Some of the books I read about evolution:
Your Inner Fish - A Journey Into The 3.5-Billion-Year History Of The Human Body by Neil Shubin
Why Evolution Is True by Jerry Coyne
The Making of the Fittest - DNA and the Ultimate Forensic Record of Evolution by Sean B. Carroll
Evolution - The Triumph of an Idea by Carl Zimmer
The Greatest Show on Earth - The Evidence for Evolution by Richard Dawkins
God's Word or Human Reason? An Inside Perspective on Creationism" by Jonathan Kane, Emily Willoughby, and Michael Keesey.
Showing posts with label Neil Shubin. Show all posts
Showing posts with label Neil Shubin. Show all posts
Thursday, April 15, 2021
Thursday, August 6, 2020
Several books and Wikipedia are my friends.
The books about evolution I have read:
Your Inner Fish - A Journey Into The 3.5-Billion-Year History Of The Human Body by Neil Shubin
Why Evolution Is True by Jerry Coyne
The Making of the Fittest - DNA and the Ultimate Forensic Record of Evolution by Sean B. Carroll
Evolution - The Triumph of an Idea by Carl Zimmer
The Greatest Show on Earth - The Evidence for Evolution by Richard Dawkins
"God's Word or Human Reason? An Inside Perspective on Creationism" by Jonathan Kane, Emily Willoughby, and Michael Keesey.
Your Inner Fish - A Journey Into The 3.5-Billion-Year History Of The Human Body by Neil Shubin
Why Evolution Is True by Jerry Coyne
The Making of the Fittest - DNA and the Ultimate Forensic Record of Evolution by Sean B. Carroll
Evolution - The Triumph of an Idea by Carl Zimmer
The Greatest Show on Earth - The Evidence for Evolution by Richard Dawkins
"God's Word or Human Reason? An Inside Perspective on Creationism" by Jonathan Kane, Emily Willoughby, and Michael Keesey.
Tuesday, June 30, 2020
Monday, June 29, 2020
Our ancestor
One very important human ancestor was an ancient fish. Though it lived 375 million years ago, this fish called Tiktaalik had shoulders, elbows, legs, wrists, a neck and many other basic parts that eventually became part of us.
Sunday, March 15, 2020
Neil Shubin wrote the excellent book "Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body". At yesterday's Wall Street Journal he wrote the article "The Viruses That Shaped Our DNA."
Wall Street Journal
IDEAS
ESSAY
The Viruses That Shaped Our DNA
Many of the traits that make these ultimate parasites so effective at transmitting diseases like Covid-19 also make them an essential part of our own genetic makeup.
By Neil Shubin
March 14, 2020
A virus is the stuff of mystery and fear, an invisibly lurking danger ready to spread explosively around the globe. The new coronavirus, like SARS, MERS and the seasonal flu, enters our bodies, finds its way inside our DNA and commandeers it to make more copies of itself. Viruses are, in many ways, the ultimate parasites.
Yet we, like every other creature on Earth, have a complex relationship with them. Many of the traits that make viruses so effective at transmitting disease also make them an essential part of our genetic makeup. As it turns out, their contributions to our genome over the eons account for a range of important human qualities.
Viruses sit at the edge of our definition of living things. They are tiny bits of genetic material enclosed by a protective shell. Alone, they sit lifeless and inert, waiting for a favorable environment in which to reproduce. Viruses are carried to their unwilling hosts by insects, droplets in the air, contact with infected surfaces and other mechanisms that bring cells of different species together.
When a virus encounters a host cell, a chain reaction of molecular events is set in motion: The virus attaches itself to the outer wall of the cell, enters inside, travels to the cell’s genome, merges with its genes and then tricks the host’s genome into making copies of itself.
The host cell becomes a factory for new viruses and can produce as many as a million of them before it dies. This explosive growth can happen simultaneously in tissues throughout the body. As the virus spreads in one individual’s body, it can escape via water droplets expelled from the air in the lungs, sweat produced by sweat glands or fluids produced by other organs, thereby passing the infection to others.
This selfish behavior makes viruses, as a Darwinian matter, enormously successful. There is an almost unfathomable number of them in and around us all the time. By some estimates, the number of viruses in the oceans alone is as large as a 10 with 31 zeros behind it. All told, there are more viruses on Earth than there are stars in the known universe.
What’s more, viruses are incredibly diverse and ever evolving. That is why we need a new flu vaccine each year and suffer from emerging diseases like Covid-19 with increasing regularity.
But researchers at the University of Utah came away with a different take on viruses while working in 2016 on a gene that plays a role in the ability to make memories. Mice with a mutation in this gene, known as Arc, can find their way through a maze with cheese in the center but—unlike mice with the normal Arc gene—can’t remember their path through the maze the next day. In humans, changes to Arc have been linked to a range of disorders, from schizophrenia to dementia. Arc is a gene that memories are made of.
To understand the gene, the team in Utah isolated the protein it made and put it under a powerful microscope. The lead researcher, Jason Shepherd, saw that the protein formed spheres that were visible at high magnification. That structure set off alarm bells for him: He was sure he had seen such spheres when he took a course in infectious diseases in his early days in graduate school. The Arc protein had spherules that looked exactly like those made by HIV, the virus that causes AIDS.
Dr. Shepherd gave the slide to viral specialists working in the building next door without telling them what was on it. The virus experts were sure they were looking at spheres made by HIV.
When the team sequenced the gene for Arc, decoding the string of molecules that make it up, they were in for an even bigger surprise. This memory gene was, for all purposes, a modified virus.
The virus that causes AIDS makes protein spheres because they protect HIV’s genes as they journey from cell to cell in its host. As it turns out, the same thing happens with the memory gene, Arc, which also works by moving genetic information from cell to cell. The viral strategy of making protein spheres, which is so dangerous in disease, works to our benefit in Arc.
Memory genes aren’t the only ones derived from viruses in our bodies. Genes that make proteins at work in the placenta, so essential for human reproduction, also arose from viruses. When a team from Germany did a computational search of the human genome, they found that as many as 85 genes derived from viruses may be at work in different parts of the brain and during pregnancy.
The past two decades have witnessed a golden age of genome projects. We have mapped the human genome, the corn genome and genomes for many thousands of species of microbes, fungi, animals and plants. With all this information, the more we look, the more we find ancient viruses hiding inside our genomes, as well as those of other creatures.
Almost 8% of the human genome is made up of viruses that once infected us but have been rendered inactive. That fact is even more astounding when you consider that genes—the part of DNA that codes for proteins—comprise only 2% of our genome. We have four times more viral genetic material inside our genome than our own genes.
Our genome is a graveyard for ancient viruses. Disabled viral fragments lie throughout; their wings have been clipped because they lack the sequences to jump from genome to genome. These viruses attacked our ancestors’ genomes eons ago, only to be disabled, and now lie as remnants of infections past. The memory gene Arc is a virus that long ago invaded, only to be put to work on an important bodily function. The tables were turned: The hacker, the invading parasite, was itself hacked to our benefit.
The ability to make spheres to move genetic material from cell to cell, so essential in the spread of infections such as AIDS, became useful to our distant ancestors. Researchers looking at the history of Arc have found that fish don’t have it, but their descendants—amphibians, reptiles, birds and mammals—do. The ancient fish that evolved to walk on land about 375 million years ago, it seems, got an infection that would change the course of history and, ultimately, our own abilities.
We live in a state of war between viral invaders and our own genome. One outcome can be that viruses take over and we become ill. The other is that viruses can be the source of new genetic inventions—fuel for evolutionary change.
