The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution

One of the most attractive features of Sean Carroll's book is that although he makes many of the same points as one can find in other popular books on biology and evolution he illustrates them with refreshingly different examples. He begins by describing the icefish of Antarctica, a living contradiction of the standard idea that all vertebrates have red blood cells in their blood for transporting oxygen to their tissues: although these fish are clearly vertebrates, they lack the haemoglobin that would make their blood red. At the very low temperatures at which they live, oxygen is much more soluble in haemoglobin-free water than it is at higher temperatures, and they can manage perfectly well without haemoglobin or, in some species, myoglobin, the haemoglobin-like protein responsible for the red colour of many muscles. Not only do they do not need haemoglobin as much as other fish, they gain a positive advantage from not having it because their blood is far less viscous than it would be if it contained a high concentration of dissolved haemoglobin. On the other hand fish that live in very cold water need to avoid freezing solid, and icefish have solved this problem as well, by evolving anti-freeze proteins that prevent their tissues from freezing. All this sets the scene for Carroll to explain how studying the DNA of icefish allows the biochemist to understand what has happened to the haemoglobin that their warmer-living ancestors had, and where the anti-freeze proteins have come from. The globin genes are still there, and still recognizable, but no longer functional. Later chapters discuss how mutations in DNA arise, and how these result in modifications to proteins, and from there to changes in function -- loss or modification of existing functions, such as colour vision and sensitivity to different odours, or the appearance of new ones. Humans, apes and most old-world monkeys have three-colour vision, for example, whereas most mammals have, at best, two-colour vision and are accordingly red-green colour-blind. On the other hand many birds and fish have four different colour receptors, and lampreys have five. Colour vision and olfactory sensitivity have tended to evolve in opposite directions: species that are mainly active in the day time tend to be strong in the former, and weak in the latter, and vice versa. Much of this is explained by the principle that functions that are not much used or not very necessary for survival tend to be lost, and one finds this illustrated in very diverse life forms. The bacteria responsible for tuberculosis and leprosy, for example, are closely related, but whereas one has retained nearly all of its ancestral genes in fully functional form, the other has lost a great many: being wholly parasitic, living only within host cells, it relies on its host for many biochemical functions that a free-living organism has to do for itself. Where do new functions come from, and what happens to genes for functions that

It's a sad commentary that any book on biology published in the US must devote pages and ink to refuting the rants of "anti-Darwinists" in that nation. Richard Dawkins ["The Selfish Gene"] holds a chair at promoting "Public Understanding of Science" at Oxford. Carroll, whose role as a professor of genetics provides firm underpinning, is establishing himself in a similar niche in the US. This book is an example of how well he can fulfill that undertaking. In his previous work "Endless Forms Most Beautiful", Carroll described some of the manifestations of the genome's activities. In this book he delves more into today's operations within the genome and how those were derived from the distant past. The author's selection of examples to explain DNA's role in life may seem bizarre at first glance: "icefish" carrying "anti-freeze" in their bodies, what humble pigeons tell us about life, and what human skin colour really means. Each of his examples carries an historical record of how they came to be that way. Evolution, he reminds us, builds upon what went before. Once a trait, no matter how "primitive", is established, mutation may improve its possibility of success down the generations. "Primitive", by the way, is a term Carroll shuns, since those traits that survive are clearly best suited for that organism in that time and place. It's important to understand that, since a good many health issues relying on genetic research must be considered in the light of environmental conditions. Infectious organisms change to cope with treatment and medicines must be developed to cope with their adaptations. This is the record of life, with the earliest genes bifurcating to form new traits with the passage of time and new conditions. Carroll's chapters address a number of life's little quirks. There's a discussion of how populations shift and divide when conditions change [stickleback fish], an account of the discovery and significance of "thermophilic" microbes found in Yellowstone Park hot springs, and how Soviet politics dabbled in science to virtually destroy agriculture in the communist empire. Every chapter contributes to learning how genetics works and why some understanding of the processes involved is important. For this reviewer, however, the author's presentation of the historical beginnings and development of eyes remains the most fascinating. Although Darwin was greatly disturbed that he couldn't conceive how eyes could have evolved, modern research has determined the process. In Carroll's hands, the mechanism producing eyes is clearly revealed and almost exquisitely explained. He shows how light perception across various species provides clues to past ocular structures. Once you have read this section, you will never be able to consider "the" eye [which is too often presumed to be human] in the same way again. The book's close, which Carroll clearly feels necessary, is somewhat depressing. Evolution shouldn't need defending -

