Conceptual artwork illustrating how humans may evolve in a future where oxygen levels decrease in the atmosphere. Outline of a human body with detailed drawings of a modified heart, lungs, kidneys and ureters. In this scenario, lungs are reduced in size and allow inhalation for speech and smell only. The olfactory bulb (an area in the forebrain involved in sensing smell) and nerves compensate for the small lungs. In the urinary system, blood capacity increases in the kidneys. The ureters have increased in size and bacteria now produce oxygen from nitrite, a compound produced from nitrate which is found in urine. Carbon dioxide is expelled in the urine.
This image forms part of a project "Below 12" which is a speculative scenario where human beings have synthetically engineered their organs to adapt to an oxygen-depleted atmosphere, as deforestation, desertification and population over-growth are contributing to a fall in the long-term loss of oxygen sources. The lowest concentration of oxygen recorded in a populated area is 12%.
High levels of nitrites in urine today (nitrituria) can often indicate the presence of unwanted bacteria which can cause urinary tract infections.