Power, Sex, Suicide summary

Before modern science emerged, the sixteenth-century Swiss alchemist Paracelsus imagined our existence as a “flame of life.” Though intended as a metaphor, it turns out Paracelsus was actually close to the scientific fact.

While humans don’t burn like candles, the process of respiration and combustion are one and the same. The act of breathing provides our cells with oxygen, which we use to burn glucose. This process is known as cellular respiration.

Bacteria have evolved since they first came into existence some 4 billion years ago. They have survived all kinds of environments – cold, hot, dry, damp – and are now varied and sophisticated.

Nevertheless, they are still single-celled organisms. Eukaryotes, in contrast, have evolved into complex entities that can think, see, hear and experience sentience, among many other abilities. Given that eukaryotic cells have evolved, we must ask ourselves: what’s stopping bacteria from transforming?

Since the development of the first eukaryotic cell, life forms became more and more complex. But why? It’s not as if evolution has a goal or endgame. In contrast to how an embryo is preprogrammed to develop into a child and then an adult, evolution by natural selection lacks such a roadmap.

So did complex life come about by chance? Was it natural selection? There is no clear answer to this question, but one of the main reasons eukaryotes have grown and become more elaborate is their energy and by extension, mitochondria.

Multicellular organisms are made up of billions and billions of cells. Every cell has an important role that contributes to the organism's well-being. If they were left to act on their own accord, cells would have no reason to be so giving. So what keeps them from selfishly multiplying in numbers? Well, evolution has a “molecular police force” in place. Known as apoptosis, this force relies on programmed cell death, or “cell suicide.”

Apoptosis is controlled by mitochondria. The mitochondria in cells are what determines when it’s time for a cell to expire.

Biologically speaking, there are two sexes: female and male. What distinguishes one from the other? Many biologists would point out that differences in chromosomes are a distinguishing feature between females and males. Typically, females have two X chromosomes, whereas men have one X and one Y chromosome.

However, there is a bigger difference between the sexes, one that is found in the passing on of mitochondrial DNA.

It’s generally accepted in biology that the bigger something is, the slower its metabolic rate, and thus the longer its lifespan. Of course, there are exceptions to this rule; birds, for example, live much longer than this rule predicts.

But for the most part, this law rings true. So, if lifespan is predicated on metabolic rate, which is a measure of how quickly our body consumes energy, then it’s clear that mitochondria play a central role in determining our lifespans.