Why Another Discussion About Evolution?

February 19, 2012

There are far fewer discussions these days about the validity of evolution than there were just a few years ago, and for good reason. For the most part, evolution is accepted by theists and atheists alike. Albeit theists add that evolution must have been guided by the Divine hand, even if the guidance was apparently through the natural processes that we can observe.  That’s an interesting discussion too, but not the one I’m attempting to target here.

The question about evolution is still very relevant to some whose conservative interpretation of their sacred writings (the Bible, the Qur’an, the Tanakh, etc) is at odds with it.  This post isn’t my attempt to put forth any new evidence or arguments – that would take more moxy than I’m able to muster!  It’s not even an attempt to put forth an exhaustive case for evolution – still too much moxy!  The purpose of this post is to provide those who object to the theory of evolution with a ready forum in which to explore the topic, in the context of the other discussions on this blog that they might be participating in.

We can observe the mechanisms of evolution first hand. For example we can observe the causes of genetic mutation, like copy errors during reproduction, and external influences like radiation, and interaction with external chemicals. We can also see how the mutations are directly related to new traits – in many cases we can trace a specific trait to a specific set of genes.

We can see natural selection in action. Natural selection happens when organisms interact with their environment. Traits that are beneficial in a certain environment give the organism a reproductive advantage. Conversely, traits that are detrimental can hinder reproduction.  Shifts in the environment can change which traits are advantageous and which traits are detrimental.  Thus detrimental traits in one environment can become advantageous traits in another. Organisms with advantageous traits are more likely to generate more offspring, thus the trait becomes predominant.

There are hardly any believers left who object to “micro-evolution”. Virtually all believers now accept that “micro-evolution” occurs. The objection is to so-called “macro-evolution”.  The terms “micro-evolution” and “macro-evolution” are differences without any real distinction – they are folk concepts rather than biological concepts.  There is however a biological concept of “speciation”. Speciation can occur when members of the same species become isolated into distinct colonies. This often happens when colonies migrate and become separated by geographical distance, or by newly formed features in the geography – like bodies of water, mountain ranges, or climate shifts.  The isolated colonies evolve independently over time, each accumulating it’s own unique set of mutations.  Over time, the drift in genetic makeup of the isolated colonies can be substantial enough so that individuals from one colony are no longer capable of producing fertile offspring with mates from the other colony.  Once this happens, the colonies are said to be different species.  Since the colonies are no longer able to share genetic traits, they can’t re-converge. From this point forward, the individual colonies, now separate species, continue to evolve independently.  As a result, their traits continue to diverge to the point where we would recognize them as different species by casual observation – they “look different”. You might think of this as “macro-evolution”.  Speciation has been observed first hand in various living plants, flies, worms, and other organisms. And of course we find countless examples of speciation in the fossil record.

We use independent means to observe that evolution has occurred over time. We can deduce a family tree (a model of ancestral relationship) based on the morphology and age of the vast number of species that are preserved in the fossil record – some quarter of a million or so species that are represented by countless individual organisms.  We can also deduce a family tree by looking at DNA of living species, to determine how close one species’ genetic sequence is to another.  For example, chimpanzee DNA is much closer to human DNA than to fruit fly DNA. Therefore chimpanzees and humans are more closely related than either humans and fruit flies, or than chimpanzees and fruit flies.  These completely independent methods of observing our evolutionary past yield virtually the same family tree.

Evolution provides an excellent explanation for the progression of single-celled organism, to cell colonies, to simple multi-celled organisms, to the more complex organisms (including us!) that we can observe today.

How can a belief in the supernatural evolve?  Is belief in the supernatural somehow a beneficial trait?  And if not, does our belief in the supernatural suggest something more to us humans than can be explained by evolution?

We humans (and some other animals to a lesser degree) have evolved the ability to think abstractly.  This enables us, among other things, to predict outcomes of hypothetical scenarios in our minds, rather than being forced to learn everything by trial an error through our physical actions.  This has clear evolutionary advantages.  This same abstract thought forms the basis for complex thinking and verbal communication – also very advantageous.

Along with abstract thought, we (and most other animals) have evolved the ability to distinguish between living organisms and inanimate objects. That is, we can tell the difference between agents, like a butterfly in our garden, and non-agents like a feather floating erratically in the breeze.  However like anything in nature, this ability is not perfect.  Sometimes we mistake agents for non-agents (we don’t recognize the panther stealing stealthily across the grassland), or we mistake non-agents for agents (a shirt hanging in a dark closet looks just like a ghost!).  From an evolutionary standpoint, it’s better to err on the side of mistaking a non-agent for an agent (don’t take any chances – that could be a predator and we might be its lunch!) than to err by mistaking an agent for a non-agent (we missed lunch because we didn’t recognize the pray).  We’ve evolved to err on the side of “seeing ghosts” than to err on the side of “getting eaten”.

Seeing “ghosts” and thinking abstractly about “what a ghost is and where ghosts come from” are a few examples of the kinds of things at the root of belief in the supernatural. We sense something that feels like it’s really there, but we can verify that it is not really there.  We then conclude that things that aren’t physical can exist (that is, we tend not to doubt the accuracy of our feelings).

Belief in the existence of abstract, unseen agents evolves through reasoning, to become beliefs in things like animal spirits. We assume that the unseen agents have a familiar origin, like agents we can see – people and animals. The belief evolves into ancestral gods when we reason that our ancestors were with us when they were alive (when we could see them), so they must still be with us now since they are still alive, but we just can’t see them. And if they are with us, they must still take care of us like they did when we could see them. If they take care of us, it means they can still make things happen – they have power to affect change in the environment. Abstract concepts of celestial gods proceed from there. This, combined with our reasoning that everything has an origin, becomes belief in creator gods.

Not every persistent trait is advantageous. Take male breasts for example.  Some traits are simply byproducts of advantageous traits, like female breasts for example.  Similarly, belief in the supernatural might be a by product of erroneous agency detection, coupled with the ability to think abstractly about “ghost” agents.  Though it could be merely a byproduct, I think belief in the supernatural actually is beneficial.  Tribes that are more organized around authority can dominate tribes that are less organized.  Belief in gods is a ready source of authority – both in terms of the belief about what the gods might require of us (we seek to appease authorities or to perhaps gain favor from them), and also in terms of the authority that self-appointed spiritual leaders claim to have – spiritual leaders claim first-hand knowledge of the gods and what the gods want: “The gods want you to put yourself in harms way to protect our village! Disobey them and the gods will kill you!”

Theists who don’t accept evolution because it conflicts with their theistic beliefs, won’t particularly like these conclusions.  That’s expected and understandable.  Shouldn’t we accept any conclusions that are most strongly supported by the evidence, even if we don’t particularly like the conclusions?  My challenge to you is this: while you examine the evidence that underpins evolutionary theory, and while you look for ways to refute the theory (Refuting a theory is a good thing by the way! Science is based in falsifying theories and cannot stand without it!), be resolved to accept whatever your reasoning suggests is the truth.

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What is the evolutionary explanation for having two sexes?

February 16, 2009

Andy asks: “What is the evolutionary explanation for having two sexes (man and woman)?” Thanks for the question, Andy!

Sexual reproduction began with simple single-cell organisms (eukaryotes). Since sexual reproduction provides much more genetic variation in a population than asexual reproduction does, it follows that species which could reproduce sexually were able to more quickly evolve in response to environmental changes than species that reproduce only asexually. It was therefore the asexual reproducers who were better able to develop into higher plant and animal forms.


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