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MOESAN
18-10-12, 22:02
I found 2 digests of a survey made in the USA (maybe one of them in DIENEKE°:
yet, one of them reported erroneous facts (enthiusasm? scoop spirit?)
here under, a abstract:


»On the coat tails of Matt Ridley’s statement that humans are no longer evolving, comes news presented at last month’s annual meeting of the American Association of Physical Anthropologists that the heads of white Americans are getting bigger. Lee Jantz, Richard Jantz and Joanne Devlin, took about 1,500 skulls dating all the way back to the mid-1800s through the mid-1980s.
What they observed is year-by year the heads of this sample are growing in volume. The skull of the average male human has grown in height by 8 millimeters and in volume 200 cubic centimeters*. In women, the corresponding increases are seven millimeters and 180 cubic centimeters. This increase in volume is about the size of a tennis ball!**
An even more unique result is the disproportionate growth of the skull compared to the rest of the body. Since the late 1800′s, skull height has increased 6.8%. But body height has increased 5.6% and femur length has only increased about 2%. Where skull height has continued to change whereas the overall heightening has recently slowed or stopped.

my observations

*: false : millimeters !!!
** : a space equiv­a­lent to a cou­ple of small peas Yet a story that recall me some others in modern surveys:
1- how was selected the different samples of different times ? Same ethnic origin, precisely ?
White American is a very unprecise concept evolving with time : Irish Catholics ? German Protestants ? British ? Same mixture in same %s ober the centuries ??? Today the phenotypical aspect of white Americans is different enough compared to the 1960's ones : less irish, british or north-Europe origins, more South-Europe and slavic...a local genuine internal evolution is not alone at work there, rather an external one : other ligneages...
2- the social origin can play here too (selection) ...
3- the skulls linear mensurations described in the abstract are limited to the head height ; it is not the all mensurations... the volume ones could be linked only to the height ones, or not ? I noticed when I was young (1966-70), yet, that Americans presented seamingly (no mean for me to check it) higher skulls as a whole than the Europeans, even the northern ones, their forehead retreating slowly and the near horizontal summit of the head being shorter : in short, less « bombing » but higher forehead as a whole, more conic form of skull (they seamed to me too having bigger teeth as a whole : true teeths or prothesis?)- in Europe I rather notice what seams a diminution of head mensurations, at least when compared to body ones (particuliarly the height body ones and the feet ones)...Maybe the evolution in Europe and in the States are not the same ?

5-the difference between complete stature and femur growths strike me too: a very big difference : an internal evolution can explain a small margin but there !...
6- quality of sampling left on side, the quantity seams to me a bit scarce (1500 for all this period of 180 years is few for a so vaste land)


nevertheless, it remains a kind of truth behind these statistics - the changes in the way of living can surely modify some body internal proportions, but do'nt forget that new ethnic groups can send new proportions too! (here we state a global diminishing of legs compared to back lenght and head height -? maybe a link between back height and head height ? - all the way, concluding about time linked evolution is to be made very carefully

LeBrok
19-10-12, 08:14
Interesting observation Moesan. Do you think these changes in body size is linked to a better diet, food quantity, and general progress in quality of life, from 1800 till now?
That would be my main explanation, because I can't see how these changes could progress so fast if only natural selection is in play. The process is too fast.

I wonder if bigger growth of head compared to the rest of the body could be explain by dawn of public education, and due to this, more use of brains by kids? Public education started in 18 hundreds in most of Europe.
You exercise a muscle and it gets bigger. Does brain expends when exercised? I think it does, but not that much as muscle.

MOESAN
19-10-12, 14:06
my first thought was to show my hésitations concerning the worth kind of survey (for the populations studied are not very the same ones), the Americans are so found of!
and I have no qualification (grade qualification, I mean) to elaborate theories about evolution of phenotypes an genotypes under environment pressure -
What I observed is that proportionaly: even concerning the same ethnic and regional population (sons of fathers if you want) the news generations are growing higher and higher, thiner and thiner, narrower shouldered, more dolichocéphalic, lighter and lighter concerning muscles, higher and higher for humerus, smaller (proportionnaly I insist) for heads (not the american evidence here) - I think I osberved too lesser differenciation concerning bones sexual differences - this is linked to the way of life and not ONLY the diet -too often quoted by people, I believe) -
but Americans (whom?) are not Europeans: they do more sports when young à(schools, university) even if after, there lost of activity and their mechanization and their diet make the opposite of a sportman of them -
I red somepart (a survey made in Stellenbosch University among rugbymen of different generations) that young students of same Afrikaner extraction was bigger (higher statured for the most) BUT WEAKER than the oldest generations and they was obliged to do a lot of artificial musculation to get the same stregntgh result as a whole - one of the explanations I red (it's old: in the 1980's?) was that oxygenation by a sportive reasonable activity or reasonable physical work, has different effects on body accordint to age, favoring long bones before adolescence but accelerating ossification (hardning) after, limiting a too far growing of skeleton ( I think I red too in other books that oxygenation is good for brain, but concerning the brain size I have no answer: intelligence seam very far to be directly linked to brain size, we see a lot of mind handicaped persons with too big brains, ofden...) - I believe that NOT THE DIET but rather the lack of physical activities is the first responsible fact of the today evolution on bodies (it seam that height began to grow significally after the 14-18 World War, giiving statures in Europe that was the ones of the X° century as a proxi - (too hard work in agricultural exploited populations with too short endogamy decresed the european statures after the Middle Ages, and it seam that brachycephally augmentation is "mechanically" linked to these shortnings of statures and the contrary is being seen nowadays in industrial countries - the most you industrialize, the fastest the growing -
so the stature is not alays indicative of health or force...
just personal thoughts of a ungraded man
sorry

