'Skeleton Keys' — a new book explores the secret life of bones

Science writer Brian Switek has long been obsessed with bones. Mostly those have been dinosaur bones, as Brian's an enthusiast who spends much time digging for, thinking about and writing about dinosaurs.

But in a new book he looks beyond dinosaurs to think about bones more expansively. He explores the evolutionary origins of bones, and the way they gave vertebrates the ability to diversify on land and sea, and to grow into the largest animals who have ever lived.

He also explores the human skeleton and how it evolved to give us our unique combination of abilities that enabled us to walk upright, make tools, and build a civilization.

And he explores the complicated and sometimes disturbing relationship we have with bones — the history of racially charged science and exploitation around bones, and the shocking modern trade in human remains.

The book is called Skeleton Keys, the Secret Life of Bone.

Listeners' favourite bones

Here are some of the responses we got for our listener contest asking "what's your favourite bone and why?"

Pamela Norton, Victoria - Winner of a copy of Skeleton Keys

My favorite bone is the smallest of our 206 bones called the stapes, or stirrup, of the inner ear. It allows me to tune in and enjoy Quirks!  What better choice?

Nicole Corrado

My favourite bone is a panda's radial sesamoid bone, because the wrist is like a thumb that holds bamboo.

Debby Lake - Winnipeg

Great broadcast! Here's a haiku to my favorite bone:

Hyoid bones help us
Breath, swallow and speak, despite
Their two sets of horns.

Lari Mitchell, Victoria

Mine is the wishbone.  Bones are at best associated with melancholy and loss. Something once living is dead.  Possibly extinct. And crime scene bones are tragic. The wishbone of a turkey (the clavial) may be a sad thing to a turkey, but at least to humans turkeys are usually eaten at a time of celebration.  Breaking the wishbone to see whose wish might come true shifts the typical dynamic of bones to celebration and hope. Well, that, a full stomach and a glass of wine or two.

Christine Adkins, Vancouver

My favourite bone is the baculum. Aka 'penis bone.' Humans have (apparently) lost this bone, but it persists in many mammals. Comparison of shapes of bacula from different species reveal fascinating variation: lengths, widths, curvatures. Apart from the obvious snicker value of this topic, the baculum is a very beautiful bone. Google images of 'raccoon baculum' for examples.

Anne Hill

It has to be the Hyoid bone. Small and subtle it anchors the tongue which is the strongest muscle in the body.

Andre Van Schyndel, Kanata

My favourite bone is the funny bone.  No, not that thing in your elbow that gives you an electric shock when you hit it on the table, in fact that's not funny at all.  No, it's that bone that tickles during a humorous experience. Oh wait, then I guess my favourite bone is the humerus. Oh wait, the bone that tickles when you laugh is the ribs so I guess my favourite bone is really the rib.  Yeah that's it, they taste good too … if the snow on my barbeque ever melts.

Sid Andrews

My favourite bone is from a bird's wing called the "carpometacarpus".  I suppose I should say bones, fused bones. Essentially equivalent to the bones that make up a front paw or hand in a mammal.  The fusion of "hand bones" allows for strength and lightness which is a great thing in a bird's wing

Grace Yip

My favorite bone is the Ethmoid, which is a cranial bone at the back / top of the nose.  I like it because it allows the olfactory nerve to travel through it and reach directly to the brain.  Also, some birds and migratory animals have biological magnetite in their ethmoid bones that allows them to sense the direction of Earth's magnetic field.

Sandar Eadie

Zygomatic bone. This bone helps to support the eye. It is my favourite bone because it helps to support the eye. It is especially important to me because my husband fell flat on his face on the street and broke several bones in his face. There was a big danger that his eye would fall out of place  and so they operated and inserted plates and mesh into his face saving the sight in the eye. So I now know how important the bone is for us all.

Robin Sutherland-Harris

My favourite bone is my husband Scott's upper distal humerus, which he shattered in a motorcycle accident last fall. This bone is now adorned with 11 screws and a metal plate, and is supported internally by a bone graft taken from a cadaver (this is my second favourite bone!). Brian Switek's comments on the function and importance of the shoulder hit close to home for our house!

Interview Transcript:

This transcript of Bob McDonald's interview with Brian Switek has been edited for length and clarity

Bob McDonald: As I mentioned you write a lot about dinosaur bones, and we've had you on our program talking about that before. But this new book is a little different. I got that when you start one of your chapters with this sentence: "Sometimes I like to just sit still and think about my bones." What are you thinking about.

Brian Switek: Well for me I'm thinking about the sort of connection that I have over 500 million years of evolutionary history in terms of how my skeleton is laid out the fact that it's living and constantly responding to the world around it.

So I can look at my hand and my arm and see not only my primate ancestors or my mammalian ancestors but my fishy ancestors going way back over 400 million years ago.  So I'm thinking about what my bones are doing but mostly about how it connects me to every other vertebrate that's that's ever existed — the sort of deep time inside that we're carrying around with ourselves constantly.

BM: Take me through that. What is the history of how bones came about?

