1. Understanding the Theory of Evolution

                To begin, let’s lay down some ground rules, the first and foremost being that the Theory of Evolution in its most general sense is true.  For me to argue for Evolution would be redundant and ineffective next to the works of far more elegant authors such as Richard Dawkins and Charles Darwin.  Also, for me to constantly consider that this theory is not true would not only be highly unnatural to me at this point but would also detract from the points I am trying to make.  That being said, I believe that my effort to remember that I did not always believe in evolution will be one of my greatest assets in writing this in a way that appeals to both sides of the argument.  So, to make sure we are all on the same page I will begin by describing what is meant (or at least what I mean) by the Theory of Evolution (by natural selection).  

Part 1: “It’s just a theory”

The Theory of Evolution is a theory and we can place both a positive and negative tone on that troublesome first word, theory.  First the positive, when you say “I have a theory” in every day conversation what you actually mean is “I have a hypothesis”.  Scientifically, to be a theory is an extremely prestigious position, only one step down from the peak in the hierarchy of ideas. At the peak are the Physical Laws: the unbreakable and omnipresent rules of the world we live in that set the parameters of every other scientific idea.  They have yet to be contradicted by any scientific knowledge.  Under the conditions of the Laws we can derive models which produce hypotheses.  If the hypotheses of a given model are consistently supported that model becomes a theory.  So, the Theory of Evolution is a general model of how things in the world work which has been supported by all the scientific data thus far.  It is not some offhand idea but an elegant mechanism which has its basis in the Laws and Logic and produces hypotheses which are relentlessly supported. 

It is also important, particularly because it is often not done (likely due to a fear to show any weakness), to emphasize the negative, the limitations, with the positive. Theories describe more complex patterns than Laws: patterns which can interact with themselves and others.  That is the general way of saying that the effect of evolution is not consistent due to interactions between evolutionary forces and between evolution and other mechanisms.  So, while the mechanism is always acting, its product can differ from what we would expect if only the mechanism of evolution was acting.  It is like cycling in the wind, if you keep pedaling in the same direction you will go a different distance or even a different direction depending on the strength and direction of the wind relative to you.  It is these interactions (statistically, both additive and interacting effects) which give Evolutionary Biologists like me something to do: we try to understand not only how evolution will act on a single trait or species but how evolution acting on multiple traits or species interact and how evolutionary mechanisms interact with other mechanisms and forces (e.g. population dynamics, migration, genetic drift, variation through time).  This is all to say that while we may assume that the Theory of Evolution is true that does not mean that just because something is selected for by evolution it will exist.

 

Part 2: “Survival of the fittest”

                The great beauty of the Theory of Evolution is that it is an amazingly simple process which leads to equally complex and far reaching results.  It is this situation, though due to different reasons, that I choose to devote so much of my time to its study and that I am inspired to write this series.  The former is due to its power and in no small part to simply how my brain works: I am terrible at memorizing facts but good at making logical leaps. With a good understanding of evolution and a common level of knowledge of humans I can deduce something about almost any field involving living things (either as the subject, creator, or the participant) even though I may know very little.  The latter, my motivation for writing all this, is due to its simplicity.  The Theory of Evolution suffers from a “a little bit of information is a dangerous thing” problem: it is simple enough that anyone can understand the basic mechanism in a few minutes and influential enough that everyone should have an opinion on it but its application is far more complex that one would guess from a first glance.  This means that those opinions, whether correct or false, are often poorly justified (tangentially, while hopefully I will be more strongly justified I am still vulnerable to this when I speak beyond what I know from the scientific literature but that freedom is the point of this being a blog). So, at the risk of empowering more people with a little bit of knowledge here is the theory:

                There are only three requirements for evolution by natural selection to occur: (a) variation among individuals, (b) differential survival/reproduction (fitness) correlated with these traits and (c) heritability of traits (children are similar to their parents).  Under these conditions the traits of the individuals in a population will change between generations, though as mentioned above the size or direction of change will, all else being equal, vary based on what other forces are also acting.  If you need evidence of (a) just go look out your window or check out the profile pictures on your Facebook page, the variation in this world, both between and within species is truly astonishing.  The evidence for (c) is equally obvious, particularly since the discovery of DNA, the medium of inheritance.  Finally, while harder to observe in everyday life, I don’t think it is much of a stretch to ask you to assume that in most every population, some individuals produce more offspring than others.  What it really comes down to when trying to decide if evolution will occur and how strong it will be is how well these requirements come together: whether the differential fitness of individuals is correlated with variation in heritable traits. Basically, does having a certain trait (or set of traits) make an individual more likely to have more offspring over their lifetime and are those offspring likely to have that trait as well. 

                The final thing I wish to clarify is what is meant by fitness in “survival of the fittest”.  Above I mentioned “differential survival/reproduction” and “offspring over their lifetime”.  What fitness means at its purest level is the rate at which an individual is able to propagate its genes into future generations.  For species with fixed generation lengths, like annual plants, this simply means the number of offspring produced or, from a probability perspective, the probability of surviving times the number of offspring produced if you are fortunate enough to survive.  Things get more complicated though if you don’t have a fixed generation length.  For example, if I have children who have their own children before my brother has his children then even if he has more offspring in then end than I do he may have a lower fitness than me since relative to him my grandchildren count towards my fitness.  As such, different strategies can be used to achieve the same level of fitness.  Evolutionary biologists simplify the recipes for these strategies by considering how an organism puts resources into the three mutually exclusive components of fitness: survival, growth, and reproduction.  I find this is easiest to imagine as a game where you start off with a given number of turns and a given number resources per a turn and you want to collect points. Each turn, your resources can either be invested into buying more turns, increasing the number of resources per a turn, or converted into points.

                While this covers the basics of the Theory of Evolution, the last point highlights one idea which possibly shapes our lives more than any other, the concept of trade-offs.  If you want to invest more into survival you have to invest less in growth or reproduction, all else being equal.  If you want to spend time reading this blog you have to sacrifice time you could be doing something else. As economists say, there is no free lunch.  I bring this up not only because it is important that we always remember that every benefit has its cost, but because trade-offs have shaped how we think and interact and are at the root of why evolution has shaped us to naturally deny evolution as it pertains to us.