Sunday, July 17, 2011

External Testicles and the Cremaster/Dartos Reflex

What would Youtube and America's Funniest Home Videos be without clips guys getting hit in the crown jewels? (Wouldn't it be interesting to know what percent of youtube views are related to this genre?)

As you well know, male humans (and other boreotherian mammals, et al) have external testicles because their optimal temperature for sperm production is below that of our core body temperature--about 94 degrees Fahrenheit.  Why, though?

  1. Optimal Enzyme Temperature
    1. Enzymes are molecule machines that help reactions take place.  Enzymes have optimal temperatures because if they are outside of that golden medium then they change shape and don't work as well (or at all).  There are enzymes that are involved in spermatogenesis like spermatogenic DNA polymerase beta and recombinase activities that are optimized at 94 degrees F.
    2. Other temperature enzymes might not have evolved yet.   The obstacles for their evolution might be quite unlikely--you'd need a new enzyme and mutations that would cause internal testicles at the same time.   Seems easier to just keep doing what we're doing.
    3. Maybe our enzymes are a throw back to cold blooded reptile, lower temp mammal or before.  So, we got hot and our testicles got to the  business of  moving.
  2. Maybe it's a throw back to ridiculous sperm competition.
    1. Perhaps there was sperm competition so intense that one of our ancestors had to move its testicles outside of its body to house them and now it's just stuck around.
  3. Maybe it's protection from internal body cavity pressures changes like from galloping, running, etc.
Since we're kind of a menagerie of evolutionary mementos having external testicles can pose some negative consequences for humans, just one of which is inguinal hernias. Male testes descend from inside the body after birth. Why aren't they on the outside in utero? Because males and females are made from the same evolutionary template. Male testes come down from roughly where the female ovaries are (their equivalent) through the inguinal canal. This usually works fine, but because evolution isn't perfect it sometimes causes some nasty hernias to come through that same hole. I'll share the most PG of the pictures I found (freaky thing to Google).
Because our external temperature is not static, nor can our testicles be.  There are two  main muscle groups that control the movement of the testicles closer and further from our warm bodies.

  • Dartos Muscle
    • This is a layer of muscle right below the skin of the scrotum.

Dartos muscle can be seen as the red, muscular layer right below the skin.
  • Cremaster Muscle
    • Provides much of the up, down lift to thermoregulate and protect.

  • Cremaster and Dartos Reflexes
    • So, evolution has a problem.  It wants our testicles to be cool, but the further out the more vulnerable they become.  The musculature above isn't just to regulate temperature.  This can easily be demonstrated by the cremaster and dartos reflexes.  Many men (and women by extension) are unaware that if the inside of the thigh is touched it causes the testicle of that side it rise closer to the body for protection.  Many men will also relate to feeling a sympathetic pain if they hear/see something extremely painful or disgusting.  I don't know if this is cremaster or something else, but I've heard from others that they experience it.  (Comment anonymously below if you know what I'm talking about, can recount a time and physiological response.)

Dolphins--are warm blooded, but with internal testicles.  Apparently they actually have veins that run near the testicles after having circulated below the skin to cool down--a.c. for their testes.

Pictures from here, here, here, here, here.

Saturday, July 9, 2011

Bible Verses that Can Be Conversation Killers

There are people that may misread what I'm writing saying that I'm trying to be disparaging to the Bible. Not at all. I'm trying to open channels of dialogue and there are particular interpretations of these verses (interpretation and original intent are different, as you well know) that can be walls to crucial conversations between ideologies/religions.  Some of the below is largely straw man, but nevertheless I've felt the influence in a number of conversations.

Let's keep the dialogue open.

Let's learn from each other.

And, "Come now, and let us reason together." --Isaiah 1:18a

  • 1 Corinthians 1:18-25,  "For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God. For it is written, "I will destroy the wisdom of the wise,
    and the discernment of the discerning I will thwart."  Where is the one who is wise? Where is the scribe? Where is the debater of this age? Has not God made foolish the wisdom of the world? For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach to save those who believe.  For Jews demand signs and Greeks seek wisdom, but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God. For the foolishness of God is wiser than men, and the weakness of God is stronger than men."
    • The dangerous interpretation/application: "You won't get it. So, why bother talking?"
    • Better possible interpretation/application: The foolishness isn't that we should be illogical.  It's that power humbled itself (Phil 2).  It's that our mind, wisdom, faculties are finite and that there's a bigger, grander truth outside of ourselves.

  • 1 Corinthians 2:14, "The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit."
    • Dangerous interpretation/application: "You can't get it.  You don't have the ability."
    • Better possible interpretation/application: We can't do it alone.  We need others to understand.

  • 2 Timothy 4:3, "For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear."
    • Dangerous interpretation/application: "You only believe what you want,anyway.  So why bother discussing?"
    • Possible better interpretation/application: Examine your own itching ears, not others.  And as the later context admonishes, "Always be sober-minded."

  • Romans 9:20-21, "But who are you, O man, to answer back to God? Will what is molded say to its molder, "Why have you made me like this?"  Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use?"
    • Dangerous interpretation/application: "Don't ask questions."
    • Possible better interpretation/application: Have intellectual humility.  In light of the nature/nurture debate, recognize much of people's weaknesses are not their fault and be patient with them.

