Showing posts with label Evolution. Show all posts
Showing posts with label Evolution. Show all posts

Thursday, July 7, 2011

Counters to Conservapedia (Part 11): Chromosome Numbers

In this Counter to Conservapedia's Counterexamples to Evolution, I get to address one of my favorite examples in human evolution: Chromosome Numbers.
from Wikipedia
Variation in chromosome count (ploidy) is impossible in evolution. One member of a species with 2 sets of chromosomes cannot mate with a member with 4. Thus, for the chromosome count of a species to change (and thus account for the variety of counts in nature) a vast portion of a species would have to evolve a new chromosome set simultaneously.
On the surface, this could seem like a legitimate argument.  But as always, we must look a little deeper to see their errors.  We should know that chromosomes package the information of DNA which help pass our genes from one generation to the next.  In humans, your mom and dad each gave you 23 chromosomes to give you a total of 46.  Each species has a specific number of chromosomes.  Dogs have 78, garden peas have 14, and the Adder's Tongue Fern carries 1,260 chromosomes.  

Mistakes in the number of chromosomes (polyploidy) usually prove lethal or at least cause many problems for the offspring.  Children with Down Syndrome are born with 47 chromosomes while other disorders have similar number mistakes.  The point being, in order to accurately pass on our species information you need the correct number of chromosomes.  

From an evolutionary perspective, closely related species tend to have the same number of chromosomes.  All of the Great Apes have 48 chromosomes in their cells.  Except for one, humans.  We only have 46, yet we are consistently groups with chimpanzees, gorillas, and orangs.  Since we know we couldn't just lose two whole chromosomes or we would die, something must have happened.  And it did.

The idea was simple.  Two small ape chromosomes must have stuck together to make a larger human chromosome.  This way, no information gets lost but we still "lose" a chromosome.  We confirmed this by analyzing human and chimp chromosomes.  Chromosomes come with two special non-coding regions.  Telomeres act as caps on the end of a chromosome (like the aglets on your shoelaces) and the centromeres show up in the middle for the processes of mitosis or meiosis.  A normal chromosome would have two telomeres and one centromere, while our hypothetical conjoined chromosome would have 4 telomeres and 2 centromeres.
from Wikipedia

When scientists scoured our blueprints, they found the Chromosome #2 fit the bill.  That chromosome has four telomeric regions, one active centromere and one inactivated centromere.  Later, scientists discovered the two ape chromosomes which came together.  Human Chromosome #2 contained all of the matching genes in the two smaller ape chromosomes.  So at some point after the human lineage split from the chimpanzees, the chromosomes combined and became the second largest chromosome in our cells.  Mystery solved!

Chromosomes do carry incredibly important information.  Losing whole chromosomes can cause serious consequences.  Yet, they act as any genetic material.  Chromosomes (or parts of chromosomes) can be duplicated, deleted, inverted, or translocated.  These chromosomal mutations play a huge role in the evolution of species and provide excellent evidence to counter the ridiculous claims of Conservapedia!

Thursday, June 30, 2011

The Rap Guide to Evolution

Baba Brinkman has put together an album called The Rap Guide to Evolution.  He produced 16 songs which are pretty guide.  I will post one track called Natural Selection which will actually roll through the whole album.  To hear the rest, you can follow this link.

Thursday, June 23, 2011

Counters to Conservapedia (Part 10): Observing Speciation

Now for our next installment of correcting Conservapedia's misconceptions of Evolution.  Here is an interesting one:
There are no historical records of anyone directly observing one species evolving into another, which would certainly be something worth writing about. Surely of the millions of species we have, someone would have witnessed one come into existence had it evolved.
This misunderstanding shows up quite often and is, as you can guess, wrong.  It presents a fundamental error in how science works.  The writers of Conservapedia seem to suggest that we can only truly know that some has happened if it is directly observed.  While science does use observation as an important tool, much of science is determined through another powerful tool, inference.  By looking at empirical evidence obtained in the field or the laboratory, scientists can make inferences about what happened.  Without inference, no criminals could be convicted without an eyewitness.  Yet, most Creationists willingly accept the results of forensic science to convict a murder on nothing more than a DNA sample.

