Monday, August 29, 2011

How Do We Tan?

How does our skin "see" UV light?  How does your skin know to get darker?   To flush with blood during a sun-burn?

If I understand correctly...

  • UV radiation around the 300 nm wavelength hits DNA (chromosome telomeres are particularly vulnerable because of their repeat series of thymine)
  • The photon elevates an electron to an outer shell on part of the molecule
  • This change in atom shape changes the molecules shape
  • The change in molecule shape makes a hickey on the DNA spiral called a pyrimidine dimer
  • The dimer stops proper DNA replication creating incomplete single stranded DNA sequences
  • These sequences combine with an enzyme (Lex A ) which then causes the expression of genes that produce enzymes that repair UV damaged DNA (nucleotide excision repair)
  • The presence of the repair enzymes (somehow) causes...
    • Flushing of blood, aka a sun burn
      • This results in
        • More repair
        • Removal of dead cells (apoptosis)
    • Increased melanin production (by melanocytes) thereby "shading" the cells from further damage
    • We know the DNA repair enzymes communicate to our skin to make more melanin because we can artificially add them to skin cell sample or cause their numbers to rise by chemically damaging DNA and it produce more melanin without UV exposure.  More here.
Real guy, real sunburn


  • Melanin dissipates 99.9% of UV radiation as heat
  • Melanin is also in parts of the fluid in your inner ear, medula, zona reticularis, adrenal gland and other neurons in the form of neuromelanin

Who knew there was more than one kind of melanin?
  • Phaeomelanin that's yellow or red
    • More common in whites/asians
  • Eumelanin that's brown

Vitamin D3

  • So why aren't all humans black?  If melanin is so great for protecting us from DNA mistakes and cancer why don't we all have it in abundance?
    • We need vitamin D3 to make healthy bones
    • UV light turns 7-dehydrocholesterol deep within the skin into vitamin D3
    • I speculate that the heavy use of clothing in colder climates, thus covering more skin, would cause a greater need for lighter skin that is better at producing vitamin D3.  Meaning, that perhaps it wasn't less UV light towards the poles that made some skin colors so light as much as it was heavy use of clothing over evolutionary time.  

What about freckles?

  • Why are freckles patchy?  Why not uniform hue across the skin?  Why do they tend to be on extremely fair skinned people?  Do they use more phaeomelanin over eumelanin?  Are they an adaptation to deal with a loss of function mutation?  Please let me know if you find any answers...
  • Freckles apparently aren't a concentration of melanin producing cells (that is what a mole is), but only a patch of normal density melanocytes that has produced melanin.

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

Works sighted [sic]:

Sunday, August 21, 2011

Anole Lizards - My Summer Playing with Anolis Carolinensis

I did some surprising math to figure out how many lizards I caught this summer.  Let's say I caught two a day (a very conservative estimation).  Times a 5 day work week.  Times 11 summer camps.  That's some where in the neighborhood of 110 lizards!  haha!  (And how many of those poor lizards were repeats!)

This summer I worked at the Challenger Learning Center's helping them put on their science summer camps.  Part of my responsibility was to help lead the recess time.  Recess was spent on a tiny island of green within a much larger bustling downtown scene.  I was perpetually amazed at how many anoles, skinks and snakes there were considering the surrounding metropolis.

This unexpected lizard catcher role came after being a part of recess for a few days and realizing both how many critters were there and how much the younger kids loved to stalk, catch and learn about these city denizens.  So, I capitalized on the opportunity and brought a terrarium from home, clear shoe boxes to view them in and did a little research so that I could pass it on.   Very shortly, me and a few other kids poking around in the bushes turned into me surrounded by up to twenty kids going on an all out "safari" (and, of course, no safari is complete without a good safari hat) stalking these fascinating critters.  I'll share some highlights.