Viruses are microscopic pieces of genetic material capable of wreaking havoc on our world and disrupting our interactions with one another. Yet new insights into genomes, and four billion years of the history of life, offer another side of the story. Each one of us is part virus, in ways that affect who we are and what we can do.
—Dr. Shubin is a professor of biology and anatomy at the University of Chicago. This essay is adapted from his new book “Some Assembly Required: Decoding 4 Billion Years of Life Using Ancient Fossils and DNA,” which Pantheon will publish on March 17, 2020.
IDEAS
ESSAY
The Viruses That Shaped Our DNA
Many of the traits that make these ultimate parasites so effective at transmitting diseases like Covid-19 also make them an essential part of our own genetic makeup.
By Neil Shubin
March 14, 2020
A virus is the stuff of mystery and fear, an invisibly lurking danger ready to spread explosively around the globe. The new coronavirus, like SARS, MERS and the seasonal flu, enters our bodies, finds its way inside our DNA and commandeers it to make more copies of itself. Viruses are, in many ways, the ultimate parasites.
Yet we, like every other creature on Earth, have a complex relationship with them. Many of the traits that make viruses so effective at transmitting disease also make them an essential part of our genetic makeup. As it turns out, their contributions to our genome over the eons account for a range of important human qualities.
Viruses sit at the edge of our definition of living things. They are tiny bits of genetic material enclosed by a protective shell. Alone, they sit lifeless and inert, waiting for a favorable environment in which to reproduce. Viruses are carried to their unwilling hosts by insects, droplets in the air, contact with infected surfaces and other mechanisms that bring cells of different species together.
When a virus encounters a host cell, a chain reaction of molecular events is set in motion: The virus attaches itself to the outer wall of the cell, enters inside, travels to the cell’s genome, merges with its genes and then tricks the host’s genome into making copies of itself.
The host cell becomes a factory for new viruses and can produce as many as a million of them before it dies. This explosive growth can happen simultaneously in tissues throughout the body. As the virus spreads in one individual’s body, it can escape via water droplets expelled from the air in the lungs, sweat produced by sweat glands or fluids produced by other organs, thereby passing the infection to others.
This selfish behavior makes viruses, as a Darwinian matter, enormously successful. There is an almost unfathomable number of them in and around us all the time. By some estimates, the number of viruses in the oceans alone is as large as a 10 with 31 zeros behind it. All told, there are more viruses on Earth than there are stars in the known universe.
What’s more, viruses are incredibly diverse and ever evolving. That is why we need a new flu vaccine each year and suffer from emerging diseases like Covid-19 with increasing regularity.
But researchers at the University of Utah came away with a different take on viruses while working in 2016 on a gene that plays a role in the ability to make memories. Mice with a mutation in this gene, known as Arc, can find their way through a maze with cheese in the center but—unlike mice with the normal Arc gene—can’t remember their path through the maze the next day. In humans, changes to Arc have been linked to a range of disorders, from schizophrenia to dementia. Arc is a gene that memories are made of.
To understand the gene, the team in Utah isolated the protein it made and put it under a powerful microscope. The lead researcher, Jason Shepherd, saw that the protein formed spheres that were visible at high magnification. That structure set off alarm bells for him: He was sure he had seen such spheres when he took a course in infectious diseases in his early days in graduate school. The Arc protein had spherules that looked exactly like those made by HIV, the virus that causes AIDS.
Dr. Shepherd gave the slide to viral specialists working in the building next door without telling them what was on it. The virus experts were sure they were looking at spheres made by HIV.
When the team sequenced the gene for Arc, decoding the string of molecules that make it up, they were in for an even bigger surprise. This memory gene was, for all purposes, a modified virus.
The virus that causes AIDS makes protein spheres because they protect HIV’s genes as they journey from cell to cell in its host. As it turns out, the same thing happens with the memory gene, Arc, which also works by moving genetic information from cell to cell. The viral strategy of making protein spheres, which is so dangerous in disease, works to our benefit in Arc.
Memory genes aren’t the only ones derived from viruses in our bodies. Genes that make proteins at work in the placenta, so essential for human reproduction, also arose from viruses. When a team from Germany did a computational search of the human genome, they found that as many as 85 genes derived from viruses may be at work in different parts of the brain and during pregnancy.
The past two decades have witnessed a golden age of genome projects. We have mapped the human genome, the corn genome and genomes for many thousands of species of microbes, fungi, animals and plants. With all this information, the more we look, the more we find ancient viruses hiding inside our genomes, as well as those of other creatures.
Almost 8% of the human genome is made up of viruses that once infected us but have been rendered inactive. That fact is even more astounding when you consider that genes—the part of DNA that codes for proteins—comprise only 2% of our genome. We have four times more viral genetic material inside our genome than our own genes.
Our genome is a graveyard for ancient viruses. Disabled viral fragments lie throughout; their wings have been clipped because they lack the sequences to jump from genome to genome. These viruses attacked our ancestors’ genomes eons ago, only to be disabled, and now lie as remnants of infections past. The memory gene Arc is a virus that long ago invaded, only to be put to work on an important bodily function. The tables were turned: The hacker, the invading parasite, was itself hacked to our benefit.
The ability to make spheres to move genetic material from cell to cell, so essential in the spread of infections such as AIDS, became useful to our distant ancestors. Researchers looking at the history of Arc have found that fish don’t have it, but their descendants—amphibians, reptiles, birds and mammals—do. The ancient fish that evolved to walk on land about 375 million years ago, it seems, got an infection that would change the course of history and, ultimately, our own abilities.
We live in a state of war between viral invaders and our own genome. One outcome can be that viruses take over and we become ill. The other is that viruses can be the source of new genetic inventions—fuel for evolutionary change.
Viruses are microscopic pieces of genetic material capable of wreaking havoc on our world and disrupting our interactions with one another. Yet new insights into genomes, and four billion years of the history of life, offer another side of the story. Each one of us is part virus, in ways that affect who we are and what we can do.
—Dr. Shubin is a professor of biology and anatomy at the University of Chicago. This essay is adapted from his new book “Some Assembly Required: Decoding 4 Billion Years of Life Using Ancient Fossils and DNA,” which Pantheon will publish on March 17, 2020.
Friday, December 27, 2019
"Neil Shubin (University of Chicago): Finding Tiktaalik, the Fossil Link Between Fish and Land Animals." Very interesting video about how Shubin's team figured out where to look for transitional fossils that explain the evolution of land animals from fish.
https://www.ibiology.org/evolution/tiktaalik/
Ever since he was a graduate student, Neil Shubin has been obsessed with finding fossils of the creature that marked the transition from fish to land dwelling animals. He explains how he scoured maps to find rocks of the right age and type that were accessible at the earth’s surface. This led him to the Canadian arctic where, in 2004, Shubin and his colleagues found Tiktaalik, a fossil of a creature with features found in both fish and tetrapods. Tiktaalik was the link between fish and land animals.
Speaker Biography:
Dr. Neil Shubin is an author and Professor in the Department of Organismal Biology and Anatomy and the Committee on Evolutionary Biology at the University of Chicago. Shubin’s research focuses on understanding the evolutionary origins of new anatomical features such as limbs. Shubin is well known for his discovery of Tiktaalik roseae, the 375 million year old fossil link between fish and tetrapods. Shubin is an elected member of the National Academy of Science, the American Academy of Arts and Sciences and the American Association for the Advancement of Science.
Ever since he was a graduate student, Neil Shubin has been obsessed with finding fossils of the creature that marked the transition from fish to land dwelling animals. He explains how he scoured maps to find rocks of the right age and type that were accessible at the earth’s surface. This led him to the Canadian arctic where, in 2004, Shubin and his colleagues found Tiktaalik, a fossil of a creature with features found in both fish and tetrapods. Tiktaalik was the link between fish and land animals.