  • Job 40:2,7-8, "Shall a faultfinder contend with the Almighty?  He who argues with God, let him answer it...Dress for action like a man; I will question you, and you make it known to me.  Will you even put me in the wrong?  Will you condemn me that you may be in the right?"
    • Dangerous interpretation/application: "I'm a bug.  I can't get it.  I shouldn't question."
    • Possible better interpretation/application:  The universe doesn't always need to make sense to be true.  It doesn't need our approval.  It stands outside of us.  Don't condemn the universe just to be right.  Don't set yourself above reality as its judge.

  • Jude 1: 18b-19, “'In the last times there will be scoffers who will follow their own ungodly desires.'  These are the people who divide you, who follow mere natural instincts and do not have the Spirit."
    • Dangerous interpretation/application: "Everyone else is lost and incapable of being reasoned with.  Their god is their stomach."
    • Possible better interpretation/application: Watch your own desires.  Consider your own motivations for believing what you do. Do as the later context says, "Have mercy on those who doubt."

  • 2 Peter 3:3-4, "Above all, you must understand that in the last days scoffers will come, scoffing and following their own evil desires. They will say, “Where is this ‘coming’ he promised? Ever since our ancestors died, everything goes on as it has since the beginning of creation.”
    • Dangerous interpretation/application: "Your not getting it was predicted.  No point in talking."
    • Possible better interpretation/application:  Not everyone has to agree with you.  That's okay.  Peace is still possible.

  • Isaiah 55:9, “As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts."
    • Dangerous interpretation/application: "I can't even get it.  You certainly can't.  No point in trying."
    • Better possible interpretation/application: Don't follow the example of others who do not forgive and are not faithful (based on context).

  • Proverbs 3:5, "Trust in the LORD with all your heart and lean not on your own understanding."
    • Dangerous interpretation/application: "Don't think.  Just blindly trust."
    • Better possible interpretation/application: As the later context says, "Be not wise in your own eyes."

Thoughts? Reactions?  Other scriptures?  Where did I go wrong in interpretation/application?

    Monday, July 4, 2011

    Fainting and Evolution

    A dear friend of mine from middle school's mother prompted this post.  She woke her husband up at 3am and said that she felt like if she didn't go to the hospital right then that she might not make it to the morning.  Due to unknown causes, she had developed a bacterial infection throughout her body.  At its worst the doctors gave her 5% chance of surviving.  Her body fought back by pulling blood from her extremities and pooling it around her intestines and stomach.  The lack of blood flow to her hands and feet caused them to turn black, go necrotic and they're now battling to save as much of her hands and feet as possible.  So far she's lost half of her right foot and the fingers of her left hand.  As someone who cares about her well being and someone who's interested in evolution I'm left wondering why the hell this's happened.  Why would the body react that way?

    Turns out sever bacterial infections aren't the only time the body pools blood around the intestines and stomach.  It's actually the reason you faint.  It happens during hypothermia.  It's a shock response.  It happens during extreme blood loss.  There's a number of situations where evolution tells your body to pool large amounts of blood around your intestines and stomach.  Let's consider some reasons why.

    • Hypothermia
      • Extremities are the greatest source of heat loss--pool it in the core to reduce heat loss
        • Downside is you're more likely to get frost bite

    • Blood Loss
      • If the blood loss is from your core near your vital organs then you're screwed.  If it's from one of your extremities and you can reduce the blood flow enough for it to clot then you just might save yourself.

    • Fainting
      • Psychosomatic Causes
        • Fear
        • Pain
        • Shock
        • The sight of blood and guts (fear?)

      • Methodology
        • The vagas nerve increases blood flow to the intestines and stomach
        • Blood flow to the extremities (including the head and brain) is reduced
        • Most common in teens and elderly--elderly because of poor blood flow, teens because of a mismatch of size and physiological capabilities
        • Brief in duration--heart rate and vasoconstriction return to normal momentarily
        • Very different from the famous fainting goats that have full body simultaneous muscle contractions
        • Also very different from opossums who are quite alert and don't just pretend to be dead, but also rotten, by secreting a foul smelling substance from their anus and frothing at the mouth

      • Possible Evolutionary Causes
        • To Play Dead
          • Limit Damage
            • If on your own you can't win maybe going limp will...
              • Buy time for the group to respond
              • Make your group feel bad that you're helpless and rally their help
          • Cause Predator to Lose Interest
            • Fight versus meal
              • Because of our size maybe a lot of predators don't think of us as a meal so much as they think of us as a threat.  Playing dead might eliminate that fear and cause them to move on.
            • Maybe many predators don't hunt out of hunger (since so many hunts are unsuccessful and they can go long, long stretches without eating [polar bears can go 8 months while hibernating with pups]), but instead hunt out of the thrill of the hunt, the chase, the excitement, a desire for power, to conquer.  Maybe by playing dead the predator might temporarily be disappointed and lose interest.
          • Not expect you to flee or fight
            • They think they can take their time eating you and then--surprise you're gone!!
        • Defecation/Excrement
          • Maybe the flood of blood once served as an aid to evacuate the bowels and cause potential predators/assaulters to be grossed out.