DNA provides strong evidence because of our unique patterns of nucleotides.  Well, each species also has a unique pattern which provides ample evidence for the inference of common descent.  The use of DNA in evolutionary biology has revolutionized our understanding of the science.  DNA studies confirm evolutionary predictions and produces new species histories.  As most people know, humans and chimpanzees share roughly 98% the same DNA, gorillas share slightly less, orangutans less and so on.  This DNA evidence allows us to infer our species place within the animal kingdom among the Great Apes.

Like DNA, we have numerous lines of fossils showing the evolution of whales, horses, camels, reptiles, birds, primates and, even, humans.  But also like DNA, these fossils help us to infer what happened in the distant past.  These do not represent direct observation, which Creationists seem to require.  Species are changing from generation to generation all around us.  We can see quickly changing in the fur color of the desert pocket mouse or the peppered moth.  Scientists went to the Galapagos Islands every year to measure the beak sizes of the population.  When a drought hit the island, they measured changes in the average beak size as the available food changed.  An important principle of evolution describes the big changes that occur to species through incremental changes from generation to generation.

But my favorite examples of evolution in action are ring species.  In Northern California, you can find a population of very diverse salamanders.  The species has spread out down both sides of the Central Valley.  While separated by a large valley and unable to reproduce with each other, the species develops two different adaptations to survive.  On one side, the population acquired camouflage to blend into the environment, on the other the population became bright colored to mimic a poisonous newt.  When the two different populations meet at the southern end of the valley, they do not recognize each other as viable mates.  As David Wake says in the following video, these populations are well on their way to become two species right before our eyes.  Please, watch the clip for a better understanding of how these cute little salamanders destroy the Conservapedia argument.

Thursday, June 2, 2011

Counters to Conservapedia (Part 9): HIV Immunity

I have strayed from one of my favorite topics: proving the writers of Conservapedia know nothing about evolution or science.  So I am bringing back the Counters to Conservapedia theme and will continue to debunk their misconceptions.  As the conservative answer to the liberal bias inherent in reality Wikipedia, Conservapedia created a list of Counters to Evolution.  As I have already refuted their statements about extinctions, genetic diversity, eyes, males and females, wisdom teeth, beauty, mutations, and feathers.  And now Conservapedia brings this interesting counter to evolution:
Evolution should have removed HIV from the human race as we would have built an immunity to it, much like bacteria do to anti-biotics, yet we have not. In fact the continued existence of disease is proof against evolution as natural selection would have left only humans who were immune to them.
This example misconstrues the rates at which evolution occurs.  Because HIV causes such a horrible disease, then humans should evolve immunity in a short period much like bacteria and antibiotics.  Bacteria develop their resistance through a basic example of natural selection.  Our antibiotics kill 99.9% of all the bacteria within the patient.  The 0.1% that survive already possess a random mutation which makes them immune to the medicine.  Those that survive reproduce through asexually reproduction by basically cloning themselves as quickly as every twenty minutes.  This process has occurred with several different bacterial strains, insects with pesticides, and in many natural cases involving venoms and toxins.

Interestingly, the writers of Conservapedia chose to attack evolution by confirming that evolution.  They complain that it doesn't happen in humans.  As you can guess, they will be wrong.

So why haven't humans evolved resistance to HIV?  The simple answer is that we are not bacteria.  Bacteria are single-celled organisms while we have 50-100 trillion cells in our body.  Some strains of bacteria can reproduce every 20 minutes, which would produce roughly over 1000000000000000000000 identical bacteria in 24 hours.  Humans average a new generation every 25 years.  Since HIV has only affected humans since the 1950's, only 2 or 3 generations have been impacted by the disease.  Basically we reproduce much slower that bacteria and genetically respond to environmental changes over longer periods of time.  Thankfully, medical advancements replace our slower genome and can help protect us from HIV exposure and affects.  So IF the genetic resistance to HIV existed it would take a long to pass through the population effectively eradicating HIV from affecting our gene pool.