Speaker Biography:
Dr. Neil Shubin is an author and Professor in the Department of Organismal Biology and Anatomy and the Committee on Evolutionary Biology at the University of Chicago. Shubin’s research focuses on understanding the evolutionary origins of new anatomical features such as limbs. Shubin is well known for his discovery of Tiktaalik roseae, the 375 million year old fossil link between fish and tetrapods. Shubin is an elected member of the National Academy of Science, the American Academy of Arts and Sciences and the American Association for the Advancement of Science.
Wednesday, December 25, 2019
A Washington Post review and a customer review of "Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin."
I have about 7 books about evolution. This is the best one.
Amazon - Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body
From The Washington Post
Reviewed by Barbara J. King
For the first time, Americans have the chance to meet an ancient ancestor. Lucy, the famous 3.2-million-year-old, human-like fossil from Ethiopia, is here on tour. For the next six years, you can visit her at museums across the country and stare into the mirror of your own past.
But in Your Inner Fish, Neil Shubin describes a fossil named Tiktaalik that makes Lucy's time on Earth seem like just yesterday. At 375 million years old, Tiktaalik (which means "large freshwater fish" in Inuit) sports a curious mix of features that mark it as an evolutionary milestone, a "beautiful intermediate between fish and land-living animals." In its fossilized bones, we see a flat head and body, a functional neck and other features that presage what's to come, all mixed in with fish features like fins and scales. Most surprising of all, Tiktaalik has a wrist joint. "Bend your wrist back and forth," Shubin instructs his readers. "Open and close your hand. When you do this, you are using joints that first appeared in the fins of fish like Tiktaalik."
Shubin, a paleontologist and professor of anatomy, made the astounding discovery of Tiktaalik, the first find of its kind, with colleagues in the Canadian Arctic in 2004. He has clearly fallen in love with this ancient fish, and conveys its significance with both precision and exuberance. "Seeing Lucy," writes Shubin, "we can understand our history as highly advanced primates. Seeing Tiktaalik is seeing our history as fish." In fact, Shubin wants us to see our history not only as primates and fish, but also as insects and worms. Exploring the 3.5-billion-year history of life on Earth, Shubin says, will yield a deeper grasp of how our bodies came to be what they are. "Inside our bodies are connections to a menagerie of other creatures. Some parts resemble parts of jellyfish, others parts of worms, still others parts of fish. These aren't haphazard similarities. . . . It is deeply beautiful to see that there is an order in all these features."
Shubin, then, turns Tiktaalik the ancient fish into a poster fossil for the elegant connections across all life-forms on our planet. This evolutionary continuity, so basic to biology, paleontology and anthropology, is the real message of the book. Shubin reveals its practical applications: The better we understand the long history of our joints and organs, the better we will be able to treat trauma and disease in our bodies.
Genes are the co-stars, with bones, of Your Inner Fish. As Shubin puts it, "DNA is an extraordinarily powerful window into life's history and the formation of bodies and organs." When scientists make a fly that lacks a certain gene, the fly's midsection is missing or altered. Frankenstein-like research of this nature helps scientists to understand more about how genes influence developmental processes. Yet how relevant is such research for understanding human development, which unfolds according to rich interaction between our genes and our environment? It's hard not to wince when thinking about the subjects of this DNA-altering lab work.
Nevertheless, Shubin's melding of fossil and genetic data is deft, and it prepares us for his central conclusion. Our lives reflect the evolutionary principle of descent with modification: "Looking back through billions of years of change, everything innovative or apparently unique in the history of life is really just old stuff that has been recycled, repurposed, or otherwise modified for new uses." How our senses work, why we get sick and even why we get the hiccups can be explained by this principle. For instance, hiccups are inherited from fish and tadpoles. We hiccup when a nerve spasm causes muscles in the diaphragm, neck and throat to contract. We gasp and take in some air, and the glottis in the back of our throat snaps shut. This tortuous path that nerves take in our body and the brain stem's response when they spasm are marvelous adaptations for gill-breathers, Shubin explains, but not entirely ideal for us.
Shubin's message convinces. Read Your Inner Fish, and you'll never again be able to look a fish in the eye (or eat seafood) without thinking about shared evolution. In two ways, though, Shubin takes a good thing too far. His passion for science enlivens every page, but some of his sentences ("True, big fish tend to eat littler fish") are overly simplified. He could have trusted his readers more.
Even more worrisome is Shubin's tendency to oversell the relatedness of fish and humans. Our common ancestry with apes is far more recent than with fish, and as a result, our inner ape dominates our inner fish. This fact is most evident when we consider behavior as well as anatomy. Do fish empathize with sick companions, grieve for dead ones or express empathy? Certainly not to the extent that apes do. Or consider the wrist joint which, as we have seen, Shubin uses to link Tiktaalik with humans. Enhanced mobility of the ape wrist joint allows chimpanzees and gorillas to gesture in ways more varied and expressive even than monkeys, a capacity that in turn enriches social communication among them.
We humans are first and foremost primates. Nevertheless, Shubin is dead right: The elegance and full emotional power of our connection with the natural world compel us to reach further back in time and deeper into the Earth's fossil layers. Visit Lucy, think Tiktaalik, and feel the connection.
Copyright 2008, The Washington Post. All Rights Reserved.
••••••••••••••••••••••••••••••••••••
Mike Morgenstein
5.0 out of 5 stars "Nothing in Biology Makes Sense Except in the Light of Evolution"
Reviewed in the United States on February 3, 2016
Format: PaperbackVerified Purchase
I'll first give my take on the book then provide a brief summary. Author Neil Shubin is an awesome man and author. His personal anecdotes came at perfect times and flowed with the book in harmony. His writing style is congenial, conversational, humorous, candid, and i'd go as far to say inspirational. Prospective readers - especially those who aren't enthralled by evolution or anatomy - might predetermine the text as being bland and heavy. It's quite the opposite; I found myself laughing many times and perhaps the only weakness of the book is that it's too short. I personally enjoy shorter books because I enjoy delving into a few different topics a month. For only 200 pages there is a hell of a lot to learn and so much great information jam-packed in an easy-to-understand way. The author is an acute articulator, and has a good habit of recapitulating unfamiliar topics. This is an unconventional evolution book. Scientist Theodosius Dobzhansky once famously said "Nothing in Biology Makes Sense Except in the Light of Evolution". This could have been the name of this book. Having read numerous evolution books before, I would have thought that attaining higher appreciation for it than I already have was an unattainable goal, but reading this book shattered that notion because my appreciation for evolution is substantially heightened. Nothing is more enlightening than finding out the truth of your existence up to your very faults.
The book is split by 11 chapters. The first four explore the theme of how we can trace the same organ in different creatures. I'll briefly summarize:
- Chapter 1-4:
The author starts by describing his legendary trip to Ellesmere Island in Nunavut, Canada. He describes the struggles and the significance of his finding: The Tiktaalik; a creature from the late Devonian period (375 million years ago) that currently holds as the most well-established evolutionary transition from fish to amphibian. I've read about the Tiktaalik before in one of Dawkin's books, but I was surprised to find out that the author of this book actually discovered it. His expedition is a fascinating read in itself because the author is a great storyteller, and seems to be a really humble, laid-back, and fun guy. He all of the latter not only when sharing his personal experiences, but when speaking on behalf of his chosen subjects as well. He describes how he ended up near the arctic - and on the Pennsylvania highways - when looking for his fossils of choice. He gives a general introduction of where and how - using paleontology and evolution - you would find fossils. He elucidates the difference between fish and amphibian (through bone structure and limbs) and mammal and reptile. There's a chapter dedicated to teeth. Teeth are important and extremely helpful when identifying or distinguishing differences among animals (i.e. reptiles and mammals). There's a chapter dedicated limb structure, specifically the hand and arm. The developmental difference between our arms and a fish's fins are very similar early on in development but become vastly different through the process (inside the egg). The author explains why and shows experiments involving the relevant genes for such functions (those involving the ZPA tissue and Sonic Hedgehog gene manipulation, there's a chapter to this called "Handy Genes").
