Author: Nick Lane
If you think you know how life appeared on this planet, this book will make you “think” again. Too often we have accepted the glib explanation that the early earth was a hotbed of gases and liquids and magically single-cellular life came into being. Once you buy that explanation we invoke Darwin’s theory of evolution to extrapolate how 3.8 billion years later you have humans dominating the planet.
The first thing you learn from this book is that the explanation is not so straightforward. Nick Lane is on the hunt to find the road that led to the last universal common ancestor (LUCA), which is the most recent organism from which all plants and animals now living on Earth are descended from. What is surprising is that despite the huge diversity in plants, sea creatures, birds and animals we are all composed of cells that look remarkably similar. All of our cells are enveloped by a semi-permeable cell-membrane containing a nucleus with the DNA encoding the genetic code that is propagated through cell division.
First, Nick outlines the huge gap in scientific thinking on the ancestors of the LUCA. There is general agreement in the scientific community that bacteria and archaea were the first to show up on this planet some four billion years ago. Nick explains how at the cellular level all plants and animals are very similar to the LUCA but vastly different from bacteria and archaea. He believes there were structural constraints that prevented bacteria from evolving into more diverse forms. Something happened a couple of billion years ago that gave rise to eukaryotes (cells, enveloped by a membrane with DNA in a nucleus inside). Nick has a theory on how this all happened.
When life first appeared on this planet, it was in the form of single cells like bacteria and archaea. Over the years these evolved but they remained morphologically simple and could not give rise to multi-cellular organisms. Then some two and half billion years ago, a magical event resulted in a bacteria being swallowed by an archeaon. Surprisingly this was a symbiotic event, and they both thrived. The bacteria morphed into mitochondria which is the powerhouse of the cell. The DNA from the bacteria eventually gravitated to form the nucleus and this gave rise to the first eukaryotes — cell with a nucleus — which is the precursor to all the multi-cellular beings that inhabit the earth.
The book is a fascinating read and you realize the big step function that we had to cross to go from bacteria/archaea to the LUCA. Nick goes on to speculate that if we find life on other planets, we are more likely to encounter a single cellular form like what we had four billion years ago. What is amazing is how at the cellular level we are all so similar. Could there have been other instances of life that have simply died out over the years?
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