Customer Reviews

The Human Fossil Record, Brain Endocasts: The Paleoneurological Evidence, Volume 3

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The Human Fossil Record Brain Endocasts--The Paleoneurological Evidence, Volume 3 is an overwhelmingly comprehensive source for paleoneurological methods and existing cranial fossil evidence. The extreme specialization of the content presented itself as an extended journal article rather than a textbook. However, Holloway, Broadfield and Yuan use language that is both scientific and technical yet accessible to those who are not familiar with the field, making it very pleasing to read. What follows should give the purchaser an excellent idea of what to expect while reading this book by providing key excerpts that illustrate the strong writing style as well as thorough and balanced analysis by the authors.

"For brain size in [primate] species, we regard the correlation, however crude, with behavior to be self-evident. We also tend to believe that organs that vary in size and that have some relationship to behavior follow a Darwinian evolutionary model. Indeed, this is basically how we tend to view our own braininess, that our brains became larger, and our larger brain sizes were selected for as we evolved because we were capable of more complex and intelligent behavior." -- This statement would lead the reader to believe that there is a positive correlation between increasing brain size and increasing intelligence. The authors rebuke this idea, however, by illustrating that extant Homo sapiens have brains that vary from 900-2000 grams without any noticeable impacts on intelligence and make criticisms of those who believe that a difference of 50 grams in brain volume between ancestral species correlates directly to an increase in brain function. What the authors do support is that differences in brain size across generations do serve as a way to quantify natural selection. This serves as an excellent example of how the authors remain relatively unbiased by analyzing information from many different points of view and siding with the consensus opinion of experts in the field before moving forward with analysis of endocasts.

"[W]e believe that the judicious use of brain endocasts can enlarge our understanding of the course of hominid brain evolution as they reveal that changes in size, both absolute and relative, and reorganization, including asymmetries, were important evolutionary developments at different times during human mosaic brain evolution." -- The authors reach this conclusion after much deliberation about what fossil evidence can and cannot be considered when evaluating endocasts. Besides introducing the main purpose of the book (to concurrently illustrate the known findings in the field of paleoneurology), the authors' conclusion summarizes the entire field of paleoneurology very well.

"The petalias most likely represent slightly different velocities of growth of the two cerebral hemispheres, with two regions in particular appearing to be affected: (1) the occipital lobe in both its posterior projection and width and (2) the frontal lobe in terms of its width. In general, when there is a combination of both left-occipital projection and right frontal width, the growth torque is correlated highly (ca. 90%) with right handedness." -- One of the most dominant form of paleoneurological evidence is the presence or absence of petalias, or hemispherical asymmetries, which are largely present in extant Homo sapiens brain endocasts as well as ancestral hominid species. Petalias arise due to hemispherical dominance (as is seen with handedness) and are not often seen or to such an extent in pongid species as in hominid species. The authors make this inference to illustrate how petalias may be an invaluable form of evidence for analyzing cognitive function of ancestral species and may be the only indication that any extinct species began to develop culturally. Never-the-less, the authors are still undecided about how reliable the identification of petalias in brain endocasts are and warn that an apparent petalia may in fact be an artifact of an unknown cause. In this case, the authors feel that more research is needed before a definitive statement can be made about the importance of petalias in the fossil record, showing great responsibility by restraining from assumptions that would be very easy to make.

The majority of the book is dedicated to the critical analysis of cranial fossils from around the Pleistocene era (denoted early human) as well as those found in specific geographical areas (Asia, Africa and Europe). Each brain endocast is analyzed according to the quality of the cranial fossil, the method for attaining its volume, surface descriptions of the brain endocast, quantitative data about regional size and the significance each cranial fossil exhibits in regards to the field of paleoneurology and paleontology as a whole.

Meningeal vasculature is addressed later in the book and confronts the notion that greater vasculature corresponds to greater cultural development. Evidence among African, Asian and European hominid fossils very clearly demonstrates an increase in vasculature that relates to an increase with culture. Neanderthal, however, shows a decline in vasculature with an increase in culture, which is counter-intuitive when examined with other fossil evidence. The presentation of these findings further supports the authors' point of view that all paleoneurological evidence must be taken with a grain of salt and only inferences can be made about human brain evolution.

On the whole, this book avoids making broad sweeping statements about human brain evolution, choosing instead to present the evidence, several plausible theories, the suggestion that the correct answer isn't yet available, and letting the reader decide for themselves what the evidence means.

To anyone considering the purchase of this book, $320 is a small price to pay to substantially increase your knowledge about this subset of paleontology and is comparable, even competitive, to what you would have to pay to have the same information taught to you at a university. It is an especially interesting read for those interested in history or science (the crossroads of which is paleontology) and will introduce you to a new perspective for analyzing present evidence in either field. By the time you are finished with the book, the authors will have presented you with a large amount of information and data that is known about human brain evolution, but a majority of the work in deciding what the evidence implies is left up to you.