Some Assembly Required
Decoding Four Billion Years || Life From Ancient Fossils to DNA
In the prologue, Neil Shubin, author of the instant classic, Your Inner Fish tells us,
“Decades spent cracking rocks have changed the way I see living things. If you know how to look, scientific research becomes a global treasure hunt for fossils of fish with arms, snakes with legs, and apes that can walk upright, all ancient creatures that tell about important moments in the history of life. In Your Inner Fish, I described how planning and luck led my colleagues and me to find Tiktaalik roseate… a fish with a neck, elbows and wrists. This creature bridged the gap between life in the water and life on land, to reveal the important moment when our distant ancestors were fish. For almost two centuries, discoveries like these have told us how evolution happens, how bodies are built and how they came into being.
“This revolution has brought us to a remarkable moment. Rocks and fossils, when coupled with DNA technology, have the power to probe some of the classic questions that Darwin and his contemporaries struggled with. New experiments reveal a multi billion year history filled with cooperation, repurposing competition, theft and war. And that is just what happens inside DNA itself. With viruses continually infecting, and its own parts at war with one another, the genome within each animal cell roils as it does its work in generation after generation. The outcome of this dynamism has been new organs and tissues, biological innovations that have changed the world.
“The history of life has been a long, strange, and wondrous trip of trial and error, chance and inevitability, detours, revolution and inventions. That path, and the way we have come to know it, is the story of this book.”
With incredible detail and narrative flair Shubin chronicles how recently researchers at Cornell University revisited Darwin’s comparison of swim bladder to lungs, using new genetic techniques. They asked: What genes help build swim bladder during development? In looking at the catalogue of genes that are active in fish embryos they found something that would please Darwin. The genes that are used to build swim bladders are the same ones used to make lungs in both fish and people. Having an air sac is common to virtually all fish, some use them as lungs, while others use them as buoyancy devices.
Shubin notes, “lungs weren’t some invention that abruptly came about as creatures evolved to walk. Fish were breathing air with lungs well before animals ever stepped onto terra firma. The invasion of land by descendants of fish did not originate a new organ — it changed the function of an organ that already existed… The change did not involve the origin of a new organ: instead the transformation was, as Darwin said more generally (and ‘presciently’) — accompanied by a change of function.
“The not-so-hidden secret is that biological innovation never came aboard during the great transition they are associated with. Feathers did not arise during the evolution of flight, nor did lungs, and limbs originate during the transition to land: What’s more these great revolutions in the history of life, and others like them could never have happened otherwise. Major changes in the history of life didn’t have to wait for the simultaneous origin of many inventions. Massive changes came about by repurposing ancient structures for new ones. Innovations have antecedents that extend deep in time, nothing ever begins when you think it does.
“This is the story of revolution by evolution. Change in the history of life follows a twisted path, filled with detours, dead ends, and inventions that failed only because they arose at the wrong time. Darwin’s five words (by a change of function), arguing that much of invention happens by a change of function of promising features, paved the way for our understanding of the origins of organs, proteins, even our DNA.
“But the bodies of fish, dinosaurs and people don’t emerge fully formed at conception. They are built anew in each generation by a recipe transmitted from parent to offspring. The mother of invention lies inside these recipes and in how, as Darwin foresaw; they could arise in one context and, as we’ll see, become repurposed in another.”
In a wonderful chapter, Embryonic Ideas, Shubin tells us how “Von Baer‘s observations about the similarity of early-stage embryos of different species caught Darwin’s eye… to Darwin’s eye the fact that creatures such as fish, frogs, and people had a common starting point means they shared a common history. What could be better evidence for the common embryonic stages in development from which they sprang?
And after a stunning tour of some of the latest embryonic ideas, there is this summarizing paragraph, “Living things do not inherit skulls, backbones, or cell layers from their ancestors — they inherit the processes to build them much like a family recipe passed along and modified during each generation, the information that builds bodies has continually changed over millions of years as ancestors pass it on to descendants. Unlike a recipe used in a kitchen, the one that builds bodies anew in each generation is written not in words, but in DNA. To understand biological recipes, then, we need to learn to read a whole new language and see new kinds of antecedents in the history of life.
With wonderful detail, Shubin shows how with the publication of On the Origin of Species, Darwin transformed the study of developmental anomalies. To Darwin, if the motor for evolution is natural selection, then variation among individuals is the fuel.
“If individuals in a species vary in having traits that look and function differently, and some of those traits enhance the success of those individuals in a particular environment, then over time, those creatures and traits should increase. If a trait is harmful, then it will diminish over time: The essence of evolution is variation among individuals. If all individuals in a population are exactly alike, evolution by natural selection could never happen… The difference among individuals is evolution’s raw material for natural selection; the more variation the faster evolution could work. Only with a rich supply of variations… could natural selection lead to major changes over time.”
Shubin concludes, “from a common toolkit come the many branches of the tree of life.”
Over and over again, from many perspectives Neil Shubin masterfully shows how modifying, redeploying or co-opting ancient genes provides fuel for evolutionary change:
He concludes:
“Genetic recipes do not need to arise from scratch to make new organs in bodies. Existing genes and networks of them can be pulled off the shelf and modified to make remarkably new things. Using the old to make the new extends to every level of the history of life, even to the invention of new genes themselves.”
And finally, “Today we are doing science we could not have dreamed of only a few decades ago. Like the history of life, scientific discovery is full of unexpected twists, turns, dead ends, and opportunities that change the way we see the world around us. The ideas we use to probe nature’s diversity are themselves repurposed and modified from those over predecessors developed decades, if not centuries ago.
The View From Behind the Couch
Your Inner Fish was one of the most remarkable science books of the past twenty years. It chronicled the astonishing story of how a handful of dedicated scientists found the fossil (tiktaalik) which was the first amphibian ever found. It revolutionized paleontology and catapulted (justifiably) Neil Shubin to world fame: His third book, Some Assembly Required, carries the story forward while deeply enriching it. Neil Shubin is a master science communicator, and a wonderful writer, in a class with Sean Carroll (who recently interviewed Neil Shubin on his popular podcast). I enthusiastically recommend his new book to everyone.
Gerald Alper
Author
Portrait of The Artist as a Young Patient
Psychodynamic Studies of the Creative Personality
His new book is
God and Therapy
What We Believe When No One is Watching