- Chapter 5-11:
In each one of these chapters, certain body parts of ours are to our distant ancestors. In other words, we get to explore, interpret, analyze, compare and contrast the our body functions with our distant ancestors. We figure out the inception of many body parts (and functions) and why they evolved to work the way they do for us. Specifically, there's a chapter on: the head, entire body, scent, vision, and ears.
Some interesting stuff by chapter: In the field of Embryology, - the study of Embryos, or fetuses - we see that all animals are alike at their very initial gestation stage, with four little swellings called arches that develop around what comes to be the throat area. This is explained in more detail in the book but the fascinating thing is that these arches, depending on the species, all come to have a different but similar function in the body as the conception process gets underway. In the book, the example of comparison are humans and our very distant ancestor shark. Cranial nerve structure is also discussed and compared. Also discussed are headless animals - primitive ones - and the origins of our notochord. There's a whole section on the similarity of active (and inactive) genes among completely different specifies. What happens if you remove tissue, or add certain DNA strands in fruitful area? The evolution of scent is interesting because fish evolving to leave the water and thus become an amphibian, it requires major changes because there are 2 kinds of smelling genes: one for water and one for air. The chapter on scent is epic and so is the proceeding one on vision and then Hearing. We can trace major events in our eyes by analyzing certain eye genes that we share with other creatures. Mammals have the same ear bones as fish, the difference being that wish don't have ears. We come to see that there's major contrast between the functions of these bones for different groups of animals, like mammals and amphibians. These differences are part of why we label an animal to be a "mammal" or "amphibian" in the first place. Our middle ear bones are the malleus, incus and stapes. We come to see that the malleus and incus evolved from jawbones.
Of the million years of life, Homo Sapiens have survived extinction and for the time being remain extant. But this doesn't mean that we don't have our problems. There's no preternatural creator ghost behind the complexity or susceptibility of our bodies, but even better: an evolutionary explanation of everything in our body from our genetic workings to our genotypes. Because of such primitive origins, our bodies aren't fully accustomed to certain things and thus thanks to our fish ancestors we develop things like hernias or hangovers. So why is this better then? For one, because it makes perfect sense! And two, by having a natural understanding of our anatomy, we can spearhead our way into the understanding of imperative issues - like disease or congenital defects - that shackle and sometimes terminate the life of many good individuals. This is very important, and so is this book. I'm grateful I read it.
Amazon - Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body
From The Washington Post
Reviewed by Barbara J. King
For the first time, Americans have the chance to meet an ancient ancestor. Lucy, the famous 3.2-million-year-old, human-like fossil from Ethiopia, is here on tour. For the next six years, you can visit her at museums across the country and stare into the mirror of your own past.
But in Your Inner Fish, Neil Shubin describes a fossil named Tiktaalik that makes Lucy's time on Earth seem like just yesterday. At 375 million years old, Tiktaalik (which means "large freshwater fish" in Inuit) sports a curious mix of features that mark it as an evolutionary milestone, a "beautiful intermediate between fish and land-living animals." In its fossilized bones, we see a flat head and body, a functional neck and other features that presage what's to come, all mixed in with fish features like fins and scales. Most surprising of all, Tiktaalik has a wrist joint. "Bend your wrist back and forth," Shubin instructs his readers. "Open and close your hand. When you do this, you are using joints that first appeared in the fins of fish like Tiktaalik."
Shubin, a paleontologist and professor of anatomy, made the astounding discovery of Tiktaalik, the first find of its kind, with colleagues in the Canadian Arctic in 2004. He has clearly fallen in love with this ancient fish, and conveys its significance with both precision and exuberance. "Seeing Lucy," writes Shubin, "we can understand our history as highly advanced primates. Seeing Tiktaalik is seeing our history as fish." In fact, Shubin wants us to see our history not only as primates and fish, but also as insects and worms. Exploring the 3.5-billion-year history of life on Earth, Shubin says, will yield a deeper grasp of how our bodies came to be what they are. "Inside our bodies are connections to a menagerie of other creatures. Some parts resemble parts of jellyfish, others parts of worms, still others parts of fish. These aren't haphazard similarities. . . . It is deeply beautiful to see that there is an order in all these features."
Shubin, then, turns Tiktaalik the ancient fish into a poster fossil for the elegant connections across all life-forms on our planet. This evolutionary continuity, so basic to biology, paleontology and anthropology, is the real message of the book. Shubin reveals its practical applications: The better we understand the long history of our joints and organs, the better we will be able to treat trauma and disease in our bodies.
Genes are the co-stars, with bones, of Your Inner Fish. As Shubin puts it, "DNA is an extraordinarily powerful window into life's history and the formation of bodies and organs." When scientists make a fly that lacks a certain gene, the fly's midsection is missing or altered. Frankenstein-like research of this nature helps scientists to understand more about how genes influence developmental processes. Yet how relevant is such research for understanding human development, which unfolds according to rich interaction between our genes and our environment? It's hard not to wince when thinking about the subjects of this DNA-altering lab work.
Nevertheless, Shubin's melding of fossil and genetic data is deft, and it prepares us for his central conclusion. Our lives reflect the evolutionary principle of descent with modification: "Looking back through billions of years of change, everything innovative or apparently unique in the history of life is really just old stuff that has been recycled, repurposed, or otherwise modified for new uses." How our senses work, why we get sick and even why we get the hiccups can be explained by this principle. For instance, hiccups are inherited from fish and tadpoles. We hiccup when a nerve spasm causes muscles in the diaphragm, neck and throat to contract. We gasp and take in some air, and the glottis in the back of our throat snaps shut. This tortuous path that nerves take in our body and the brain stem's response when they spasm are marvelous adaptations for gill-breathers, Shubin explains, but not entirely ideal for us.
Shubin's message convinces. Read Your Inner Fish, and you'll never again be able to look a fish in the eye (or eat seafood) without thinking about shared evolution. In two ways, though, Shubin takes a good thing too far. His passion for science enlivens every page, but some of his sentences ("True, big fish tend to eat littler fish") are overly simplified. He could have trusted his readers more.
Even more worrisome is Shubin's tendency to oversell the relatedness of fish and humans. Our common ancestry with apes is far more recent than with fish, and as a result, our inner ape dominates our inner fish. This fact is most evident when we consider behavior as well as anatomy. Do fish empathize with sick companions, grieve for dead ones or express empathy? Certainly not to the extent that apes do. Or consider the wrist joint which, as we have seen, Shubin uses to link Tiktaalik with humans. Enhanced mobility of the ape wrist joint allows chimpanzees and gorillas to gesture in ways more varied and expressive even than monkeys, a capacity that in turn enriches social communication among them.
We humans are first and foremost primates. Nevertheless, Shubin is dead right: The elegance and full emotional power of our connection with the natural world compel us to reach further back in time and deeper into the Earth's fossil layers. Visit Lucy, think Tiktaalik, and feel the connection.
Copyright 2008, The Washington Post. All Rights Reserved.
