Your Inner Fish by Neil Shubin

Author and Title
Shubin, Neil. Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body

Sir Richard Owen
Sir Richard Owen noticed similarities between the limb bones of various species, before Darwin. The general pattern was one bone in the upper arm, two bones in the lower arm, several small bones in the wrist, then the bones of each of the fingers.

The Fins of Fish
The fish fin does not follow this pattern. Instead of one bone attaching to the shoulder, it has four or more parallel bones attaching to the shoulder. The fin of the lungfish also has several bones, but arranged serially, going away from the shoulder, rather than in parallel. Only one of these bones attaches to the shoulder. The fin of the fossil fish Eusthenopteron has one bone attaching at the shoulder, followed by two bones further out, followed by several more bones even further out.

The Wrist and Hand
Shubin, with his student Ted Daeschler and mentor Farish A. Jenkins, Jr., discovered the first fish with a wrist, the Tiktaalik, in the Canadian Arctic. Next in the course of evolution, after the Tiktaalik, came the amphibian Acanthostega fossil. It has one bone at the shoulder, followed by two bones after the elbow, followed by several digits in parallel.

Genetics of Asymmetry
The author also talks about the genetics of limb development in the embryo. The concentration gradient of the Sonic hedgehog (sic) protein influences the zone of polarizing activity (ZPA). The ZPA is what causes the hand to be asymmetrical, with the pinky and one side and the thumb at the other. The gene for Sonic hedgehog was discovered in 1980 by German scientist Christiane Nüsslein-Volhard and American scientist Eric Wieschaus. The relationship between the Sonic hedgehog protein and the ZPA was discovered by Robert D. Riddle, Cliff Tabin and colleagues at Harvard in the early 1990s.

The fact that invertebrate eyes, such as those of insects, and vertebrate eyes are so different has always posed a problem for theorists of evolution. Invertebrate eyes increase surface area by having many folds in their light-gathering tissue, while vertebrate eyes have bristle-like projections. Detlev Arendt discovered a marine annelid worm called the polychaete that has two kinds of eyes, an invertebrate eye and a vertebrate proto-eye. It has also been discovered that the gene, Pax 6, that controls the differentiation of tissue into eyes is very similar in invertebrates and vertebrates.

Fish have no middle-ear bones. Reptiles and amphibians have one middle-ear bone. Mammals have three ear bones (and a pinna). All of the middle-ear bones evolved from the curved gill arch bones of fish. The stapes (stirrup) evolved from the hyomandibula of the reptile, which connects the jaw to the skull. The hymandibula, in turn, evolved from the second gill arch bone of fish. The malleus (hammer) and incus (anvil) evolved from bones in the back of the reptilian jaw, which in turn evolved from the first gill arch bone.

Three percent of the mammalian genome is devoted to genes that code for receptor proteins that bind odor molecules. In primates with color vision, many of these genes have become non-functional. We have traded smell for vision.

The Hard Parts
For their hard parts, mollusk and crustacean invertebrates, use chitin and calcium carbonate. In vertebrates, hydroxyapatite is the mineral that gives bones and tooth enamel their hardness. Hydroxyapatite first appeared in teeth, not bones, which were then made of cartilage. The upper and lower teeth of mammals fit well together (occlusion), but this is not true of reptiles.


When a Gene Makes You Smell Like a Fish by Lisa Seachrist Chiu


When a Gene Makes You Smell Like a Fish: And Other Amazing Tales about the Genes in Your Body by Lisa Seachrist Chiu

Human Genetics

This is a rather technical book on human genetics. Recent research is described, with plenty of names of researchers and institutions of research. A background in college biology would be helpful for understanding most of the material. It is mainly about diseases that are caused by defective genes, including:

  1. Metabolic diseases that cause smelly or colored chemicals to be excreted in urine and sweat,
  2. Wilson’s disease, which involves copper metabolism,
  3. Marfan Syndrome, which affected one of my favorite actors, Vincent Schiavelli, (4) Huntington’s Disease, which runs in families,
  4. Fragile X Syndrome, which causes mental retardation,
  5. the blood-clotting disease hemophilia, and
  6. male-pattern baldness.


Some genetic diseases more common among some ethnic groups, such as Amish cerebral palsy, Mennonite maple syrup urine disease, and Celtic hereditary hemochromatosis.


The author also discusses epigenetics, which is about whether a gene is turned on or off. Since females have two X chromosomes and men only one, in females one of the two X chromosomes is turned off, so males and females will produce equal amounts of the gene’s protein product. However, which of the two X chromosomes is turned off, the one from the woman’s mother, or the one from the woman’s father, varies from cell to cell in the body. Thus all females are chimeras. This mechanism also gives rise to calico cats.

Recombination Activating Genes

The author mentions the recently discovered recombination activating genes (RAG1 and RAG2), that are involved in creating a wide diversity in the antigen-binding specificity of antibodies and cellular adaptive immunity. It appears that they were transferred from a virus or a bacteria by horizontal evolution to a primitive fish millions of years ago.


The Japanese people are a combination of the original Jomon inhabitants of the islands and Korean immigrants called Yayoi. The Ainu of Hokkaido are similar to the Jomon. The inhabitants of Honshu, Shikoku and Kyushu are more similar to the Koreans. The author claims that the Japanese language is an isolate, but the physiologist Jared Diamond and some linguists have written elsewhere that Korean and Japanese have a common ancestor.

Lactose Intolerance

Lactose intolerance is the rule for most peoples of the world. When children grow up, they generally stop making the enzyme for digesting the milk sugar lactose. However, some peoples, such as northern Europeans, have developed a tolerance for milk into adulthood. It appears to have evolved among a cattle-herding people, the Udmerts (Votyak), who lived between the Ural mountains and the Volga river several thousand years ago. Drinking cow milk by adults and lactose tolerance then spread to Europe.