Causes of hyperventilation
HV: the main reflex/drive
As we just discussed, most of the time our lungs were developing and evolving in conditions when the CO2 content was high (up to 7-12% during the first stages of lungs' development), with gradual decline, and low O2 values (about 1% or less during the first stages). During these stages the process of control of breathing by the nervous system was also developed. Since this primitive air had very little O2, our evolutionary predecessors could get more oxygen in tissues only by breathing more.
Any stressful situation, digestion, search for food, mating, playing, and any other activity required more oxygen. How? By breathing more. Hence, hyperventilation became the fundamental reflex or drive, as soon as first lungs (or prototypes of human lungs) appeared on Earth. Only totally peaceful stress-free rest had low metabolic rate where heavy breathing would not give any advantage for survival.
The drive to hyperventilate, as it is easy to notice is even more fundamental for humans than the drives to drink, eat, mate, etc. Why? Because when the human baby is born, the first things it starts to do is to breathe heavily as if expecting that air has very little O2 and a lot of CO2. (All developing or survived human cultures and tribes have used swaddling of infants to ensure their survival and good health, as we discussed a few pages ago.)
Most people die in conditions of severe hyperventilation, when this primitive reflex again gains the control of the human brain and sufferers frantically gasp for air, as if, again, expecting to get more oxygen.
Hence, hyperventilation is the main in-built reflex or drive of the human organism.