••••••••••••••••••••••••••••••••••••
Mike Morgenstein
5.0 out of 5 stars "Nothing in Biology Makes Sense Except in the Light of Evolution"
Reviewed in the United States on February 3, 2016
Format: PaperbackVerified Purchase
I'll first give my take on the book then provide a brief summary. Author Neil Shubin is an awesome man and author. His personal anecdotes came at perfect times and flowed with the book in harmony. His writing style is congenial, conversational, humorous, candid, and i'd go as far to say inspirational. Prospective readers - especially those who aren't enthralled by evolution or anatomy - might predetermine the text as being bland and heavy. It's quite the opposite; I found myself laughing many times and perhaps the only weakness of the book is that it's too short. I personally enjoy shorter books because I enjoy delving into a few different topics a month. For only 200 pages there is a hell of a lot to learn and so much great information jam-packed in an easy-to-understand way. The author is an acute articulator, and has a good habit of recapitulating unfamiliar topics. This is an unconventional evolution book. Scientist Theodosius Dobzhansky once famously said "Nothing in Biology Makes Sense Except in the Light of Evolution". This could have been the name of this book. Having read numerous evolution books before, I would have thought that attaining higher appreciation for it than I already have was an unattainable goal, but reading this book shattered that notion because my appreciation for evolution is substantially heightened. Nothing is more enlightening than finding out the truth of your existence up to your very faults.
The book is split by 11 chapters. The first four explore the theme of how we can trace the same organ in different creatures. I'll briefly summarize:
- Chapter 1-4:
The author starts by describing his legendary trip to Ellesmere Island in Nunavut, Canada. He describes the struggles and the significance of his finding: The Tiktaalik; a creature from the late Devonian period (375 million years ago) that currently holds as the most well-established evolutionary transition from fish to amphibian. I've read about the Tiktaalik before in one of Dawkin's books, but I was surprised to find out that the author of this book actually discovered it. His expedition is a fascinating read in itself because the author is a great storyteller, and seems to be a really humble, laid-back, and fun guy. He all of the latter not only when sharing his personal experiences, but when speaking on behalf of his chosen subjects as well. He describes how he ended up near the arctic - and on the Pennsylvania highways - when looking for his fossils of choice. He gives a general introduction of where and how - using paleontology and evolution - you would find fossils. He elucidates the difference between fish and amphibian (through bone structure and limbs) and mammal and reptile. There's a chapter dedicated to teeth. Teeth are important and extremely helpful when identifying or distinguishing differences among animals (i.e. reptiles and mammals). There's a chapter dedicated limb structure, specifically the hand and arm. The developmental difference between our arms and a fish's fins are very similar early on in development but become vastly different through the process (inside the egg). The author explains why and shows experiments involving the relevant genes for such functions (those involving the ZPA tissue and Sonic Hedgehog gene manipulation, there's a chapter to this called "Handy Genes").
- Chapter 5-11:
In each one of these chapters, certain body parts of ours are to our distant ancestors. In other words, we get to explore, interpret, analyze, compare and contrast the our body functions with our distant ancestors. We figure out the inception of many body parts (and functions) and why they evolved to work the way they do for us. Specifically, there's a chapter on: the head, entire body, scent, vision, and ears.
Some interesting stuff by chapter: In the field of Embryology, - the study of Embryos, or fetuses - we see that all animals are alike at their very initial gestation stage, with four little swellings called arches that develop around what comes to be the throat area. This is explained in more detail in the book but the fascinating thing is that these arches, depending on the species, all come to have a different but similar function in the body as the conception process gets underway. In the book, the example of comparison are humans and our very distant ancestor shark. Cranial nerve structure is also discussed and compared. Also discussed are headless animals - primitive ones - and the origins of our notochord. There's a whole section on the similarity of active (and inactive) genes among completely different specifies. What happens if you remove tissue, or add certain DNA strands in fruitful area? The evolution of scent is interesting because fish evolving to leave the water and thus become an amphibian, it requires major changes because there are 2 kinds of smelling genes: one for water and one for air. The chapter on scent is epic and so is the proceeding one on vision and then Hearing. We can trace major events in our eyes by analyzing certain eye genes that we share with other creatures. Mammals have the same ear bones as fish, the difference being that wish don't have ears. We come to see that there's major contrast between the functions of these bones for different groups of animals, like mammals and amphibians. These differences are part of why we label an animal to be a "mammal" or "amphibian" in the first place. Our middle ear bones are the malleus, incus and stapes. We come to see that the malleus and incus evolved from jawbones.
Of the million years of life, Homo Sapiens have survived extinction and for the time being remain extant. But this doesn't mean that we don't have our problems. There's no preternatural creator ghost behind the complexity or susceptibility of our bodies, but even better: an evolutionary explanation of everything in our body from our genetic workings to our genotypes. Because of such primitive origins, our bodies aren't fully accustomed to certain things and thus thanks to our fish ancestors we develop things like hernias or hangovers. So why is this better then? For one, because it makes perfect sense! And two, by having a natural understanding of our anatomy, we can spearhead our way into the understanding of imperative issues - like disease or congenital defects - that shackle and sometimes terminate the life of many good individuals. This is very important, and so is this book. I'm grateful I read it.
Tuesday, December 3, 2019
My favorite book about how evolution works.
I have bought and read 7 books about the evidence for evolution and how evolution works. All these books are excellent but if someone wanted to buy just one book about evolution I would recommend "Your Inner Fish".
AMAZON - Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body Hardcover – January 15, 2008 by Neil Shubin
Out of the 7 books about evolution I own, this is the only book that completely ignores the know-nothing science deniers. The author just assumes these morons for Jeebus don't exist.
Shubin explains the 3.5 billion year history of life and it is a fantastic story.
From page 135 of the hardcover book:
"In the fossil record, we see nothing but microbes for the 1st 3.5 billion years of earth history. Then, suddenly, over a span of perhaps 40 million years, all kinds of bodies appear."
What happened? I suggest buying the book because the explanation is too long to write here.
Hint: About one billion years ago the amount of oxygen increased dramatically.
I only read books about science that are very interesting and easy to understand, and that's one of the reasons I recommend Shubin's book. I suggest read the Amazon customer reviews at Amazon product reviews.
AMAZON - Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body Hardcover – January 15, 2008 by Neil Shubin
Out of the 7 books about evolution I own, this is the only book that completely ignores the know-nothing science deniers. The author just assumes these morons for Jeebus don't exist.
Shubin explains the 3.5 billion year history of life and it is a fantastic story.
From page 135 of the hardcover book:
"In the fossil record, we see nothing but microbes for the 1st 3.5 billion years of earth history. Then, suddenly, over a span of perhaps 40 million years, all kinds of bodies appear."
What happened? I suggest buying the book because the explanation is too long to write here.
Hint: About one billion years ago the amount of oxygen increased dramatically.
I only read books about science that are very interesting and easy to understand, and that's one of the reasons I recommend Shubin's book. I suggest read the Amazon customer reviews at Amazon product reviews.
Saturday, November 9, 2019
You want to click "Your Inner Fish". The videos are very interesting and very well done. It explains the "350 million years of evolution to produce the amazing machine we call the human body".
Your Inner Fish
In the News: Your Inner Fish – A Scientific Adventure
National Academy of Sciences
Have you ever wondered why people look the way they do? Why our hands and feet have five digits instead of six? Why we stand on two legs instead of four? It took 350 million years of evolution to produce the amazing machine we call the human body and in Your Inner Fish, a three-part series based on the best-selling book of the same name, author and evolutionary biologist Dr. Neil Shubin looks into the past to answer these and other questions.