BS: We might think that bones and skeletons are basically synonymous because that's how it is in our own bodies. But even looking around us now, we know that's not entirely true. Sharks and rays, for example, have skeletons but they're not made of bone. They're made of cartilage,  which is the stuff in your nose and your ears and your joints.

So the layout of the skeleton came together starting around 500 million years ago. The bone itself or the direct precursor bone didn't show up until about 455 million years ago and it started as external armor, the substance called aspidin, and it was much more like teeth than the bones that we have inside ourselves now.

Once that happened that mineralization the ability of the body to create this hardened protective material got co-opted on the insides of the skeletal framework.  So basically the order of operations was we get the layout of the skeleton, those fish get covered in a bony material, that material starts to mineralize inside. So basically the bones inside of our bodies are the remnants of this armor plating that our ancestors had way back when fish were just a 'maybe' in terms of evolutionary success.

BM: So at the beginning we had exoskeletons and then the skeleton on the inside literally took over the world. On both the seas and the land we had these giant animals that came about. What was the secret to bones that allowed that to happen?

BS: It's really the way that bone is structured. So bone — and this is true for us as it is for a T-Rex or a horse or a rat or a hummingbird or any vertebrate that can think of — bone is made of primarily two parts. There's hydroxyapatite, which is the mineral part of bone, and then there's collagen which is a protein and the flexible part of bone. So this gives bone both strength and flexibility. And that's what allowed the biggest dinosaurs that ever existed, these animals are over 120 feet long and upwards of 45 tons, to be able to support their bulk.

You know it's just this incredibly durable and responsive and flexible natural material that supports bodies in a way that exoskeleton can't do.  I love monster movies and there's a classic called THEM about giant ants, and if ants actually got to that size they'd bust at the seams. There are certain things that happen with the physics of surface to volume ratios if you're trying to hold things in. If you only have an exoskeleton there's going to be more and more pressure to bust that exoskeleton open the bigger you get.

So by having skeletons on the inside we're able to circumvent that problem and a whole range of evolutionary possibilities opens up that wouldn't have been possible otherwise.

BM: In addition to talking about our skeleton and how incredible it is in terms of our anatomy you talk about bone itself, which is what an engineer might call a self-healing composite. Why is bone itself so great in your mind.

BS: It's incredibly responsive. It's something that I didn't really appreciate until I started researching this book, and it's I think it's easy to forget because it grows and changes at a time scale that we're just not attuned to.

I mean it should be relatively obvious like we're not born with our adult skeletons — that would be awful for a lot of reasons. We're born relatively small with about 260 bony pieces, many of which are held together by cartilage, particularly in our skulls. Our skulls have to be flexible so that we can be born at all and those coalesce over time as we grow into about 206 bones.

And the fact that our bones can do all that — our body is a living system that's just as responsive as our skin or muscles or our nerves or anything else. And it's really critical to our bodies, not only allowing us to move in the ways that we do but for example that our bones carry marrow that give us our blood cells that are bones can be changed in pretty dramatic ways but not affect the rest of our health. I think that's what made bones such an evolutionary success is that it's able to respond and and change over time.

BM: You devote the second half of your boat book more to how we treat bones. And one of your chapters is about the amazing discovery of this the skeleton of Richard III. Now it's a great story, of course, but you like this story for what it tells us about what bones can reveal to us about the past.

BS: That's right. So the second half of the book is basically the afterlife of bone.  In terms of Richard III, I picked his story not because he was famous but because the analysis that the anthropologists an archaeologist carried out on his bones was the star treatment that pulled out all the stops. They did C.T. scans, geochemical analysis and isotopes inside of his bones looking at the pathologies on his his skeleton. There is all this different information that you can get from the skeleton. Our bones are time capsules in a way.

So there's a gross anatomy. So for example Richard III had scoliosis. There is a sideways kink in his vertebral column that gave him a shorter stature. He didn't have a hunchback like Shakespeare wrote about in the play, but he was a little bit shorter.

In his bones there were chemical signatures left over from what he drank and what he ate and they're related to the areas in the country that he was living. And by looking at the different signatures in different bones in his skeleton they're able to look at these isotopes in his femur and in one of his ribs and compare the different times that these isotopes would have been laid down. Once he became king his diet changed and the sort of food that he was eating was different, was fancier and was coming from these regions.

So our skeletons not only are beautiful and know even macabre depending on how you look at them, but they really record so much of our lives. You can look at the skeleton and see not only the evolutionary history or the cultural history but the individual history of a person.

BM: You wind up your book on a slightly lighter note, trying to work out how your own bones could be immortal as those of the dinosaurs that you study. How is your immortality going?

BS: Well I'm still living for now — I have no plans to join the fossil record quite just yet.

But I like thinking about that because bones are really the one part of ourselves that have the greatest potential of lasting for millions and millions of years. I like to think about maybe 10 million years in the future when some other form intelligent life with science either evolves or visits or whatever it's going to do, if they found my skeleton what would they be able to tell from my bones?

Whether I actually join the fossil record or not will remain to be seen, but I like thinking that if I did, some time millions of years in the future, what would my skeleton be able to say about me and how I fit in to this tree of life that we all belong to?