Adaptations à la course d’endurance

Les chercheurs sont longtemps passés à côté de l’idée que les humains pouvaient être de bons coureurs d’endurance. Jusqu’au début des années 1980, il était couramment admis que la bipédie avait donné aux humains primitif de grands avantages via la marche, mais que nous étions de piètres coureurs, notamment parce que l’on s’arrêtait au constat de nos faibles qualités de sprinteurs.

Mais dans les années 1980, un chercheur, lui-même marathonien, David Carrier, a émis l’hypothèse que nos ancêtres aient pu être d’excellents coureurs d’endurance, et que cette qualité aurait pu les aider en permettant la pratique d’un type de chasse particulier, appelé chasse à l’épuisement. Passée pratiquement inaperçue, l’idée a été reprise une vingtaine d’années plus tard, et est depuis considérée comme une hypothèse plutôt robuste, même si elle ne fait pas l’unanimité. Elle est par ailleurs renforcée par des études morphologiques et génétiques.

Par ailleurs, l’idée que les premiers coureurs aient couru nus-pieds laisse entendre que la technique de course naturelle des humains est différente de la technique utilisée par les coureurs chaussés (attaque sur le milieu du pied pour la technique naturelle, sur le talon pour les coureurs chaussés), et pourrait expliquer que ces derniers se blessent souvent. La question reste très débattue, et l’intérêt d’apprendre à courir pieds nus pour retrouver une foulée naturelle est âprement discuté.

1. Adaptations à la course d’endurance
2. Implications modernes


Adaptations à la course d’endurance

L’inactivation d’un gène il y a deux ou trois millions d’années a pu améliorer les capacités d’endurances de nos ancêtres.

Human-like Cmah inactivation in mice increases running endurance and decreases muscle fatigability: implications for human evolution
Jonathan Okerblom et al.
Proceedings of the royal society, 2018
https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2018.1656

Taken together, these data suggest that CMAH loss contributes to an improved
skeletal muscle capacity for oxygen use. If translatable to humans, CMAH loss
could have provided a selective advantage for ancestral Homo during the
transition from forest dwelling to increased resource exploration and hunter/gatherer behaviour in the open savannah.
Les pleines capacités d’endurance du genre Homo sont atteintes il y a 1 millions d’années. Le développement des capacités d’endurance est corrélé au développement du cerveau.

Economy and Endurance in Human Evolution
Herman Pontzer
Current biology, 2017
https://www.cell.com/current-biology/fulltext/S0960-9822(17)30567-5

The appearance of skeletal traits related to endurance (e.g., larger limb joints, spring-like plantar arch) in Homo was somewhat mosaic, with the full endurance suite apparent only ∼1 million years ago. The development of endurance capabilities in Homo appears to parallel the evolutionary increase in brain size, cognitive sophistication, and metabolic rate.
Un auteur en désacord avec l’idée que les modifications anatomiques des premiers humaines soient directement liées à l’amélioration des capacités de course d’endurance.
These bones where made for jogging : an analysis of the lower limb skeletal evidence for the endurance running hypothesis
A complete suite of anatomical features related to endurance running is not seen until Homo ergaster at 1.8 million years ago. However, a mosaic of these features is present in earlier Australopiths. This, combined with the lack of evidence for long range projectile weapons in the Pleistocene, indicates thes features may have been positively selected for to increase walking efficiency and increased endurance running capabilities were just a fortunate by-product. Currently, there is insufficient evidence to support the notion that anatomical changes observed in early Homo evolved to increase running capabilities.
Voir plus bas, Franciscus & Trinkaus, 1988, pour les bases de l’évolution du nez depuis les pré-humains.

Investigating the case of human nose shape and climate adaptation
Zaidi et al.
Plos Genetics, 2017
https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1006616

The evolutionary reasons for variation in nose shape across human populations have been subject to continuing debate. An import(ant ?) function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tract.

D’extraordinaires capacités de course d’endurance n’ont probablement pas été très utiles pour le charognage.
Endurance running and its relevance to scavenging by early hominids
Graeme Ruxton & David Wilkinson
Evolution, 2013
https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.2012.01815.x
Our model estimates that nonhominin scavengers will generally be able to reach the carcass within 30 min of detecting a plume of vultures above a nearby carcass. We argue that endurance running over periods greater than 30 min would not have provided a selective advantage to early hominins through increased scavenging opportunities. However, shorter distance running may have been selected, particularly if hominins could defend or usurp carcasses from other mammalian scavengers.

