skeleton evolution inHumans

[MOESAN]

An old believing was that the Human brain will be evolving regularly towards larger dimensions, so his skull.
Nevertheless, without real measures it's true, I think I observe - since say three generations - decreasing dimensions of skull level (at least at the horizontal level: length+breadth) among new generations, spite stature is still encreasing. BTW, this skeleton evolution, very often attributed to better diet so health, is more marked among high social classes spite the lower classes are today very better fed. It seems to me, as I said already before, that this evolution is tied to less physical activity in young age, maybe less oxygenation too, and lead to higer statures so vertical increase, but NOT to broader dimensions. Not at all a gain in robusticity or health, maybe? By physical ectivity, I don't meanby force hard work which can be bad...

 

[Vallicanus]

An old believing was that the Human brain will be evolving regularly towards larger dimensions, so his skull.
Nevertheless, without real measures it's true, I think I observe - since say three generations - decreasing dimensions of skull level (at least at the horizontal level: length+breadth) among new generations, spite stature is still encreasing. BTW, this skeleton evolution, very often attributed to better diet so health, is more marked among high social classes spite the lower classes are today very better fed. It seems to me, as I said already before, that this evolution is tied to less physical activity in young age, maybe less oxygenation too, and lead to higer statures so vertical increase, but NOT to broader dimensions. Not at all a gain in robusticity or health, maybe? By physical ectivity, I don't meanby force hard work which can be bad...

Do you mean that modern people have smaller skulls as regards posterior-anterior length or what?

 

[MOESAN]

¤Vallicanus
Yes, at first sight, but I have no metrics to support it. What seems sure is that the today skulls tend to be smaller compared to the rest of the body. BTW I don't affirm that the vertical aspect (height) didn't know some encrease.
On a forum which I forgot the name, someones evoked a survey about US Skulls between the 1800's and later times (not on alive people, so surely not so recent, if I don't mistake), showing an encrease in braincase volume. Funnily enough, a journalist wrote the difference was of the volume of a tennis ball when in reality it was of a table tennis ball!
What is sure is that our skeletons are changing. I don't know what value to accord to these results: were the people taken in account exactly of the same origins and social classes???
According to some surveys, the faces of the people were stronger (bigger, and more robust) before and knew a decrease between the 1400's and our times. Even more compared to the skull.
BTW in a synchronic population, as a whole, faces sizes tend to increase as allover stature increases. In the diachronic aspect we see the contrary.
Other thing I think I remarked is that among the new people with this kind of longer and narrower bodies we see more and more around us in towns, whatever the basic structure of the body (endomorphic, ectomorphic, brachyskele, dolichoskele (limbs proportions) ...) the humerus length is proportionally longer relative to the cubitus one (and the clavicle one), compared to previous generations; I see in this a lack of arms physical activity (?)

 

[MOESAN]

a confirmation of hat I was thinking for a long time. I think the stress needs by reaction more robusticity than only lengths increase.

[... On the other side of the world, in Germany, scientists have discovered another bizarre development: our elbows are shrinking. Christiane Scheffler, an anthropologist from the University of Potsdam, was studying body measurements taken from school children when she noticed the trend.

Children’s skeletons were becoming more and more fragile every year
To see exactly how much their skeletons had changed over time, Scheffler undertook a study of how robust, or “big boned”, children were between 1999 and 2009. This involved calculating their “frame index”, which is how a person’s height compares to the width of their elbows. Then she compared her results with those from an identical study that was 10 years older. She found that the children’s skeletons were becoming more and more fragile every year.

“And so we were thinking about that, what could be the reason,” says Scheffler. Her first idea was that it could be genetic, but it’s hard to see how a population’s DNA could change that much in just 10 years. The second was that perhaps the children were suffering from poor nutrition, but this isn’t really a problem in Germany. The third was that today’s youth are a generation of couch potatoes.


To find out, Scheffler conducted a new study – together with some colleagues this time – in which she also asked the children to fill out a questionnaire about their daily habits, and to wear a step counter for a week. The team found a strong link between how robust the children’s skeletons were and the amount of walking they were doing.

It’s already well known that every time we use our muscles, we help to increase the mass of the bones that support them. “If you use them again and again, they build more bone tissue, which is measured as a higher density and bigger girth of bone,” says Scheffler. The children’s shrinking skeletons look like a straightforward adaptation to modern life, since it doesn’t make sense to grow bone that you don’t need.

But there was one surprise lurking in the data: walking was the only type of exercise that seemed to have any impact. Scheffler thinks this is because even the most avid sports fans actually devote very little time to practising. “It’s not helpful if your mother takes you in the car for one or two hours per week,” she says.

And though no one has looked at whether the link holds up in adults, it’s likely that the same rules apply: it’s not enough to simply hit the gym a couple of times a week without also walking long distances. “Because our evolution tells us that we can walk for almost 30km (19 miles) per day.” ...]

 

[MOESAN]

abstract (in French!) of a study (rather a compilation of diverse works) made by Belgian scientists, concerning corporal dimensions:

[...Évolution séculaire d’autres mensurations
L’évolution séculaire ne se limite naturellement pas à la taille mais implique l’ensemble des dimensions et des proportions corporelles. Par rapport à la taille, le diamètre biacromial (roughly said something comparable to shoulders breadth), la longueur des bras (total) et les dimensions thoraciques diminueraient. Concernant les diamètres du bassin, la littérature est contradictoire (Susanne et Bodzsar, 1998 ; Susanne et coll., 2001) mais indique souvent un type de silhouette plus longiligne, comme en Belgique (Susanne, 1993 ; Vercauteren et coll., 1998), Suède (Lindgren, 1998) et Allemagne (Jaeger, 1998) (figure 1.14), bien que des différences régionales et socioéconomiques existent. ...]

I can translate into English if something asks for it. But it's kind of an "international French" (half medical).
ATW it confirms what my eyes saw. It's a pity they don't speak of Cranial diameter and things like that...

 

[MOESAN]

Elsewhere the diverse studies confirm the highly genetical heredity of body measures, but exposes also the diverse external mesologic input, among them the psychological stress on children (lost of height, but sometimes obesity not linked to excess of food...)