Interestingly, there are some people who are immune to HIV.  That's right.  Some sex workers in Africa carry a gene that makes them resistant to being infected by the virus.  Even with repeated exposure to the pathogen, they did not contract it.  Viruses enter a host cell by mimicing a receptor on the cell surface.  Those people immune to HIV simply lack the particular receptor which HIV uses to get into the cell.  But even then, that would not guarantee the end of HIV as viruses also evolve reproducing at a faster rate than we do.  Viral evolution explains why you need a new flu short every year and why we now have multiple strains of HIV.

So to review: Conservapedia complains about evolution because we don't evolve as fast as bacteria do.  But we are far larger, more complex and reproduce much slower than bacteria.  Even with these disadvantages, some of us are already immune to HIV which could potential spread throughout the species.  HIV immunity causes no problems for the theory of evolution and actually makes a great example of evolution at work.

Monday, May 23, 2011

Dawkins on the Beauty of Life

The Ancestor's Tale may be one of my favorite popular science books ever, except for maybe The Greatest Show on Earth.  Both books were written by the most prominent evolutionary biologist in the world, Richard Dawkins.  If anyone wants to understand evolution and our place within life, I suggest you read these two books.  We may disagree on matters of Religion and God, but his clarity and knowledge of science overwhelms me.

In The Ancestor's Tale, Dawkins lays out a history of the human body by taking us on a pilgrimage.  During our trek backwards through time, we meet up with all the other species making the path.  Our closer cousins join us sooner than our more distant relatives, but all the species on Earth eventually converge to the same point the last universal common ancestor (LUCA).  As groups join us, they bring their stories that tell us something more about evolution.  It is a long, long book, but good science and good information.  I recommend it strongly.

In this video, Dawkins makes the closing statement from the book about the beauty of life.  It is good.  I promise.


Wednesday, May 18, 2011

South Park on Evolution

Always out to mock anyone and anything, South Park took on The Theory of Evolution.  In this case, they show a teacher who really doesn't accept evolution presenting the topic to the class.  As you can expect, his explanation leaves a lot of stuff out and would create more misconceptions among the students. Sadly, this kind of thing happens throughout the country. Though, I doubt that even the worst high school teachers would not use this kind of language.

Enjoy! (Warning: Language- it is South Park!)

We need our science teachers better prepared to present SCIENCE to our students.  As our country falls behind in science and math, we only need to look to the above example to figure out why.  Too many science teachers either outright reject modern science or feel uncomfortable teaching it because of ignorance or intimidation.  Until we can get past this problem, our children and future will continue to suffer through horrible explanations of science like the kids from South Park.

Friday, April 29, 2011

The Evolution of Creationism

In humor you will find truth.  This comic strip from Calamities of Nature speaks volumes about the evolution of creationism.  Cultural evolution works in similar ways to biological evolution, except bad ideas will stick around much longer than bad genes.  
Calamities of Nature

Thursday, April 21, 2011

Sad Video

This video pops up on the internets every once and a while.  It is either very scary or very sad.  These high school students have received a very poor education from their "science" teacher who doesn't seem to know very much about the topic he was hired to teach.  It is appalling that this could happen, be video taped, and the guy would still keep his job.

I vote that this is a sad video.  Enjoy?

Thursday, February 10, 2011

Counters to Conservapedia (Part 8): Feathers

Here's the next installment of my responses to Conservapedia's list of misunderstandings about evolution.  This is one of their arguments:
The development of feathers, which could not have conceivably "grown" from the scales of dinosaurs.
From A modern bird and archaeopteryx
First of all, Because you can not conceive of a mechanism doesn’t mean one doesn't exist.  That simply means that we haven’t discovered it yet.  Science, and truth, does not depend on your personal understanding.

