Reticulate Evolution and Humans: Origins and Ecology

September 22nd, 2009 Leave a comment Go to comments

Arnold, ML. 2009. Reticulate Evolution and Humans: Origins and Ecology. Oxford University Press. 233 pp. ISBN 978-0-19-953958-1.


The primary goal of this book is to demonstrate the extent to which genetic exchange between divergent lineages has shaped the evolution of myriad organisms that are related to us, have coevolved with us, or simply share the world we live in.  A secondary goal revolves around the author’s argument that a similar pattern of reticulate evolution has shaped human prehistory, which he bases on evidence from analogy (e.g. the prevalence of this pattern in numerous primates), molecular biology, and the fossil record.  By design this human-centric book is broad in scope, and yet manages to remain fairly brief as a result of its form, which is a fairly methodical treatment of the issue that draws heavily from evidence in the current literature.  The first chapter introduces the reader to the concept of a web (rather than a tree) of life, focussing on classic studies animals, plants, and prokaryotes that have demonstrated the importance of reticulate evolution in structuring organismal diversity.  The next two chapters focus on examples of hybridization in both non-hominine (e.g. monkeys, lemurs, and lorises) and hominine (Pan, Gorilla, and Homo) primates, and include a brief discussion of evidence for reticulate evolution in Australopithecus.  With regards to the fossil record in particular, the author lists three possible pieces of evidence that reticulation has occurred: (1) mosaic morphology containing traits diagnostic for both the fossil species of interest and for another species with known temporal and geographic overlap; (2) intermediate/transitional phenotypes, (3) individuals with anomalous developmental patterning.  He explores these issues in the fourth chapter, focusing on evidence from the fossil record of the genus Homo, as well molecular and other evidence.  The next three chapters focus on beneficial organisms, including those utilised by humans as companions, burden bearers, fuel, clothing, and recreation (e.g. dogs, cats, donkeys, plant and animal materials used for clothing, for building, and for drugs); those utilized as animal foods (e.g. fish, birds, sheep, goats, cattle, antelope, pigs, rabbits) and plant foods (e.g. potato, wheat, rice, maize, apples, sugarcane); and those responsible for human disease (e.g. human disease vectors, pathogens, roundworms). The author concludes with a final brief chapter summarising his primary goal, and provocatively points out that understanding the degree to which genetic exchange has structured our world also has practical purposes, as it is essential both for conservation-related reasons (i.e. the importance of protecting hybrid lineages), and for controlling the spread of human disease and thereby mitigating against future human suffering.

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