Book review: 'The Fish Within', Neil Chaubin.

Believing in the correctness of the theory of evolution is one thing, and witnessing it in action with the help of countless small and large examples in every part of our body is quite another.

Humans, and neuroscientists have known this for years, are creatures that like to find connections. This is what our brain does best, more or less: it constantly examines the world around it and tries to find a sense in it that will help us survive. The winter was particularly rainy, and the harvest was very successful - maybe there is a connection between the events? I should water the plants well.

Perhaps this is the reason why when relationships that were hidden from us suddenly become apparent to us - we derive great pleasure from it. Perhaps this is why I enjoyed so much 'The Fish Within', a book by Neal Chaubin (Attic Books, Yedioth Ahronoth, translation: Adi Marcuse-Hess).

Neal, professor of anatomy at the University of Chicago, reveals to us the history of our bodies. Human-like creatures have only existed in the world for a few million years, but within us are hidden exciting and fascinating traces of an anatomical history of over three billion years. In the same way that a child's face contains mixtures of features from both parents, so our anatomy, genetics, and chemistry betray our familial kinship to primitive bacteria that floated in an ancient sea in the days when Earth was but a young brat. Simply put, we are an improved model (more or less, as we will soon see) of all those creatures that came before us.

Here is a fascinating example of this family connection.
Hiccups are a common and familiar phenomenon. Hiccups are the result of a spasmodic contraction of the respiratory muscles that causes a rapid entry of air into the lungs. Immediately after the spasm, our trachea closes, the air is suddenly stopped and the familiar 'hic' sound of hiccups is obtained. The hiccups originated in the days when we were still fish, and later amphibians. how?

The nerves responsible for breathing come out of the brain stem, an area located at the bottom of the brain. This is a remnant of the fish body structure, and it remains as it was. The brain, however, has changed its position: the neck has lengthened and the distance between the brainstem and the respiratory organs in humans is significantly greater than in fish. The simplest evolutionary solution to the distance problem is to lengthen the nerves - therefore they must travel back and forth around the upper body until they reach their destination. The long nerves are vulnerable to various disorders that will lead to the hiccups spasm.

Obstruction of the trachea after that convulsion is a known phenomenon in amphibians, such as tadpoles for example. It is essential for breathing underwater: during the spasm, water enters the gills, and the trachea closes suddenly to prevent the water from entering the lungs. It can be seen that the same actions that stop hiccups in humans will stop breathing in tadpoles: for example, stretching the respiratory muscles (equivalent to a large inhalation of air and holding the breath) and an excess of carbon dioxide (breathing into a paper bag, for us). The hiccups, then, are a remnant of a design that was successful at the time in the fish and amphibians, but not so successful in us.

Using examples like the last one, Neil Chauvin reviews our close relationship with other animals in the past and present. The examples are taken from an incredible variety of fields: the study of ancient fossils, the anatomy of sharks and jellyfish, genetic sequences of amoebas and flies, and much more. Time and time again, in light language and at eye level, Neal drives the nail of understanding deeper into the wall: nature invents a certain mechanism once, then uses it again and again and again in a variety of forms and roles in creatures that are completely different from each other. Did you know that there is a fossil of a fish, whose armor on its back is made entirely of...teeth? Masses of dense and hard teeth, to protect against other teeth, biting. The same mechanism - a variety of roles.

'The Fish Within' is an amazing, inspiring book. Believing in the correctness of the theory of evolution is one thing, and witnessing it in action with the help of countless small and large examples in every part of our body is something else. Discovering the hidden connections between us and the rest of the natural world will undoubtedly produce in the reader a feeling of pure pleasure, not to mention transcendence. 'The Fish Within' is a must read, one of the best I've read in recent years. recommended!

[Ran Levy is a science writer. His book "Perpetum Mobila: On Physics, Eternal Machines, Charlatans and Everything in Between" was published in 2007 by the Ma'ariv Library. www.ranlevi.co.il]