2

votes

Why aren't our calves in front?

Answered on August 19, 2014
Created February 01, 2011 at 5:32 PM

This has nothing to do with diet, but it is an interesting evolutionary biology question. Banging your shin (which nearly always happens from the front) hurts like hell and can cause injury. Having the bone exposed that way seems like a design flaw. Why didn't we evolve to have our calves protect the bones by being in front of the tibia? The muscles of the hips cross over bones in all directions, so I think the calves could have the same attachment points and still work from the front. Any ideas? (I know this is a weird one!)

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 16, 2011
at 06:42 AM

Just saw your comment. I wouldn't worry about it if you don't want to!

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 06:54 PM

Paul, I'm going to try to rewrite my whole answer in the next few days and explain everything better. I'm looking for illustrations now of the anterior muscles.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 09, 2011
at 05:19 AM

Much later response, sorry. It seems like what you added in your edit makes the problem even stranger: these tendons attached to the muscles that pull the toes up are moved out of the way by these "pulley" ligaments you speak of. So it's as if the muscles *could have* been in front of the shin, yet the body went out of its way (so to speak) to put them to the side of the shin ...

C61399790c6531a0af344ab0c40048f1

on February 02, 2011
at 07:58 PM

Yeah - no desks to walk into in paleo times

5ccb98f6ae42ce87e206cf3f6a86039f

(11581)

on February 02, 2011
at 02:55 PM

No coffee tables in caves.

E0b0d94cebef8ed2371d02ec2ecb5461

(94)

on February 02, 2011
at 04:32 AM

evolution produces sufficient results, not optimal ones...to say that any system is the most efficient is just wrong

5672b2d190891342389e764cc4056ca9

(1304)

on February 02, 2011
at 01:27 AM

Very good question... I always wondered why we don't have wings to fly away from dangers...

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 02, 2011
at 12:54 AM

Good answer, Rob. We do have muscles that pull the fronts of our feet up to our knees (I'm doing it right now). And they are kind of on the "front" of the leg -- but it's just that they're a little to the side, and not directly in front of the tibia. So maybe Glenn's question could be about those muscles, the ones that are kind of on the side of the front. Why don't they block the bone? I guess you've sort of answered this already: still about the most direct path?

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 02, 2011
at 12:46 AM

OK, then, what designer thought it was a good idea to make the sperm so temperature-sensitive?

A6e2b231f69366ce825476c5a6dcfff6

(1967)

on February 01, 2011
at 10:22 PM

I think there aren't as many threats to shins in nature. Your foot will get in the way. I'm not saying it doesn't happen, but I usually hit my shin on coffee table's and similar man made things.

5e36f73c3f95eb4ea13a009f4936449f

(8280)

on February 01, 2011
at 08:00 PM

Well, it's there because it is highly temperature sensitive. If it gets too hot, it reduces the motility/liveliness of the little guys. External = cooler temperatures.

50637dfd7dc7a7e811d82283f4f5fd10

(5838)

on February 01, 2011
at 07:44 PM

Lol, right? well played haha

E91fd339d760ed76cc72570a679ebf5a

(2369)

on February 01, 2011
at 06:09 PM

Someone asked me this recently and for once I didn't have a good evolutionary answer for why our shins are so unprotected and exposed to injury. Stump the paleos!

77877f762c40637911396daa19b53094

(78467)

on February 01, 2011
at 06:06 PM

My theory is that hunter-gatherers weren't as clumsy as the processed food/grain eating people of today and didn't bang their shins to begin. Me personally? I notice I am not clumsy anymore since avoiding grains, dairy and all processed food. It was affecting me that much.

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7 Answers

7
82166cc32b6cf26de33b69f58fb583b1

on February 01, 2011
at 09:23 PM

The muscles of the hips cross over bones in all directions, so I think the calves could have the same attachment points and still work from the front.

Muscles of the hip pull in various directions, yes, but that doesn't mean they are located out of line with their attachment points. They are in fact located as directly in line as possible with their attachment points.

All muscles are located this way because any other arrangement would be less efficient. Natural selection optimizes our bodies for efficiency.

The calf muscles pull our heels toward the backs of our legs. The calf muscles are located between those points so they can draw the points toward each other. Any other location for the muscles would be less efficient.

Our lower legs have to be designed efficiently so we can run fast. That's why nature makes lower legs as thin as possible and locates the leg muscles as high as possible. The lighter the foot and lower leg, the faster and longer we can run. That's why animals that run a lot have skinny lower legs and heavier upper legs.

As with all engineering decisions, this design requires a tradeoff. As the lower leg gets lighter, it becomes more fragile and breaks more easily. This is bad. But it's also bad if the animal can't run fast. Natural selection weighed the two criteria and struck a balance.

Now, it's true that some muscles wrap around bones. The supinator of the forearm is an example. When our hand is pronated, the muscle twists around the radius like this:

why-aren't-our-calves-in-front?