MOESAN
07-03-13, 19:57
I add here a post that is not completelty in line with the problems of populations of different times -
just an observation concerning a survey (found in DIENEKES) about robusticity of inferior limbs in men, linked to genetic heritage but also to physical activity and environment - my only remark is that MOBILITY is an imprecise word: hunter-gatherers could have been mobile (and they had) but this mobility is not by obligation synonym of far emigrations... an ma can run a marathon race around a stadium or between two towns: the story is the same concerning sport, not concerning civilisation and colonization

here the D's post:
http://1.bp.blogspot.com/-g7MF6TdERU0/UTYXboDlClI/AAAAAAAAIrk/9uNnXkmQyEY/s400/1-s2.0-S0047248413000092-gr2.jpg (http://1.bp.blogspot.com/-g7MF6TdERU0/UTYXboDlClI/AAAAAAAAIrk/9uNnXkmQyEY/s1600/1-s2.0-S0047248413000092-gr2.jpg)
The idea of Pleistocene remains having "extremely active and mobile lives" is consistent with the hypothesis that people moved around during prehistory, and did not simply grow roots after their initial colonization of the planet, as some models of "Paleolithic continuity" have affirmed.

Journal of Human Evolution doi:10.1016/j.jhevol.2013.01.004

Extreme mobility in the Late Pleistocene? Comparing limb biomechanics among fossil Homo, varsity athletes and Holocene foragers

Colin N. Shaw, Jay T. Stock

Descriptions of Pleistocene activity patterns often derive from comparisons of long bone diaphyseal robusticity across contemporaneous fossilized hominins. The purpose of this study is to augment existing understanding of Pleistocene hominin mobility patterns by interpreting fossil variation through comparisons with a) living human athletes with known activity patterns, and b) Holocene foragers where descriptions of group-level activity patterns are available. Relative tibial rigidity (midshaft tibial rigidity (J)/midshaft humeral rigidity (J)) was compared amongst Levantine and European Neandertals, Levantine and Upper Palaeolithic Homo sapiens, Holocene foragers and living human athletes and controls. Cross-country runners exhibit significantly (p < 0.05) greater relative tibial rigidity compared with swimmers, and higher values compared with controls. In contrast, swimmers displayed significantly (p < 0.05) lower relative tibial rigidity than both runners and controls. While variation exists among all Holocene H. sapiens, highly terrestrially mobile Later Stone Age (LSA) southern Africans and cross-country runners display the highest relative tibial rigidity, while maritime Andaman Islanders and swimmers display the lowest, with controls falling between. All fossil hominins displayed relative tibial rigidity that exceeded, or was similar to, the highly terrestrially mobile Later Stone Age southern Africans and modern human cross-country runners. The more extreme skeletal structure of most Neandertals and Levantine H. sapiens, as well as the odd Upper Palaeolithic individual, appears to reflect adaptation to intense and/or highly repetitive lower limb (relative to upper limb) loading. This loading may have been associated with bipedal travel, and appears to have been more strenuous than that encountered by even university varsity runners, and Holocene foragers with hunting grounds 2000–3000 square miles in size. Skeletal variation among the athletes and foraging groups is consistent with known or inferred activity profiles, which support the position that the Pleistocene remains reflect adaptation to extremely active and mobile lives.

good evening, peace (and love, if possible, otherwise a good drink!)

Templar
07-03-13, 20:20
What I observed is that proportionaly: even concerning the same ethnic and regional population (sons of fathers if you want) the news generations are growing higher and higher, thiner and thiner, narrower shouldered, more dolichocéphalic, lighter and lighter concerning muscles, higher and higher for humerus, smaller (proportionnaly I insist) for heads (not the american evidence here) - I think I osberved too lesser differenciation concerning bones sexual differences - this is linked to the way of life and not ONLY the diet -too often quoted by people, I believe) -

So men are slowly becoming weaklings. Just as I suspected.

MOESAN
09-03-13, 00:19
So men are slowly becoming weaklings. Just as I suspected.

Yes, for me. The human population growth and the important help of medecine and technic produced the illusion of physical amelioration of the specie through our human champions performances when it concerned only sportive elite - (and yet our champions are very specialized and not at all very performant concerning every body skil, except decathlonians...

so when we speak about ancient human subroups and about their skeletons this modern evolution shows we have to keep in mind that every kind of them was the result of genetic and way of life interaction, and that, same robustness can be shared by groups of different stature heights and that different robustness can suit to groups of same stature height - I say that because I red some "scrambling" surveys that divide Neolithic populations of Europe into a western one qualified as, "gracile" and an eastern one qualified of "robust" when in fact realtiy was more complex...
that said, 'robust' aspect of bones is not always the proof of true robustness of skeleton for that depends on several factors, and notonly mass, for I think before knowing more...

Templar
09-03-13, 02:25
Yes, for me. The human population growth and the important help of medecine and technic produced the illusion of physical amelioration of the specie through our human champions performances when it concerned only sportive elite - (and yet our champions are very specialized and not at all very performant concerning every body skil, except decathlonians...



What are your thoughts on how the recent obesity epidemic in North America and parts of Europe is changing populations in an evolutionary way. Do you think that people with faster metabolisms become more and more common (because the ones with super slow ones will die out eventually). How would this affect the bone structure of populations. Fat sometimes is beneficial when it comes to gaining muscle mass quickly (I.E. the bodybuilding bulking phase/stage), this might be relevant to the big picture as well.