On The Nature of Evolution

The use of the word polygamy to describe a man taking more than one wife (e.g. early Mormons) is an incorrect use of the word.  Polygamy, in fact, is a general word meaning only the possession during a lifetime of more than one mate.  Both males and females can be polygamous.  The word people are looking for to describe the Mormons (and others like them) is polygynyPolyandry is its inverse.  The definitions used above are of strictly the anthropological sort, however. Biologists speaking more generally of species’ behavior rather than human culture would use these terms to refer to simultaneous multiple sex partners.  And no, I’m not talking about threesomes – just mating with multiple partners over a certain period of time.  More specifically, polygyny refers to a mating system in which fewer males than females contribute to the next generation, and most males fail to reproduce at all.  In this situation, male competition for mates is intensified.  We see this effect in many species, exemplified in those that involve “harems” (e.g. apes, lions).  In these species, the “alpha” males tend to do all the reproducing; lesser males can only mate with females by fighting for the right to party.  The evolutionary result of all this is the “alpha” males’ genes are passed on, and the lesser males’ genes are not.  This result is increased by the fact that males of aforementioned species tend to murder all the young of a harem they take over from another male, so as to ensure only their genes get passed on, and not those of a competitor.  The consequence of all of this?  Those males with traits that give them an edge over other males will have a great advantage, and their children will reflect those traits as well.  Mutations that improve on these advantageous traits will be selected for, as those individuals go on to have many more young than those who do not have such traits.  So what are the traits in question?  Aggression.  Increased Body Size.  Tendancy For Risk Taking. 

I mention all of this only to illustrate the nature of evolution by natural selection – so widely misunderstood by so many people.  People who write off evolution as “random chance” miss the whole point.  Mutation is random (of course, arguments can be made that some mutation is not entirely random, mutagens and UV rays being notable examples).  But mutation is only half the story.  Selection (see above) is the other half, and it is the exact opposite of random.  Once you begin thinking about traits and behavior in terms of the evolutionary advantage they confer upon their individuals, a whole world of understanding opens up to you.  You start to see the effects of natural selection everywhere.  Any behavior or trait you come across inevitably spawns the thought “now how did that evolve? Why was it selected for?  What hypothesis could I make that would explain this? In the example above, the primary trait to be explained is the natural aggressiveness of males in polygynous species, when compared to females.  Many people explain away the difference between males and females in this regard with solutions like “greater levels of testosterone.”  Well, sure.  But why do these males have greater levels of testosterone?  The answer is in their societies, males born with increased amounts of testosterone were stronger, bigger, more aggressive than those that were not born this way.  They defeated these other males in fights.  They mated with most of the females.  And lo and behold, their children inherited their traits.  A new, larger generation of males with heightened testosterone levels went on to do the same thing.  Before you know it, why, nearly all the males are this way!  And then, somewhere in the wilderness, another Child of Mutation is born, with yet higher testosterone levels, and went on to kick ass and take names as only he knew how.  Of course, males with lower testosterone levels still mated with some of the females.  They got lucky in fights sometimes, or another predator killed the stronger male, or something.  Variation of testosterone levels endured.  But over time, on average, it increased. 