Follow that adventure now on PBS
Darwin's Insights Continue to Inspire the Academy's Work
The ideas of Charles Darwin and the concept of evolution by natural selection continue to have a profound influence on modern biology – they permeate almost every area of scientific exploration. The Academies have long been involved in educational activities and publications on many aspects of evolution. For example, in 2008 the Academies published Science, Evolution, and Creationism, to help people who are interested in evolution better understand its underlying principles and how evolution is an integral component of scientific research and thinking.
In 2009 the National Academy of Sciences joined many other organizations in the international scientific community to celebrate the 'Year of Science,' which commemorated Darwin’s 200th birthday and the 150th anniversary of the publication of his masterwork On the Origin of Species. Information about some of the events we hosted as part of this celebration can be accessed through our event archive.
In 2010, the National Academy of Sciences awarded its most prestigious award, the Public Welfare Medal, to Dr. Eugenie Scott, Director of the National Center for Science Education, for her distinguished work to "…improve public understanding of both the nature of science and the science of evolution” (from comments by Dr. Ralph Cicerone, President, National Academy of Sciences during the presentation of the Public Welfare Medal).
In 2011, the Academies organized a convocation to bring together people from the life sciences community to explore ways to infuse concepts of evolution into all areas of biology education. Thinking Evolutionarily: Evolution Education Across the Life Sciences (2012) explains the major themes that recurred throughout the convocation held in Washington, D.C. They include the structure and content of curricula, the processes of teaching and learning about evolution, the tensions that can arise in the classroom, and the target audiences for evolution education. Videos from plenary sessions, interviews with participants, and resources from the convocation that led to this report may be accessed here.
In 2012 the Academies also released the report A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas as a first step toward developing the next generation of K-12 science education standards. The study of evolution is one of the themes running throughout this report with section LS4 focusing specifically on biological evolution. The Next Generation Science Standards were published in April 2013.
Research about evolution also has served as the basis for technical reports and research conferences that have been hosted by the National Academy of Sciences in past years. They include:
2008
Biogeography, Changing Climates and Niche Evolution
In the Light of Evolution, Volume II: Biodiversity and Extinction
Origin and Evolution of Earth: Research Questions for a Changing Planet
In the News: Your Inner Fish – A Scientific Adventure
National Academy of Sciences
Have you ever wondered why people look the way they do? Why our hands and feet have five digits instead of six? Why we stand on two legs instead of four? It took 350 million years of evolution to produce the amazing machine we call the human body and in Your Inner Fish, a three-part series based on the best-selling book of the same name, author and evolutionary biologist Dr. Neil Shubin looks into the past to answer these and other questions.
Follow that adventure now on PBS
Darwin's Insights Continue to Inspire the Academy's Work
The ideas of Charles Darwin and the concept of evolution by natural selection continue to have a profound influence on modern biology – they permeate almost every area of scientific exploration. The Academies have long been involved in educational activities and publications on many aspects of evolution. For example, in 2008 the Academies published Science, Evolution, and Creationism, to help people who are interested in evolution better understand its underlying principles and how evolution is an integral component of scientific research and thinking.
In 2009 the National Academy of Sciences joined many other organizations in the international scientific community to celebrate the 'Year of Science,' which commemorated Darwin’s 200th birthday and the 150th anniversary of the publication of his masterwork On the Origin of Species. Information about some of the events we hosted as part of this celebration can be accessed through our event archive.
In 2010, the National Academy of Sciences awarded its most prestigious award, the Public Welfare Medal, to Dr. Eugenie Scott, Director of the National Center for Science Education, for her distinguished work to "…improve public understanding of both the nature of science and the science of evolution” (from comments by Dr. Ralph Cicerone, President, National Academy of Sciences during the presentation of the Public Welfare Medal).
In 2011, the Academies organized a convocation to bring together people from the life sciences community to explore ways to infuse concepts of evolution into all areas of biology education. Thinking Evolutionarily: Evolution Education Across the Life Sciences (2012) explains the major themes that recurred throughout the convocation held in Washington, D.C. They include the structure and content of curricula, the processes of teaching and learning about evolution, the tensions that can arise in the classroom, and the target audiences for evolution education. Videos from plenary sessions, interviews with participants, and resources from the convocation that led to this report may be accessed here.
In 2012 the Academies also released the report A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas as a first step toward developing the next generation of K-12 science education standards. The study of evolution is one of the themes running throughout this report with section LS4 focusing specifically on biological evolution. The Next Generation Science Standards were published in April 2013.
Research about evolution also has served as the basis for technical reports and research conferences that have been hosted by the National Academy of Sciences in past years. They include:
2008
Biogeography, Changing Climates and Niche Evolution
In the Light of Evolution, Volume II: Biodiversity and Extinction
Origin and Evolution of Earth: Research Questions for a Changing Planet
2009
In the Light of Evolution: Two Centuries of Darwin
Evolution in Health and Medicine
In the Light of Evolution: The Human Condition
Microbial Evolution and Co-Adaptation: A Tribute to the Life and Scientific
Legacies of Joshua Lederberg
2010
Understanding Climate's Influence on Human Evolution
2011
In the Light of Evolution: Cooperation
2012
In the Light of Evolution: Brain and Behavior
The Social Biology of Microbial Communities: Workshop Summary
National Summit on Strategies to Manage Herbicide-Resistant Weeds: Proceedings of a Symposium
The Human Microbiome, Diet, and Health: Workshop Summary
2013
In the Light of Evolution: Human Mental Machinery
Have you ever wondered why the human body looks the way it does? Why our hands have five fingers instead of six? Why we walk on two legs instead of four?
It took more than 350 million years for the human body to take shape. How did it become the complicated, quirky, amazing machine it is today?
Your Inner Fish delves deep into the past to answer these questions. The three-part series, which premiered April 9. 2014, reveals a startling truth: Hidden within the human body is a story of life on Earth.
That's because the evolution of humans can be traced into the distant past, to the earliest forms of vertebrate life on land and even to the earliest forms of life on Earth. Each of us carries the genetic imprint of creatures that lived hundreds of millions of years ago. From them, we inherited our most remarkable features — as well as quirks like bad backs and hernias.
The series is full of revelations that will surprise many viewers. Among the key insights: Our hands evolved from the fins of prehistoric fish. Our skin, hair and teeth can be traced to early reptiles. And our remarkable color vision is a legacy from ancient primates.
Based on a best-selling book by paleobiologist Neil Shubin, this scientific adventure story takes viewers from Ethiopia to the Arctic Circle on a hunt for the many ways that our animal ancestors shaped our anatomical destiny. Shubin has spent much of his life studying our ancient ancestors — searching for the deep pedigree of Homo sapiens. Using both the fossil record and DNA evidence, he traces various parts of our body's structure to creatures that lived long, long ago. Along the way, he makes it clear that we can thank our fishy origins for many human characteristics.
Endowed not just with scientific expertise, but also with natural wit and a talent for storytelling, Shubin puts all these discoveries in context. He travels from fossil-hunting expeditions in the Arctic to the deserts of Ethiopia and to the high plains of South Africa. And he reveals insights from scientists who have identified genes that we still have in common with distant forebears. He weaves together this information from past and present to demonstrate that we humans have a lot more in common than you might think with monkeys, reptiles and even fish.
The series is both an epic saga and a modern-day detective story — by turns surprising, funny and deeply profound. Come face-to-face with your "inner fish" in this completely new take on the human body. After seeing the world through Neil Shubin's eyes, you'll never look at yourself in quite the same way again!