  • I have somewhat mixed feelings about having created a small army (several hundred of kidsover the summer) of kids that now love catching lizards.  haha  But, you can't love what you don't know, though.    And, hopefully they will learn to love and protect nature form playing with it (as opposed to just torturing unsuspecting lizards).
  • Here's the technique I taught the elementary school kids:
    • The Cat
      • Go into stealth mode.  Crouch.  Stalk.  Slow motion.  Blend into the background.
    • The Snake
      • Cock your arm back.  Coil up ready to strike. Move your shoulder in the direction of the prey.
    • The Heron
      • I've seen herons rock their head back and forth before striking prey.  I've been told this can be to triangulate distance, but I also think it may be to take on a "blowing in the wind" branch appearance.  Anyway, it does work if you want to inch your hand towards a lizard.   It's almost like they get a little mesmerized similar to a snake charmer.
    • The Fakey
      • Another technique is to draw their attention to your other hand while you get the other ready to strike.
    • The Strike
      • Aim a little towards where you suspect they'll run and unleash that arm to attack!

Family Ties

Anoles are a part of the iguanidae family of lizards and as such have a fascinating biogeography.  The iguana family can be found in three locations in the world: the Americas, MADAGASCAR and FIJI/TONGA.  That should truly blow your ever loving mind.  Think about where those are in the world.  That's almost exactly every third of the Earth!

How?  Why?

There was a time in the world when South America, Africa and Madagascar were connected and all contained iguanas.  Time passed.  The continents separated.  The iguanas died out on Africa, but stayed in Madagascar and S. America.

How can we explain Fiji and Tonga?  They're 8,000 kilometers from South America!  Some intrepid pregnant iguanas or family of iguanas must have had to drift on the southern equatorial current thousands of miles surviving off fat and perhaps a downed tree!  How many thousands journeyed without making it before that one or few!!!??!!  Unbelievable!


Why do anoles have bright white bellies?  To blend in when predators look from below up at them! They look like the bright sky!


These lizards have pigment filled pores within their scales that can dilate and constrict changing the amount of pigment exposed.  They come in three flavors: yellow, blue and browny black.  Put yellow and blue and you make green!  Some, however, have a mutation that turns off the yellow pigment leaving them a bright blue!

Mirror Attack

Put a mirror slowly in front of a large male anole and they'll display their dewlap and complete several pushups in territorial anger.  Great clip of David Attenborough doing this:

Van der Waal Toes

Anole toes have millions of adhesive hairs on their soles that are so sticky they can walk upside down on glass.  Good overview of the Van der Waal dipole forces that are causing this:

Parietal Eyes

Did you know that many lizards, amphibians, fish and sharks have a third eye?!?!?!  And I can't believe I spent my whole life up to this point and didn't know it!!  This eye sees in the blue/green range and could be involved in circadian rhythms by releasing neurotransmitters like melatonin.  It may also have a function in sunning.  When lizards (and us) go in to the sun, their irises constrict giving the brain the impression that the sun dimmed.  How can they always have a uniform measuring stick for light brightness?  By having an eye without an iris!  As a side note, mammals and birds have lost their parietal eye, but archaeopteryx had one!

Discussion questions:  Why do the males have dewlaps?  Why are the males larger than the females?  Why are there more greens than browns here in Tallahassee vs Orlando?  What's countershading good for?  What do you think they eat?

Works sighted [sic]:
3d skull:,_Irwin

Images from here, here, here, here, here, here, here, here.

Sunday, August 14, 2011

Mismatched - From African Savannah to Concrete Jungle

 We're cavemen living in suburbia.  Time and technology have changed, but we're still left with a brain designed for life in an extinct past.  Times changed, but we've remained the same.  So, what exactly has changed?  Where are we the most mismatched?  Where do our weaknesses lie?

