Humain diminué ?

Les rêves transhumanistes envisagent à court terme une humanité augmentée. Mais cette humanité que l’on veut augmenter, n’est-elle pas pour l’instant une humanité diminuée, par bien des aspects ? Disons que ça peut s’argumenter…

Manthropology: The Science of Why the Modern Male Is Not the Man He Used to Be [Présentation]
Peter McAllister
St Martin’s Press, 2010

Stature et densité osseuse diminuées depuis le paléolithique

Genetic contributions to variation in human stature in prehistoric Europe [PDF]
Cox et al.
PNAS, 2019

Décroissance stature paléo Cox et al. 2019

Recent origin of low trabecular bone density in modern humans
Chirchir et al.
PNAS, 2015

Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

Gradual decline in mobility with the adoption of food production in Europe
Ruff et al. [PDF]
PNAS, 2015

Together these results strongly implicate declining mobility as the specific behavioral factor underlying these changes. Mobility levels first declined at the onset of food production, but the transition to a more sedentary lifestyle was gradual, extending through later agricultural intensification. This finding only partially supports models that tie increased sedentism to a relatively abrupt Neolithic Demographic Transition in Europe. The lack of subsequent change in relative bone strength indicates that increasing mechanization and urbanization had only relatively small effects on skeletal robusticity, suggesting that moderate changes in activity level are not sufficient stimuli for bone deposition or resorption.

Gradual decline in mobility, Ruff 2015

Gracility of the modern Homo sapiens skeleton is the result of decreased biomechanical loading [Texte]
Ryana & Shaw
PNAS, 2015

Analyses of mass-corrected trabecular bone variables reveal that the forager populations had significantly higher bone volume fraction, thicker trabeculae, and consequently lower relative bone surface area compared with the two agriculturalist groups. There were no significant differences between the agriculturalist and forager populations for trabecular spacing, number, or degree of anisotropy. These results reveal a correspondence between human behavior and bone structure in the proximal femur, indicating that more highly mobile human populations have trabecular bone structure similar to what would be expected for wild nonhuman primates of the same body mass. These results strongly emphasize the importance of physical activity and exercise for bone health and the attenuation of age-related bone loss.

La stature et la corpulence des chasseurs-cueilleurs étudiés par l’ethnologie sont souvent très faibles.

Energy Expenditure and Activity Among Hadza Hunter-Gatherers [PDF]
Pontzer et al.
American journal of human biology, 2015

La masse moyenne des humains semble commencer à décliner avant le néolithique, laissant supposer de possibles stress ayant préludé à une modification du mode de vie.

Body mass and encephalization in Pleistocene Homo [Abtract]
Ruff et al.
Nature, 1997

Ruff et al. 1997

Age relations of cardiovascular risk factors in a traditional Melanesian society: the Kitava Study [PDF]
Lindeberg et al.
American journal of clinical nutrition, 1997

Taille, poids Kitava Lindeberg 1997

Differential Reproductive Success and Body Size in !Kung San People from Northern Namibia
S. Kirchengast
Collegium anthropologicum, 2000

Stature et poids des !Kung 2

Evolutionary Perspectives on Human Nutrition: The Influence of Brain and Body Size on Diet and Metabolism [Abstract]
Leonard & Robertson
American journal of human biology, 1994

Taille, poids et alimentation Leonard Robertson 1994

Sociétés industrielles

Les chercheurs considèrent les athlètes d’aujourd’hui comme de bons modèles pour les humains préhistoriques.

Human athletic paleobiology; using sport as a model to investigate human evolutionary adaptation [Texte]
Longman et al.
American journal of biological anthropology, 2020

sportsmen and sportswomen are invaluable to anthropologists because they are more representative of past populations than the average person. Numerous metrics indicate that contemporary Western society is growing more sedentary. Jobs are becoming less physically demanding, screen time is increasing (time spent using a computer or phone, watching a television or playing video games), as is time spent sitting (see Owen et al., 2010). As a result, the average member of sedentary Western society may not be a representative model for investigations of biomechanical and energetic aspects of evolved habitual activities such as running, or even walking.

L’état physique des jeunes hommes a considérablement diminué en 40 ans.

The mean distance achieved in the 12-min running test decreased by 337 m (12.2%, P e 0.001) between the peak in 1980 and 2015. The relative number of conscripts who ran less than 2200 m increased from 3.6% to 25.9% (P e 0.001) between 1980 and 2015, and the proportion who ran more than 3000 m decreased from 25.1% to 6.5% (P e 0.001). The relative number of conscripts who achieved an excellent or good muscle fitness index decreased from 66.8% to 40.1% (P e 0.001) between 1992 and 2000, and remained unchanged between 2000 and 2010. However, the proportion who achieved a poor muscle fitness index increased from 8.1% to 31.4% (P e 0.001) between 1992 and 2010.

Les femmes du néolithique étudiées ici semblaient avoir dans le haut du corps la force physique d’avironeuses de haut niveau.

Prehistoric women’s manual labor exceeded that of athletes through the first 5500 years of farming in Central Europe [Texte]
Macintosh et al.
Science advances, 2017

Prehistoric female tibial rigidity at all time periods was highly variable, but differed little from living sedentary women on average, and was significantly lower than that of living runners and football players. However, humeral rigidity exceeded that of living athletes for the first ~5500 years of farming, with loading intensity biased heavily toward the upper limb. Interlimb strength proportions among Neolithic, Bronze Age, and Iron Age women were most similar to those of living semi-elite rowers. These results suggest that, in contrast to men, rigorous manual labor was a more important component of prehistoric women’s behavior than was terrestrial mobility through thousands of years of European agriculture, at levels far exceeding those of modern women.

