my newest class..........

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Genes and the Human Condition (From Behavior to Biotechnology) is my latest venture into Coursera's offerings.

I thought the glimpse of epigenetics that we got in What a Plant Knows was really interesting.  One of my Plants classmates said Coursera has a class on epigenetics, so I went to check it out.  The epigenetics prof said we'd better have a foundation in basic genetics, and listed a bunch of classes that could give us that foundation.

My first thought was -- "I know about basic genetics."  My second thought was -- "Yeah, well, you thought you'd remember algebra, too........."

Um.  Yes. 

Hmmm.

I took a look at the list of recommended genetics classes.  Genes and the Human Condition is six weeks long.  I joined it two weeks into the course, when I was still in Plants and Dinos.  Only this week have I been seriously listening to Genes (starting when the class was half over).

It is really dense!  Many lectures, all densely packed with (fascinating) content.  So far, I am really impressed.  They are doing a very good job of presenting the content, with lots of interesting examples and great analogies ("Your personal genome is like two cookbooks -- one from your mother, and one from your father.  You may get two identical recipes for a  particular dish, or you may get two different recipes."  And clips holding bunches of pages shut, standing in for tightly folded DNA that isn't being expressed....  Excellent visual!).


I'm not expecting to "pass" this class (by doing all the work up to whatever standard they are setting) as I have joined the class so late.  I do expect to listen to all the lectures (perhaps more than once!).  I don't know if I'll learn enough to be able to keep my head above water in the epigenetics class, but that's ok -- I'm learning a lot of very interesting stuff!

This morning I listened to a lecture about genomics.  When he talked about comparing one genome to another (human to chimp, say), he said we may care more about what is different than about what is the same.  We and chimps are exceedingly closely related.  Chimps are more closely related to us than they are to gorillas......

Here's something he talked about that was completely new to me.

That's an adult human skull on the left, and an adult chimp's skull on the right.  Whose skull is in the middle?

That's a baby chimp's skull.  !!!  I was really surprised that the baby chimp's skull looks so much more like ours than like the adult chimp's!  The flat face, the domed skull, the relatively small teeth.........

Another thing he mentioned is the differences in placement of the opening in the skull for the spinal chord.  When a critter walks upright on two feet, the opening is underneath.  When a critter is quadrupedal, the opening is nearer the back.  The baby chimp has the bipedal arrangement...........

I was already familiar with the concept of pedomorphism -- adults retaining juvenile characteristics.  Adult golden retrievers look a lot more like puppies than do adult wolves.  Drop ears and broad skulls are "baby dog" characteristics, as is extremely friendly behavior.  When we breed dogs to be friendly and trustworthy (less like wolves), we also get a puppy-like look (not necessarily on purpose, it's just what happens when we breed for the behavior we want).

How interesting to learn that we ourselves are pedomorphic!  We are very like adult baby chimps in many ways, and not just in our looks.  He mentioned that babies are usually more curious, exploratory, experimental than adults, and speculated that is a set of traits adult humans exhibit far more often than adults of other species...........


He also mentioned the front-to-back ridge at the top of an adult chimp's skull (to which the chimp's powerful jaw muscles are attached) as something that both baby chimps and humans lack.

Almost a year ago I caught the end of an extremely interesting program on NOVA.  A scientist accidentally discovered that all humans share a flaw in the DNA that enables strong jaw muscles.  (That link is to my blog post on the topic, which details what I remembered hearing, the day after I saw the program.  In the comments on that post, my friend Carolyn kindly offers a link directly to the NOVA program.)

Skulls begin as a collection of bones, which fuse into one as the animal gets older.  The incredibly strong jaw muscles of chimps (and gorillas) have to be attached to incredibly strong bone.  This requirement for very strong skull bones (to support those intensely strong jaw muscles) means that chimp skulls must fuse when the chimps are about three years old.  Brains cannot continue to grow in size once the skull is fused.

The NOVA program speculated that our pitifully weak jaw muscles (in comparison to our chimp or gorilla cousins) makes it possible for our skulls to fuse MUCH later (in our 20s, up to age 30), which makes it possible for our brains to grow and grow.....

The baby-like domed skulls humans retain in adulthood, which house our big brains, might not have been possible without that "weak jaw muscle" DNA mistake.  !!!

I love it when I can listen to a genomics lecture and link it back to what I know about dogs, and what I learned last year about jaw muscles and brain sizes...........  !!!  Many things are wrong, in our modern world, but the ability to be exposed -- SO easily! -- to all of this information is just super. 

This is an excellent time for a curious person to be alive!



Digression -- I am still boggled by that "Gorilla jaw muscles are the size of human quadriceps" thing!  Quadriceps.  *Quadriceps*.   !!!  Whoa.  !!!  End of digression.

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