  • Monogamy/Polygamy
    • Why is it that if men supposedly rule the world that polygamy is nearly completely eradicated in the world?  Seriously!!  This is a great question!  If for the complete history of humanity we've been polygamist why is that now we've chosen to reject it?  Well, author Robert Wright says that it might be the first evidence of the the democratization of the world and that it wasn't women that fought for monogamy, it was the men.  Here's why: women in a polygamist society are better off--all the women get a mate and the mates are typically all high quality (that's how they get more than one woman).  The men on the other hand don't have equal results--some men get a lot of women and some men get none.   There came a time in history, though, where the lower class men wouldn't take not having a  woman.  Through coalition these lower class men could oust the women-hogging upper class men.  It is possible that one woman per man was the first inalienable right (for men).
  • In-Group/Out-Group or Tribalism
    • "It really boils down to this: that all life is interrelated. We are all caught in an inescapable network of mutuality, tied into a single garment of destiny. Whatever affects one directly, affects all indirectly. We are made to live together because of the interrelated structure of reality. Did you ever stop to think that you can't leave for your job in the morning without being dependent on most of the world? You get up in the morning and go to the bathroom and reach over for the sponge, and that's handed to you by a Pacific islander. You reach for a bar of soap, and that's given to you at the hands of a Frenchman. And then you go into the kitchen to drink your coffee for the morning, and that's poured into your cup by a South American. And maybe you want tea: that's poured into your cup by a Chinese. Or maybe you're desirous of having cocoa for breakfast, and that's poured into your cup by a West African. And then you reach over for your toast, and that's given to you at the hands of an English-speaking farmer, not to mention the baker. And before you finish eating breakfast in the morning, you've depended on more than half of the world. This is the way our universe is structured, this is its interrelated quality. We aren't going to have peace on earth until we recognize this basic fact of the interrelated structure of all reality." Martin Luther King 
    • There was a time that it paid to mistrust your neighbor.  40% of neanderthal skulls found have signs of being bashed in by blunt trauma suffered by their fellow man.  In that reality evolution built in to us a mistrust of outsiders and a loyalty to the group.  As MLK so well put above, though, the days when that was acceptable have long passed.  Trade and interdependence are the essential characteristic of today's life.  This evolved mistrust, however, is the reason of so much of the bigotry, racism,  and nationalism that plague our world.  How much blood has been spilled because we can't learn to trust each other because several hundred thousand years ago it paid to not trust each other?  It makes my heart break...
    • Could be that the invention of 'evil' comes from this source--mentally label people in such a way that you can justify killing/mistrusting them.
  • Technology
    • I have only a couple of pet peeves (I like to think I'm pretty chilax).  One is getting lost.  I go bazonkers.  Another is technology that isn't doing what I want it to.  Recently I was down a lap top and had to use a back up 12 year old lap top.  There were times when I wanted to beat the thing into a fine powder it was so slow.  And who hasn't hit a piece of technology (Car?  Computer?  Jammed printer?) at some point?  Why do we do that?  Because we're evolved to work with volitional agents that respond to power, threat or pain.  Technology doesn't--another example of being mismatched.
    • Speaking of which, I think one of the sources of a lot of our conflict is lack of face time.  Throughout our evolutionary history we've fought and made up face to face.  Now email, enclosed cars, phones, etc obscure a vital means of 'humanizing' people--seeing the facial expressions of another person.   I've noticed this in my self when I'm furious with road rage at someone in front of me in traffic.  I'll speed around them and finally be able to see their face, I immediately calm down and suddenly find other explanations for their driving foibles other than their pure evil nature.
  • Emotions
    • We're evolved to survive and reproduce, not be fulfilled and happy.  Much of our paranoia, mania, insecurities, complexes, anger management issues, depression and emotional irrationality is now quite counter productive.  But, we're stuck with expired phenotypes.
  • Agency
    • We're evolved to process enormous amounts of data to compile heuristic and predictive explanations of why people do the things they do--agency, personality, soul, spirit.  To navigate the social realm with any modicum of success we must do this.  We also do it with other realms--we infuse humans, things, technology, objects, the universe with personality, volition, agency, a soul.  Not saying this is necessarily a bad thing, but it is a relic of evolutionary history.
  • Single Motherhood/Gone Are the Villages
    • One in four kids in America is raised by a single mother (and 72% of black kids).  While something similar might have happened in our evolutionary past, yesteryear we undoubtedly had something we largely lack today--strong networks of cooperative women, villages.  It may be that there have always been dead beat dads, but coalitions of women--cousins, aunts, sisters, mothers--would raise children together.  The villages are all but gone.  Single mothers are the "widows and orphans" spoken of in scripture that we ought to support and care for. 
  • Food
    • It used to pay to pig out on fat, salt, sugar and carbs.  Now, not-so-much.
  • Drugs
    • Hallucinogens coopt a system not evolved for them.   We aren't evolved to know how to moderate ourselves to their power and excess and addiction often ensue.
  • Porn
    • It's kind of funny to think about.  Why should a picture arouse someone?  You can't exactly reproduce with a photo.
  • "We find genocide boring."--Sam Harris
    • Clearly we're not evolved to think of millions and billions of lives.  We're evolved to care about a small hand full of genetically related individuals.  The fact that we can yawn at the suffering, plight and death of millions, but crave news on celebrities is a testament to this fact.
  • Money
    • We just don't know how to use the stuff.   We don't know how to save, to spend, to give, to make it.  So many simple studies show this--we'll take a pay out now over a higher yield later (in our evo. past there's no point in saving if you starve to death) and we fear loss more than we like good prospects (better to keep what you have than risk it).
  • Short Term vs. Long Term
    • There were times in our evolutionary past that it paid to screw people over in the short term--rape, theft, lying, etc.  It's our goal to create a society where that doesn't pay, but the programming is still there.
  • Who are the people that we ought to focus more effort on caring for since our evolutionary programming doesn't facilitate that?  For example, we're programmed to care for kids, relatives, close friends, etc., but who are those that we're morally obliged to, but we often don't have that emotional spur to care for?
      • The elderly
      • Those different from us
      • Those distant from us
      • Those not well known by us
      • Nonrelatives