La poigne des millenials serait sensiblement plus faible que celle des générations précédentes, et on retrouve une perte musculaires dans d’autres parties du corps.

Comparative study of millennials’ (age 20-34 years) grip and lateral pinch with the norms [Extraits]
Fain & Weatherford
Journal of hand therapy, 2016

Strength scores were statistically lower that older normative data in all millennial grip strengths, with the exception of the women in the age group of 30-34 years. Specifically, this statistically significant trend was observed in all male grip strengths, as well as in women in the age group of 20-24 years (bilateral grip) and 25-29 years (right grip). However, the lateral pinch data reflected was similar to the older norms with variances of 0.5-1 kg.

Letter to the Editor
Comparative study of millennials (age 20-34 years) grip and lateralpinch with the norms [Abstract]
Hollmann & Schifferdecker-Hoch
Journal of hand therapy, 2017

…our findings show comparable and continuous effects in
back and neck musculature. […] From the combined findings, it seems that the loss of muscular strength is a systemic issue and it is most likely that such effects will also occur in other body regions.

Capacités cognitives

Les études portant sur les capacités cognitives et le QI sont particulièrement sujettes à biais, effets d’annonce et orientations idéologiques. Elles sont toujours à prendre avec une extrême prudence.

The negative Flynn effect : a systematic litterature review [PDF]
Dutton et al.
Intelligence, 2016

The Flynn Effect (rising performance on intelligence tests in the general population over time) is now anestablished phenomenon in many developed and less developed countries. Recently, evidence has begun toamass that the Flynn Effect has gone into reverse; the so-called‘Negative Flynn Effect.’In this study, we presenta systematic literature review, conducted in order to discover in precisely how many countries this reverse phe-nomenon has been uncovered. Using strict criteria regarding quality of the sample and the study, we found ninestudies reporting negative Flynn Effects in seven countries. We also discuss several possible explanations for thenegative Flynn Effect as an attempt to understand its most probable causes.

Were the Victorians cleverer than us? The decline in general intelligenceestimated from a meta-analysis of the slowing of simple reaction time [PDF]
Michael A. Woodley et al.
Intelligence, 2013

The Victorian era was marked by an explosion of innovation and genius, per capita rates of which appear to have declined subsequently. The presence of dysgenic fertility for IQ amongst Western nations, starting in the 19th century, suggests that these trends might be related to declining IQ. This is because high-IQ people are more productive and more creative. We tested the hypothesis that the Victorians were cleverer than modern populations, using high-quality instruments, namely measures of simple visual reaction time in a meta-analytic study. Simple reaction time measures correlate substantially with measures of general intelligence (g) and are considered elementary measures of cognition. In this study we used the data on the secular slowing of simple reaction time described in a meta-analysis of 14 age-matched studies from Western countries conducted between 1884 and 2004 to estimate the decline in g that may have resulted from the presence of dysgenic fertility. Using psychometric meta-analysis we computed the true correlation between simple reaction time and g, yielding a decline of −1.23 IQ points per decade or fourteen IQ points since Victorian times. These findings strongly indicate that with respect to g the Victorians were substantially cleverer than modern Western populations


La myopie semble être pour une large part induite par les comportements modernes.

Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050
Holden et al.
American academy of ophtalmology, 2016

Myopia and high myopia estimates from 2000 to 2050 suggest significant increases in prevalences globally, with implications for planning services, including managing and preventing myopia-related ocular complications and vision loss among almost 1 billion people with high myopia.

An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia [Texte complet]
Cordain et al.
Acta ophtalmologica scandinavia, 2003

humans, living in the original environmental niche for which our species is genetically adapted (as hunter-gatherers), are either slightly hypermetropic or emmetropic and rarely develop myopia. Myopia occurs when novel environmental conditions associated with modern civilization are introduced into the hunter-gatherer lifestyle.

Mâchoire, Dentition

Incongruity between Affinity Patterns Basedon Mandibular and Lower Dental Dimensions following the Transition to Agriculture in the Near East, Anatolia and Europe [Texte complet]
Pinhasi et al.
PLOS One, 2015

In the case of hunter-gatherers there is a correlation between inter-individual mandibular and dental distances, suggesting an equilibrium between these two closely associated morphological units. However, in the case of semi-sedentary hunter-gatherers and farming groups, no such correlation was found, suggesting that the incongruity between dental and mandibular form began with the shift towards sedentism and agricultural subsistence practices in the core region of the Near East and Anatolia.

Origins of Dental Crowding and Malocclusions : An Anthropological Perspective [Abstract]
Rose & Robbly
Compendium , 2009

These analyses suggest it was not the reduction in tooth wear that increased crowding and malocclusion, but rather the tremendous reduction in the forces of mastication, which produced this extreme toothwear and the subsequent reduced jaw involvement.Thus, as modern food preparation techniques spread throughout the world during the 19th century, so did dental crowding.

Sur les traces de l’homme le plus rapide de tous les temps [Article]
Pierre-Jean Vazel
Le Monde, 2012

La vitesse de déplacement de vingt-trois Homo Sapiens pieds nus a pu être estimée d’après les dimensions des empreintes de course conservées dans du sable argileux stratifié. Le meilleur, « T8 », a rétroactivement été flashé à 37,3 km/h. Le plus vieux sprint du monde ? « Ces hommes étaient probablement en train de chasser le kangourou, la vitesse atteinte par T8 était un pic sur une des onze foulées après une embuscade », nous explique le Dr Steve Webb, coauteur de l’étude parue en 2006 dans le Journal of Human Evolution.

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