Skip to content


by Bill Meacham on May 18th, 2012

If we want to know what human nature is – and we do, as that will tell us how to live a fulfilling and happy life – then we have to understand evolution. The theory of evolution describes how generations of living organisms change over time. Humans are living organisms. We are subject to and products of the same evolutionary pressures as all other living things. Understanding how we got to be as we are gives us insight into how we function. Knowing that, we can adjust our actions so as to function well.

It is called the theory of evolution, but “theory” does not mean conjecture, speculation or mere opinion. The term in its scientific sense means a well-supported body of interconnected statements that explains observations and can be used to make testable predictions. The theory of evolution has been confirmed over and over again.(1) No serious biologist takes it as anything but fully established. In the words of Theodosius Dobzhansky, author of a major work on evolution and genetics, “Nothing in biology makes sense except in the light of evolution…. Seen in the light of evolution, biology is … the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts, some of them interesting or curious but making no meaningful picture as a whole.”(2)

It is unfortunate that religious fundamentalists, misusing the term “theory,” regard evolution as unproven. Some go so far as to say that all the evidence that leads us to believe in the immense age of the universe and the proliferation of species over time, as opposed to instanteous creation some 6000 years ago, were planted by the creator merely to give the appearance of great antiquity. Dobzhansky, a Christian, has this retort: “It is easy to see the fatal flaw in all such notions. They are blasphemies, accusing God of absurd deceitfulness. This is as revolting as it is uncalled for.”(3)

The religious believer may view evolution as God’s way of creating the world. The pantheist mystic may view evolution as the One Being’s way of unfolding and coming to know Itself over time. The secularist, the atheist or the merely agnostic may view evolution as the way living beings have propagated themselves, blindly and without foresight, in increasing diversity and complexity. Regardless of your opinion on the ultimate purpose of it all, it is important to understand how evolution works because the theory reflects reality, and basing your actions on reality works out much better than not. So the rest of this essay is a summary of the theory of evolution.


The term “evolution” in a general sense means a process of change or growth, often taken as a process of continual change from a simpler to a more complex state. In biology, the term refers to two things:

  • The observed fact that the distribution of inherited traits in a population of organisms can change from generation to generation.
  • The theory that the various types of animals and plants we find around us, including ourselves, originated in earlier types and that their differences are due to modifications in successive generations.

The basic concept of biological evolution as we understand it today is surprisingly simple. Charles Darwin, its originator, called it “descent with modification.” The concept is this:

  • An organism’s offspring may vary slightly from the organism itself. Offspring may have slightly different traits from the parents or the same traits in different degrees.
  • Organisms typically produce more offspring than can survive and reproduce, given the resources available such as food, shelter, sexual mates, etc. Hence, there is competition for such resources.
  • In the competition for resources, some variations have an advantage over others. For example, one child’s beak may be slightly better at picking up small seeds than another’s, or one child may have slightly better eyesight than the other and hence be better able to find food and avoid predators.
  • The individuals with advantageous variations have more offspring than those without.
  • Since traits are heritable (are inherited from parent to child), this causes the population, over time, to contain more of the favorable variations and fewer of the unfavorable ones.

Darwin called this process “natural selection,” as opposed to artificial selection, the intentional breeding for certain traits that produces such differences in the same species as the Great Dane and the Chihuahua. The underlying mechanism is the same in both kinds of selection: certain individuals have more offspring than others, so their traits become more widespread in the population of that type of organism. A subset of natural selection called “sexual selection” is a result of competition for mates. In order to have offspring, an individual must not only survive but reproduce. Competition for mates, most often among males for females, selects for traits that enable males to dominate other males, such as horns and antlers, and for traits that attract females, such as plumage and other adornments.

This process happens slowly but inexorably. The variation between parent and offspring is most often minuscule, but over enough generations large changes result. A series of small, incremental changes can, given enough time, produce the extraordinary variety of speciation we find around us.(4)

This process is not purposive.(5) No organism intends to produce a better beak or a better eye. It is merely a fact of life that those with favorable variations tend to have more offspring than those without, each of which in turn have the favorable variation. Among that generation’s offspring, those that further amplify the favorable variation have more offspring, and so on for generations. Conversely, unfavorable variations tend to die out over time. We should not take phrases such as “designed by natural selection” as implying a conscious, deliberate designer.

What is inherited is a trait, a feature of an organism such as eye color. Traits are passed from generation to generation as discrete units. Gregor Mendel conducted a famous study in which he mated pea plants, some of which had purple blossoms and some of which had white. The offspring did not have pale purple blossoms, but rather some had purple and some white, in distinct proportions.