Sunday, August 7, 2011

Evolutionary Psychology--Bird's Eye View

(...I should be more specific concerning the title--a bird that's flying really high. haha)

So, recently I've been working at a local science center in Tallahassee, FL helping teach a summer camp on wild animals.  During the week it's been fun to ask the kids what their favorite animal is.  My reply to that question?  Humans.  Humans, hands down, are the most interesting creature in [known] existence.  And I think we don't think like that enough (as evidenced by kids objections to my answering that way--"Nuh-uh!  Humans aren't animals!!!").  If we can only step back every once and a while and be in awe at how far  humans have come from our past we may not get so bogged down in  how much further we could improve cognitively and morally.  So, anyway, hear this blog with that in mind--we are the coolest animal with the most complex, cooperative, creative, generous, altruistic, intelligent, selfless, deep, moving, powerful, transcendent behavior, relationships, society and thought processes.

What is evolutionary psychology?  It's a way of explaining how we got the brain that we have--why we think and act the way that we do.  There are two big categories when thinking about this that are highly intangled--survival and reproduction.

How did our brain help us survive?
  • Practical stuff like finding food, killing it, defending yourself from predators and assault.
  • Sharing/Reciprocal Altruism
    • Animal example to elucidate our similar past: Vampire bats can only survive something like 1-3 days without a high quality meal.  They have a problem, though.  On average an individual bat will only come a cross a good meal every 7 days.  So, what do they do?  They share and they keep tabs on who owes them, who they owe, who is good about repaying and who is good about forgiving debts.  Sounds a lot like us, yes?  It is!  Just in the same way that bats will shun those that don't share (according to observations/experiments) so humans make coalitions of trust and reciprocity.  I've heard numbers estimating that something like a third of all ancient human births didn't survive unto adulthood.  So, small nutritional differences over time between humans that are good at reciprocal altruism can make a huge difference over deep time.  This slight behavioral/cognitive differences  eventually got us to the fair centric species that we are today.  Think of the last fight/argument that you had.  Was it not about fairness?  I would imagine so.  We care very much about fairness and selective pressure is why.

  • Kin Selection
    • Looked at from the perspective of the gene, a gene doesn't just care about being passed on through one individual, but also getting the same copies of that gene being passed on through relatives.  Consider some of the strange things nature brings forth--bees that sting themselves to death (since their stinger detaches and pulls out their intestines at the same time) and communal animals, like ground squirrels, offer warning calls that endanger themselves (by making their position known and therefore more likely to be eaten) but save their relatives.  Darwin knew the strangeness of this perceived selflessness when he said, "Such simple instincts as bees making a beehive could be sufficient to overthrow my whole theory."  We can see this in ourselves when we consider our preferences for family.  Would you rather save one family member or 100 strangers on the other side of the Earth?  1000?  10,000? 100,000?  1 billion?  Why is being adopted and genetic relation often such a big deal to kids?  Why is blood thicker than water?  Because our ancestors that gave preference to their relatives were more likely to survive and reproduce!  
    • This selective pressure can explain much of the selflessness, generosity and good will that humans exhibit--our genes think it will help our relatives survive (even if we're not really related to those we're helping.  In the past our tribes were such that everyone we'd help we were most likely related to in some way).