In the Light of Evolution: Two Centuries of Darwin
Evolution in Health and Medicine
In the Light of Evolution: The Human Condition
Microbial Evolution and Co-Adaptation: A Tribute to the Life and Scientific
Legacies of Joshua Lederberg
2010
Understanding Climate's Influence on Human Evolution
2011
In the Light of Evolution: Cooperation
2012
In the Light of Evolution: Brain and Behavior
The Social Biology of Microbial Communities: Workshop Summary
National Summit on Strategies to Manage Herbicide-Resistant Weeds: Proceedings of a Symposium
The Human Microbiome, Diet, and Health: Workshop Summary
2013
In the Light of Evolution: Human Mental Machinery
Have you ever wondered why the human body looks the way it does? Why our hands have five fingers instead of six? Why we walk on two legs instead of four?
It took more than 350 million years for the human body to take shape. How did it become the complicated, quirky, amazing machine it is today?
Your Inner Fish delves deep into the past to answer these questions. The three-part series, which premiered April 9. 2014, reveals a startling truth: Hidden within the human body is a story of life on Earth.
That's because the evolution of humans can be traced into the distant past, to the earliest forms of vertebrate life on land and even to the earliest forms of life on Earth. Each of us carries the genetic imprint of creatures that lived hundreds of millions of years ago. From them, we inherited our most remarkable features — as well as quirks like bad backs and hernias.
The series is full of revelations that will surprise many viewers. Among the key insights: Our hands evolved from the fins of prehistoric fish. Our skin, hair and teeth can be traced to early reptiles. And our remarkable color vision is a legacy from ancient primates.
Based on a best-selling book by paleobiologist Neil Shubin, this scientific adventure story takes viewers from Ethiopia to the Arctic Circle on a hunt for the many ways that our animal ancestors shaped our anatomical destiny. Shubin has spent much of his life studying our ancient ancestors — searching for the deep pedigree of Homo sapiens. Using both the fossil record and DNA evidence, he traces various parts of our body's structure to creatures that lived long, long ago. Along the way, he makes it clear that we can thank our fishy origins for many human characteristics.
Endowed not just with scientific expertise, but also with natural wit and a talent for storytelling, Shubin puts all these discoveries in context. He travels from fossil-hunting expeditions in the Arctic to the deserts of Ethiopia and to the high plains of South Africa. And he reveals insights from scientists who have identified genes that we still have in common with distant forebears. He weaves together this information from past and present to demonstrate that we humans have a lot more in common than you might think with monkeys, reptiles and even fish.
The series is both an epic saga and a modern-day detective story — by turns surprising, funny and deeply profound. Come face-to-face with your "inner fish" in this completely new take on the human body. After seeing the world through Neil Shubin's eyes, you'll never look at yourself in quite the same way again!
Saturday, April 13, 2019
Wednesday, February 27, 2019
This transitional fossil is our ancestor.
Wikipedia - Tiktaalik
Tiktaalik /tɪkˈtɑːlɪk/ is a monospecific genus of extinct sarcopterygian (lobe-finned fish) from the Late Devonian Period, about 375 Ma (million years ago), having many features akin to those of tetrapods (four-legged animals).[1]
Unearthed in Arctic Canada, Tiktaalik is technically a fish, complete with scales and gills - but it has the flattened head of a crocodile and unusual fins. Its fins have thin ray bones for paddling like most fishes', but they also have sturdy interior bones that would have allowed Tiktaalik to prop itself up in shallow water and use its limbs for support as most four-legged animals do. Those fins and a suite of other characteristics set Tiktaalik apart as something special; it has a combination of features that show the evolutionary transition between swimming fish and their descendants, the four-legged vertebrates - a clade which includes amphibians, reptiles, birds, mammals and humans.[2]
It and similar animals may possibly be the common ancestors of the broad swath of all vertebrate terrestrial fauna: amphibians, reptiles, birds, and mammals.[3] The first well-preserved Tiktaalik fossils were found in 2004 on Ellesmere Island in Nunavut, Canada.
Contents
Description[edit]
Tiktaalik provides insights on the features of the extinct closest relatives of the tetrapods. Unlike many previous, more fishlike transitional fossils, the "fins" of Tiktaalik have basic wrist bones and simple rays reminiscent of fingers. The homology of distal elements is uncertain; there have been suggestions that they are homologous to digits, although this is incompatible with the digital arch developmental model because digits are supposed to be postaxial structures, and only three of the (reconstructed) eight rays of Tiktaalik are postaxial.[4]
However, the proximal series can be directly compared to the ulnare and intermedium of tetrapods. The fin was clearly weight bearing, being attached to a massive shoulder with expanded scapular and coracoid elements and attached to the body armor, large muscular scars on the ventral surface of the humerus, and highly mobile distal joints. The bones of the forefins show large muscle facets, suggesting that the fin was both muscular and had the ability to flex like a wrist joint. These wrist-like features would have helped anchor the creature to the bottom in fast moving current.[5][6]
Also notable are the spiracles on the top of the head, which suggest the creature had primitive lungs as well as gills. This attribute would have been useful in shallow water, where higher water temperature would lower oxygen content. This development may have led to the evolution of a more robust ribcage, a key evolutionary trait of land-living creatures.[7] The more robust ribcage of Tiktaalik would have helped support the animal's body any time it ventured outside a fully aquatic habitat. Tiktaalik also lacked a characteristic that most fishes have—bony plates in the gill area that restrict lateral head movement. This makes Tiktaalik the earliest known fish to have a neck, with the pectoral girdle separate from the skull. This would give the creature more freedom in hunting prey either on land or in the shallows.[6]
Tiktaalik is sometimes compared to gars (esp. Atractosteus spatula, the alligator gar) of the Lepisosteidae family, with whom it shares a number of characteristics:[8]
- diamond-shaped scale patterns common to the Crossopterygii class (in both species scales are rhombic, overlapping and tuberculated);
- teeth structured in two rows;
- both internal and external nostrils;
- tubular and streamlined body;
- absence of anterior dorsal fin;
- broad, dorsoventrally compressed skull;
- paired frontal bones;
- marginal nares;
- subterminal mouth;
- lung-like organ.
