115 of 123 people found the following review helpful
Rich, textured and diverse overview.,
This review is from: What Evolution Is (Science Masters Series) (Hardcover)
This is a very good introductory overview of evolutionary theory, suitable for the enthusiastic novice, the educated skeptic, the qualified biologist, or for those who simply wish to know what has been going on in this fascinating field for the last 150 years and more of scientific enquiry.
The writer, Ernst Mayr, only recently passed away aged over 100, and had been through a good deal of this scientific development, and is therefore in a unique position to approach the subject. Jared Diamond (author of 'The Third Chimpanzee', 'Guns, Germs and Steel') describes the result: "there is no better book on evolution". Whilst a little skeptical of this hyperbole, I decided to check it out, and wasn't disappointed.
Discussions range from the philosphical (everything in this Earth seems to be in a state of flux" p7), to the palaeontological ("the older the strata in which a fossil is found...the more different the fossil will be from living relatives" p13-although see also the occassional stasis of the genotype on p278-79), to the embryonic (eg 'recapitulation'-an important point), to the modern discovery of 'transposable elements' (gene jumping and copying-p100). Important developments in the theory include the 'branching theory' of Darwin (p19), to the theory of common descent (p21), to discussions of biogeography (species distribution), molecular biology (including the molecular clock), to the formation of new genes by doubling and insertion, leading to diversification (p108-9). The reader will find all the scientific development and current investigations exhaustive, but (hopefully!) rarely exhausting.
The causes of speciation have come along way since Darwins 1859 Origin: allopatric,dichopatric, peripactic, sympatric (not found in mammals p180), instantaneous (chromosome doubling), parapatric, and hybridisation. Concepts to ponder over-in case of being caught out at parties.
The historical background of 19th century philosophy is introduced (for which modern day philosophy is a little embarrassed) including 'essentialism' (constant essence of species ie "a natural kind"-with variants either irrelevant or accidental), and 'finalism' (the belief that everything moves toward greater perfection -eg Kant, and others), as compared to Malthus', Wallace's and Darwin's 'population thinking' (the study of variation in populations-a crucial concept).
3 theories of evolution are based on essentialism -transmutationism (origin of new types by mutation or saltation), transformationism-gradual change to a new natural 'type' by the influence of the environment, including use and disuse or inheritance of acquired characters (ie Lamarckism), and orthogenesis-the propensity of the living world to move towards perfection (typified by Kant, amongst others). (There are querks possible in these examples-for example some transmutational theories may be non-essentialist- however these 'higher arguments' are sometimes over semantics as much as over concepts). 'Essentialism' was certainly one of the most significant ideological barriers to evolutionary thought, and still is today. (Some present day philosophers still seem obsessed by it-see 'Darwins Dangerous Idea' by Daniel Dennett for a good discussion of philosophical issues and debate).
Having little time for 'labels' I have never bothered with such labels as 'Darwinism', 'Neo-Darwinism' etc etc, but after reading this book, I found that my position is mostly that of 'Darwinism' anyway. (Some relief, I think, whatever 'Darwinism' may mean).
A good summary of 'Darwinism' is provided (p86):
1) non-constancy of species
2) descent from common ancestor
3) gradualness (but see also below for semantical distinction with punctuationism)
4) diversity (by species multiplication)
5) natural selection (but see also Baldwin Effect below).
These basic tenants have been thrown around and debated for over a century, but it is becoming increasingly obvious that most variants of these ideas amongst evolutionary debates, do not, in fact contradict these basic principles (eg punctuated equilibrium-page 270-"punctuated equilibria, which at first sight, seem to support saltationism and discontinuity, are in fact strictly populational phenomenon, and therefore gradual"). I'm not sure I agree with this point, although I can see the contention is at least partly semantical.
To get some flavour from the book, rather than from me, some veritable gems include:
"sweeping generalisations are rarely correct in evolutionary biology" p271.
"there is no justification in the widespread assumption that consciousness is a unique human property"
"Selection seems able to to recruit genes in new developmental processes that previously had seemed to have other functions" p113.
"Species are groups of interbredding natural populations that are reproductively isolated from other such groups" p166.
"An organism has to be well adapted as a whole, but it also must be able at all times to cope with its ancestral genome" p154.
"There is alot of structure in the genotype that cannot be discovered and explained by a purely reductionist approach" p145.
"Surely when a population suddenly encounters an extremely adverse situation, the more genetically diverse it is, the greater the chance that it contains genotypes that can better cope with the environmental demands" p105.
"some groups speciate profusely, whereas in others speciation seems to be a rare event" p271.
"most of the variation of genotypes available for natural selection in a population is a result of recombination, not of mutations" p280.
"biological causes and natural selection are dominant in background extinction, whereas physical factors and chance are dominant in mass extinction" p203.
"most new evolutionary lineages arise by budding rather than by splitting" p191.
"rate of speciation is apparently primarily determined by ecological factors" p186.
"Any behaviour that turns out to be of evolutionary significance is likely to be reinforced by the selection of genetic determinants for such behaviour" (eg the Baldwin Effect p137-a very important concept).
And my favourite-"the phenotype of the individual as a whole ..is the actual unit of selection" p126.
One final point -the final discussion of human evolution, and in particular, evolutionary aspects of human behaviour is understandably brief-that is for the present century to unravel!
A wellspring of clean, clear, refreshing information, for the thirsty soul.