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Library of Alexandria: Nature vs Nurture: The Debate Is Framed Wrong - It's All About Ranges

January 11, 2013


The great debate between what matters more, nature or nurture is as pervasive as ever.  For such a long time people would argue about which mattered, nature or nurture, with each side yelling at each other that one or the other is what matters for human traits and characteristics. Gradually people in the middle began pointing out that, quite clearly, it is both. That, generally speaking, both nature and nurture are responsible for human traits and characteristics. You would think that this would be the end of it but all this did was shift the goal posts a bit.  Now, rather than argue which is responsible, the argument has become which is more influential or more important. This new framing of the debate is just as silly as before in my opinion and I hope to explain why here.

Yes, both nature and nurture are important for the development of human characteristics and traits. Yes, depending on which characteristic or trait is being looked at one or the other might be more "influential" to the end result of development. Yes, there are some traits, diseases, and disorders that are 100% genetic and there are some diseases that are 100% environment. It all comes down to what specific thing you are talking about. However, for the sake of simplifying an already complex topic a bit we are not going to focus on diseases and disorders or other outliers that fall into the 100% category. These things are not typically what are being discussed when the nature vs nurture debate flairs up and this is still the wrong way to frame the discussion.  In my opinion, the proper way to look at the nature vs nurture debate is in terms of ranges of potential.  Put simply, for any characteristic nature is going to provide a potential range and environmental influences are going to determine where within that range a person falls.

Lets make things very simple and look at height.  Height is great for this discussion because a persons final height is so incredibly clearly a function of both nature and nurture. I person with poor environmental conditions, namely extremely poor nutrition, is going to be much shorter than they otherwise would have been if they had proper nutrition during development. But lets take a look at this closer and what it means.

When an individual is conceived their genes come together in a way that determines a potential range for their full grown adult height.  This range is essentially at the top end the absolute best case scenario.  If the developing individual experiences all of the right things at all of the right times this is the height that they can possibly become and without significant medical intervention there is no possible way for this individual to grow taller than this.

On the other end of the spectrum you will find the shortest possible height the individual could become.  Essentially, if everything that could possibly go wrong (without killing the individual) goes wrong this is the height they will grow to be.

This height range exists for every individual and based on various environmental factors every individual will, in the end, find themselves somewhere within this range for height. What is important to remember, however, is that this range exists for every human trait in some form or another.

Do not get me wrong, this gets incredibly complicated very fast and we by no means know or understand all of the genetic and environmental influences for all but a very few traits.  Interestingly, most of what we understand best are those 100%ers, which I think is part of the reason why the debate raged on like it did.  The 100% items are the least complex because they are influenced by the least number of factors.  A person with for example a trait like sickle cell is relatively simple. When a person is conceived they inherit two genes responsible for encoding hemoglobin S.  If one of these genes is abnormal this system does not function properly and the individual has what we describe as the sickle cell trait. The same is true for the other side of the 100% coin. If a person has X virus or bacteria present in their system they are have the corresponding condition.

Now what about everything else?  More complex traits are complex because they are influenced by a larger number of factors.  In some cases this may mean a large number of genetic factors, in some it could mean a large number of environmental factors, or the most complex situation which would be a large number of genetic and environmental influences.

Take for example intelligence. Lets, for the sake of discussion ignore the controversy surrounding the way we define and measure intelligence.  Intelligence is clearly very complex and absolutely  a function of many genetic and environmental influences.  Still, the range I describe above will exist for every individual's intelligence, despite the complexity and our not knowing all of the factors.  Interestingly, because of the complexity of the brain the range is quite large and will range from the absolute best case scenario leading to the most "intelligent" that person could ever become and the worst case which for this example would include  environmental influences such as severe brain damage putting an individual way at the other end of the intelligence spectrum.  However, even ignoring catastrophic brain injury and other brain trauma and disorders that are obtainable through poor environmental misfortune there will be a slightly less broad range for any given individuals intelligence.

Where a lot of the controversy comes into play on a lot of the individual traits being looked at is when different groups are compared to each other.  Gender, Ethnicity, Nationality, Age, and so on.  Often times we look at statistics and reports that compare the averages of different groups. This is not really all that helpful but it is great for stirring up controversy and thus revenue for the news organizations reporting on the issue. What we should really be looking at are the population ranges and then looking to do what we can to modify environments to maximize the good traits and minimize the bad traits in every population.

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At April 9, 2013 at 10:56 PM , Anonymous Anonymous said...

I think I agree with your position. We each have have a bucket of genetic legos for every numerically measurable trait, but these can be arranged into a house in a variety of ways by the environment.

You mention statistical values being reported for different demographics as especially divisive and rarely productive. I agree, of course. However, imagine if thorough, irrefutable scientific studies demonstrated a real gap in inherent range between two groups, based on ethnicity or gender. Would it be possible to take rational action on that conclusion in a non-discriminatory way, or do you think "discriminatory" is the wrong word for the phenomenon (perhaps, "specialization")?

Or what if, perhaps, the range is shown to be equal but different environmental factors maximize those traits depending on demographic categories. How would (or should one) go about setting up ideal facilitation for growth for the different groups without running into issues of segregation, "separate but unequal" or so on?

Not criticizing you at all, mate, but you seem bright and you pose an interesting question. As such, I'd like to hear what you think about a few possible consequences of answering that question.


At August 8, 2013 at 10:12 AM , Blogger Paul D Pruitt said...

There's nature and nurture but what about choices? Doesn't that determine human traits and characteristics too? Also if epigenetics is determined by environments, can't individuals make choices as to which environments to place themselves in? If we are talking about height, can't individuals make choices about what amounts to feed themselves?

At August 8, 2013 at 10:23 AM , Blogger Daniel Kroner said...

The "choices" any individual makes at any point in time are the result of the combination of their biology + all experiences/environmental influences. Choice is an illusion, unless you introduce some type of non-physical force/entity into the picture (soul) for which there is currently no evidence.


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