So there have been some arguments that the photoic sneeze, contagious yawns, contagious puking, and even the smile are vestigial behaviors. I think these have all been debunked in recent years, but I was just wondering are there any human behaviors that are believed to be truely vestigial? What evidence do we have to support these theories? What about non human behaviors?
From one of Cecil’s columns, I visited the coelacanth web page, and saw there that observers have sometimes seen coelacanths “standing on their heads.” One theory was that this is a vestigial behaviour.
http://www.dinofish.com/behav.htm
Yeah, I’ve seen the bit about the coelacanths, but it seems the jury is still out on this one. If it’s vestigial, there seems to be no theories of what it might be vestigial of. The other theories posited that it is due to the rostral organ (electric field receptor) being fooled by the electric field from the submersibles that were used to study them…
Here’s a crack pot theory about a behavior (or more accurately, perhaps, response) that I think might be vestigial: the giggling response to being tickled.
I notice that people are most ticklish in the places where you would have to touch them if you wanted to upend them (if they were standing) or turn them over (if they were prone). For example, people are ticklish on the soles of the feet where you would touch them if they were standing and you wanted to upend them and they are ticklish around the armpits and upper thighs where you would touch them if they were prone and you wanted to turn them over like a turtle. I think the giggling response to tickling is a vestigial response to attempts to upend us or turn us over from the time when we were turtles.
What about goosebumps? They seem to a vestigal response from the days when we were all as hairy as Robin Williams. (Although it would seem like you would just look more fluffy with all of your hairs standing up.)
The year round female sexual availability is probably a vestigal response from way back to encourage continuous male-female bonding.
Children’s fear of the dark is/was a survival mechanism. The cavetoddlers who did not have it wandered away from the fire and were eaten by saber toothed cats. Fear of the dark goes away about the time the cavechildren knew enough to not wander away.
When confronted by threatening animals, there is a tendency to yell at it and wave one’s arms. This apparently works with large cat predators (I can’t speak from experience here) but does not work on canine predators (even domestic dogs are not deterred by this). Supposedly this shows that our ancestors were confronted with feline predators not canine predators when we were developing out on the African plains.
There is sound frequency much higher than that used for speech were the human ear shows a great deal of sensitivity. I forget the frequency but it is up there where the frequency of screams resonate. We were screaming at each other as a communication medium for a much longer time than we have been talking. (Actually, that explains a lot.)
You mentioned the smile. I always wondered what the social interactions among our distant ancestors were that made bearing one’s fangs a way of expressing pleasure or happiness.
mipsman,
You wrote:
I think this is more physiological than behavioral…
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(Although it would seem like you would just look more fluffy with all of your hairs standing up.)
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Have you ever seen a scared or angry cat? All the hairs standing up on their back certainly make them seem more ominous and less cuddly.
I’m not sure I agree with this. Actually, young children are not likely to be afraid of the dark unless they’ve been spoonfed the traditional fairy tales of ogres under the bed and monsters in the closet. Adults seem to be more afraid of the dark than children… In other words, I think it’s a learned behavior.
Again, I think this is a learned or reasoned response. Children, when attacked by animals, instinctively tend to turn their backs, run, or fold up. BTW, most dogs I’ve ever been around are indeed deterred by yelling and flailing.
Natural selection may have favored individuals who are more likely to hear the screams of terror or warning from their peers, but I’m not sure I would classify this as a vestigial behavior.
Well, there is a bit of a difference between baring one’s fangs and smiling, but I catch your drift. Perhaps it was a non verbal way of saying, “Hey. I like you. In fact, I like you so much that I would share my food with you, but, as you can see, I have no food… But I really do like you.”
JoeyBlades,
FWIW, Both of my sons have always been afraid of the dark; my one year old will scream bloody murder if he is left in his crib with the lights off and has done so for at least the last nine months.
I agree with “Cornflakes”. (Does that make me Froot Loops?) A fear of the dark is just another manifestation of a general fear of the unknown or unfamiliar.
Does fear count as being “vestigial”?
What about “hunger”? Or, a reflex? Or, an instinct? How would you define “vestigial” to differentiate between such things???
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
The theory I heard on this is that when we stretch our mouth like we are smiling then try to talk our voices get higher. We tend to associate higher voices with smaller things are children, both things that we consider to be less threatening. So, we smile to say “See! I’m small and harmless.”
Except that the vocalization aspect has faded and we are left with just the facial expression. Which does count as a vestigal response, I suppose.