But still, the supinator is located as directly as possible between its attachment points. The bone is in the way so the muscle wraps around it, but still, the muscle takes the most direct possible path. This is different from what you are suggesting for the calf muscles. Your suggestion would make the muscle lie outside the most direct path.

Edit: I've oversimplified a bit. I should add that some tendons are wrapped with bands of ligaments that redirect the direction in which they pull. The ligaments act almost like pulleys. The muscles that straighten our fingers and lift our toes are in this category. These ligaments allow the muscles to be out of line with their attachment points.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 02, 2011
at 12:54 AM

Good answer, Rob. We do have muscles that pull the fronts of our feet up to our knees (I'm doing it right now). And they are kind of on the "front" of the leg -- but it's just that they're a little to the side, and not directly in front of the tibia. So maybe Glenn's question could be about those muscles, the ones that are kind of on the side of the front. Why don't they block the bone? I guess you've sort of answered this already: still about the most direct path?

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 09, 2011
at 05:19 AM

Much later response, sorry. It seems like what you added in your edit makes the problem even stranger: these tendons attached to the muscles that pull the toes up are moved out of the way by these "pulley" ligaments you speak of. So it's as if the muscles *could have* been in front of the shin, yet the body went out of its way (so to speak) to put them to the side of the shin ...

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 06:54 PM

Paul, I'm going to try to rewrite my whole answer in the next few days and explain everything better. I'm looking for illustrations now of the anterior muscles.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 16, 2011
at 06:42 AM

Just saw your comment. I wouldn't worry about it if you don't want to!

6
Medium avatar

(3259)

on February 01, 2011
at 07:42 PM

Fellas...shins are the least of our worries. What "designer" thought it was a good idea to hang our most sensitive and evolutionarily critical organs in a thin sack on the outside or our bodies?! I mean c'mon.

5e36f73c3f95eb4ea13a009f4936449f

(8280)

on February 01, 2011
at 08:00 PM

Well, it's there because it is highly temperature sensitive. If it gets too hot, it reduces the motility/liveliness of the little guys. External = cooler temperatures.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 02, 2011
at 12:46 AM

OK, then, what designer thought it was a good idea to make the sperm so temperature-sensitive?

50637dfd7dc7a7e811d82283f4f5fd10

(5838)

on February 01, 2011
at 07:44 PM

Lol, right? well played haha

6
5e36f73c3f95eb4ea13a009f4936449f

(8280)

on February 01, 2011
at 06:08 PM

Muscles only pull. They don't push. If your calves were in the front, you would have problems walking. Not sure the foot would even work as it is.

4
8e75344356f4a455185ee52da0b90bf2

on February 01, 2011
at 06:37 PM

I don't think that it is a 'design' flaw, it's just how animals' rear limbs evolved. That's the most efficient configuration.I'm pretty sure that all animals rear limbs are basically the same in structure (exceptions being sea mammals whose hind legs have atrophied).

From birds to horses to alligators to kangaroos to primates the hind leg structure is almost identical - the only difference is length of bone and how we locomote (is that a word?)

The shin question is moot - what we think of as a shin is much higher up on, say, a horse (their stifle is our knee, their hock is our heel) and in much less danger of banging. We aren't THAT far from our 4 legged stance (in evolutionary terms).

So a horse is short from hip to stifle (knee)long from stifle to hock (our heel) and from hock to fetlock (our toe joint) and walks on his single toenail. A kangaroo stands upright like us but is also long from stifle to hock and hock to toe joint and hops.

Primates are long from hip to knee and knee to heel ... but then we have very (relatively) short bones from there and we walk in our unique heel-toe gait.

Same bones structure just different parts on the ground and different movement.

It was set the same way hundreds of millions of years ago and all of us - alligators, kangaroos, horses, and humans have evolved differently to use it as best suits us.

Sorry so long! This stuff fascinates me. :D

E0b0d94cebef8ed2371d02ec2ecb5461

(94)

on February 02, 2011
at 04:32 AM

evolution produces sufficient results, not optimal ones...to say that any system is the most efficient is just wrong

2
Medium avatar

on February 01, 2011
at 06:19 PM

There's always one satyr at every party.

1
3f5bbb444498a24f1a9720d75fa7c903

on February 01, 2011
at 08:14 PM

Because if you bang your shin, it will have little to no effect on your reproductive ability. You'll survive the bang and still pass on the calf/shin genetics to your offspring. We can only evolve with the genes we have, which call for a calf in the back (as another reply stated). Natural selection for traits tend to select for genes that are potentially in the genetic code (barring a beneficial mutation of some sort). Then you must add in the the ability to pass on that code to offspring. Basically, we work with the genes we are handed down, and if we can tweak them for a reproductive advantage, then changes may occur but otherwise, we'll just go on banging those shins.

0
Cab7e4ef73c5d7d7a77e1c3d7f5773a1

(7304)

on February 01, 2011
at 06:02 PM

To push forward they would need to be in the back I believe. I'm no anatomy expert, but I don't know how they'd push us forward from the front.

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