Testosterone levels are only an example of one type of selection.  A favorite (or perhaps not) of the biologists (and an oft-cited example) is that of the peacock’s tail.  Why should it have evolved?  In modern terms, it’s like the guy who uses his food money to finance a car.  Sure, you look great, but you’re starving to death.  A peacock expends a huge amount of resources to grow that tail.  Those are resources he could be spending on making more peacocks, or growing bigger, or running away from predators.  So why is it that it evolved?  Crudely (and with apologies to the girls reading this), it goes like this:  Buzz the Peacock wants to get laid.  That’s pretty much all he wants, aside from staying alive long enough to get laid a lot of times.  The problem is, Buzz has a limited amount of resources.  He needs a nice car (tail) to impress the ladies, but he doesn’t have enough money (resources) to afford to buy a nice car and still feed himself properly.  Unfortunately for Buzz, in his species, females really like nice cars.  The bigger, the flashier, the more expensive, the better.  Get a nice enough car, and you’ll have to beat off the ladies with a stick.  So Buzz has a decision to make.  He can keep on driving his old beat-up Pinto and never get laid, or he can buy a Corvette. Of course, if he buys that Corvette, he’ll go hungry, and besides it attracts the cops (predators) more than his other car.  But, hey, that doesn’t matter, ‘cause the girls love it!  As a result, Buzz dies an early death from malnutrition, but leaves more descendents than his neighbor, Phil, who opted to keep his Pinto and eat better.  Of course, they both lose out to Dirk, who went on a fast to finance his Porsche, and died in a month, but got laid more than both of them did put together.  There are more of Dirk’s kids than there are of Buzz, and more of Buzz’s kids than those of Phil.  All of their children inherited the behavioral characteristics of their fathers.  Before you know it, the kids of Buzz and especially Dirk dominate the population.  Sure, Phil’s kids live longer, but they leave few descendents.  The phenomenon described here is that of Sexual Selection.  A corollary of natural selection, it describes traits that would not have come about otherwise but for the sexual preferences of females.  These preferences can be arbitrary, or not, but in the end they have a huge effect on the traits and behaviors of the males of these species. 

Now, I am not just going to amuse y’all with hypothetical ancedotes.  Evidence for these phenomena exist, and are well documented.  I will begin with sexual selection.

Author’s note:  the following is paraphrased from   Richard Dawkins’ book The Blind Watchmaker, pages 213-215, 1996 Edition.

The study in question was done by Malte Andersson, a Swede.  He was not studying peacocks, but rather another type of bird with an especially long tail, the long-tailed widow bird in Kenya.  As Dawkins puts it “Andersson’s experiments were make possible by a recent advance in technology: superglue.”  Andersson reasoned as follows:  if sexual selection in this instance is correct, and males with longer tails really do mate more than males with shorter tails,  then it should be possible to make a male really attractive to females by giving him an extra-long tail.  Andersson captured 36 male widow birds, dividing them into four groups of nine.  One group of nine birds had their tail feathers trimmed to an extra-short length.  The trimmed tails were then superglued to the ends of the tails of the second group of nine birds, giving them extra long tails.  The third group of nine was left alone, as a control group.  The final group of nine had their tails trimmed, then superglued back onto the same individuals,  as a test of whether or not the superglued tails would be detectable by the females, or affect the males in any unusual way.  If sexual selection in this particular species was in effect, and if the experiment (e.g. tails trimmed and superglued) did not affect the indivuduals adversely, Andersson expected this result:  the males with artificially shorter tails should mate less than those with artificially longer tails.  The males with unchanged tails should mate along the average, as should the males with cut and re-glued tails.  The result?  Males with artificially elongated tails attracted nearly four times as many mates as males with artificially shortened tails.  Those in the two control groups had intermediate success.  [/end of paraphrase]

Natural selection, in contrast to the sexual selection illustrated above, has more evidence supporting it (because sexual selection is less widespread), but is more difficult to prove so conclusively (because experiements cannot be made so easily as those with the mating habits of birds, and also because the effects of natural selection tend to express themselves more much more slowly than those of sexual selection).  Experiments, however, can be done, and have been done.  One example is as follows. 

Because mutation, the powerhouse of evolution, occurs in such tiny increments (e.g. small changes in the vast genetic code of an organism), it is difficult to look at two organisms, an ancestor and a descendant, and demonstrate exactly how one became the other.  The fossil record is spotty (as the Creationists never tire of reminding us), and thus little evidence can be presented from the fossil record that will convince people who have not studied biology or paleontology for many years.  To one who has studied bones and fossils for a long time, the fossil record may indicate much in the way of evolution (e.g. the changes in jaw or arm structure over time), to the casual observer, they are just fragments of bones that pretty much look the same.  Therefore, to demonstrate an effect we must focus on things at a scale where natural selection itself becomes apparent.  That scale is that of complex molecules.