There is a notorious book for creationists titled _Evolution: The Fossils Say No!_ It gets right to its point in its title which accomplishes two things. One is to claim that fossils do not say what overwhelmingly biologists and geologists say they say. The other is to emphasize that fossils are the chief evidence evolution can muster. That might have been true a hundred years ago, but now, even if we had no fossils to study, we would still have wonderfully abundant evidence of evolution happening and just how it happened. We can now look directly at the DNA in animals that have evolved from previous ancestors and see indubitable chains of linkage. Sean B. Carroll, a professor of genetics, relates the stories scientists are coaxing from the molecules of genes in _The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution_ (Norton). He points out in his preface that there is wide public acceptance and understanding of DNA testing in solving crimes; DNA can provide testimony about who was present at a crime scene with far more trustworthiness than fingerprints or eyewitness recollection. Yet polls consistently show that something like half of the public in the United States are more likely to go with the anti-Darwinian ideas in _Evolution: The Fossils Say No!_ than they are to subscribe to the theory of evolution. It is Carroll's aim to have readers consider the DNA evidence for evolution as strong as DNA evidence from crime scenes, and his clear and entertaining book does just that. "Every evolutionary change between species, from physical form to digestive metabolism," he writes, "is due to - and recorded in - DNA. So, too, is the 'paternity' of species. DNA contains, therefore, the ultimate forensic record of evolution." Carroll's book gives plenty of fascinating instances of evidence for that DNA record. He starts with a fish that has no red blood cells. Before it was found, biologists taught that all vertebrates had red blood cells containing the hemoglobin that carries oxygen, and when there were stories of fish without blood in the Antarctic, they were assumed to be just stories. But in 1954, biologists were amazed to read a report of the icefish, so called because it looks transparent; it has no red blood cells to block the light. There is no fossil record for these fishes, but the DNA is there, although it could only tell the story of the icefish's evolution forty years after their blood was first sampled. The DNA that codes for red blood cells in fish and the rest of us is there, but only partially, and in an eroded form that cannot work. One of the lessons Carroll consistently draws is that in evolution, there is a "use it or lose it" dictum. Genes change, even if mutation rates are low; if the change is deleterious, it might be that the organism is sufficiently wounded that it gets no chance to pass the gene on. It also might be that other genes make up for the change, and if so, the changed gene g

This is the story of Natural Selection, presented in a compelling, easy to follow, and well researched manner proponents of Theological Creationism and/or Darwinism Evolution will appreciate, and perhaps move closer to the much needed reconciliatory position of Church and Scientist. Author Sean B. Carroll is very clever in presenting fundamental movements in the change and alteration of DNA in a way that hopefully not be rebuked or rebuffed by creationist: by studying genetic alterations by presenting changes that occurred in microbes and animals such as antactic fish, colobus monkeys, and dolphins, Carroll allows the reader to easily understand this very strong, fundamentally sound position of DNA related genetic based evolution. Carroll easily but thoroughly explains that the DNA of a specific gene directly related to a specific trait, when altered as a result of natural selection, changes the original structure of the gene itself. When genetic duplicating occurs, the structures are never quit 100% the same, and so, natural selection's alterations begin. If the variant change is not adaptable or is not capable of survival, then the gene fades away, allowing for additional variants to take hold and sustain itself. In `The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution' by Sean B. Carroll readers interested in furthering their understanding regarding the rift between Creationism and Darwinism will find unquestionable scientific data that Carroll uses to support genetic enhanced Darwinism. Nevertheless, this is one good and fascinating read that all readers, regardless of your scientific background or not will really enjoy. For those of us interested in a more detailed understanding of Evolution, this is a must read. Well done.

Richard Dawkins wrote a very enjoyable book titled The Ancestors Tale. It traces our evolution backwards, from humans, through apes and monkeys and so on, back to simple one-celled organisms. It tells the who of evolution: which species were descended from which. The Making of the Fittest tells the how and why: how variations appear in organisms and why they survive, or don't. This is the story of natural selection. Darwin told the story, but a lot more has been learned since then, especially in recent decades, and Sean B. Carroll has been one of the discoverers. But, unlike many researchers, he can write a readable book for beginners. Carroll focuses on DNA because that's of prime importance. When DNA is copied, for the reproduction of the cell or the organism, the copy is not always exact. The new variant is usually harmful, but might be helpful. Carroll shows, using elementary arithmetic, why helpful variants occur and prosper much more often that most people would guess. Keep in mind that, when a bad gene does come along, the organism usually dies and the gene disappears from the pool. The good genes usually accumulate. Carroll tells the story mostly through examples. For example, we humans are descended from animals that could see only 2 colors. Carroll tells of the duplication of the gene for one of the colors and the mutation of the second copy to react to a third color. (I simplify; Carroll tells more of the story.) Duplication and subsequent mutation of genes is very important in evolution. It allows organisms to develop new capabilities without losing the old. Another important mechanism involves genes which control the expression of other genes. Even with no change in a given gene, a change that causes the gene to be expressed in a new place or at an additional stage in development can give rise to a new capability with no harm to the old. (Again I simplify.) Gene duplication, changes in gene expression, and other mutations leave traces in our DNA and these give clues to our ancestry. This fact explains the book's subtitle. More important to Carroll, these traces also demonstrate natural selection at work. To give a personal example, an examination of my genome would show that the gene which shuts off lactose digestion in adults had been knocked out by mutation; as a result, I have a source of nutrition that is not available to most humans. There's not much that one has to know to read this book. It probably helps to know that a gene is a segment of DNA and that the sequence of its bases determines the sequence of amino acids that makes up a protein. However, Carroll explains this. I haven't been a beginner for a few decades now, but I think Making of the Fittest will be accessible to a bright high-school. As elementary as it is, it still has information that is of interest to me. The most important concerns the evolution or the eye. (He doesn't indicate the value of a cup-shaped eye: the animal can