The History of Life: A Very Short Introduction by Michael J. Benton
My rating: 5 of 5 stars
This book reminded me a little bit of The Ancestors Tale, albeit the latter traces the history of life in reverse chronological order. The author of this title in the OUP's A Very Short Introduction series, is Michael J. Benton. He is a distinguished professor of vertebrate palaeontology at the University of Bristol.
The book starts off with the basics and builds up, chapter by chapter, on top of the previously covered topics. The introduction is a good summary of cladistics, phylogenetics, and the concepts of synapomorphy and evolutionary trees. I'm going to write a brief summary of each chapter in order to solidify my knowledge, and also to give an overall impression of the book for the prospective reader.
The first chapter is on the Origin of life. It begins with the search for the earliest discovered evidence of life on earth, and deals with the particular difficulties of dating the oldest rocks. Of course, there would be no discussion about the origin of life without mentioning of the Miller-Urey Experiment. This is followed by the evaluation of different theories such as hyperthermophilic theory, RNA world hypothesis and their likely role in the primitive self-replicating vesicles. It continues with the rise of the first fossils: basically microfossils and stromatolites. There is a long gap between the 3.4 billion-year-old stromatolites and microfossils and the next occurring fossils in the geological record.
Chapter 2 deals with the origin of sex. The British evolutionary thinker John Maynard Smith has talked about the two-fold cost of sex. In sexual organisms only one of the sexes can bear offspring, and half of ones offspring's genome is shared/combined with another member of the population with opposite sex (contributing only half the genome halves the fitness).
Next, the aurhors asks the question; which came first, Eukaryotes or Prokaryotes? The answer seems simple enough; prokaryotes. The main evidence for this comes from the endosymbiosis theory that proposes eukaryotes originated when large prokaryote cells engulfed smaller prokaryotes. This chapter goes on into some details of great oxygenation event in about 2.3 BYA which made all the subsequent evolutionary innovations possible.
The origin of multicellularity is another topic explored in this chapter. The benefits of multicellularity include; better feeding, predation, locomotion, and infinite morphological possibilities lacking in unicellular life. Thereupon, the author scrutinizes the Neoproterozoic snowball-Earth hypothesis which states the earth was once completely frozen over. This chapter ends with an apt description of the wonderful Ediacaran fauna found in Ediacara Hills by Reg Sprigg. I can’t believe I have spent the last couple of years so close to this outstanding discovery in South Australia! :-)
Chapter 3 is all about the Cambrian explosion. I especially liked the depth in which the author goes into explaining the origin of the hard body parts and skeletons when they first evolved here. In the part on trilobite evolution, he mentions how paleontologists have been able to dissect the trilobite’s eye (the lens is a calcite crystal that survives unaltered by fossilization), and they have look through them to see the world as a trilobite might have seen the world 500 million years ago. On the Brachiopod evolution, Benton concludes that even though they have survived until today, they were much more prominent in the Palaeozoic era.
The evolutionary arms race between predator and prey must have been a major selective force driving the magnificent radiation of the early sea creatures. The apparent mismatch between molecular data and the fossil evidence of metazoans is discussed later in the chapter. The term 'phylogenetic fuse' is used to describe such a state, where a major group (here metazoans) diverges, as it’s indicated by the molecular data, but the fossil record appears much later in time.
Chapter 4 is all about the origin of life on land. All life on land came from the sea, including land plants which colonized the land in the late Ordovician. It is an interesting fact that before this date there was no soil on land! The land plants transformed the surface of the planet forever. The main challenges of the terrestrial environments for the first colonizers were desiccation, support, and upright growth against a strong force of gravity. The origin of tetrapods is next. Tiktaalik is a fish which fits the bill as a transitional fossil in sea-to-land evolution. It is fascinating to observe that Pentadactyly (having five digits) was not a fixed feature in the early tetrapod evolution. As it’s put in the book, “There is nothing fundamental about five digits, and indeed modern work in developmental biology shows that this is true.”
Chapter 5 is focused on the evolution of forests and giant flying insects in the Carboniferous. The chapter end with a discussion of the amniotic egg which was an evolutionary invention that allowed the first reptiles to colonize the land more effectively that previous radiations.
The last three chapters are devoted to different theories of causes of mass extinctions, paleoclimatology, modern ecosystems and last bot least, human evolution. On human evolution, the author rightly points out that the occurrence of the genus homo has not been the goal of evolution. Cockroaches are as much the pinnacle of evolution as are we. Evolution is not teleological, and odes not have any predetermined plans. If you could rewind the tape of life and replay it, it is extremely unlikely that humanoids would have risen again.