Viswanathan K's Thoughts

Life has been changing the environment almost from the minute it got started. In Origin Story , David Christian points out that almost 3 billion years back, cyanobacteria evolved photosynthesis: H 2 O + CO 2 + energy from the sun = Carbohydrates + O 2 As a result, carbon dioxide levels started falling in the atmosphere. But the oxygen levels did not start rising, at least not for some time. Why not?   As this BBC podcast says, the reason is obvious once you hear it: oxygen is among the most reactive elements in the universe. Ergo, the released oxygen reacted with pretty much everything out there and never stayed “free” in the atmosphere.   But eventually, all the oxygen “sinks” were full. And then the oxygen levels in the atmosphere began to rise massively and rapidly, all the way from practically non-existent levels to 35% (Current levels are 21%). This spike in oxygen levels was lethal to most life forms back then for a reason that’ll sound very weird to us fr...

Did a rise in oxygen levels in the atmosphere lead to the rise of complex life forms? The question doesn’t make sense at first. We know life adapts to whatever is available. By that token, oxygen levels can at most be the backdrop for however life evolved, but surely they cannot be called a causative factor…   In case of oxygen though, things are very different, writes Nick Lane in his book named (what else?) Oxygen : “The most obvious basis for a causal link is energy production.” Huh? “Oxygen releases more energy from food than do sulphur, nitrogen or oxygen compounds acting as oxidants… The length of any food chain is determined by the amount of energy lost from one level of the chain to the next.”   Without oxygen, that efficiency is less than 10%. Put differently, it means each step of the chain gets only 10% of the previous step. Here is the key point: “Below a 1% threshold, there is not enough energy available to eke out a living.” Do the maths, and ...