An improved ability to reproduce is pretty much the ultimate result of natural selection.  If a mutation takes place that improves the ability of an organism to reproduce (such as the increased testosterone levels as described above), that mutation will natually become dominant in the population.  However, why look at it only from the scope of organisms this large?  If a mutation takes place that improves the ability of molds to reproduce, well then, that mutation will become dominant in the population.  If a mutation takes place that improves the ability of bacteria to reproduce, guess what?  It will become dominant.  Hell, if a mutation takes place allowing viruses to more effectively penetrate cells, insert their DNA, and reproduce themselves via the copying machinery of the cell, well then that mutation will naturally become dominant among the viruses.  Our experiment deals with structures of the approximate complexity of viruses: RNA. 

RNA, or ribonucleic acid, is fundamental to all living things.  It differs from DNA only in the type of sugar used to form its structure (ribose instead of deoxyribose) and a nucleotide.  Without a doubt, it is among the most complex molecules known.  It is speculated that RNA was the precursor to DNA in ancestral organisms, as it shares much of the information storage and self-replicating abilities of DNA.  It would take too long to describe the following experiment in detail – I would have to write several more pages!  Therefore, I am going to summarize the results, and give those interested the ability to research it on their own.  Let me just say that the experiment I described involving RNA was done in 1960 by Sol Spiegelman and colleagues.

Author’s note:  the following is paraphrased from   Richard Dawkins’ book The Blind Watchmaker, pages 131-133, 1996 Edition.

A long row of test tubes was set out, each containing a solution of RNA-replicase, a protein “copying-machine” that copies any RNA it comes across.  Showing how this happens exactly is beyond the scope of this article; I encourage anyone interested to examine the nearest cell biology textbook.  The test tubes also contain raw materials for RNA synthesis, required if any copying is to be done.  You can’t make a car if you don’t have any steel.  A tiny amount of RNA is dropped into the first test tube, and copying ensues.  Now, some of the genetic material solution from the first test tube is dropped into the second, and the process repeats itself.  Now, a drop from the second test tube is used to seed the third, and so on.  Occasionally, after millions of generations of copies (and this happens within each test tube, because of the quantity of the molecules), copying errors, or mutations occur.  Most of the time, these mutations are detrimental, but sometimes, these mutations increase the ability of the RNA molecules to reproduce themselves with RNA -replicase.  If the mutation is detrimental, that particular verision of RNA only copies itself a few times in its test tube.  If, however, the copying mutation is beneficial, that version of RNA replicates itself rapidly, quickly overtaking the test tube with copies of itself.  When that test tube is used to seed the next, the next test tube is quickly overtaken by copies of the *improved* RNA.  If we examine the RNAs in a long succession of test-tubes, we see what can only be described as evolutionary change.  But it goes further than that.  The scientists repeated the experiment, this time adding a kind of poison to each test tube (ethidium bromide), known to inhibit the ability of RNA to replicate itself.  As expected, the first test tube of RNA replicated far less than that of the control group described above.  However, as each test tube was used to seed the next, an amazing (or perhaps, expected) thing happened.  As mutations occurred, some proved resistant to the poison, and dominated the replicated population.  As those were used to seed the next, the mutated RNA increased in population.  In only 100 generations of test tube seeding, the experimenters created a version of RNA that could self-replicate in extremely high concentrations of ethidium bromide, 10 times as concentrated as the poison that could retard the replication of RNA of the original strain. [/end of paraphrase]