“Sometimes I think the web is just a big plot to keep people like me away from normal society.” — Dilbert
I would think a primitive (or alien, or whatever) would consider a smile to be a threat. Baring the teeth so obviously can only mean an impending bite attack! How it got to be a gesture of humour is almost as big a mystery as why we laugh…
I’ve heard shivering when cold is a vestigial behaviour. It makes more sense to shiver, and heat up the skin, if you have fur to keep the heat in. With naked humans, it really just causes us to die of hypothermia faster. If you’re shivering, and you can’t get warm by going inside or putting a sweater or slicing open a freshly-killed caribou, you shouldn’t spend your energy shivering. You should jog in place or wave your arms or some’in’.
cornflakes wrote:
The question is, are they afraid of the dark or are they afraid of isolation. Neither of my daughters were ever afraid of the dark until they were exposed to scary stuff on TV.
Jinx asks:
Well, I was referring to vestigial behaviors in the sense of degenerate ingrained behaviors that could be traced back along our ancestral/evolutionary tree. Hunger pangs are triggered by chemical response and therefore physiological in nature, so I wouldn’t count that. In fact, most true reflexes are physiological, which is not to say they are not vestigial - just not behavoral.
Boris B writes:
Now, I think we’re on to something. I don’t know of any physiological cause and there’s a certain logic to this being the vestige of a previously desirable behavior, as opposed to merely a random physical anomaly.
Good point. Maybe the fear of darkness should more accurately be called the fear of being alone in the dark. I think that most kids can accept being left in the dark so long as someone is with them.
While the one year old hates to be left alone, he will go ballistic if the lights are turned off. While he wakes up crying in the night, he wakes up screaming if it’s dark. If he’s in our bed, he doesn’t cry at all; he just bats at our faces.
Oh, c’mon, now! Shivering is also a physiological response! And, fear is also chemical, if you want to get technical! How do you draw the line? We’d be flatlining without physiological responses!
Now, picking your nose…that might be that answer you seek! Or, making noises with the arm pits…?
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
Jink wrote:
I’ll address the second point first: True, all behaviors are driven by physiological stimulii at some level. We can’t completely eliminate the physiological mechanisms and still have anything that we would call a behavior. Where do I draw the line? At the cause. I’m looking for behaviors that do not have a physiological cause.
I’m not saying that shivering is not a physiological response, I’m only acknowledging that it might not be physiological. There are certainly no specialized vestigial shiver muscles or nerve structures. There might be some chemical trigger, but this strikes me as being a bit unlikely since we shiver when we’re cold, we shiver when we’re afraid, we shiver when we’re exhausted, and we shiver when we pee [wink]. How are these factors related? Is it likely that the brain triggers the same chemical response under such a wide array of conditions? I don’t know…
At least with shivering, I can think how this might be related back to beneficial behaviors of our predecessors.
Shivering when you’re cold - increase blood flow and produce heat.
Shivering when you’re afraid - react quick to danger and get away.
Shivering when you’re exhausted - keep muscles active to avoid cramping.
Shivering when you pee - shake off those last drops and prevent infection.
That might explain why women don’t seem to get pisshivers… Hey, somebody call Cecil!
I’m not writing a thesis or anything. It was just something that I was curious about and I’m theorizing to myself that there’s no such thing as a vestigial behavior. I thought the collective intelligence of this group might rise to the challenge and help me test my little theory.
What about a nervous tick?
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
Man, Cecil is quick! The answer to JoeyBlades’ question:
http://www.straightdope.com/classics/a4_225.html
Just for the record, here: The dictionary definition does not discriminate when defining “vestigial”…whether a physical structure (appendix) or a chemical function of the body (at a macrolevel) or the cells (microlevel). There are even cell structures which may well be “vestigial” or we have yet to determine their purpose. For example, as I recall, the endoplasmic recticulum may be deemed “vestigial”. Also, as I recall, the full function of the mitochondria is not totally understood, and it is unclear if some functions are defunct. I think we have more to learn about the Golgi bodies, too, as I recall…but I haven’t dabbled in bio in quite awhile! Aye, Cap’n! I gotta catch up on my sci-tech journals - as Scotty might say! 
Why do you?
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
I meant to say:
Maybe the defintion is being misunderstood?
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
The response to nails on a blackboard is thought to be vestigial of the reaction to shrieks. The pitch is similar to a monkey’s warning shreik.
You could make a case that our reaction to “beauty” is vestigial.