The decline and fall of the human empire Why our species is on the edge of extinction

Without drastic action, "Homo sapiens will disappear from the Earth within the next 10,000 years," according to this unpersuasive warning. Nature editor Gee (A (Very) Short History of Life on Earth) argues that modern humans' relatively limited genetic diversity combined with predicted population declines in most countries risks setting humans on a path toward extinction. He points out how Neanderthals' even narrower genetic diversity put them at an evolutionary disadvantage when competing for resources with Homo sapiens, forcing them to either mate with sapiens or die out. Unfortunately, Gee's solution for humanity to avoid a similar fate by establishing space colonies defies logic. According to Gee, the isolation of space would aid humanity's survival by producing genetically distinct subpopulations that can interbreed with groups on Earth or elsewhere in space to create offspring with the best traits of both communities, in a similar fashion to what happened after Homo erectus diversified into Neanderthals, Homo sapiens, and other human species more than 315,000 years ago. However, this argument is severely undermined by Gee's discussion of how isolated breeding pools risk concentrating genetic deficiencies and vulnerability to disease, natural disasters, and other mass casualty events, as befell the Neanderthals. This strains credulity.Agent: Jill Grinberg, Grinberg Literary Management. (Mar.)

A wide-ranging look at the human past and the possibility of our species' extinction. Gee, an author and a senior editor atNature magazine, begins his book with a survey of human evolution, emphasizing the fact that humanity is the sole survivor of a number of hominid species. Our cousins include the Neanderthals, the Denisovans, and several other species, some of whom our ancestors interbred with before driving them to extinction. Moreover, we have gone through several population bottlenecks, resulting in a lack of genetic diversity--Gee says that a single tribe of chimpanzees has more genetic diversity than the entire human race. This affects, for example, our susceptibility to inherited and epidemic diseases. Another factor in our vulnerability is our dependence on agriculture, which has allowed our population to grow dramatically but also makes us highly dependent on an extremely narrow range of food sources. The Irish potato famine is just one example of what can go wrong. The "Green Revolution" that began in the 1960s increased the productivity of food crops, but at the same time it spurred an even greater surge in the number of people consuming those crops. Recently, however, there has been a drop in fertility--partly a result of more women becoming educated and deciding to opt out of motherhood. Is this a harbinger of a drastic worldwide drop in population? Is extinction--ultimately the fate of all species--closer than we suspect? The author suggests that one way, possibly the only way, to avoid short-term extinction is for humanity to expand beyond the single planet it has so far called home. Gee takes a surprisingly lighthearted approach, with frequent quips and allusions to pop culture. Given the seriousness of the subject, this makes for a more enjoyable read than one might expect. A serious but nonetheless entertaining look at the human race's long-term prospects. Copyright (c) Kirkus Reviews, used with permission.