Second, we have discovered a lot about the evolution of feathers which Carl Zimmer outlines in an article for National Geographic (read it here).  Bird feathers are marvels of the biological world which have perplexed many scientists.  Shortly after Darwin published On the Origin of Species, paleontologists unearthed archaeopteryx with a mixture of avian and reptilian traits.  Most importantly, this bird/reptile had feathers.  Later on, scientists discovered more similarities between our modern birds and the extinct dinosaurs.  Theropod dinosaurs (T. rex and Velociraptors) shared many anatomical and behavioral similarities with birds, but most importantly they had feathers even though they were far to big to fly.  It seems the fight evolved from reptiles with feathers, rather than feathers evolving in flying reptiles.

This enormous collection of fossil evidence linking birds and dinosaurs still does not answer the original puzzle: how do avian feathers evolve from reptilian scales?  The answer begins like most evolutionary problems during development.  Feathers erupt from the skin called a placode, which is the same way scale develops.  While the reptilian placode expands horizontally (gets wider), the avian placode elongates into the bristle shape which modifies through evolutionary history into the feathers we see today.  You can follow this pattern by observing the development of chicks.

To add an intriguing twist, the development of feathers is controlled by gene which researchers discovered in modern alligators who definitely don't have any feathers!

Monday, January 17, 2011

Our Extended Family

The Smithsonian Institute recently reopened their Hall of Human Origins with new fossils and new models.  I am very eager to go check it out.  But since I have no time, I will have to be satisfied with pictures.

Scientific American has a slide show of our extended family.  It looks pretty good.  Check it out!

Thursday, January 13, 2011

Counters to Conservapedia (Part 7): Mutations

Here is the next segment in response to Conservapedia's Counterexamples to Evolution.  I enjoy this because, I love to answer questions about evolution.  Anyways, here is part 7:
From InteliHealth: Not all mutations are destructive.
Mutations cause a loss of information, rendering it mathematically impossible for mutations to advance the complexity of life. Similarly, entropy (disorder) increases over time, making it impossible for order to increase on its own.
Some mutations result in loss of information, while others can produce information.  Deletions, translocations, etc can lose information.  However, duplications provide the ultimate opportunity for new functions to develop.  

In a duplication, a segment of DNA (gene) becomes copied.  Both copies are fully functional and produce proteins.  In this case, changes to one of the copies will not affect the health of the individual as the other copy still produces a protein.  Such instances allow for possibly beneficial changes can accumulate in the copy of the gene.

And remember, natural selection doesn’t favor all mutations equally.  Bad mutations get weeded out quickly (you die), neutral mutations do not receive any selection pressure, and beneficial mutations spread very quickly through the population.

To conclude, not all mutations have a negative effect.  Some mutations do not affect the organism at all and can be found in non-coding DNA.  Following these Single Nucleotide Polymorphisms (SNPS) help us to solve crimes and determine paternity, but also show us the patterns of common ancestry in modern organisms.

Note: The Entropy Example will return later and I will give a much more detailed response to that.  Here I will simply dismiss it as they seem to not understand the point of the Second Law of Thermodynamics.

Wednesday, December 29, 2010

Counters to Conservapedia (Part 6): Beauty

Time for another tidbit from Conservapedia's Counterexamples to Evolution post:
Evolution cannot explain artistic beauty, such as the brilliant autumn foliage and staggering array of beautiful marine fish, both of which originated before any human to view them; this lacks any plausible evolutionary explanation.

“Beauty is in the eye of the beholder.”  We define beauty as something that produces an appealing sensation in our minds.  That which we define a beautiful, may produce no result in another species.  Remember, to a fly, a pile of dung is more beautiful than brown sand and clear water.

Beauty results from the wiring of our brains to interpret our surroundings.  Beauty itself does not exist outside of the mind.  Things were not beautiful and then we evolved to recognize it.  Instead, we describe things as beautiful due to our brain's perceptions.  