Paleobiology[edit]
Tiktaalik generally had the characteristics of a lobe-finned fish, but with front fins featuring arm-like skeletal structures more akin to those of a crocodile, including a shoulder, elbow, and wrist. The fossil discovered in 2004 did not include the rear fins and tail. It had rows[9] of sharp teeth indicative of a predator fish, and its neck could move independently of its body, which is not common in other fish (Tarrasius, Mandageria, placoderms,[10][11] and extant seahorses being some exceptions; see also Lepidogalaxias and Channallabes apus[12]). The animal had a flat skull resembling a crocodile's; eyes on top of its head; a neck and ribs similar to those of tetrapods, with the ribs being used to support its body and aid in breathing via lungs; well developed jaws suitable for catching prey; and a small gill slit called a spiracle that, in more derived animals, became an ear.[13][not in citation given]
The fossils were found in the "Fram Formation", deposits of meandering stream systems near the Devonian equator, suggesting a benthic animal that lived on the bottom of shallow waters and perhaps even out of the water for short periods, with a skeleton indicating that it could support its body under the force of gravity whether in very shallow water or on land.[14] At that period, for the first time, deciduous plants were flourishing and annually shedding leaves into the water, attracting small prey into warm oxygen-poor shallows that were difficult for larger fish to swim in.[7] The discoverers said that in all likelihood, Tiktaalikflexed its proto-limbs primarily on the floor of streams and may have pulled itself onto the shore for brief periods.[15] In 2014, the discovery of the animal's pelvic girdle was announced; it was strongly built, indicating the animal could have used them for moving in shallow water and across mudflats.[16] Neil Shubin and Ted Daeschler, the leaders of the team, have been searching Ellesmere Island for fossils since 2000[5][17]
Classification and evolution[edit]
Tiktaalik roseae is the only species classified under the genus. Tiktaalik lived approximately 375 million years ago. It is representative of the transition between non-tetrapod vertebrates (fish) such as Panderichthys, known from fossils 380 million years old, and early tetrapods such as Acanthostega and Ichthyostega, known from fossils about 365 million years old. Its mixture of primitive fish and derived tetrapod characteristics led one of its discoverers, Neil Shubin, to characterize Tiktaalik as a "fishapod".[5][19]
Tiktaalik is a transitional fossil; it is to tetrapods what Archaeopteryx is to birds, troodonts and dromaeosaurids. While it may be that neither is ancestor to any living animal, they serve as evidence that intermediates between very different types of vertebrates did once exist. The mixture of both fish and tetrapod characteristics found in Tiktaalik include these traits:
- Fish
- fish gills
- fish scales
- fish fins
- "Fishapod"
- half-fish, half-tetrapod limb bones and joints, including a functional wrist joint and radiating, fish-like fins instead of toes
- half-fish, half-tetrapod ear region
- Tetrapod
- tetrapod rib bones
- tetrapod mobile neck with separate pectoral girdle
- tetrapod lungs
Phylogenetic position[edit]
2006 - 2010[edit]
The phylogenetic analysis by Daeschler et al. placed Tiktaalik as a sister taxon to Elpistostege and directly above Panderichthys preceded by Eusthenopteron. Tiktaalik was thus inserted below Acanthostega and Ichthyostega as a transitional form[20] and a true "missing link".[21]
Such order of the phylogenetic tree was initially adopted by other experts, most notably by Per Ahlberg and Jennifer Clack.[22] However, it was questioned in a 2008 paper by Boisvert at al. who noted that Panderichthys, due to its more derived distal portion, might be closer to tetrapods than Tiktaalik or even that it was convergent with tetrapods.[23] Ahlberg, co-author of the study, considered the possibility of Tiktaalik's fin having been "an evolutionary return to a more primitive form."[24]
2010 - now[edit]
In January 2010, a group of paleontologists (including Ahlberg) published a paper[25] accompanied by extensive supplementary material[26] (discussed also in a Nature documentary[27][28]) which showed that first tetrapods appeared long before Tiktaalik and other elpistostegids. Their conclusions were based on numerous trackways (esp. Muz. PGI 1728.II.16) and individual footprints (esp. Muz. PGI 1728.II.1) discovered at the Zachełmie quarry in the Holy Cross Mountains (Poland). A tetrapod origin of those tracks was suggested based on:
- distinct digits and limb morphology;
- trackways reflecting quadrupedal gait and diagonal walk;
- no body or tail drag marks;
- very wide stride in relation to body length (much beyond that of Tiktaalik or any other fish);
- various size footprints with some unusually big (up to 26 cm wide) indicating body lengths of over 2.5 m.
Track-bearing layers were assigned to the lower-middle Eifelian based on conodont index fossil samples (costatus Zone) and "previous biostratigraphic data obtained from the underlying and overlying strata"[25] with subsequent studies confirming this dating.[29][30][31]
Both Tiktaalik's discoverers were skeptical about the Zachelmie trackways. Edward Daeschler said that trace evidence was not enough for him to modify the theory of tetrapod evolution,[32] while Neil Shubin argued that Tiktaalik could have produced very similar footprints[33] (in a later study Shubin expressed a significantly modified opinion that some of the Zachelmie footprints, those which lacked digits, may have been made by walking fish[34]). However, Ahlberg insisted that those tracks could not have possibly been formed either by natural processes or by transitional species such as Tiktaalikor Panderichthys.[25][35] Instead, the authors of the publication suggested ichthyostegalians as trackmakers, based on available pes morphology of those animals.[25] However, a paper published in 2015 that undertook a critical review of Devonian tetrapod footprints called into question the designation of the Zachelmie marks and instead suggested an origin as fish nests/feeding traces.[36] An earlier study in 2012 indicated that Zachelmie trackmakers were even more advanced than Ichthyostega in terms of quadrupedalism.[37] Grzegorz Niedźwiedzki's reconstruction of one of the trackmakers was identical to that of Tulerpeton.[38][39]
Prof. Narkiewicz, co-author of the article on the Zachelmie trackways, claimed that the Polish "discovery has disproved the theory that elpistostegids were the ancestors of tetrapods",[40] a notion partially shared by Philippe Janvier.[41] There have been a number of new hypotheses suggested as to a possible origin and phylogenetic position of the elpistostegids(including Tiktaalik):
- their phylogenetic position remains unchanged and the footprints found in the Holy Cross Mountains are attributed to tetrapods but as a result there are at least six long ghost lineages separating Zachelmie trackmakers from various elpistostegalian and ichthyostegalian species;[25]
- they were "late-surviving relics rather than direct transitional forms";[38][42]
- they were "an evolutionary dead-end";[43]
- they were a result of convergent or parallel evolution so that apomorphies and striking anatomical similarities found in both digited tetrapods and elpistostegalians evolved at least twice.[44][45][46]
It should be noted that convergency is considered responsible for uniquely tetrapod features found also in other non-elpistostegalian fish from the period like Sauripterus (finger-like jointed distal radial bones)[47][48] or Tarrasius (tetrapod-like spine with 5 axial regions).[49]
Estimates published after the discovery of Zachelmie tracks suggested that digited tetrapods may have appeared as early as 427.4 Ma ago and questioned attempts to read absolute timing of evolutionary events in early tetrapod evolution from stratigraphy.[45]
Until more data become available, the phylogenetic position of Tiktaalik and other elpistostegids remains uncertain.
Discovery[edit]
In 2004, three fossilized Tiktaalik skeletons were discovered in rock formed from late Devonian river sediments on Ellesmere Island, Nunavut, in northern Canada.[50][51] Estimated ages reported at 375 MYA, 379 MYA, and 383 MYA. At the time of the species' existence, Ellesmere Island was part of the continent Laurentia (modern eastern North Americaand Greenland),[52] which was centered on the equator and had a warm climate. When discovered, one of the skulls was found sticking out of a cliff. Upon further inspection, the fossil was found to be in excellent condition for a 375-million-year-old specimen.[5][17]
The discovery, made by Edward B. Daeschler of the Academy of Natural Sciences, Neil H. Shubin from the University of Chicago, and Harvard University Professor Farish A. Jenkins, Jr, was published in the April 6, 2006, issue of Nature[1]and quickly recognized as a transitional form. Jennifer A. Clack, a Cambridge University expert on tetrapod evolution, said of Tiktaalik, "It's one of those things you can point to and say, 'I told you this would exist,' and there it is."[6]
The name Tiktaalik is an Inuktitut word meaning "large freshwater fish".[3] The "fishapod" genus received this name after a suggestion by Inuit elders of Canada's Nunavut Territory, where the fossil was discovered.[52] The specific name roseaecryptically honours an anonymous donor.[54] Taking a detailed look at the internal head skeleton of Tiktaalik roseae, in the October 16, 2008, issue of Nature,[55] researchers show how Tiktaalik was gaining structures that could allow it to support itself on solid ground and breathe air, a key intermediate step in the transformation of the skull that accompanied the shift to life on land by our distant ancestors.[56]
See also[edit]
Other lobe-finned fish found in fossils from the Devonian Period:
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