Your Inner Fish, Neil Shubin – Review

Your Inner Fish is all about human evolution.

By looking at fossil records, genes and life on earth today we can work out where we came from and its fascinating.

It is no exaggeration to say this book will change the way you look at the world.

Chapter 1: Finding Your Inner Fish

375 million years ago a fish called Tiktaalik appears in the fossil records in Greenland.

With its flat head and primitive limb-like fins the Tiktaalik fossil is a sea dwelling fish evolving to being a land living animal.

It was cleverly discovered by Shubin and his colleagues after studying the geology of the area and making precise predictions about the fossil record.

Chapter 2: Getting a Grip

By looking at animals with limbs scientists noticed animals as diverse as bats, horses and frogs all have a common design for their limbs, the only thing that changes is the shape and size of the bones.

Humans can rotate our hands relative to our elbows,using a pivot point. This lineage can be traced back to Tiktaalik who could also bend its elbow.

Life in and out of water is not that clearcut with some ancient and modern day fish having lungs.

It appears that fish began growing limbs to escape the water and the fierce predators that lived there.

Chapter 3: Handy Genes

Each cell in our body contains the genetic code to make the whole body.

Different genes are active in the different cell types and genetic switches help assemble us. Interestingly the gene responsible for limb and fin development is the same.

This points to the fact that the evolution of limbs from fins did not require any new genes.

Chapter 4: Teeth Everywhere

Looking at teeth gives us lots of clues about our genetic heritage.

Mammals have a single jaw bone and top and bottom teeth which match up. Reptiles have jaws with many bones and replace teeth continually. Primitive fish like Lampreys have no jaws and feed by attaching themselves to other fish and feeding on their body fluids.

Human teeth reveal that we are all purpose eaters, having incisors specialised to cut food, canines in the back and molars in extreme back to shear or mash food.

Our teeth are the hardest parts of our bodies, Hydroxyapatite giving them their hardness.

The primary purpose of teeth is to allow us to eat things that are bigger than our mouths.

Chapter 5: Getting Ahead

In this chapter we learn that the essence of our heads goes right back to worms.

The muscles in the head are attached to the brain and organs. The nerves in the head look very much like the wiring in an old building, not making logical sense. They have evolved that way to accommodate other features eg. giraffes neck.

Chapter 6: The Best Laid (Body) Plans

The plans for our bodies goes back to fish and if you think about it that’s quite logical. Their bodies are lined up like ours, they have heads and spines.

Animals in other lineages such as sponges and jellyfish have fundamentally different body plans.

Chapter 7: Adventures in Bodybuilding

In experiments using bacteria, predation has been shown to produce multi cellular organisms from single celled ones over a number of generations.

Around 1 bn years ago bacteria began eating each other and at the same time oxygen levels increased in the atmosphere which allowed for multi cellular organisms to survive.

We evolved from these multi cellular organisms, with cells specialising and eventually leading to skeletons and limbs.

Chapter 8: Making Scents

Our sense of smell goes back to being a fish.

Lampreys and Hagfish have single nostril and extract odours from water. Lungfish have 2 kinds of nostrils, external and internal which is similar to the structure we have.

Mammals developed a much greater sense of smell and in fact a whole 3% of the human genome is devoted to smell.

Humans though, like other primates with colour vision, have a diminished sense of smell. Apparently there was an evolutionary trade off between the 2.

Dolphins have no sense of smell and use what was their noses as blow holes to blow out water.

Chapter 9: Vision

The eyes capture light and transmit it to the brain where it is processed.

An amazing 70% of our sensory cells are used for vision.

Fascinatingly, the origin of the eye can be traced right back to bacteria!

There is a single gene which triggers the formation of the eye called pac 6 and this is the same in many creatures with eyes.

Chapter 10: Ears

The history of the inner ear can be traced to ancient fish and the neurons even further.

Mammals’ middle ears are different to other species, having 3 bones.

Interestingly one jelly fish, the Box Jelly fish has 20 eyes, though no other type of jellyfish has eyes.

Chapter 11: The Meaning Of It All

Looking at a human is like looking back in time through our evolutionary heritage. Some of our features started with bacteria, some with fish, others as mammals.

If we look at other animals it becomes apparent which parts are similar. We have many similarities to a Polar Bear, fewer with a Turtle and fewer still with a regular fish.

Many human illnesses are a result of our sedentary lifestyle when our bodies are built for an active one.

Epilogue

We should embrace scientific study without fear.

Maybe it will give us a deeper understanding of human nature and help us cure illnesses

Rating:

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