Optimal running speed and the evolution of hominin hunting strategies
Steudel-Numbers & Wall-Scheffler
Journal of human evolution, 2009
https://www.sciencedirect.com/science/article/abs/pii/S0047248408002364

The belief in the lack of optimal running speeds in humans is based, however, on a number of early studies with experimental designs inadequate for the purpose of evaluating optimality. Here we measured the energetic cost of human running (n = 9) at six different speeds for five minutes at each speed, with careful replicates and controls. We then compared the fit of linear versus curvilinear models to the data within each subject. We found that individual humans do, in fact, have speeds at which running is significantly less costly than at other speeds (i.e., an optimal running speed). In addition, we demonstrate that the use of persistence hunting methods to gain access to prey at any running speed, even the optimum, would be extremely costly energetically, more so than a persistence hunt at optimal walking speed. We argue that neither extinct nor extant hominin populations are as flexible in the chosen speeds of persistence hunting pursuits as other researchers have suggested.

Il a été argumenté que les chasseurs-cueilleurs contemporains ne pratiquent pas la chasse à l’épuisement. Il semble difficile d’en tirer des conclusions sur le comportement des premiers humains, avant l’invention d’armes sophistiquées ou la domestication du chien et du cheval. De plus, l’absence d’observation de chasses à l’épuisement de la part des ethnologues ne reflète peut-être pas l’incapacité des chasseurs cueilleurs à mener ces chasses, mais seulement l’incapacité des ethnologues à les documenter (note : quelques cas de chasse à l’épuisement ont été tout de même observés, l’un d’eux a même été filmé).
The endurance running hypothesis and hunting and scavengingin savanna-woodlands
Pickerins & Bunn
Journal of human evolution, 2007
https://www.originalwisdom.com/wp-content/uploads/bsk-pdf-manager/2019/05/Pickering-and-Bunn_2007_TheEnduranceRunningHypothesis.pdf
We agree with the opinion ofBramble and Lieberman(2004)that earlyHomorequired a high-quality diet, which in-cluded a substantial meat component, and that it was thus a ca-pable carcass forager. However, our understanding of thepaleoenvironment, paleoecology, and archaeology of earlyHomosites, reviewed here, makes us dubious about their fur-ther suggestion that ER might have been employed regularlyand successfully in service of that foraging pursuit. We are re-luctant to assign to earlyHomothe impressive tracking skillsof the Kalahari San, when the cognitive and meat-foragingabilities of Plio-PleistoceneHomoare active research issues.The behavioral pattern that selected for ER in the genusHomoremains unclear, but it seems likely that hunting andscavenging contributed minimally, if at all.
The Evolution of Endurance Running and the Tyranny of Ethnography: A Reply to Pickering and Bunn (2007)
Daniel Lieberman et al.
Harvard Library, 2007
We will never know for sure why and how ER capabilities
evolved, but the modern ethnographic record is a limited, biased,
and sometimes misleading source of evidence to test hypotheses
about how ESA hominids hunted and scavenged.
The challenge for paleoanthropologists is to explain the past
436 D.E. Lieberman et al. / Journal of Human Evolution 53 (2007) 434e437
in terms of testable hypotheses derived from actualistic studies
and middle-range research without succumbing to the ‘‘tyranny
of ethnography.’’
The relevance of persistence hunting to human evolution
As pointed out by Lieberman et al. (2007), Pickering and Bunn (2007) made several flawed assumptions. Persistence hunting may have been more common before the invention of the bow-and-arrow or the domestication of dogs and horses. The
apparent scarcity of ethnographic records of PH does not imply that PH was rare
it could simply be that anthropologists who were able to observe PH were rare. Over the last 50 years, hunter-gatherers in the Kalahari have experienced drastic changes, and the recent observations of PH may simply represent the tail-end of a dying tradition. In the absence of a better hypothesis, PH and scavenging remain plausible explanations for the evolution of ER.
The evolution of marathon running : capabilities in humans
Daniel Lieberman, Denis Bramble
Harvard library, 2007
https://dash.harvard.edu/bitstream/handle/1/3716644/Lieberman_Marathon.pdf?sequence=3
Humans have exceptional capabilities to run long distances in hot, aridconditions. These abilities, unique among primates and rare among mammals,derive from a suite of specialised features that permit running humans to store andrelease energy effectively in the lower limb, help keep the body’s center of massstable and overcome the thermoregulatory challenges of long distance running.Human endurance running perfonnance capabilities compare favourably withthose of other mammals and probably emerged sometime around 2 million yearsago in order to help meat-eating hominids compete with other carnivores.
Persistence hunting by modern hunter-gatherers
Louis Liebenberg
Current anthropology, 2006
https://www.journals.uchicago.edu/doi/abs/10.1086/508695
Endurance running may be a derived capability of the genus Homo and may have been instrumental in the evolution of the human body form. Two hypotheses have been presented to explain why early Homo would have needed to run long distances: scavenging and persistence hunting. Persistence hunting takes place during the hottest time of the day and involves chasing an animal until it is run to exhaustion. A critical factor is the fact that humans can keep their bodies cool by sweating while running. Another critical factor is the ability to track down an animal. Endurance running may have had adaptive value not only in scavenging but also in persistence hunting. Before the domestication of dogs, persistence hunting may have been one of the most efficient forms of hunting and may therefore have been crucial in the evolution of humans.

