Human Evolution
A history of specific changes in the past 2.5 million years

Anthony Zimmerman
Book review
published in The National Catholic Bioethical Quarterly
Spring 2004
Reproduced with Permission

Ian Tattersall, The Monkey in the Mirror. Essays on the science of what makes us human, A Harvest Book, Harcourt, Inc., San Diego, New York, London, 2002, XIV + 205 pp. Index.

Tattersall's book is a happy combination of anthropological science and common sense observations, sans ideological preaching. Being curator of human evolution at the American Museum of Natural History, and a foremost researcher himself, he walks us through the science of his subject with easy stride.

The author, however, avoids specific mention of a human spiritual soul throughout the book. For many readers this may be a negative, depriving the book of insights that ought to be there.

There are eight loosely connected essays united in some fashion by the thread of their relevance to human evolution. Science and religion are not opposed, he observes.

The theory of evolution, which in essence is the notion that "all life forms are broadly descended form a single common ancestor" (p. 29), in no way threatens the basis of social morality and cohesion. The ready acceptance of evolution, now nearly universal, is largely due to the observance of the similarities in body structure among the multitude of species that populate the globe.

In the preface author Tattersall states that the book is at odds with beliefs of the 1960's that man's evolutionary history is a linear progression from primitive to modern, from imperfect to perfect, from Australopithecus to homo erectus to homo sapiens. Instead of linear gradualism he posits long periods of stasis without substantial changes, then saltations "out of the blue" of bodily changes that came upon the scene suddenly and fully formed. His explanation is innovative and plausible:

Schwartz suggests that new forms of these regulatory genes originate by the same mechanisms as other genes and thus they are most likely to arise in the recessive state. Each new individual receives two copies (alleles) of each gene, one from each parent. These alleles may be dominant, or they may be recessive. A dominant allele will be expressed in the individual even if only one copy of it is present; recessives require two copies to be expressed. Thus newly emerged recessives will remain "silent" in the population until there are enough of them in the gene pool to make it likely that both parents will pass them along. At this point the anatomies - potentially radically new in the case of homeoboxes - will appear abruptly in the population, with no prior warning. Here, then, is a mechanism whereby major anatomical novelties can suddenly arise within species. And once they are in place, of course, natural selection can take its course with them, whether positive or negative (p.47).

Hominid evolution has three major steps, 1) upright bipedal position at perhaps 4.4 million years ago, 2) tool making at 2.5 myr ago, and 3) the appearance of the modern body build seen in the Turkana Boy 1.6 myr ago.

The earth gradually changed much of its broad ring of tropical forest into savannah grasslands when it began to cool 5 myr ago. When Lucy the Australopithecine appeared 3.2 myr ago she walked upright, but her short body of 3.5 feet could hardly see over the tall savannah grass. Venturing far from home may have been difficult and dangerous. Her proportions were ape-like. We have no fossil body of a tool maker of 2.5 myr ago. The new body-build of the Turkana Boy of 1.6 million years ago was clearly a human form, and his size, which would have been at least six feet at adulthood, would enable his kind to stride over the grasslands and into other continents. Ice ages came and warming eras succeeded them, oscillating at intervals of 100,000 years. Consequent environmental changes influenced the directions of migrations. The homo sapiens body-build appears have arrived somewhat more than 100 kyr ago.

Neanderthals inhabited much of Europe from about 200 kyr to 27 kyr ago, At the latter date they disappeared completely. Anthropologists identify Neanderthals as a separate species from homo sapiens, being reproductively incompatible. Both species appear to have lived side by side in the Levantine from about 100 kyr to 40 kyr ago. They co-inhabited parts of Europe also from 40 kyr to 27 kyr ago. The author hints at violence on the part of the culturally superior homo sapiens. But I think that during those 13,000 years (!) there must have been periods of peace.

Cro-Magnon, a homo sapiens, came to Europe suddenly, fully developed as to modern body structure, and infinitely superior in culture over the Neanderthals. Where he came from is not well documented, but "modern morphology was established in some populations at least by about 100 kyr ago" (p.147). They may have developed in Africa.

The Cro-Magnons brought to Europe more or less "the entire panoply of behaviors that distinguishes modern humans from every other species that has ever existed" including sculpture, engraving, painting, human ornamentation, music, notation and other (p.140).

The author then moves into the area of human cognition and symbolism. We homo sapiens people mentally collect objects that we observe into a huge number of categories to which we attach names. By so separating the elements by names we are able to manipulate mental symbols that correspond to what we perceive within ourselves and beyond ourselves. "Of course intuitive reasoning still remains a fundamental component of our mental processes; what we have done is to add the capacity for symbolic manipulation to this basic ability" (p. 154).

It is here, I believe, that a dose of Plato-Aristotle-Thomas would clarify matters. What can the author's word "intuition" mean other than immaterial thought; and what can "separate elements to which we give a name" be other than universals, which we traditionally recognize as being spiritual and immaterial in nature. Perhaps the author recognizes immaterial realities here without wanting to name them, for political reasons.

Do read this book. It will help you to thank God for creating us via evolutionary pathways.