How do we adapt to extremes environments?

(R)Evolutionary Endurance

How do we adapt to extremes environments?


In the long evolutionary history of homo sapiens, we have faced and even embraced many difficult environments. Our success as a species is most likely to be a result of going beyond mere survival in challenging conditions and instead performing well as a result of 1) multiple short term physiological responses and behavioural changes, and 2) longer-term, species-specific evolutionary adaptations.

‘Extreme Terrestrial Environments: Life in Thermal Stress and Hypoxia. A Narrative Review’ provides us with an insight into how we perform in, and our responses to, both acute and chronic, extreme environmental stressors.

Coping and surviving extreme stressors relies upon a number of physiological adaptations including those that are ‘distal’, occurring over many generations, such as natural selection, and ‘proximal’, taking place over the course of a lifetime. The latter includes acclimatisation, including adjustments to physical traits, within days, weeks or months, of extreme stimuli, and habituation, which reduces psychological and physiological stress responses upon repeated presentations of extreme stimuli.

In response to hot environments, and to maintain appropriate body temperatures, our physiological responses usually include sweating, and an increase in blood flow, whilst modified behaviour may involve seeking shade, and the removal of clothing. Differing, but comparable responses are evident in response to the extreme cold. Studies into cold water swimmers and divers have found multiple adaptations, evidenced by shivering occurring later following a cold stimulus when compared with those not cold-water adapted, increased cold tolerance, and changes to heat loss in the limbs. The exact nature of many of the biological changes remains unclear, but evidence does suggest mental processes play a key role. Further studies, that may be of particular interest to extreme sports participants in cold or wet environments, have identified that prolonged exertion can leave the individual more susceptible to hypothermia.

Considerations for those in mountain environments include the challenges from reduced levels of oxygen, known as hypoxia. High altitude natives, such as Tibetans, exhibit a number of physiological and morphological differences when compared with lowlanders, including increased lung capacity, oxygen diffusion capacity and arterial oxygen saturation. A lowlander visiting altitudes above 4000m will experience reduced physical performance, responding in part by hyperventilation and vasoconstriction, the constriction of blood vessels resulting in increased blood pressure. Pre-exposure to hypoxic situations, along with appropriate medication can improve an individuals performance.

Such research provides useful insight, and potential benefits, regarding preparation for, and survival in extreme environments. To provide a complete psychophysiological view and enable the best support, psychological changes both in the short and long term, should receive increased attention.

Reference

Burtscher M, Gatterer H, Burtscher J and Mairbäurl H (2018) Extreme Terrestrial Environments: Life in Thermal Stress and Hypoxia. A Narrative Review. Front. Physiol. 9:572. doi: 10.3389/fphys.2018.00572

 

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