What passes these discrete traits from generation to generation is the gene, the fundamental physical and functional unit of heredity. A gene is a segment of nucleic acid that, taken as a whole, specifies a trait. Genes are contained in chromosomes, which are composed of DNA (deoxyribonucleic acid), a polymeric molecule found in cells of the body. DNA governs the production, growth and reproduction of the cells of the body. The current understanding of biological evolution, developed since Darwin’s time, recognizes the gene as a fundamental, if not the fundamental, unit of natural selection.

Functionally, genes pass traits from generation to generation. They do this by replicating themselves from parent to child. Physiologically, the same chemical structure appears in the child as was found in the parent. In combination with other genes and triggered by environmental influences, the genes cause the parent’s traits to appear in the child. The term “trait” includes physical forms, such as bone density or eye color, behaviors such as sounding mating calls in certain seasons, and mental abilities or talents such as stereoscopic vision, empathy or language.

Genes are not the only replicators. Ideas, symbols, behaviors and other elements of culture replicate as well. Genes replicate from generation to generation; their cultural analogues, dubbed “memes,” replicate from mind to mind through writing, speech, gestures, rituals and the like.(6) The principles of evolution apply the same: like a gene, a meme is a replicator, except memes replicate contemporaneously between minds rather than historically between bodies. Just as genes are subject to competition – the ones that replicate to the next generation are those that help their host bodies to survive and reproduce – so also are memes: only those that are catchy enough to secure attention in human minds replicate from mind to mind. What makes a meme catchy can be something as trivial as a memorable tune or limerick, or something that has continuing usefulness, such as ideas that hold cultures together.


So there is an abbreviated account of evolution. What does it mean for understanding human nature? To know what we are we must understand where we have come from. It is not just in our physical form that we have evolved, but in our mental capacities and in our cultures as well. Are we, then, merely products of our evolutionary heritage, unable to change? No, but in our attempts to change, it certainly helps to understand what we have to work with. Understanding that inherited traits are the result of natural selection can help put in context findings about how we humans actually function in the world, a topic to which I intend to turn in future essays.


(1) See, for instance, the section titled “Predictive Power” in Wikipedia, “Evolution as fact and theory.”

(2) Dobzhansky, “Nothing in Biology Makes Sense Except in the Light of Evolution.”

(3) Idem.

(4) There are three sources of variation: mutation, gene flow and genetic shuffling through sexual reproduction. Mutation happens when environmental influences cause tiny changes in the chemical structure of genes, altering their functioning, or when cells divide and imperfectly replicate their DNA. By far the majority of mutations are destructive, degrading the gene’s ability to do its job of directing the growth of organs and characteristics, but some enhance that ability, or change it so that the result is advantageous. Gene flow refers to the transfer of genes between populations of an organism. Individuals from one population mate with individuals of another and transfer genes between them. Genetic shuffling through sexual reproduction causes the combination of genes in each child to differ from that of its parents. In species that reproduce sexually, each individual has two copies of every gene (specifically, each has two strands of DNA, each of which contains chromosomes, which contain genes). In sexual reproduction, the child gets some genes from the mother and some from the father, and the combinations vary with each child.

(5) Religious or mystical thinkers may postulate a divine purpose that guides the process of evolution, but the science of biological evolution does not need that hypothesis to explain the process.

(6) Dawkins, The Selfish Gene, chapter 11, pp. 189-201.


Dawkins, Richard. The Selfish Gene, New Edition. Oxford and New York: Oxford University Press, 1989.

Dobzhansky, Theodosius. “Nothing in Biology Makes Sense Except in the Light of Evolution.” American Biology Teacher vol. 35 (March 1973) reprinted in Evolution versus Creationism, J. Peter Zetterberg ed., ORYX Press, Phoenix AZ 1983. Available online at as of 14 May 2012.

Wikipedia. “Evolution.” On-line publication, URL = as of 2 February 2009.

Wikipedia. “Evolution as fact and theory.” On-line publication, URL = as of 14 May 2012.

Wikipedia. “Meme.” On-line publication, URL = as of 16 May 2012.

From → Philosophy

  1. steve spindler permalink

    Wonderful job, Bill. We miss you on Saturday mornings.


  2. Excellent essay!

  3. Rich permalink

    Hi, Bill. Enjoyed the discussions at the wine bar the other day.

    You said the following above: “Understanding how we got to be as we are gives us insight into how we function.” I’m wondering if you are familiar with the discussion of function from Larry Wright. You might find that interesting. His original discussion is found in “Functions”, Philosopical Review, 1973, vol. 82, pp 139-168. As I understand it, the article is pretty much the basis for modern philosphy of science’s take on functions. What makes it relevant to your statement is the direct relation between evolution and function. If I recall correctly, he suggests that a thing can be said to have a function if its function can explain how that thing came to be. In the case of biological function, the function of something (camoflauge, say) can explain the existence — survival — of the animal that has the camoflauge (and thereby the existence of the organism’s camoflauge). For an artifact, the function would be the purpose for which the artifact was created, if not for which it would not exist.