The beautiful tail advertises this male's fitness.
With respect to the “staggering array of beautiful marine fish” and birds (which they forgot), the dazzling colors we see are advertisements to their potential mates.  Those colors and patterns make the species unique, so that they don’t mate with the wrong species.  The colors also display the fitness of the individual- bright colors require more energy and means that you are more healthy.  Think about the peacock and his tail.  The bright colors and multitude of eyespot show his fitness.  In studies, birds with bigger tails gained more mates, produced more healthy offspring.

Monday, December 27, 2010

High School Test on The Theory of Evolution

When debating creationists, I am always amazed by their ignorance of the science of evolution.  For the most part, Creationists are not stupid people but often very intelligent and highly productive members of society.  Unfortunately, they don't understand the science.  This would not matter until they begin attacking evolution through their own misunderstandings and misconceptions.

To test some basic knowledge, I am going to post some of the questions from the actual test that I give to my students on The Theory of Evolution.

Thursday, December 23, 2010

Counters to Conservapedia (Part 5): Wisdom Teeth

I scrolled down the list a little further to find this gem from the List of Counterexamples to Evolution from Conservapedia:

We have the perfect number of teeth to fit in our mouths. While creationism perfectly accounts for that result, evolutionism predicts a contrary result: As our faces evolved from chimpanzee-like faces to human faces, the shortening of the muzzle would have caused the teeth to become overcrowded in the mouth.
    Where to begin?  I almost think this is an example of Poe's Law (Sarcasm masquerading as Fundamentalism), but I will approach it as a "serious" argument.
    OralMD.Com: Wisdom Teeth another vestige of evolution!

    Many humans have too many teeth.  In fact, I had to have my wisdom teeth removed because of the impact they would have on my other teeth.  Many people go through this same process- clearly.  We do not have the "perfect number of teeth to fit in our mouths".  

    Let's look a little deeper.  One way to divide the primate group is by dentition (pattern of teeth).  New World Monkeys have a dental pattern of 2 incisors, 1 canine, 3 premolars and 3 molars (1/4 of mouth).  Old World Monkeys, Apes and humans have a different pattern of  The third molar in humans we know as the Wisdom Teeth.  From this we conclude that  OWM, Apes and humans shared a common ancestor after the NWM.

    Next, we can look at the muzzle of hominids.  Chimps and other apes have a muzzle that sticks out in front of the nose (bigger jaw = more room for teeth).  On our line to the other hominid species, the muzzle gradually shortens to our modern profile.  That shortening crowds the teeth which have not changed, thus producing the problem of the wisdom teeth.  Variation with in the human family, shows that some of us don't need to have our wisdom teeth removed, while others do. 

    Monday, December 13, 2010

    A Teacher on Evolution

    Perhaps no topic intrigues me more than evolution: the theory and the controversy.  During my time in Grad School, I studied the impact of religion in schools and eventually the Christian teachers who teach evolution.  One major assumption shows through any discussion of evolution and creationism: there are no Christians who accept evolution as a scientific explanation.

    I grew up in Winton-Salem.  This is where I went to school and I went to church.  My first encounters with evolution were a joke.  My "science" teacher did not believe in evolution and refused to discuss it.  At that time, I was okay with not learning anything new.  Now I am disgusted that I allowed that lack of education to occur.  It was my church that introduced me to Darwin and evolution.  Many of the arguments that I learned were based on a misunderstanding of evolutionary theory, misinformation, or poor logic.

    As I graduated high school with my Southern Baptist Church as my only source of information about evolution, I took off for college.  I was effectively armed with a distrust of evolution and many arguments to defeat any evolutionist.  In high school, I did not think of myself as an eager anti-evolutionist, but my freshmen biology course proved me wrong.  However, the fascination with evolution was just beginning.  When my professor began the chapter on evolution, I went so far to write an angry email (my only correspondence with this teacher) using the arguments that had been engrained in my head.  I even made a speech in my English class against evolution.

