William Collins (2017)

ISBN: 978-0008226299


Reviewed by Ian Mowll


This is a fascinating book primarily about cephalopods which are sea creatures such as squid, octopus and nautilus.

In the Cambrian period (about 500 million years ago), there was an explosion in the diversity of life forms, probably due to the increase in predation and therefore the need to evolve all sorts of senses to both hunt and defend. At this time, humans and cephalopods shared a common ancestor which was a worm-like creature. Here there was a split with a vertebrate branch from which humans evolved, and the cephalopods. 

This split produced a different experiment in ‘intelligent life’ with the cephalopods. These creatures developed a nervous system which is more distributed and less centralised than mammals. And the author contends that they are smart in terms of being curious, flexible, adventurous and opportunistic.

There are many amazing facts about the cephalopods. For instance, cuttlefish have sacs of pigments which are controlled by muscles and mirrors near the surface of their skin to filter and then reflect light. These two attributes mean that they can change colour in myriad ways. One friendly cuttlefish was nicknamed Matisse by the author as he was so colourful and rapidly changed colour. One moment he was dark red with veins and stripes and less than a second later he was completely yellow like the sun.

The book also touches on other areas such as why animals have different lifespans and even the challenging question what is consciousness?

Towards the end of the book, the author talks about overfishing and the chemical changes in the sea due to human activity. He points out that Nature can generally absorb shocks to its system until it gets into overwhelm and then collapses. He cites the collapse of the honey bee population which was probably due to multiple causes such as a fungus, pesticides and climate change. The honey bees were able to live with these stresses until the combined effect became too much and their population collapsed. The author worries that the seas are being affected by overfishing, acidification (due to CO2 in the atmosphere) and pollution. The combined effect could cause a sudden collapse in the ecosystems of the sea.

He ends with this thought-provoking comment: There are many reasons for us to appreciate and care for the oceans, and I hope this book has added one; when you dive into the sea, you are diving into the origin of us all.