Le grand fessier, muscle essentiel dans notre évolution. Il semble avoir une utilité modeste pour la marche, mais beaucoup plus importante pour la course.

The human gluteus maximus and its role in running
Daniel Lieberman et al.
Harvard library, 2006
The human gluteus maximus is a distinctive muscle in terms of size, anatomy and function compared to apes and other non-human primates. Here we employ
electromyographic and kinematic analyses of human subjects to test the hypothesis that the human gluteus maximus plays a more important role in running than
walking. The results indicate that the gluteus maximus is mostly quiescent with low levels of activity during level and uphill walking, but increases substantially in activity and alters its timing with respect to speed during running. The major functions of the gluteus maximus during running are to control flexion of the trunk on the stanceside and to decelerate the swing leg; contractions of the stance-side gluteus maximus may also help to control flexion of the hip and to extend the thigh. Evidence forwhen the gluteus maximus became enlarged in human evolution is equivocal, but the muscle’s minimal functional role during walking supports the hypothesis that enlargement of the gluteus maximus was likely important in the evolution of hominid running capabilities.
Article considéré comme fondateur dans la théorie de l’homme coureur d’endurance et chasseur à l’épuisement. Il reprend l’essentiel des travaux des années 1980 de David Carrier, en y ajoutant toutefois des considérations physiologiques importantes.
Endurance running and the evolution of Homo
Dennis M. Bramble, Daniel E. Lieberman, 2004
Lieberman 2004

The loss of functional body hair in man: the influence of thermal environment, body form and bipedality
P.E. Wheeler
Journal of human evolution, 1985

An insulating layer of body hair is crucial to the thermoregulatory energetics of most mammals. Only some highly specialized aquatic forms and a few fossorial and terrestrial species which experience special heat stress problems have evolved a naked skin. Man’s body size and form suggest that his naked skin is associated with the prevention of hyperthermia in hot climates rather than an aquatic ancestry. The reduced direct solar radiation exposure of hominids in open equatorial environments, resulting from their unique bipedal posture, may explain the absence of this characteristic among other savannah mammals of comparable body mass.

Le deuxième article de David Carrier pointe les particularités énergétiques de la course humaine. Alors que les autres animaux possèdent pour chaque type d’allure (pas, trot galop) une vitesse optimale de course, l’énergie dépensée par les humains à la course semble peu influencée par la vitesse (résultat surprenant, tout de même). De plus, la plupart des quadrupède dissipent leur chaleur par la respiration, en haletant, alors que les humains la dissipent plus efficacement, en transpirant.

The energetic paradox of human running and hominid evolution
David Carrier, 1984
https://www.jstor.org/stable/2742907
https://carrier.biology.utah.edu/Dave%27s%20PDF/energetic%20paradox.pdf

 

This analysis of the morphology and physiology of human locomotion, although incomplete and largely speculative, sug- gests that man is a primate that has become specialized for (among other things) endurance running […] . Exercising anthropoid primates can dissipate heat more rapidly than certain cursorial mammals. This suggests that the earliest hominids may have been more effective at heat loss than many other contemporary mammals. Furthermore, early australo- pithecines were fully bipedal. As a result, they were probably not constrained to the typical 1:1 breathing pattern of running quadrupeds. Consequently, it is possible that one of the impor- tant factors which differentiated hominids from other an- thropoids, and ultimately led to the evolution of H. sapiens, was the occupation of a new predatory niche. This hypothet- ical niche was that of a diurnal predator which depended upon exceptional endurance in hot (midday) temperatures to disable swifter prey animals.

