Your Inner Fish By: Neil Shubin From common parts came a very unique construction. A guide to… Made by: Declan Duggan.

Your Inner Fish By: Neil Shubin

“From common parts came a very unique construction.”

A guide to…

Made by: Declan Duggan

Chapter 1: Finding Your Inner Fish• Shubin and his team were searching for the link

between animals that lived in water and those that could survive on land

• After narrowing down the critical time-period to roughly 375 million years ago, the paleontologists determined that best places to look would be sedimentary rocks on the beds of ancient streams

• Their search took them to the Canadian Arctic, which is where they thought they had the best chance of finding ancient streams from the Devonian Period

Chapter 1: Finding Your Inner Fish

• In 2004, the team found what turned out to be the perfect intermediate between fish and land-living animals, and named it Tiktaalik

• Tiktaalik had scales on its back and fins with fin webbing like fish, but also had a neck and a flat head with eyes on the top

• It also had bones that correspond to the upper arm, forearm, and the wrist joints

Tiktaalik

Specialized fins with bones

Neck

Flat head with eyes on the top

Chapter 2: Getting a Grip

• One of the key characeristics that made Tiktaalik different was that it had a joint at the end of its fins which had spaces for four other bones, which is essentially the origin of the human wrist

• Tiktaalik had the capability to do pushups because of its unique bone structure

• Tiktaalik also displayed the beginnings of the ball and socket joints

Chapter 2: Getting a Grip

• Tiktaalik’s body structure, with its flat head and eye location, as well as its limbs which allowed it to crawl along on its belly, also enabled it to live primarily in shallow streams where bigger predators would not be as much of a disturbance

• The origins of our legs and arms are not just related to Tiktaalik, but rather many other fish including Eusthenopteron

Chapter 2: Getting a Grip

• The first examples of fingers were found in amphibians like Icanthostega

• Full feature of wrist and ankle bones found in 250 million year old reptiles

• Our ability to walk on our hind legs is due to the fact that our elbows and knees face opposite directions – a trait we share with all mammals

Chapter 3: Handy Genes• Sonic Hedgehog Gene:– Gene present in all limbed animals that is active in

the zone of polarizing activity (ZPA), which essentially guides the development of our fingers and makes the pinky side different from our thumb side.

– Not only does knowing this help us understand certain mutations, but it gives insight into how closely we are related with other forms of life as scientists can look for the same gene in every other animal with fingers

Chapter 4: Teeth Everywhere

• Why teeth?– Structure of teeth give paleontologists clues about

an organism’s diet and lifestyle– Often the best preserves parts of fossils due to

their hardness– Development of teeth changed the competitive

landscape

Chapter 4: Teeth Everywhere

• Teeth develop by an interaction of two layers of tissue in developing skin– Layers approach, cells then divide, layers change

their shapes and produce proteins– Same process as with all structure that develop

within the skin (hair, scales, feathers, sweat and mammary glands)

Illustration © Kalliopi Monoyios

Chapter 5: Getting Ahead

• Every bone in our head traces back to either a rod, a plate, or a block

• Within our skulls, there are 12 nerves known as cranial nerves which supply the muscles that help us bite, talk, or move our eyes/head

• These 12 nerves originate in one of four gill arches in the developing embryo– The same structures these nerves supply originate

in one of the same arch

Chapter 5: Getting Ahead

• 1st arch: Trigeminal nerve originates in arch one, which corresponds with the jaw and ears

• 2nd arch: Facial nerve• 3rd Arch: Glossopharyngeal nerve• 4th Arch: Vagus nerve• Each nerve’s complex path relate to the fact

that they supply structures that originate from their respective arches

Illustration © Kalliopi Monoyios

Chapter 5: Getting Ahead• Amphioxus: a 530 million year old worm with

a nerve chord along its back and a notochord parallel to this, but without a backbone– Humans also have notochords, but ours breaks up

and becomes part of the discs which constitute our vertebrae

– When a disc is ruptured, a jelly-like substance which was once in the notochord can pinch nerves

– This is part of our relationship with ancient organisms

Amphioxus

Illustration @ Kalliopi Monoyios

Chapter 6: The Best-Laid (Body) Plans

• The work of Karl Ernst von Baer found that all organs in any animal originate in one of three germ layers in a developing embryo– Ectoderm: forms much of the outer part of the

body and the nervous system– Endoderm: forms many of the inner structures of

the body which includes the digestive tract and other glands associated with it

– Mesoderm: forms tissue in between the guts and skin, including our skeleton and muscles

Illustration © Kalliopi Monoyios

Chapter 6: The Best-Laid (Body) Plans

• Hilde Mangold: Scientists who discovered a small patch of tissue that was able to direct other cells to form an entire body plan, named the Organizer– What makes up the Organizer? • Richard Harland (UC-Berkeley) discovered a gene,

which he named noggin that does exactly what the Organizer should after he injected it into an embryo and found it developed two body axes

Chapter 6: The Best-Laid (Body) Plans

• Mark Martindale and John Finnerty conducted an experiment to test what would happen if the body-building gene from an animal with a complex body plan (a frog) was switched with one from a sea anemone.– The result was that the frog developed extra back

structures, as if it were injected with its own Noggin gene

Chapter 7: Adventures in Bodybuilding

• 1947: Australian mining geologist Reginald Sprigg discovers what turns out to be the earliest bodies within fossils in South Australia, which turned out to be roughly 600 millions years old

