At the Water's Edge : Fish with Fingers, Whales with Legs, and How Life Came Ashore but Then Went Back to Sea

This is the first book I have read by Carl Zimmer, so I didn't know what to expect. When I first read the title and thought about the subject matter, I assumed this book would be somewhat drab to me. To the contrary, I found Zimmer's coverage of the subject quite interesting, and I was pleasantly surprised by his thorough coverage of this subject. But let's face it, the transition from water to land, and back again in some cases, are really pivotal periods in evolutionary history. It is important to have a grasp on what exactly happened here. If that is of any significance to you, Carl Zimmer has done a brilliant job of explaining the history.Zimmer takes us on a remarkable journey through time attempting to piece together the available evidence to make sense of the transition of life from water to land. In chapter two, he introduces a concept known as exaptation, which captures the idea of an evolutionary adaptation that is later co-opted for different use later on. It seems likely that many functions employed by the land-based tetrapods may have been in development long before they began their adventures on land. I enjoyed the detailed explanation of the development of limbs and hands in chapter three; I thought this material was well presented. For example, Pere Alberch and Neil Shubin noticed a sequence in the development of limbs - each one formed by the same short chain of events. They could actually sketch out the growth with a set of symbols, delineating the development of a limb like a sentence. This came to be called the homology of growth. It explains why you never see triple thighs or other such anomalies; the branching rules just don't allow for it. In chapter four, yet another powerful concept is introduced - correlated progression, where change in one character (feature or attribute of an organism) may influence change in another, such that the rate of change of the two characters is not independent. He continues on with an explanation of lung evolution and the development of amniotes.From chapter five on, the discussion turns to the cetaceans (large aquatic mammals such as dolphins and whales). Evidence indicates that these creatures actually descended from land animals. Zimmer provides an in-depth analysis of the evolutionary history of the whale from the early Archaeocetes (meaning ancient whales) such as Pakicetus to the present day cetaceans.When reading this book, one must keep in mind that it was written in 1998. Today, in 2012, we have fourteen years of additional research and advances that change the picture somewhat. Zimmer alluded to these future developments in chapter nine when describing the conflict in findings between the fossil record and the emerging field of molecular phylogeny (the craft of building gene trees) at that time. Whales were thought to have descended from the mesonychians, an extinct group of hoofed carnivores. However, evidence since then, and the emerging genetic data of that time indicate a relationship to the artiodactyls instead. Nevertheless, there is such a wealth of historical data presented that it is still definitely worth the read.

At The Water's Edge is about about the evolution of large and important changes in species; Zimmer focuses on change in habitat, the move from sea to land, and then back to sea.Zimmer begins by describing different fish lineages and concentrates on the branch that leads to our own chordate subphylum, the tetrapods. How and why did legs evolve? How did our left and right walking motion appear? Zimmer reveals a surprising answer. Tetrapods, legs, and walking did not evolve to help fish survive on land; they evolved to help fish swim in shallow swampy river deltas at the ocean's edge. These features allow fish to move more efficiently among the river plants and to sneak up on prey more easily. Once the left right motion was established, it was easy for fins to strengthen. At some point there came a need to move from puddle to puddle, or perhaps to escape predators, or to lie in wait out of the water. Strong alternating fins, which had evolved in a purely aquatic environment, were ideally suited to these new tasks.To emphasize this original unplanned use of an existing feature, Zimmer uses Stephen Jay Gould's strange neologism "exaptation" rather than a more familiar term like pre-adaption. Zimmer prefers exaptation because pre-adaptation somehow implies that the final use of a thing was planned from the beginning. Zimmer emphasizes that it was not.Once he's done with how tetrapods appeared and then came to land, Zimmer makes an about face and returns to the seafollowing whales and dolphins. Here too we find surprises. Early whale ancestors probably behaved like crocodiles and alligators. They would stay in the water with only their eyes and nose protruding, waiting for a land based prey to come close. Later, Zimmer describes echolocation, one of the most complex and useful features of cetaceans. Dolphins and many whales have a superb sonar system that works by echoing clicks out and back in through a fat-filled cavity in their forehead called the melon. The melon acts as a sound lends letting dolphins "see" small objects hundreds of feet away. How can such a useful and complex organ evolve? The current hypothesis is that the melon's first function in early whales was simply to block the nasal passage during deep dives, to keep water out. Once it existed, it probably provided very rudimentary echolocation which gave natural selection something to work with. Another exaptation.Another topic Zimmer touches often is cladism, which is the sorting of species into a genealogical table by identifying key features. Features common to a group of species can imply a common ancestor even if we haven't found any trace of the ancestor itself. Two cladistic schools are at this moment fighting it out: the biological and morphological school one side, and the genetic school on the other. The schools often arrive at different conclusions. The strength of the biological school is that its discoveries are practical; key features mean something concrete like a backbone (chordates) or a melon (dolphins and many whales). However, key features are very difficult to identify. Genes on the other hand are easy to identify and to compare among different species. Also, there's a mechanical logic to genes that readily lends itself to cladistic sorting. However, genes often don't mean anything, i.e. have no effect on how the organism works, and they can mutate at random, appearing and disappearing for no reason. Each camp will probably have to find a way to learn from the other.Charles Darwin famously called his Origin of Species "one long argument", by which he sought to establish Natural Selection as the main means of evolution. You might take Zimmer's book as one short argument to establish exaptations and cladism as the main engines of macroevolution.

