone to public school., as it has been claimed that people who are nurtured (Ie:Home educated) will not gain the social skills that are nessecery to be able to work in a proper enviroment, and may suffer from delusions of grandeur and have an ego the size of a planet.

However, there will are some disadvantages to letting the child develop on their own, for example whilst in a public school, they suffer bullying, and have very low self esteem which in turn could lead to depression.

Alot of parental orginisations today believe that one of the best ways to raise a child is to use the best "bits" from both of the different methods.

And that folks, is all I can bloody remember of my notes

[elderdan]

Might as well ask if Earth is a planet of daylight or of nighttime. Everything is a mix of both. The ask the question is to imply a dilemma that doesn't exist.

--The Elder Dan

[Ace Pace]

Dart, all that means is that you necro this thread when you return from break.

Personally, genetics plays an initial role, but as we all know, brainwashing can take over, and nurture is nothing but very gentle good intentioned brain tweaking.

[Caz]

To facilitate debate, we'll take a look at a case study: the controversy over the XYY chromosomal deformity.

1. Introduction

Efforts to make use of increasing knowledge about the genetic component of human development and behavior have been a frequent source of serious ethical controversies. Support among geneticists, other scientists and the educated public for the eugenics movement, which advocated efforts to improve the human race by controlling presumed heritable characteristics, resulted in such misguided governmental policies early in this century as the large-scale sterilization of "inferior" individuals. Legislation authorizing such forms of social engineering was met with increasing criticism from those who questioned the morality of such practices as well as those who doubted the validity of simplistic biologically determinist models of complex human social behavior.

The reaction to the extreme and horrific use of eugenics measures by the Nazis in their campaign to promote the superiority of a cleansed Aryan "race" resulted in a temporary hiatus in research and development in applied human genetics. By the 1960s, however, increasing understanding about the genetic causes of such specific conditions as Down's Syndrome and sickle cell anemia were again arousing support for efforts to seek genetic explanations - and perhaps improvements - for a wide range of human "deficiencies" from various sorts of socially deviant behavior to susceptibility to environmental hazards.

The explosive growth of facile genetic engineering technologies and, in particular, the potential applications of the information gained through the Human Genome Project is destined to greatly amplify both the quantity and the variety of ethical concerns related to attempts to screen, control, manipulate or modify people based on their genetic predispositions.

A frequent underlying theme in disputes over "progress" in applied human genetics is rooted in the nature-nurture controversy. Those who do research into the genetic factors related to complex human problems are seen by their opponents as diverting attention from and ultimately undermining attempts to ameliorate the socioeconomic conditions related to the problems. In the view of these opponents, genetic differences are likely to be less important than social inequalities in determining most human behavior. Furthermore, they argue that the end result of a biological determinist perspective is discrimination against, rather than help for, those who are deemed inferior or defective.

The XYY controversy offers a case study that dramatically illustrates many of the ethical issues that arise when efforts are made to explore the social implications of human genetic differences.


2. Background

In 1961, a paper was published in the medical journal Lancet reporting the first man to be discovered with an extra Y chromosome in his cells, in addition to the normal male complement of one X and one Y. Within the next few years research reports appeared that purported to show that

XYY males were predisposed to violent and criminal behavior. This claim was widely publicized in

the news media. By the mid-1960s XYY was being referred to as the "criminal chromosome." In 1968 lawyers in at least two cases succeeded in persuading juries that their clients were less culpable for their crimes because they were XYY males. If this was not sufficient to persuade the public that XYY individuals were potentially dangerous social misfits, the erroneous report that a vicious serial killer of eight student nurses in Chicago was an XYY male surely had that result.

As is often the case for sensationalized, premature publicity about unproven scientific findings, the subsequent research that debunked the connection between the XYY karyotype and any demonstrable link to anti-social behavior received very little publicity. Thus the myth persisted that males with an extra Y chromosome were likely to manifest excessive violence and other undesirable social traits. This fallacious association even made its way into biology textbooks.

Several research projects underway during the 1960s were aimed at examining the actual prevalence of the XYY karyotype in the general population and attempting to explore whether there were any phenotypic consequences, including predisposition to any form of abnormal social behavior. One such study was carried out by Harvard child psychiatrist Stanley Walzer and Harvard Medical School geneticist Park Gerald. By 1968 they were screening all newborn males at Boston Hospital for Women and following up by studying the development of those with abnormal karyotypes like XYY or XXY. The research was funded by a grant from the Centers for Studies of Crime and Delinquency of the National Institute for Mental Health.

(Source: http://www.wmich.edu/ethics/ESC/cs5.html)

The XYY issue remains hotly debated, and aside from the obvious ethical questions of testing newborns and "implied consent," there are also some key issues regarding the nature versus nurture debate now that the XYY findings have been published and circulated for a full generation:

By telling a child who's tested and confirmed with XYY of this research, are we subconsciously 'dooming' that child to criminal behaviour, via means of social stigma that becomes brainwashing?

And if a delinquent child is subsequently tested and found to be XYY positive, are we therefore decreasing his or her chances of rehabilitation from his or her behaviour due to the parents suddenly feeling as though they don't have to take responsibility for discipline?

[Mayabird]

I must echo Cynical Cat here. The example I use is a potential genius who ends up being a street urchin sniffing glue in [pick your favorite third-world city]. Genetics is a start. It usually isn't destiny. Maybe if all things were equal, genetics would be 90+%* of the influence, but all things aren't equal.

Case in point: if one identical twin has schizophrenia, the other has a 50% chance of also having schizophrenia. They have the same genes, they could grow up together, but one could end up schizophrenic and the other could be 'normal.' If genetics was everything in this case, both should just be schizophrenic, in the same way twins born with cystic fibrosis genes would both have CF. Unless there's been some recent discovery while I've been away, no one knows what the unknown factor is, but it would seem to be something environmental.


* I pulled that number out of my backend.