    Coincidentally, Larry is a long-time faculty member at my former graduate program at UC Riverside. I had the great experience of TAing for his critical thinking class.

    My concentration in grad school was mental content, specifically what’s known as “content externalism”, or the Twin Earth stuff. The Wrightean notion of function is commonly used by philosophers of mind to explain the relation between the world and the content of thought. I happen to think that’s the wrong tree entirely. Larry himself is quite the Wittgensteinean and probably wouldn’t much align himself with that sort of business.

    Back to your statement, I’m not sure about the relevance of evolution to
    understanding the state of humans today. My initial feeling is that we can just look at humans today, independent of how they got to today. Going back to mental content, Donald Davidson suggested that having a history was necessary for having mental content. It’s the somewhat bizarre Swampman thought experiment. See I don’t think history is necessary for mental content — well, not as a conceptual truth about thought. Similarly, I think I’d be suspect about a connection between an organism’s needs/goods/ends and its history. I would say I’m neutral on the question of whether there’s a connection between an organism’s function and its history.

    Having written that, I’m now wondering… Wright’s functions lend themselves to attributing function to an animal’s part or subsystem. I don’t know that they can be used to attribute function to an entire organism (or species?) I’d be interested in seeing if that can be done.



    • Thanks for the tip about Larry Wright. I have downloaded his paper and look forward to perusing it. (I got it from jSTOR via Austin Public Library. They have access to a ton of journals, which I find convenient and exciting.)

      You say > My initial feeling is that we can just look at humans today, independent of how they got to today.

      Yes but having a plausible story how we got to be as we are helps us think of possible other implications, including how to deal with what we are and how we behave.

      You say > Wright’s functions lend themselves to attributing function to an animal’s part or subsystem. I don’t know that they can be used to attribute function to an entire organism (or species?) I’d be interested in seeing if that can be done.

      There is a whole design discipline called Permaculture that looks at physical systems such as gardens and landscapes and how each element functions to provide inputs to and utilize outputs from other elements. Companion planting is an example, and there are many more. See my “Permaculture Ethics and the Chain of Benefits” at I don’t know whether this is a different sense of “function” from Wright’s.

  4. steven harp permalink

    “It is merely a fact of life that those with favorable variations tend to have more offspring than those without, each of which in turn have the favorable variation. Among that generation’s offspring, those that further amplify the favorable variation have more offspring, and so on for generations. ”

    Can you give me a field study supporting this claim? Or, some direct experimental evidence? Anything besides the self-evident proclamation weighted with established authority. It may seem an obvious truth, but for Aristotle it was obvious that a heavy object would fall faster than a light object. It was so obvious that no one bothered to check it out for 2000 years because no serious thinker considered it “as anything but fully established.”

  5. Stephen Fretwell permalink

    Sigh. Bill, you should have prayed for deliverance from mental haunting spirits before you wrote this. Just on the outside possibility that such beings might exist, as, say, viruses invade the minds of dogs, and make them mad. Because, if such spirits do exist, you might well write such a subtly confused summary, and never know why.

    Your confusion is embarrassing because of your references to artificial selection, which you admit is readily observable. So, if some higher intelligence is operating on earth. it could very well be using such artificial selection to be producing all the biological diversity we see. This would not be evolution.

    Scientifically, we get a measure of plausibility for an idea from induction. What is going to happen is probably what has already happened. Artificial selection has been observed, natural selection maybe, maybe not. So artificial selection is the more likely cause.

    But, such would need a god-like intelligence to drive it. How likely is that? Again, every known biological creature we have ever observed on earth co-exists with other, god-like creatures, which sometimes use intelligent design to artificially select them or other creatures to mold their biological form and function. Most are themselves unaware of the existence of the god-like living beings they interact with ecologically. So, again by induction, we humans are likely also co-existing with such higher beings, of which we are only dimly aware. We certainly have extensive adaptations (religion) that make most sense if we suppose that such god-like higher beings are a part of our ecosystem.

    But, Bayesian scientific tests of the plausibility of the existence of such higher beings, about 2000 now, have proved that such higher beings exist beyond reasonable doubt. This effectively disproves evolution by natural selection. Granted,adaptation and modification by descent are probably true, as is the time scale suggested. But, the idea of Intelligent Design in scientifically much more plausible.

    Remember, theology was and still is the queen of the sciences, which is the king of truth. If you do the truth table on theological inquiries, you will find that not taking these matters into consideration in your experimental design means that you will always find them irrelevant, whether they are true or not. The disinformation spiritual agents, if they are truly out there, will block your discovery of them, unless you block that effort. Untrue, of course, prayers are meaningless. But if true, they are an essential part of any experimental design. Either way, left out, you foolishly conclude that they don’t matter.

