I just finished reading the latest book by Neil Shubin, Some Assembly Required. I thought it was a splendid book and, besides this recommendation, will offer a few comments. If you want a detailed synopsis of the book, I suggest the review by my colleague Paul Braterman on the blog 3 Quarks Daily. Some Assembly Required is a history of evolutionary biology from Darwin to the present, from fossils to DNA. Shubin takes a biographical or historical approach (or a biographical/historical approach) in much of the book, but his topic is largely an answer to the question famously posed by Darwin’s contemporary St. George Jackson Mivart: what would be the use, for example, of an incipient wing? How, for that matter, could a fish evolve fins for walking and lungs for breathing at the same time? As Shubin puts it,
If entire bodies have to change for any great transformation, and many features need to change simultaneously, then how could major transitions happen gradually?
That states the central problem of book, and Shubin spends the rest of his time solving it. The book is at root a science book, but sometimes it reads almost like a historical novel. I enjoyed the capsule biographies of many of the scientists, some of whom were familiar names and some of whom were not.
I was particularly interested in a segment about Linus Pauling and his colleague Emile Zuckerkandl. I found the chemistry somewhat hard to understand, particularly when Shubin referred to amino acid molecules as being charged (I understand now that they may have charged arms and of course they ionize in solution, but I still do not know precisely what charge was referred to). At any rate, Zuckerkandl, through a series of “connections,” not least a connection to Einstein, managed to escape Nazi Germany and ultimately to collaborate with Pauling, who was by then already well known. Pauling set Zuckerkandl to work on the proteins in hemoglobin. Zuckerkandl measured the mass and charge of various proteins and deduced that human hemoglobin was more closely related to ape hemoglobin than to frog or fish hemoglobin. He hypothesized that the similarity between human and ape hemoglobin was the result of evolution. Indeed, Pauling and Zuckerkandl inferred that “the more proteins of two species differed from each other, the longer the time those species have been evolving independently from a common ancestor.” If proteins evolved at a constant rate, then they could deduce when two species diverged; they had discovered the molecular clock, a concept that Shubin says was “utterly outrageous when it was first proposed[.]” The more I read, the more I wondered why I had never heard of Zuckerkandl.
If Zuckerkandl and his molecular clock were ignored, they were not alone. When Barbara McClintock enrolled in Cornell University, women were not allowed to major in genetics. Instead, she majored in horticulture and discovered her now-famous jumping genes in corn. Shubin shows that jumping genes are of critical importance for evolution, but no one paid attention when McClintock discovered them. Similarly, Lynn Margulis proposed that the organelles in eukaryotic cells were originally freely swimming bacteria or algae. According to Shubin, her paper received 15 rejections. Science eventually caught up with her, when it turned out that the DNA in mitochondria and chloroplasts was unrelated to the nuclear DNA of the cell itself. Francisco Mojica was likewise ignored when he discovered a mechanism that bacteria use to protect themselves against virus infections.
If you like salamanders and personal essays, you will love the chapter called “Loaded Dice” (I did). Shubin uses the concept of convergent evolution (a term he never actually uses) and shows that, for example, unrelated lizards on isolated islands develop similar morphologies and, as is more well-known, marsupials in Australia have evolved into marsupial wolves, flying squirrels, moles, and groundhogs, and even extinct lions, wolves, and saber-toothed tigers. He concludes,
The history of life is not wholly a crapshoot of contingent events. The dice are loaded by the ways genes and development build bodies, by the physical constraints of environments, and by history. In each generation, organisms have inherited recipes – written in their genes, cells, and embryos – to build organs and bodies. This inheritance … can make certain pathways of change more likely than others.
In other words, in Stephen Jay Gould’s terminology, if we replayed (actually, re-recorded) the tape of life, we would get the same result. Here, I think he did not convince me; he rewound the tape only to, roughly speaking, the extinction of the dinosaurs. From then on, I grant, even if the asteroid had never struck, creatures similar to those we see today may have evolved, though I am less certain about technological beings. But what if we wound the tape back to the time before some eukaryote assimilated an algal cell, and that event never happened? Creatures today, I daresay, would look very different. Shubin quotes Lillian Hellman, “Nothing, of course, begins at the time you think it did.” I think perhaps he did not apply her dictum rigorously enough to the question of contingency.
I was also rather taken by the story of Susumu Ohno, a musician who likes to translate the structure of proteins into concert pieces. Ohno photographed chromosomes of mammals from shrews to giraffes, cut them out, and compared the chromosomes of these diverse species. He noted that the numbers of chromosomes varied widely from species to species. Then he got the idea to weigh the paper cutouts and discovered that the total weight of the chromosomes of each species was the same.
Mostly, I thought that the science in the book was straightforward, and (apart from the discussion of amino acids) I understood it without difficulty. I was somewhat surprised when Shubin wrote that we have all descended from a sea squirt; surely that was too much of an oversimplification and he should have said common ancestor. In the same way, there was no need to avoid such terms as convergent evolution, exaptation, and maybe trace fossil; without those terms it might be hard for an inexperienced reader to seek further information. And, finally, I truly enjoyed the drawings by Kalliopi Monoyios; I thought some of them, however, such as the figures on pages 79 and 99, needed further explanation, possibly including labels.
The editor in me thought there were very few puzzling or infelicitous comments or sentences, but I stumbled over the statement that the Jurassic was named “for its distinctive features.” It was actually named after the Jura Mountain range in France. The story of how Archaeopteryx found its way into the British Museum was one of the more interesting anecdotes in the book, but I keep wondering who “the doctor” was. I would not have minded another figure here and there, as when he describes “the classic pattern of one bone, two bones, wrist bones, and digits.” Words like metamorphosis and development should have been defined, not to mention decidual stromal cell. A single, anodyne sentence regarding Linus Pauling and vitamin C seemed inadequate. Shubin’s use of the term “selfish gene” was not precisely the same as the definition used by Richard Dawkins, and I thought that Shubin might have made a comment to that effect.
I think that I will leave with the final paragraph, which you might consider the bottom line,
When you know how to look, you can see billions of years inside the organs, cells, and DNA in all living things and relish our connections to the rest of life on the planet.
Acknowledgment. Many thanks to the National Center for Science Education for providing a review copy of the book. NCSE is currently offering Some Assembly Required as a donation premium for donations of $100 or $10/month. In addition, John Harshman, Andrew Petto, Joe Felsenstein, Paul Braterman, Stephen Matheson, and Nick Matzke helped me understand a couple of murky concepts. If I still do not understand, it is not their fault.