• What allowed bodies to arise?– Biological glue between cells which make up the

structure of different parts of the body– The ability of cells to communicate with each other

using words written as molecules– Amount of oxygen in the atmosphere

Chapter 7: Adventures in Bodybuilding

• Structure of bones:– Hydroxyapatite: strong when compressed, less

strong when twisted or bent– Collagen: strong when pulled, collapses when

pushed together– Proteoglycan: shaped like a 3D brush with a long

stem and lots of little branches which attract water, causing it to swell up and become like gelatin

How to Isolate DNA1. Take tissue from plant or animal2. Add salt and water3. Put into blender to mash up4. Add dish soap to break up the membranes which

surround the cells5. Add meat tenderizer to break up the proteins which

surround the DNA6. Add rubbing alcohol• The result should give two distinct layers of liquids

with clear alcohol on the top. The DNA should attract to the alcohol, and goopy white blob should eventually form

Chapter 8: Making Scents• Mammals have over a thousand genes involved with the sense of

smell– The genes involved with the sense of smell are present in every cell,

but only active in the nasal area• However, humans have over three hundred genes involved with

our sense of smell which are completely useless– They are used by other mammals– It seems humans are part of a group of mammals who have “traded”

smell for vision through the years• In 1991, Linda Buck and Richard Axel discovered the large family

of genes that ultimately give us our sense of smell– This adds to the understanding of our history as fish, amphibians, and

mammals

Chapter 8: Making Scents

• Buck and Axel Experiment– Created a hypothesis regarding what the genes

that make odor receptors might have looked like– They found that genes that had the characteristic

structure of the receptor they fit into– Found that all the genes were only active in

tissues involving the sense of smell, and also found a very large number of these genes

Chapter 8: Making Scents

Molecules from a flower are sensed by receptors in the nose, which send a signal to the brain. Each smell has is made up of different molecules which attach to different receptors in the nose.

Illustration © Kalliopi Monoyios

Chapter 9: Vision

• Our eyes, along with all of the parts that make up the eye, have histories as organs– As we trace back the history of each of these parts in organs,

we see how many other forms of life we are related to • Our eyes are similar to cameras

– Light from outside enters, focused on screen at back of eyeball

– Light passes through cornea, and the amount of light is controlled by the iris

– Light then passes through the lens which focuses image– Screen where light is projected is known as the retina

Chapter 9: Vision

• Our camera-like eye is common among all creatures with a skull

• Every animal uses the same type of light capturing molecule, known as an opsin– We can trace the history of the eye by looking at differences in

the structure of the opsins• It seems that our color vision relates to the changes in the

flora of the earth– Color vision would help primates distinguish between fruit and

leaves to help them pick the most nutritious – It is estimated that our color vision arose around 55 million years

ago

Chapter 9: Vision

• In the early 1900’s, Mildred Hodge discovered a gene which controlled the development of our eyes, called the eyeless gene

Eyes: From primitive light-capturing devices to our own camera-like lens

Illustration © Kalliopi Monoyios

Chapter 10: Ears• The same gill arch that forms part of the jaw of a reptile

forms ear bones in mammals – this is a significant relationship between mammals and reptiles

• Ears show the transition from reptiles to mammals, or in other words, from water to land

• The jaw bones of reptiles are what form the three middle ears bones of mammals– The origin of the stapes was a transformation from a jaw support

bone to an ear bone and occurred when fish started to walk on land

– The malleus and the incus developed from the bones at the back of a reptile jaw and signified the origin of mammals

Chapter 10: Ears

• Our inner ear has three functions:– To aid in hearing– To tell us which way our head is tilted– To tell us how fast our head is accelerating or

stoppingOur inner ear is the most ancient part, and reveals the most about our connection with the rest of life

Illustration © Kalliopi Monoyios

Chapter 11: The Meaning of it All

• Biological Law of Everything– Everything living thing on this planet had parents– Descent with modification

• Each of us has our own lineage which can be identified by biological features

• Why history makes us sick:– Humans are really a recipe for problems – take the body

plan of a fish, dress it up to be a mammal, contort until it can walk on two legs, talks, thinks, and can control its fingers, and there is a lot of areas for concern

Chapter 11: The Meaning of it All

• Obesity– James Neel developed a hypothesis stating that

humans were adapted to a “boom-bust” existence– He proposed that our bodies could store energy to

be used later, which would work well in a boom-bust existence

– However, since rich foods are available 24/7, obesity ensues as the excess energy is stored as fat• This leads to diabetes, high blood pressure, heart

disease

Chapter 11: The Meaning of it All

• Our sedentary lifestyles lead to another set of problems– Pooling of the blood due to lack of circulation

caused by walking, and the valves fail– Hemorrhoids from too much time sitting down

Sources

• Shubin, Neil. Your Inner Fish: a Journey into the 3.5-billion-year History of the Human Body. New York: Pantheon, 2008. Print.

• "Your Inner Fish: Teaching Tools." Tiktaalik Roseae: Home. Web. 29 Sept. 2011. <http://tiktaalik.uchicago.edu/book-tools.html>.