In a recent post on IFLScience, they discussed the role of genetics in the growth of insects. However, it neglected to discuss the evolutionary reasons for why insects are not as large as say the Meganeura monyi, a foot long ancestor of the modern-day dragonfly that was prominent during the oxygen-rich Carboniferous Period, about 300 million years ago. I will profess, I know little about genetics, but I do know a little about oxygen. Why does that matter? Oxygen levels in the atmosphere are critical for driving the growth of these giant insects; the Carboniferous atmosphere was more oxygen-rich than any other period before or since.
The Carboniferous: Oxygen then, carbon dioxide now
At this point you might be wondering why on earth I would be discussing insects on a health and fitness blog. Well its one part side interest, one part education, and all parts cool! It is also ironic that the period of the highest oxygen levels also gave birth to coal and oil we burn today. But all the early oxygen gave a huge boost to early life. How high were those oxygen levels? Roughly 35%. This is more than 60% greater than our current 21% oxygen atmosphere. Early on, that oxygen helped giant plants form lignin, a key structural component and the main component of coal now. The higher oxygen content means a thicker atmosphere, which would offer those early insects more lift, thus allowing large insects the ability to fly. For flyers and non-flyers alike, more oxygen supports oxygen delivery because insects rely on diffusion of oxygen through their exoskeletons, not a cardiovascular system like us. In other words, big insects simply cannot deliver enough oxygen support life in our current “dilute” atmosphere. Interestingly, the Permian extinction of 95 percent of all life some 250 million years ago was followed by a drop in oxygen to about 15%.
Vitamin O: Fueling Human Performance
OK, so this is where you might be asking, “What does this have to dip with human performance?” In some ways, nothing, but I prefer to look at the possibilities of “WHAT IF?” In this case, what if our current atmosphere was 35% oxygen? Specifically, how would an increase in oxygen content affect actual endurance performance? Here’s where we diverge from paleobiology to exercise science. Recall my article, Training and Racing at Altitude. Here I discussed the specific implications of increasing altitude on cycling power output, as well as timing your arrival at altitude prior to competition. Moving from sea level to about 1500 m (5000 ft) you could expect about a 10% decrease in performance, while an altitude of about 3000 m (Leadville), results in about a 20% drop. But what would your performance look like in an atmosphere packed with almost double the oxygen? The figure below illustrates the outcome in dramatic fashion.
The lesson to learn here is that all that excess oxygen would have a profound impact on human performance at altitude. Specifically, we would be able to perform normal sea-level performances up to about 5000 m, which is approximately the same altitude as the highest permanent settle, La Rinconada, Peru (5100 m). Even more astounding is that climbing Mt Everest without supplemental oxygen would become significantly easier; one could expect only a 25-30% drop in performance at 29,000 ft! The downside, however, is that the air density would be higher at sea-level, increase aerodynamic drag, actually decreasing sea-level performances. The reason is that at sea-level, oxygen carry capacity would still be restricted to red blood cell mass/hemoglobin, so that great oxygen content would only make the air thicker, or harder to move through.
In summary, understanding pre-historic atmospheric conditions help us understand the past, as well as contemporary human performance. Much is often made about oxygen content in the atmosphere “thins” as we go up, but in reality the oxygen content stay stable, while the (partial) pressure is what pushes that oxygen into the blood. As you go higher, overall pressure goes down, making it harder to get the oxygen carried. However, simply pumping more oxygen into the atmosphere might improve altitude performance at the cost of sea-level performances.