The Human Scrapbook

I wanted to put into pictures the idea birthed here.    When we look in the mirror a myriad of generations and strange ancestral creatures peer back, if only we have the eyes to see it.  It's fun to think this way!  Examples abound and I post it now quite incomplete in hopes that I'll come back to it here and there and continue to amass great examples.

Teeth -  Possibly from small dermal plates

Jaw - You chew with a rib.

 

Hair - Well, hair had to come from somewhere.  Reckon it was modified scales.

Fingernails - More modified scales.

Arms and Legs - It's a different way to look at gymnastics as dancing on fins...

This dude's 73.  

Tail - I sit where my ancestors swam.

Ears - It should be a little weird to think that my ancestors breathed through the equivalent of my Eustachian tubes coming from my ears.

Nose - Fish have noses; they just don't go anywhere.  Amphibian evolution involved those pits deepening and finally opening to the palate.

Pix picked:
http://kingsenglish.info/2011/04/17/escaped-by-the-skin-of-my-teeth/
http://flickrhivemind.net/Tags/bellyscales/Interesting
http://wildwhales.org/2011/02/offshore-killer-whales-a-diet-discovery/
http://www.life123.com/beauty/hairstyles-hair-care/layered-hairstyles/layered-hairstyles-for-long-hair.shtml
http://www.tattooingtattoo.com/cross-tattoos-2/back-tattoos-for-men/
http://enb150-2011f-thb.blogspot.com/2011/11/amphioxus.html?z
http://photoblog.msnbc.msn.com/_news/2009/09/03/4352115-
http://outlier.deviantart.com/art/Australian-Lungfish-3886569
http://onefatfish.wordpress.com/2011/04/08/22/
http://mad.blog.dccomics.com/tag/jay-leno/
http://www.muscleandstrength.com/forum/general-chat/64462-random-bodybuilding-thread-2.ht
ml
http://www.managemylife.com/mmh/questions/247358-broke-tail-bone-several-years
http://www.chicagoparent.com/magazines/web-only/october-2010/when-it's-time-to-see-an-ent
http://wonderaday.com/blog/The_Underwater_World_Of_Indonesia/
http://www.gigwise.com/news/49325/Michael-Jacksons-Nose-Could-Collapse-From-MRSA-Superbug

The Palate - Yet Another Difference Between Mammals and Other Vertebrates

You wanna know one of the biggest reason that mammals are special?  We chew.

In fact, only mammals chew. (Pretty much.  It's hard to make absolute statements in biology.)

More on this here.

The gist:  We mammals have evolved warm bloodedness because it helps us move quickly and with sustained energy (reptiles have to bask in the sun, etc. to get warm).  Hot bodies are costly, though--they burn something like 10 times more energy than being cold blooded.  Not only do warm blooded animals have to eat way more (big snakes can go months without eating--try that sometime!), but we have to get every possible calorie out of the food we eat--and fast!  Thus, we chew.  So, what does it take to chew?  Proper teeth, of course.  And...the ability to breath and chew.  Not choking to death is nice, too.

Therefore, the palate was born.  The palate is the bone/flesh separating you nasal passage from your mouth.  I never would have realized this, other than through reading about evolution, but other critters like birds and most reptiles (with the exception of crocodilians who hold their food underwater to drown it without, hopefully, drowning themselves) don't have palates.  They breath through their mouth.

Birdy mouth nasal passages entering mouth (it's the thin slits in the middle of the roof of the mouth):

http://yourownvet.com/?tag=how-to-warm-baby-birds

http://en.wikipedia.org/wiki/Palate

Dinos were mostly mouth breathers.
http://faculty.plattsburgh.edu/thomas.wolosz/turbinates.htm  (And images below.) 

Mouth Breather

Not Mouth Breather

Also Not (they're exceptions to the rule)

Teeth - Why We Lose 'Em and How Other Animals Are Different

Why do we lose our teeth as kids?  It's such a common occurrence that unfortunately we don't really stop to think about the evolutionary implications.

The conventional wisdom is that we need bigger teeth as our jaw gets bigger.  Well, why don't our teeth just get bigger then?  They could certainly grow if they wanted to.  Doesn't it seem like an energetically profligate endeavor to build teeth just to toss them away?  Yes, it does.  So, why?

After having those thoughts my mind had an exciting jump: maybe it's an evolutionary tie over from when our ancestors teeth shed all the time!  