    • It's also related to the strongly in-group/out-group mentality that humans have--trust and take care of your relatives, distrust and exploit outsiders.  This is readily evident in the labeling that people use for others in an us/them paradigm--spicks, crauts, towel heads, niggers, japs, chinks, etc.  They're labeling others as something sub-human so that mistreating them isn't objectionable.  The below is a fascinating clip showing just how trusting humans can be of their in-group.  Also see here.
    • For the math of kin selection see Hamilton's Rule.

How has our brain helped us to reproduce?

  • By Being a Peacock's Tail
    • Something like half of our genome encodes for the brain.  So, if you have a good brain that usually says that section of your genome is pretty good and if that section is pretty good then there is a good chance that the rest of it is pretty good.  Put simply: if you're smart then you have good genes and are worthy of reproducing with.
    • Also, our brain is physiologically costly.  Something like a quarter of our resting metabolism goes straight to feeding our three pound lump of electrical fat between our ears.  So, if you can feed a brain then you must be pretty healthy.  This is just like the peacock's tail--if you can make a big, pretty tail and deal with the attention it draws from predators then you must be pretty well off.
  • By Gaining Status
    • How do you explain the risky, thrill seeking, death whishes that some people have?  How do you explain the ridiculous amount of money, time and talent that people pore into their appearances, hobbies and acquired skills?  We're communal animals that needed to stick together to survive.  To stick together everyone needed a place--a rung on the social latter.  These 'places' got other things stick to them--higher status people got more of the share of food and more mates.  The lower status people put up with it because they either couldn't change the situation or it would be more costly to fight it and risk being ostracized than ousting the higher status individuals.  Once that system is put in place it can create an incredibly interesting rat race of trying to gain status to gain resources/mates (and specialization to compete in different categories, or nervousness to motivate avoiding confrontation/ostracization, low self-esteem/confidence, depression and all sorts of other interesting things to keep people in their place to maintain social cohesion).
    • “We’ll do anything for respect, including not act like animals.” --Robert Wright

    • Sexy Son hypothesis
      • We not only care about our own genes being passed on and our relatives, but we care about our kids passing on our genes.  This is where things get a little out of hand.  Take for example the peacock's tail we've already discussed.  A female might not want a male with a big pretty tail because she's concerned with having healthy kids.  She might do it just because her sons will have big, pretty tails and are therefore more likely to reproduce.  Let that go lose on a population over deep time and some weird things can result.  Take a human example--Stockholm syndrome, or the love of a psychotic kidnapper.  Why would a woman fall in love with her kidnapper, rapist or ass hole boy friend?  Maybe, evolutionarily, her sons if they also turn out to be rapists, kidnappers, and ass holes are more likely themselves to reproduce.  More here.
Just think about what this is literally.  
Short Term vs. Long Term Investment
  • A category that is both applicable to survival (like reciprocal altruism) and reproduction (kin selection) is how much investment to make in a relationship.  Toadfish are a good example.  There are 'good' toadfish dads that make dig a hole in the mud to make a crater nest perfect for protecting eggs from predators and current.  There are also 'bad' toadfish dads that look like females and sneak into the nests of 'good' toadfish dads while they are externally fertilizing a female's eggs and inseminate them with their own sperm.  One dad invests very little and actually exploits others for his own gain and the other invests heavily in his offspring.  There's also the classic prisoner's dilemma example.  It's essentially a thought experiment that shows that working together is beneficial in the long term, but not always in the short term.
This will only be funny after you understand and/or read the wiki linked above:

There's way more, but hopefully that'll wet your appetite!

    Pictures from here, here, here, here.