Robert Wright’s new book, “The Evolution of God,” is ambitious and erudite. He’s read an enormous amount of biblical and Koranic scholarship, and summarizes it in often fascinating detail. His assiduous labors into the origins of the idea of God have erected a colossal edifice. In the last 50 pages or so, Wright tosses an undersized and feeble theory over its parapets to justify all this effort. Though it’s sure to stimulate a lot of discussion, this is a thoroughly wrongheaded book.

Here’s a summary of the theory Wright offers. Human beings, he writes, “are ‘designed’ by natural selection to be good out of obligations to others, for fear of the disapproval of others, in pursuit of the esteem of others.” Cultural evolution — the passage of human groups from small bands of hunter-gatherers to chiefdoms and then on to states and empires — builds on the ingredients of this “design” to create a moral economy, which leads to the discovery of “moral truths,” which are sanctioned in religious organizations as the orders of gods, or, ultimately, of God, the all-knowing, law-giving, all-powerful Being.

“If history naturally pushes people toward moral improvement, toward moral truth, and their God, as they conceive their God, grows accordingly, becoming morally richer, then maybe the growth is evidence of some higher purpose, and maybe — conceivably — the source of that purpose is worthy of the name divinity.”

There are a lot of assumptions in that sentence, but the most powerful one for Wright’s argument is the assertion that “history naturally pushes people toward moral improvement.” Is this the moral improvement that after 5,000 or so years of Western religion gave us Nazism? Wright’s arguments are silent on this question, because they have already asserted the answer — that as a species we’re somehow morally superior now to our ancestors wandering out of Africa. How do we know? Because we have found the idea of God. This is tautology, not proof.

Wright’s a smart guy, so he knows he’s on the horns of a dilemma with this theory. Objections come from two directions. First, nothing he writes will have any effect on true believers, who accept the prophetic revelations of their respective Abrahamic faiths (Judaism, Christianity, Islam) as divine gifts conveyed directly to His people by an omniscient creator God. I believe Wright’s account of monotheism’s evolution is correct historically, but evangelical minister Rick Warren won’t buy what he’s selling, let alone the Muslim Brotherhood. He’s trying to pick up a prophet’s staff, but it’s heavy lifting.

Wright shows how the beliefs espoused in the Abrahamic religious texts evolved in the caldron of ancient power struggles. This is not a new idea — it goes back to 19th-century scholarship. There were, likewise, lots of charismatic leaders around the time of Jesus claiming to be the Messiah, and competing candidates, such as the Egyptian god Osiris, offering a road to eternal salvation. Wright shows how early Christianity borrowed from pagan beliefs and advocated religious tolerance in order to carve our space within Roman society. Again, nothing new here.

Wright doesn’t presume to speak about the veracity of any particular religious beliefs but instead claims interest only in how the evolution of these beliefs reflects something fundamental about human history. But he does assert that we are somehow better off with what monotheistic religion teaches — as the inheritors, that is, of “moral imagination” and the notion of toleration — even if the ultimate source of that legacy is biological rather than divine.

Wright’s favorite notion is the contrast between zero-sum and nonzero sum games, which is the explanatory shotgun he aims at every issue. (He’s also written a book entitled “Nonzero: The Logic of Human Destiny” — his use of the notion of “destiny” another example of his contrarian view about “purposeful” evolution.) In a nonzero sum game, all players benefit from cooperation and toleration. The global economy (when it’s working) is a nonzero sum game. When a consumer in Portland buys shoes made in China, we are not diminishing China’s economy but contributing to it, even as we get a great deal on footwear.

In the ancient world, the evolution of the idea of God vacillated between periods of conflict and cooperation, segueing between nonzero and zero-sum situations. Insofar as religion and the idea of God contribute to a nonzero sum polity, this evolution is, in Wright’s term, “progressive.”

The second strain in Wright’s argument has to do with this belief in purpose and progress in human history. Natural selection may have equipped us for “moral” action, but it doesn’t mean there is any larger purpose for our intelligence. Our brains and our intelligence are not a “better” adaptation to the planet than a dolphin’s sonar — they just get us through the world in a different way. But Wright doesn’t see things so modestly from the human perspective.

Perhaps more tellingly, there is nothing in his argument to convince anyone that the moral acuity of a citizen of a modern nonzero sum polity is superior to that of a hunter-gatherer. Imagine a Pacific Islander, or an Amazonian, living in a rainforest with no knowledge of the biblical God, and put in front of him or her evidence of the Holocaust, and ask: Was this right? What answer would you expect? And weren’t those perpetrators the inheritors of that “moral imagination”?

Wright insists nonetheless that there is a “moral order in the universe,” contrary to what scientists such as the Nobel Prize-winning physicist Steven Weinberg think. Wright believes that this moral order has evolved as “religion.” In Wright’s view, and contrary to the anti-teleological view of the majority of scientists, evolution shows “purpose,” in that animals, from simple to complex, try to eat, try to breath, try to reproduce — they exhibit, he insists, purposeful (rather than merely instinctual) behavior. And within this context, evolution, whether biological or cultural, according to Wright, has a “design,” if not a “designer.” We’re headed somewhere, and in Wright’s view it’s a better place — unless, of course, we screw it up.

Wright’s heroic efforts to find a place for the religious impulse within a scientific worldview is not convincing. Understanding that human beings evolved in a random — that is, not purposeful — way through the working of natural processes of selection that apply to all creatures is sufficiently humbling, and yokes our existence to that of all the other struggling species with whom we share the planet. The Buddha somehow knew that, without Darwin to guide him, and without needing a divinity to tell him it was true.

THE EVOLUTION OF GOD
Robert Wright
Little, Brown and Co.
$25.99, 576 pages