Sure, as creationists and their ilk are wont to say, evolution “is only a theory.”  And while I know this subject has been harped upon ad absurdum in the archives of SEB, let me say it again:  theories are, by their very definition, well-supported by evidence.  Copernicanism is a theory.  Relativity is a theory.  Quantum Electrodynamics is a theory.  I’m listening hard, but I don’t hear anyone questioning the results and predictions of these theories, despite of the fact that at least the inner workings of the last two listed are just as mysterious to the average Joe as that of evolution by natural selection.  The reason Copernicanism, relativity, and QED are not attacked by those with an ideological axe to grind is because they do not, at first glance, seem to contradict anything in the ideological framework of those who object to evolution.  Oh, but they used to, didn’t they?  I seem to recall that Galileo was threatened with torture, imprisonment, and death at the stake (he ended up with lifelong house arrest) for his support of Copernicanism – the theory that the Earth went around the Sun, rather than vice-versa. Giordano Bruno, was actually burnt at the stake for the very reasons that Galileo was placed on house arrest.  But I am not going to stop there.  I am going to suggest some good reasons for the Creationists and their ilk to challege other tenets of science.  Geology, to begin with.  According to the geologists and paleontologists, fossils and ancient rocks were created millions of years ago, by slow geological processes of the earth.  Would you challenge these scientific disciplines?  Of course, look at Kent Hovind and his Dinosaur Adventure Land.  Well, the method by which those rocks and fossils are dated, radiocarbon decay (and other types of decay), is controlled by the weak nuclear force – a force explained to extreme accuracy by quantum mechanics.  This science is certainly mysterious to many people – why not challenge it as well?  Special relativity states that as an object’s speed approaches the speed of light, times slows down relative to the observers.  Could this be the reason for the long lifespans of those described in the Bible? Perhaps they were living just outside a black hole, which as general relativity would tell us, has the same effect as high speeds in terms of time dilation.  You cannot pick and choose which scientific disciplines you want to believe.  You can question them all you want, but if you want to be taken seriously, you must challenge them with evidence.  Not ideology. 

I could go on, but I grow tired of this argument, and I don’t want to bore my readers.  If I have not included references you are interested in, please let me know here, and I will post them.  Let me say in conclusion that I am not a biologist any more than I am a physicist, just a CS Major who like to read books.  Therefore, if I have gotten my facts wrong, feel free to post corrections.  I will be glad to hear from you. 

8 thoughts on “On The Nature of Evolution

  1. Excellent overview.

    Dawkins also covers much of the same material (and more) in The Ancestor’s Tale: A Pilgramage to the Dawn of Evolution and Climbing Mount Improbable, which I haven’t quite finished.

    Just a couple of comments on your opening. In Ancestor’s, Dawkins presents a graph showing harem size vs male to female mass ratio for a number of species of seals. He goes on to observe that most species are either polygamous (your usage) or monogamous and that polyandry is relatively rare. As to humans

    “Even so, by the standards of seals and many other animals, we are only slightly dimorphic [mass ratio]. Less so than gorillas but more than gibbons. Perhaps our slight dimorphism means our female ancestors lived somewhat monogamously, sometimes in small harems. Modern societies vary so much that you can find examples of almost any preconception.”

    He goes on to indicate that wealth or clout with the chief might serve as substitutes for physical size.

    Incidentally, contrary to what we (guys) might like to believe, we are not equipped for dimorphism.

  2. Incidentally, contrary to what we (guys) might like to believe, we are not equipped for polyandry.

    Well, it depends, does it not, on what you mean by “equipped”.  A very sticky point indeed.  We almost certainly are not evolved to be strictly monogamous, but apparently males and females have different strategies.  Complex and hotly debated.
    There’s lots of literature about this.  A good starting place is “The Myth of Monogamy”, by Barash and Lipton.

  3. The bigger, the flashier, the more expensive, the better.  Get a nice enough car, and you’ll have to beat off the ladies with a stick.  So Buzz has a decision to make.  He can keep on driving his old beat-up Pinto and never get laid, or he can buy a Corvette.