It's not quite that simple, but with a little web research found that there's lots to learn about teeth that I had no idea about!  Enjoy the below!

Different Teeth Growth Strategies:

1 Set of Teeth Called Monophyodonts - Rabbits/Lagomorphs and Toothed Whales

2 Sets of Teeth or Diphyodonts or Those with Deciduous Teeth - All Mammals, with a Few Exceptions

Polyphydonts or Those with Multiple Sets of Teeth - Reptiles, Amphibians, Fish, Manatees, Elephants

Alligators (croc above) can  have 80 teeth at once and go through 3000 teeth in a lifetime.

Manatee jaw with 'marching molars' that come in in the back and drop out towards the front.

Not the greatest picture, but this shows a mammoths 'marching molars' slowly emerging from deep within the jaw.

No Teeth! - Baleen Whales, Ant and Termite eating Pangolins and Anteaters

No teeth here!  Just baleen!

No teeth here!  Just tongue!

Toothless pangolin skull

Toothless anteater skull

The Most Neurologically Complex Tooth: the Narwal.  The tooth is multipurpose and is used in feeding, navigation and mating.

Longest Tooth - Straight-Tusked Elephant

Heaviest Tooth - Columbian Mammoth

Gene Found in Chickens that Inhibits Tooth Growth .  Best part of this: it can be turned off and chickens can have teeth.  

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

Works sighted [sic]:

Multi-Row Teeth Gene Found: http://www.sciencedaily.com/releases/2009/02/090226160751.htm

http://today.msnbc.msn.com/id/29411799/ns/today-today_healthhttp://www.thedailyweird.com/miscellaneous/racist-toothpaste/
http://discovermagazine.com/2010/sep/17-20-things-you-didn2019t-know-about-teeth?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+DiscoverMag+(Discover+Magazine)&utm_content=Google+Reader
http://www.earthlife.net/mammals/teeth.html
http://en.wikipedia.org/wiki/Tooth
http://en.wikipedia.org/wiki/Hyperdontia
http://www.answers.com/topic/dental-development
http://nimbleit.squarespace.com/simple-curiosity/2007/7/6/why-do-we-have-baby-teeth.html
http://www.npr.org/templates/story/story.php?storyId=5230538

http://www.bioone.org/doi/abs/10.2992/0145-9058(2004)36[159:EODRIM]2.0.CO;2

Only Mammals Chew

Great stand up comedians have a gift at pointing out the obvious in everyday life and making everyone in the audience say in their mind, "That's so true!  I've never thought about that, but it's so true!"  This is one of those things.  Only mammals chew.

Try to think of an exception.  

I mean really chew.  Not tear up, bite through, or rip apart, but really gnaw, masticate, mash up.

How interesting.

Why?

Doesn't seem to be an easy answer, but some of it has to do with our endothermia - warm bloodedness.  To sustain warmbloodedness, which keeps enzymes and proteins at their optimal temperature for physiological fine tuning, we need constant energy inputs of high quality foods.  In contrast, reptiles, like snakes, can go months in a semi-dormant phase that doesn't require the constant fueling of the 'fire' of warmbloodedness.  Mammals can't.  A simple way of putting it is that reptiles can wait for their chemical digestion to break down their food, but mammals are in too much of a hurry (with exceptions).  We need it now and mechanical break down offers that.

Herbivorous mammal teeth:

Carnivorous mammal teeth (take note of molars, which semi-only occur in mammals):

Herbivorous reptile teeth:

Carnivorous reptile teeth:

There are two exceptions that I should mention, though.

Gizzards:

Pretty much all birds, a few fish, a good number of insects 'chew' using a muscular sack in their gut called a gizzard.  This can use grit/pebbles or in the case of larger dinosaurs even up to stone size rocks to crush up their food.  There are even some insects and mollusks that use chitinous 'teeth' plates in their gut to 'chew'.

Some reptiles do chew.  Most notably dinosaurs like hadrosaurus.  Chewing in dinosaurs is one of the reasons it's been speculated that they might have been warm blooded.

Also, there was one crocodilian that was recently unearthed that seemed to have chewed as well:

http://www.scientificamerican.com/blog/post.cfm?id=crocodile-relative-might-have-chewe-2010-08-04

Why this is neat:

It highlights how species are integrated systems.  Who would have thought that a tooth innovation might have started the whole process and paved the way for a metabolism innovation.