In other words the problem is that ALL participants haven’t read the article, not that none have read it. So calm down, guys, I’m sure Pat’s comment was not directed at you. It was directed at me — and I don’t mind.

As far as Pat’s theory is concerned, as I see it, that’s pretty close to the sort of thing Trinkaus may have had in the back of his mind. And it’s also more or less the impression I get from reading the media reports. But maybe the worst aspect of this whole matter is that the difference between changes wrought during a single person’s lifetime and changes wrought over thousands of years appears to have been left ambiguous.

In any case, assuming Trinkaus was referring to the former and not the latter, then we are left with the assumption that all human toe bones, down to the present time are innately “robust,” and only become “gracile” through the wearing of footwear, which looks to me like a huge boner.

And if the latter, then, with all due respect to Pat, the adaption would have had to take place within a very short time, not from the Paleolithic to the present, but from an earlier point in the Paleolithic to a somewhat later one. Far too short a time for the process Pat describes to have taken place.

Sorry but Trinkaus leaves me unimpressed.

With all due respect, I know who you are and do not appreciate your shameless jab, where you said there was a “lack of reading of the original article.” I read the article and find no explicit nor implicit discussion on the genetics of robust toe development in this paper, nor is there any inference to the heritability or selection of robust toe development throughout evolutionary time. That being said, your argument is out of the scope of this paper.

Trinkhaus examines the observation that footwear affects the robusticitiy of toe development in the fossil record. In his studies, he notes that footwear reduces strain from the toes, and the bones of the feet deposit less bone in response. The toe bones ultimately appear to be more gracile and have a different morphology than toe bones of individuals who were not habitual footwearers. He looks at the fossil record and investigates samples to see if they resemble the bones of individuals who wear footwear, or if they resemble the bones of individuals who walk barefoot. He finds that in two samples, the bones resemble that of a footwearing individual and suggests footwear was present 40,000 years ago.

From what I can tell, you’re making a completely different claim, again out of the scope of this paper, which suggests that gracile toes, an inherited trait, possibly fit into shoes better and affected the survivability of the individual… Offering a selective advantage.

Furthermore, your argument suggests there has been a positive selection towards gracile toes — but looking at the figure from the paper (which I linked above) we see that in modern populations, individuals exhibit a wide variation phalange morphology. This doesn’t support your hypothesis. If gracile toes were at one period more advantageous than robust ones, we wouldn’t be seeing a disproportionate amount of robust toes, would we?

I believe this is your first time commenting here, and since you decided to post behind an alias, I decided to respect your decision to remain pseudonymous. But, like I said, I know who you are and in the future, will not hesitate to call you out if you say that all participants didn’t read the paper and then offer up an argument that is completely out of the scope of the paper being discussed.

Kambiz

What is not completely clear to me is whether he sees such alterations as occuring over thousands of years due to some form of gradual “adaptation,” or over the lifetime of a single individual. I was hoping that you or Kambiz might have found some quote from one of the papers that makes THAT point clear, but apparently not. (Unless there is something in the quotes you provided that does make that particular point unambiguously but is over my head.)

It seems to me that if he really wanted to make the point you guys are seeing, he’d have taken a look at the way human feet develop over time today. In other words, the simplest and most logical way to assess what happens to feet during a single lifetime of wearing shoes is to compare the feet of very young humans with those of older humans from the same general population. And IMO I really doubt very much that you would find dramatic differences of the sort he’s referring to. Because what that implies is that the feet of very young children in, say, New York City or LA or Boston or wherever, would have a more “robust” bone structure than those of adults. That makes no sense to me.

I’m also bothered by the assumption that the earlier, “robust” state of these toe bones represents their default condition, because clearly if footwear can distort those bones then certainly a lifetime of walking barefoot over rough terrain can also distort them. Which means that the correlation between the “robust” state of the leg bones and the “robust” state of the foot bones that he finds in the older samples is very unlikely to mean what he implies it means.

I realize I’m over my head here as far as the technical stuff is concerned, so I could be totally off base. But so could be the many thousands of people reading all the many reports on this research, who might very well get the totally wrong idea that human feet “evolved” from “robust” to “gracile” over thousands of years due to the use of footwear.

What interests me more, however, than the question of the origin of footwear, is the broader issue that’s been raised in our discussion regarding the difference between three very different modes of assessing physical remains:

1. as representing a condition determined purely by genetic inheritance.

2. as representing a condition determined largely by environmental conditions.

3. as representing a condition determined largely by culture.

This may already be old news to you guys, but I’ve never thought of it this way until now. Not only the feet, but many parts of the body could very well be altered by either the environment or cultural practices or both, to the point that it could be all but impossible to meaningfully distinguish among the three possibilities. For example the “robust” condition of the lower limbs that Trinkhaus finds in the Neanderthal samples could have been caused by stresses induced through walking or running day in day out over very rough terrain. Hands could very quickly become gnarled in similar fashion over time, giving the bones a more “robust” appearance than they’d have had if these people had lived under less stressful conditions. And who knows what the Neanderthal toes might have looked like if Neanderthals had been farmers living relatively quiet lives in sedentary communities.

It seems as though the only way to make an assessment in purely genetic terms — i.e., strictly in terms of inheritance ruled by Darwinian adaptation — would be to examine the skeletal remains of small children.

Since the foot provides the contact between the body and the substrate, and since the use of footwear with a semi-rigid sole will alter the distribution of mechanical forces through the foot, it might be possible to perceive differences in the relative hypertrophy of portions of the foot in response to changes in habitual biomechanical loads through the pedal skeleton.

This next quote comes from the Trinkaus and Shang paper:

There is marked decrease in the robusticity of those bones, in the context of little change in overall lower limb robusticity (Trinkaus, 2006a), between the Middle Paleolithic early modern and late archaic humans on the one hand, and Middle Upper Paleolithic (Gravettian sensu lato) humans on the other hand. Since there is no meaningful change in the overall biomechanical load levels placed on these Late Pleistocene human lower limbs, through mobility and burden carrying (Trinkaus, 2006a), this reduction in lesser toe robusticity can only be interpreted as indicating localized mechanical insulation from
ground reaction forces during heel-off and toe-off. Since the pedal digital flexor muscles plantarflex the toes into the substrate in these latter portions of the stance phase (Reese et al., 1983), an artificial reduction, or dispersal, of that ground reaction force must have taken place.

So what Trinkause is saying is that wearing shoes caused an alteration in the biomechanical forces affecting the metatarsals. The metatarsals responded to the changed stress by altering the patterns of bone deposition and resorption.

Look at it this way. If you were to measure your heart rate, pulse, respiration, etc., now, then run a mile and measure them again they would be completely different. Gradually, they would return to the measurements obtained while you were at rest. Such a change is neither transmissible to your offspring nor a distortion of your basal metabolism, rather they represent a normal physiological reaction of your body to increased stress and its subsequent reduction. Same deal with wearing shoes, or not wearing shoes. Your metatarsals undergo a physiological change and respond to that stress and/or lack thereof.