Carl Zimmer brings the organizational skills of an experienced journalist and surprising literary talents to present an exquisite, up to date, narrative on the evolution of tetrapods, emerging from the water as amphibians and returning as cetaceans. In this book, he reports on the latest fossil discoveries, the prominent scientific researchers and the direction of their scientific analysis with style, and more importantly, great clarity. Some portions of At the Water's Edge are not easy for armchair paleo-buffs to comprehend, but Zimmer does an admirable job explaining the function of mesenchyme cells and hox genes. What I enjoyed most about this book, was the way Zimmer follows the trail of scientific discovery, documenting every bit of evidence, like a well-tuned detective novel. It's a compelling tale of interaction between paleontologist, geneticists, geologists and embryologists over many years. New fossil specimens demand a reworking of the evolutionary chronology. Our knowledge about the origins of tetrapods, our ancestral forbearers, is enhanced through the process of discovery. What I enjoyed most about Zimmer's work is the sense of objectivity and balance that comes from the third party perspective of a journalist. While Gould, Eldredge, Conway-Morris, Fortey and Bakker provide paleophiles books of great personal insight and passion, At the Water's Edge is completely satisfying in it's precise reportage. This is Zimmer's first book... I hope he's started another!

Brilliant - read it twice.

Fundamental aspects of our becoming human, in its historic context , written in an easily understood and exciting manner.

Hi, also ich Studiere Biologie und während der einen Vorlesung hatuns unser Professor ein Paar Bücher vorgestellt, die es sehr interessantfand.Dieses war eines davon und ich bin sehr froh, dass ich es mir gekauft habe.Es geht darum, wie Lebewesen aus dem Wasser auf das Land gegangen sindund wie andere Landlebewesen sich wieder dem Wasser angepasst haben.Vielleicht kommt es einem am Anfang, wenn man den Klappentext ließt und sich dasCover anschaut sehr wissenschaftlich rüber, aber das schöne an diesem Buch ist, dasses wie eine Geschichte, also wie ein Roman erzählt wird.Viele wissenschaftliche Aspekte und informationen werden sprachlich sehr schön verknüpftund es macht einem wirklich Spaß es zu lesen. Man fühlt sich nicht überhäuft von Fakten,vielmehr ist es eine sehr spielerische Art und Weise, an den Inhalt ranzugehen.(Bsp: Am Anfang erzählt er wie er Tauchen war und beschreibt seine Gefühle und Eindrücke,wie sich das Gewicht der Sauerstoffflasche auf seinem Rücken anfühlt, Wie die Luftblasen nachoben Steigen, wie er einen "Yellowfish" beobachtet und plötzlich ein anderes tier vorbeischwimmtund er zusammen mit dem "Yellowfish" dem Tier hinterher schaut...)Ich habe mir das buch auf Englisch gekauft und es ließt sich wirklich sehr gut! Also wer nur in derSchule Englisch hatte, wird keine Probleme haben.Ich finde das fast alle, die in diesem Themenbereich interessiert sind, dieses Buch lesen können. Es ist reich anwissenschaftlichen Aspekten aber sehr locker geschrieben und auch Unterhaltsam.Meiner Meinung nach, also sehr empfehlenswert.

Von den ersten Mikroben über die Fische bis hin zum Menschen. Die epische Geschichte des Lebens auf der Erde, anschaulich geschrieben. Das Buch zeigt den Werdegang des Lebens von bescheidenen Anfängen bis zur heutigen Formenvielfalt, die Verwandtschaftsbeziehungen der Arten und die gemeinsamen Vorfahren. Sicherlich nichts für religiöse Zweifler, denn ein Schöpfer wird nicht benötigt. Wer sich aber auf Naturwissenschaften und deren Erkenntnisse (samt eindeutiger Belege) einlassen kann, der wird mit diesem Buch reich belohnt.

I have read a couple of books about evolution so far. Even though I have some basic understanding, my knowledge wasn't enough to always fully understand the biological descriptions. Carl Zimmer focuses on a special topic in macroevolution and that's why it is difficult to follow him if one doesn't have a solid understanding of the matter. Furthermore he provides extensive background information on the scientists he is referring to in his books which bored me at times. Nevertheless, I have learned a lot from this, even though I have skipped two chapters.