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How Climate Change and Natural Selection Has Made Us Super Athletes
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“Bipedalism lets us not to spend to much energy to move. A human use 1/4 the amount of a chimpanzee.”
How Climate Change and Natural Selection has made us Super Athletes
“Fast Woman Runner.” Edition.cnn.com, Edition.cnn.com, 11 2011, https://edition.cnn.com/2012/04/11/sport/olympics-2012-campbell-brown/index.html.
5.5 million years ago, with the progressive closing of the Panama isthmus, generated the first cooling of the earth: it led to an aridification of eastern and western Africa. In the light of this climate change, scientists have sketched the evolution of our ancestors. In the savannas, in the east and south of Africa, our ancestors progressively exacerbate the bipedalism, colonising savanas while maintaining their characteristics, allowing them to get shelter in the trees. Their legs are shorter, their arms were more developed, and their feet kept their grip capacities. Those primates are regrouped into the genus of australopithecus. We all know the most famous representent, Lucy, a young woman who lived 3.3 million years ago.
Evolution has shaped us to run.
How Body changes have made us marathon runners? Savana development has probably enabled an environmental pressure favoring more and more bipedalism. Bipedalism leads to a series of adaptations in our body:
Foramen magnum located in the extension of the spin, migrates towards the center of the skull in order to better stabilize the head. The spine becomes sinuous and acts as a shock absorber. Pelvis shortens and enlarges, to guarantee balance (moving forward on two legs is not as stable as 4 legs) and at the same time it accompanies the growth of the head (the opening of the female pelvis conditions the maximal size of a newborn baby that will have to go thought). The knee centers and thickens, loses flexibility although it guarantees better balance. Gluteus maximus, the largest muscle
in the human body develops in order to assure power and endurance when running.
The foot flattens while the foot planter stifen, it loses its grip capacities but can now when flattened on the ground furnish more energy for propels. Finally the over development of the tendon boosts our capacity of running. This ligament acts as a spring by accumulating ⅓ of the energy released by the running at each stride to restore for the next stride. The achilles tendon measures 10 cm, 10 times more than a chimpanzee.
Our cousin the Chimpanzee has been optimized to alternate from trees to ground. In fact, it is the climate that has made us athletes programmed for endurance running.. The foot grip becomes useless as the trees dwindle. On the other hand the standing position coupled with the trichromatic and tridimensional vision allows us to see further away for predators or food. The standing position also autorises better regulation of the body temperature. Standing in a vertical position our body is less exposed to the sun and it's probable that the loss of hair coincides at that time to allow a better function of the corporal cooling. The veins network that flows under our skin and removes the surpler of heat. In fact the hair never really disappears (there is as much hair in humans and in chimpanzees!), but it lightens and becomes thinner to the extent of becoming almost invisible. In addition to the armpits and the sexual organ region, only the head has retained the fur as a natural protection against the sun. Our african ancestors had of course a darker skin and frizzy hair to maintain freshness. Sweat glance multiplies to allow the regulation of the temperature by releasing sweat.
The face flattens because the skull straightens. The ear anatomy expands because the inner ear, related to the balance, is more solicited. The size of the olfactory system reduces in size and therefore in performance because the face has flattened. As buccal cavity develops, our ancestors' vocalises more sound range which will allow them to develop language. And a better audition allows them to hear this wide range of sounds.
Adapting to our new environment
Finally the brain is going to grow in size during the next upcoming 2-3 million year, develop new areas, and lead to the progressive amergins of cognition as shown by the element of our forehead. The increase of intelligence and the capacity of communication go together with the better adaptability of all biotops. Canine shrink. Probable sign of the modification of our diets, as our ancestors became omnivorous which is a major advantage to adapt to different environments. Bipedalism allows us to spend much energy to move. A human uses ¼ energy less than a chimpanzee. Being omnivorous allows us to spend less energy in digestion, run faster because our digestive organs are smaller. Our entire body structure is made for the race. Our body structure is one of a racer. It protects our organs when we run. In addition, our noses allow us to breathe more air than chimpanzees, and our larynx going down to the throat eases the influx of oxygen in our lungs so that we are capable of controlling our breath with muscles.
Comparing us now and back then we have seen these many changes in our body and our body can go from a tree creature to an athlete runner so that we could adapt to our environment. The most important changes we have seen are: the extended standing position, stiff foot, lengthened bones of the limbs, flexible spine, reduced dentition, a complete omnivorous diet, smaller bowel, reduced hairiness, and an abundance of sweat glands made so that the Homo (Sapiens, Herectus, Habilis…) is the only mammal table to run a marathon under the midday sun.
“Fast Woman Runner.” Edition.cnn.com, Edition.cnn.com, 11 2011, https://edition.cnn.com/2012/04/11/sport/olympics-2012-campbell-brown/index.html.
Testot, Laurent. Cataclysmes: Une Histoire Environnementale De lhumanité: Document. Voir De près, 2018.
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