    I continued taking biology courses, in particular every evolution course that I could get into.  The more information that I uncovered, the more logical evolution came to be.  At first I realized that it was impossible to deny natural selection.  Sometimes, the individuals with the best adaptations will be more likely to survival.  The allele frequencies would change, thus the populations could change over time.  Even with my newfound acceptance “microevolution” I was still whole-heartedly against “macroevolution”.  It took more time and more evidence for me to change my mind and to finally accept that populations of the same species can be separated from each other long enough to be considered different species.  Either they will not mate with each other or they cannot, either way they are now two separate species.

    How does evolution affect religion?  The truth is, I don’t know.  I know that as a teacher, I will not tell other people what to believe.  In the science classroom, I am going to teach the scientific theory of evolution.  If you want your child to learn creationism, go to Sunday school; but science should be reserved for science.  I will agree that a specific, literal interpretation of the Bible leaves no room for evolution.  But not all Christians believe that the Bible is literal.   But once again, that is a theological argument that should be made in either Church or a comparative religions class.  We should realize that there are Christian science teachers, who will continue to teach evolution.  Evolution does not have to destroy your faith, it may require you change your view of your faith.  Faith is what we believe in the absence of evidence, not in spite of evidence.  Once again, why would God give us the ability of reason, and expect us not to use it.

    Thursday, December 9, 2010

    Does Natural Selection Make Us Selfish?

    In a simple answer:  Not really.  The important aspect of Natural Selection is that certain traits that allow you to survive and produce offspring will always be selected for because now you get to have children.  In some cases of some species, selfishness is selected for because it allows individuals to gather more resources and in effect more mates.  In other cases, cooporation allows for the group to have access to the resources, which makes the population healthier and those better able to produce more offspring. 

    Sometimes, both forces (selfishness and cooperation) affect a population.  In Chimpanzees and other social animals, all organisms work together to warn each other about predators and other dangers.  While at the same time a social hierarchy ensures that only the dominant male (or female) gets to mate with the opposite sex.  The other organisms are left in the cold with no opportunity to produce offspring (except for some tricky business behind the back of the alpha).

    Seed Magazine has an interesting article about destroying the idea that Natural Selection only describes selfishness and says nothing about Altruism (helping others).  The group dynamics of nature's populations show this interesting battle between looking out for the group and looking out for oneself.

    Thursday, December 2, 2010

    Counters to Conservapedia (Part 4): Males and Females

    From Conservapedia's List of Counterexamples to Evolution:
    For evolution to be true, every male dog, cat, horse, elephant, giraffe, fish and bird had to have coincidentally evolved with a female alongside it (over billions of years) with fully evolved compatible reproductive parts and a desire to mate, otherwise the species couldn't keep going.
      From The University of Arizona
      This misunderstanding shows up often.  People seem to think that one organisms changes into the next species one at a time.  Evolution does not involve an individual independently transforming into a new species.  

      Here is what really happens.  A large population of reproducing individuals (with both males and females) become two smaller, isolated groups (with both males and females).  Over time, their DNA changes, leading to new characteristics and “signature” adaptations.  Some changes will be beneficial, while others will not.  Eventually, the two smaller groups will have accumulated enough changes from each other that they are no longer considered to be of the same species.  They no longer recognize each other as a possible mate.  At no point does a new species spring up because one male evolves at the same time as one female.  

      The group changes over time.  That is evolution.

      Wednesday, December 1, 2010

      The Downside of Evolution put up this article by Rob Dunn (from North Carolina) about the disadvantages we all face from having evolved.  I enjoyed Neil Shubin's Your Inner Fish and this list covers many things from his book.  It is important to show these interesting side effects to evolution.  Our bodies show the hallmarks of our past and disprove Intelligent Design "Theory".

      I will summarize the list by giving the list, but I will let you go to the original article to find out more:
      1. Cells (endosymbiont theory)
      2. Hiccups
      3. Backaches
      4. Hernias
      5. Choking
      6. Naked Body
      7. Goosebumps
      8. Wisdom Teeth
      9. Obesity
      Honorable Mentions: Male Nipples, Blindspots in the Middle of the Eye, Muscles for Ear Wiggling, Tailbones

      Evolution acts as a tinkerer remodels upon an existing structure.  New species do not appear out of nothing (de novo), but through the incremental changes of successive generations.

