Centuries have shown us that as far as knowledge and technologies improve, humans are able to surmount challenges previously considered impossible. Less than forty years ago, some scientists believed that prolonged human occupation of altitudes over 3000 meters was impossible. (In fact, this remains a belief among those for whom comfort is the main objective in life). How-ever, such perspectives fail to consider the growing evidence that humans (and animals) have an extraordinary adaptive capacity to survive in the most difficult environments presented on the planet. From the 19th century it was claimed that Mt. Everest was impossible to climb, through Malloryґs inconclusive effort to the ultimate oxygen-assisted success of Norgay and Hillary (and later Messner and Habelerґs oxygen-less ascent), demonstrated hundreds of times that humans have the physiological capacity to ascend the highest point of the Farth. Careful preparation of the expeditions, experience, persistence and extraordinary stamina allowed Sir Edmund Hillary and Tensing Norgay to stand on the top of the mountain—and such is the approach of those who have followed. But the remarkable conclusion to be drawn from the history of such feats, combined with our current knowledge of the potentialities of human physiology, is that not only humans can ascend to such altitudes, but that they can dwell there, as well. Human excursions to the highest realms of the planet, under acute conditions without complete adaptation and with imminent risk of death, demonstrate that sufficient mechanisms of tissue oxygenation are present to warrant such radical conclusions as prolonged habitation at these same extreme altitudes. We have noted that in severe CMS and in the example of the woman with CMS and triple hypoxia syndrome, patients continue to arrive ambulatory at IPPA for consultation with a paO2 of around 35 mmHg. Such extreme hypoxic states can be sustained over several weeks, if not treated promptly. These low paO2 values are comparable to those estimated for humans at the summit of Mt. Everest [13]. Increased polycythemia is related not only to the severity of respiratory insufficiency— other factors play a role, as many researchers pointed out at the 4th World Congress on Mountain Medicine and Physiology Arica, Chile 2000 [14]. If we acknowledge that individuals with advanced pathological lesions are able to adapt to such hypoxic conditions as shown above, normal people should be able to do so even more easily (with the qualification that there are different individual and ethnic capacities). Further-more, when a patient with CMS has a low paO2, it is as if he or she were actually living at a higher altitude. In order to better illustrate this, we present an adapted graph plotting paO at different altitudes to depict at what relative altitude CMS patients are living (Fig. 4). Thus, the forgoing observations have led to the formulation of our hypothesis that human beings can adapt to the altitude and hypoxic conditions found at the summit of Mt. Everest. Such adaptation, of course, is predicated upon adequate protection from the cold, appropriate shelter and proper nutrition for such an environment. Furthermore, our hypothesis stipulates gradual exposure to increased hypoxia over extended periods at intermediate altitudes, though within an individual’s lifetime. We can summerize that, prolonged human occupation is possible at such extreme altitudes as Mt. Everest. If history is any guide, it may be inevitable, as well. Hematological adaptation to high altitude conserves energy expenditure of the pneumodynamic and hemodynamic pumps which work harder at the beginning of acute exposure to hypoxia (such as happens during exercise and after phlebotomy), in the interim of adaptation at the tissue level. The first, then, is an acute phase and the other is a chronic phase. Of course, we are not suggesting that colonies could be established on the summit of Mt Everest. But we are convinced that the physiological attributes of humans allow for such possibility of adaptation to extreme hypoxia. Life is possible anywhere on this planet, providing adequate nutrition and housing, and enough time is allowed for gradual adaptation. This knowledge permits us to understand the mechanisms of adaptation to tissue hypoxia in such a manner that may someday be applicable and beneficial to habitation of such adverse environments. In this paper we have tried to explain the foundations of our hypothesis that humans have the capacity to adapt to life on the summit of Mt Everest in one generation. If there is no first generation in a new environment we cannot expect that other generations will follow. The latter affirmation suggests that humans are already genetically prepared for life in the highest point of the planet—although not every single human being. Some will be genetically incompatible or incapable, as for example those suffering pulmonary fibrosis or Down’s syndrome or thousands of other genetic variations in people living at sea level which are not conducive to high altitude adaptation. Acknowledgement: To Michael Moretti for the English correction of the manuscript and to the Instituto Geografico Militar for their invaluable assistance with the research in Chacaltaya