Le tout premier article suggérant des capacités d’endurances particulièrement développées chez les êtres humains. La bipédie permet de libérer les poumons des contraintes liées à la course (principalement au galop). Les humains ont donc la capacité de découpler leur rythme de course de leur respiration, et donc de maintenir très longtemps leur vitesse de course, là où les animaux ont besoin, à partir d’une certaine vitesse, de s’arrêter pour respirer.
Running and breathing in mammals
Dennis M. Bramble, David Carrier, 1983
https://www.researchgate.net/publication/16350157_Running_and_breathing_in_mammals
Quadrupedal species normally synchronize the locomotor and respiratory cycles at a constant ratio of 1:1 (strides per breath) in both the trot and gallop. Human runners differ from quadrupeds in that while running they employ several phase-locked patterns (4:1, 3:1, 2:1, 1:1, 5:2, and 3:2), although a 2:1 coupling ratio appears to be favored.
La forme du nez peut aussi avoir été utile à réguler la température de l’air inspiré. Elle change dans le même laps de temps que les autres modifications anatomiques liées à la course.
Nasal Morphology and the Emergence of Homo erectus
Franciscus & Trinkaus
American journal of physical anthropology, 1988
https://onlinelibrary.wiley.com/doi/pdf/10.1002/ajpa.1330750409

Modern humans, among extant hominoids, possess a unique projecting, external nose whose basic structure is reflected in a series of skeletal features including nasal bone convexity, an internasal angle, lateral nasal aperture eversion, prominence and anterior positioning of the anterior nasal spine, an acute angle of the subnasal alveolar clivus, and an expansion of the breadth of the nasal bones relative to that of the piriform aperture. This anatomy appears with the emergence of Homo erectus ca. 1.6 million years ago. Although it undoubtedly evolved in the context of craniofacial and dental reduction during hominid evolution, it appears to have been primarily a response to the need for moisture conservation in an arid environment via turbulence enhancement and ambient cooling of expired air. Its appearance at this time in hominid evolution, in conjunction with the presence of a fatigue- resistant locomotor anatomy characteristic of archaic members of the genus Homo, indicates a shift to increasingly prolonged bouts of activity in open and arid environments.

Implications modernes

Evidemment, s’il se confirme que la course d’endurance a eu une importance aussi grande pour nos ancêtres, si notre physiologie a si fortement évolué en conséquence, alors nous devons être parfaitement adaptés à la course. Mais alors, comment se fait-il que les athlètes, de haut niveau comme du dimanche, se blessent aussi souvent ? Il est suggéré que la manière dont on pose le pied, quand on est chaussé, et particulièrement avec des chaussures à fort amorti, est différente de la manière naturelle de courir, et pourrait expliquer un certain nombre de blessures.
Une thèse entière de kinésiologie sur la meilleure façon de poser le pied quand on court.
Rearfoot, mid/forefoot, and barefoot running : Biomechanical differences related to injury
Elizabeth Rose Boyer

Une étude qui trouve que l’attaque talon est plus économe que l’attaque médio-pied, du moins pour les vitesses relativement faibles.

Rearfoot striking runners are more economical than midfoot strikers
Ana Ogueta-Alday et al.
Medecine & science in sport & exercise, 2014
https://www.researchgate.net/publication/256436455_Rearfoot_Striking_Runners_Are_More_Economical_Than_Midfoot_Strikers

Effects of Footwear and Strike Type on Running Economy
Daniel Perl et al.
Medecine & science in sport & exercise, 2012
https://pdfs.semanticscholar.org/5632/9749cfe1243f206a6c4fe4919c14253a9072.pdf

 


Et un peu de littérature, un livre que l’on ne saurait trop recommander (même s’il prend quelque libertés avec les questions scientifiques) :
Christopher McDougall, Born to run, éditions Gérin, 2012.

Born to run