Did human evolution proceed in an inevitable fashion? Can we attribute our origins solely to natural selection, or were more mischievous forces at work?

These are the questions investigated by anthropologist Jeff McKee. He argues that if we were to wind back the clock to our split from ancestral apes, evolution would proceed differently. Ever since our ancestors first stood up on two feet, natural selection undoubtedly was an important factor in guiding human evolution. But McKee shakes the standard notion that natural selection steered early hominids toward particular environmental adaptations. The fossil remains of our ancestors reveal a different story one of an adaptable hominid with no particular direction. It becomes clear that the evolutionary road to Homo sapiens was not paved solely by natural selection; indeed, there was no road to follow. There was just a dim path cut out by prehistoric coincidences and contingencies. Had any link in the evolutionary chain of events been slightly different, then our species would not be as it is today . . . or our ancestors may not have survived at all. 

With equal doses of humor and awe, McKee illustrates how the chain of evolution has been riddled by chance, coincidence, and chaos. He uses familiar examples, noting that many of us exist as individuals because of chance meetings of our parents. From the present back through prehistory, chance is at the heart of our creation is chaos. The classic example of chaos is the butterfly effect: a single butterfly, flapping its wings, causes a tiny change in the atmosphere, which in turn amplifies to affect the course of storms on another continent. McKee ties such examples of unpredictability to fossil evidence and computer simulations, revealing the natural coincidences that shaped our evolution. Although chaos exacted an evolutionary price by limiting the powers of natural selection, it also made us what we are. One can only conclude that human beings were neither inevitable nor probable.

 Are humans too good at adapting to the earth’s natural environment? Every day, there is a net gain of more than 200,000 people on the planet—that’s 146 a minute. Has our explosive population growth led to the mass extinction of countless species in the earth’s plant and animal communities?

Jeffrey K. McKee contends yes. The more people there are, the more we push aside wild plants and animals. In Sparing Nature, he explores the cause-and-effect relationship between these two trends, demonstrating that nature is too sparing to accommodate both a richly diverse living world and a rapidly expanding number of people. The author probes the past to find that humans and their ancestors have had negative impacts on species biodiversity for nearly two million years, and that extinction rates have accelerated since the origins of agriculture. Today entire ecosystems are in peril due to the relentless growth of the human population. McKee gives a guided tour of the interconnections within the living world to reveal the meaning and value of biodiversity, making the maze of technical research and scientific debates accessible to the general reader. Because it is clear that conservation cannot be left to the whims of changing human priorities, McKee takes the unabashedly neo-Malthusian position that the most effective measure to save earth’s biodiversity is to slow the growth of human populations. By conscientiously becoming more responsible about our reproductive habits and our impact on other living beings, we can ensure that nature’s services will make our lives not only supportable, but also sustainable for this century and beyond.