    Well, it’s not really a decision.  Buzz the peacock is kinda stuck with the “car” from birth.  I think when it gets phrased as a “decision”, it gives the creationists fuel. 

    In short, the horny peacocks will overrun the pinto driving peacocks.

  4. More specifically, polygyny refers to a mating system in which fewer males than females contribute to the next generation, and most males fail to reproduce at all.

    Zilch alluded to this already, but:
    I think it’s important to mention why (relative) monogamy (or at least non-preferential polygamy) is a nice middle ground: it is more advantageous for females to be polyandrous and more advantageous for males to be polygynous, no matter what situation you’re in, because females have an interest in concealing the parentage of their children (if the men don’t know which ones are theirs, they’ll protect them all) and in getting the strongest sperm to impregnate her and because males have an interest in spreading their genes as far and wide as they can, and in making sure their genes outnumber others’.  To state the obvious, females are exempted from the desire to spread genes because they can only have one child at a time and they maximize their multiplication by simply becoming pregnant.  As for why there’s a need to spread genes at all is a stickier question, but there is a need to reproduce and these are the forces at work.  As such, in mainly polygynous situations, the females often try to subvert the males in attempts to conceal parentage.  Monogamy (or at least non-preferential polygamy) is a nice little compromise because children are protected and each male can contribute to the gene pool without wasting time on aggression, body size, etc.  I think monogamy was probably essential to the development of culture, but that’s going off-topic.

    Anyway, because of the females’ situation, true polyandry is quite rare.  It’s only really advantageous when the gestation period is short and males are doing the childraising, as with some species of birds.  It helps if females produce more than one offspring per gestation.

    Variation of testosterone levels endured.  But over time, on average, it increased.

    And to make matters more complicated, it’s not purely testosterone that’s responsible.  Aggression is controlled by a whole lot of genes and at least 3 different hormones.  This means 2 very important things:

    1. That changes to enhance aggression or other characteristics are not concrete changes; they can be affected by many things including codependence, environment, etc.

    One example of this is skin color, which is determined by a host of genes such that children end up being somewhere between the shades of their parents, but never darker or lighter (except in the case of a mutation in that generation).  Skin color can additionally be affected by any number of environmental, nutritional, and other factors.

    2. That changes to enhance a given characteristic may bring other unrelated characteristics, such as the multi-tasking nature of genes may suggest.

    Sadly, all my notes are packed away halfway across the world, but one exmaple would be if a gene that caused incessant sneezing also caused the hair to be blue.  Vast oversimplification.

    I note this because many people like to point out the inability of genetics to explain behavior, etc.  My response to this is that we are just beginning on the field of genetics.  The structure of DNA itself has been known less than 100 years.  Of course we don’t understand how it all works, but we are beginning to pick out the lines and trace them back.  And the truth is that as far as the basics are concerned, genetics is quite an accurate predictor.  Things like blood type, diseases like Huntington’s, and other examples show that it’s not just a bunch of hooey, and show that genetics is a lot more likely to produce an explanation/answer than the Bible or other methods.

    Also wanted to drive home that the whole crux of the matter is reproduction.  If a genetic mutation makes you more likely to survive—ex. you can live for 5 years on nothing but cheese whiz, but then you die before you can reproduce, it’s a meaningless mutation and will never be passed on.  Likewise, good mutations could be lost because of accompaniment by fatal mutations or illnesses.

    Sickle-cell anemia is another excellent example for natural selection.  (Note: genes come in pairs.)  People who carry sickle-cell anemia (have one sickle-cell gene and one normal gene) have increased resistance to malaria.  Babies born with 2 sickle-cell genes are miscarried.  Long, long ago on the African continent, where malaria was quite a problem, someone had a mutation for sickle-cell.  The related sickness and the probability that one out of four children of carriers would be miscarried were outweighed by the overwhelming advantage of survival to reproductive age.  Natural selection, baby.

    I suppose there’s no real point here, just wanted to add to the fun.  I love this stuff.

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