      Wednesday, November 17, 2010

      Robert Sapolsky on Our Metaphorical Brains

      Robert Sapolsky, a Stanford professor, studies primates and what makes us human.  In an online commentary from the New York Times, Sapolsky explains how our brain differs from other animals.  The structure of our brains grow out of the same building blocks as everything else.  The neurons of all animals follow the same structure and work the same way.  Our main advantage is shear numbers.  

      We have 100 billion neurons which create a seemingly infinite number of synapses and pathways.  Some scientists hope to build a connectome to show how each neuron communicates with another.  We have almost finished the complex connectome of model nematode, C. elegans.  The human connectome shows several orders of magnitude more complexity and is years away.  But even without visualizing every connection in the brain, we can understand the importance of these synapses to human capabilities.  Sapolsky notes our unique language center (Broca's Area), fine motor area, and neuron-dense frontal cortex.  Specifically, our frontal cortex controls emotional reactions, personalities, decision-making, and planning abilities.

      However, Sapolsky points to our use of metaphors and symbols to describe reality.  He describes a person eating rotten food.  That person's neurons in their insula will remember the disgusting food and the need to vomit.  The same neurons will fire when a person smells the same food or think about eating similarly disgusting food.  Interestingly, those neurons will fire when we hear a story which "makes us sick" or react to something that it morally disgusting.  We didn't invent anything new, but built upon the existing model.  

      We see the same situation in pain response.  Neurons fire when our body senses pain, but the same neurons fire when the see someone else in pain.  We feel their pain, sometimes almost literally.  The effects of clinical depression disappear when medicines block the actions of neurotransmitters associated with pain.  Perhaps depression manifests because of extreme empathy.

      In many ways, our brains confuse the literal and the metaphorical reality.  The same neuronal circuitry fire in each case - disgust, pain, cleanliness, temperature, or touch.  Because evolution doesn't have to make new structures, our language symbols latched onto the neural networks already associated to the literal response.  Unfortunately, this rigging can confuse our decision-making and create subconscious biases.  Or we can use these responses to alter (control?) other people.  People have found all kinds of tricks to put people into an appropriate frame of mind to get what they want.

      We still have much to learn about the brain itself.  We have even more to learn about the evolutionary changes to the brain which made us human.  

      Wednesday, October 27, 2010

      Counters to Conservapedia (Part 3): The Eye

      Here is another installment of my counters to the Conservapedia's Counterexamples to Evolution.  This week, good design:

      Parsimonious repetition of design elements throughout creation, e.g. the eye's appearance in remarkably different species. For such complex structures to arise repeatedly via evolution is impossible, as evolution is an inherently random and historically contingent process.[3]

      Not all eyes are exactly the same, thus not an example of parsimony.  That eyes became a feature in many species shows their usefulness.  In fact, photoreception is an ancient trait found in the very early common ancestors, which does relate to parsimony.  From a simple light receptor, different organisms have developed compound eyes, camera eyes, slit eyes, etc.  More closely related organisms have much more similar eyes than less similar species.  All mammals share a similar anatomy of the eye, while different species have a few unique adaptations- for instance monkeys and apes have tri-color vision while other mammals do not.  

      The benefits of sensing the environment make eyes a very important and useful adaptation.  You can imagine an ancient paramecium population.  The ability to sense the light around you can provide almost instant benefit.  Or a look at animals and being able to see the movements of predators can help you protect yourself.  In any situation, photoreception dramatically increases your chances of survival.  

      Except when it doesn't.  Cave dwelling animals have lost the need to see in their environments and no longer use their vestigial eyes.  They still grow eyes during their development, but do not use them for any purpose of survival.  That these cave dwellers retain their eyes shows their common descent from ancestors in a lighted environment.  

      For more on the evolution of eyes, check out this Nova video from the PBS Evolution series.

      The eye demonstrates the remarkable power of evolution through natural selection.