    Remember, friend philosopher, Diogenes could not find an honest man, and therefore would probably have rejected you as well. Robert Trivers echoes this problem in modern science. And most dishonest men deceive themselves first, so that they can lie more effectively. The authorities on this matter, mostly atheists, are notoriously untrustworthy.

    So, not your usual level of brilliance.

    • You say
      > if some higher intelligence is operating on earth. it could very well be using such artificial selection to be producing all the biological diversity we see. This would not be evolution.

      I alluded to this by saying “The religious believer may view evolution as God’s way of creating the world.” I think divine artificial selection would indeed be a form of evolution, but perhaps we are quibbling about words.

      • Stephen Fretwell permalink

        The original statement of evolution was the origin of species by means of natural selection, and the word, e- (out of) -volution (the life cycle) explicitly implies natural, and not artificial selection. Evolition would be the term for the intelligent design implied by the origin of species by means of artificial selection.

        Hence, the mocking, “The origin of specious by the selection of natural means.”

  6. steven harp permalink


    You have presented evolution as this singular stylized opposition between Neo-Darwinism and a fundamentalist creationism. There is another view that does not require the leaps of faith on either of these two sides. The Neo-Darwinian view is the attempt to explain the higher in terms of the lower and is part and parcel of materialist metaphysics.

    But in a broader empirical view, genes don’t evolve, ecosystems evolve. Organisms don’t evolve, whole systems evolve. No system is separable in its entirety as either part or whole. The idea of emergence is a manmade fabrication. The concept of emergence is a description not an explanation.

    There is no denying life’s progression in this. It does not counter the fact that simple precedes the complex in the temporal order. There is no need to deny anything in the sequence that carbon dating tells us transpired. The question at issue is the means by which this advance is effected.

    There seems to be a sense that Neo-Darwinian evolution is beyond criticism, either scientifically or philosophically. Quoting biologist Lewis Thomas, “Evolution is our most powerful story, equivalent in its way to a universal myth.” One is either a Neo-Darwinian or a fundamentalist creationist or a believer in spiritism. Neo-Darwinism has become a new fundamentalism in the minds of many. There is another alternative. I suggest readings in the following demonstrating the incompleteness of Neo-Darwinism:

    • Evolution in Four Dimensions -Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life, by Jablonka and Lamb.
    • A Third Window, Natural Life Beyond Newton and Darwin, By Robert Ulanowicz
    • Reinventing the Sacred, A New View of Science, Reason and Religion, by Stuart Kauffman
    • The Rainbow and the Worm, The Physics of Organisms, by Mae Won Ho
    • Darwin’s Black Box, The Biochemical Challenge to Evolution, Michael Behe
    • Mathematical Challenges to the Neo-Darwinian Interpretation of Evolution, Paul Moorhead (one might also look at the separate calculations of Hoyle, Crick, and M.P. Schutzenburger in this regard.)
    • Jonathan Wells, Icons of Evolution
    • Johnjoe Mcfadden, Quantum Evolution
    • Michael Polanyi, Personal Knowledge

    These are works by mainstream and well-known authors. There are many other such works showing Neo-Darwinism as the paradigm going down. It is the topic on which current thought is most confused and mistaken. It is the kingpin of the modern mind because from the standpoint of that mind so much has come to rest on it – modernity is more invested in this doctrine than any other. Its anti-theological significance seems to outweigh its scientific value.

    Neo-Darwinism is the claim that everything about man, his complete complement of faculties and potentials, can be accounted for by a process of natural selection that works mechanically on chance variations in genetic coding. Any one of the above readings will show the narrow slice of the big picture that Neo-Darwinism represents in the origin of species and descent of man.

    It should perhaps be noted that one can criticize this theory without having an explanation of the origin of species. One could criticize the theory of phlogiston without knowing current explanation for combustion. No theory is final and as Popper says, there can be no final statements but only a series of succeeding propositions.

    With the advent of molecular biology it is becoming increasingly difficult to account for the evolution and irreducibility of complexity at the molecular level in terms of chance variation and selection. Such necessary chance events to account for the astounding complexity at the cellular level requires a greater time span than the age of the universe. It is plausible that there are organizing principles at the molecular or quantum level. (see Mae Won Ho and Michael Behe) And when one looks at organizing principles at the atomic level one must then look at the very constants of nature that govern all physical behavior. So design in this sense is inescapable. Design is inherent in the universe. Consider the atom.

    • Thanks, Steven. You’d probably be interested in a new book by Edward O. Wilson, The Social Conquest of Earth, which argues that the long-discounted notion of group selection actually has a lot of evidence for it. Evolution takes place not just in individual organisms but in organisms that live in groups as well. Jonathan Haidt’s recent The Righteous Mind discusses the implications of that fact for understanding how religion and morality have formed and how they both influence contemporary politics.

Leave a Reply

Note: XHTML is allowed. Your email address will never be published.

Subscribe to this comment feed via RSS