The Emergence of Animals: The Cambrian Breakthrough

by Dianna L. Schulte McMenamin, Mark A.S. McMenamin, Dianna L.S. McMenamin, et al.

Book Overview

The authors explore the late Precambrian and earliest Cambrian fossil record to explain the Cambrian phenomenon and discuss the possibility of a major turnover in marine ecology at the beginning of the Cambrian period or whether a new, improved type of animal appeared at this time. They support their often controversial conclusions with photos and illustrations of fossils, some never before published.

• Format: Paperback
• Language: English
• ISBN: 0231066473
• ISBN13: 9780231066471
• Release Date: April 1990
• Publisher: Columbia University Press
• Length: 217 Pages
• Weight: 0.70 lbs.
• Dimensions: 0.6" x 5.9" x 8.9"

Customer Reviews

A little out of date but still very good

Although it's a little out of date now, The Emergence of Animals: the Cambrian Breakthrough by McMenamin and McMenamin is a very nice, easy to read overview of the PreCambrian-Cambrian diversification of animal populations. Both the Edicarian and the Burgess Shale fauna are discussed extensively as are stromatolites, as one would expect, since these are the primary fossil and trace fossil representations of the biota of the period. The limitations of this material, and the rarity of fossilization of animals without hard body parts is also pointed out to the reader. In particular, the difficulty of positively identifying remains of early life is pointed out by the primary author who himself misidentified a geological phenomenon for a biological one. The likelihood that there existed a long era of evolution prior to the apparent "explosion" in the Cambrian is discussed as is the chemical and geological evidence for such precursors. While the book by J. William Schopf, Cradle of Life : The Discovery of Earth's Earliest Fossils, is more current and goes into greater detail about the discovery of early life, what forms evidence takes, how it can be mistaken, what information is derived from study of the remains, and what indirect evidence tells us about the early earth, it might be a little too much information for those who are only casually interested in the topic of fossils. The McMenamin book might be a better place to begin, while the Schopf book would be a good follow-up for those who want more information.

Points to ponder about the emergence of animals on earth

In this book McMenamin and McMenamin set the stage and provide their thoughts about the emergence of animals on earth. Contents of the book include the following:1) The Cambrian explosion -- this section provides a brief introduction to the "explosion" of shelled animal fossils in Cambrian rock formations, following the Precambrian rocks that lack such fossils, and leaves off talking a bit about the Ediacaran fauna -- a fauna that is found in Precambrian rock strata.2) Aliens here on earth? -- this section deals with the issue of trace fossils vs body fossils, and continues discussing the relevance and significance of the Ediacaran fauna as evidence of Precambrian (animal?) life. The authors also provide a helpful overview of Ediacaran fauna including photos and illustrations of them.3) The mudeaters -- this section deals with psuedofossils (apparently disturbances in ancient mud/sediment layers), misidentifications of those as being fossils when they are not, etc. The authors then go on to discuss possibilities of animal life that were real makers or Precambrian trace fossils.4) Small shelly fossils -- this section presents ideas about the earliest assemblages of shelly fossils at the Precambrian - Cambrian boundary, including the "Tommotian fauna." 5) The golden spike -- this section addresses the process and uncertainty of identifying a definitive boundary marker that hails the beginning of the Cambrian era. (This is no small issue, and the beginning time mark of this era has shifted farther and farther back in time as we learn more about the history of life.)6) Rifting of Rodinia -- this section addresses the possibility that the emergence of animal life may well have been associated with a period of glaciation, as well as other pieces of evidence that help to unravel the sticky problem of describing the emergence of metazoan animal life.7) The garden of Ediacara -- this section addresses trophic strategies for acquiring energy and nutrients anomg early animal life on earth.8) Ecological feedback and intelligence -- this section addresses the effects of feedback mechanisms on the emergence of life. For example, the emergence of grazing herbivores led to the demise of previously ungrazed stromatolite beds...nothing had eaten them before. That consequently opened up more open space on the substrate, and in ecological and evolutionary space for other kinds of autotrophs to gain a toe-hold in new community structures. This section also addressed the significance of symmetrical animals bearing eyes and better developed nervous systems than ever before.9) Precambrian oxygen -- this section provides an overview of the development of an atmosphere on earth that is suitable for sustaining animals that rely on respiration. By the Cambrian, the atmosphere attained an O2 level of about 2%...apparently a critical level needed to sustain respiring life.10) Ecological chaos and innovation -- this section add