Many biologists beg to differ: Evolution isn't completely random, they say, and neither is it geared to produce humans.
The pope's words raise the question: Are Catholicism and evolution in conflict?
Several prominent Catholic scientists said their religion was perfectly compatible with science, and the only apparent problem in the homily came from the way the pope mischaracterized evolution as random. Far from being haphazard, natural selection imposes order on the natural world, as do the laws of physics and chemistry.
If the pope knew biology as well as he does theology, he'd be well within scientific consensus, said Brown University biologist Ken Miller, who is Catholic. "The pope needs a science adviser."
Others say statements in the homily reflect a long-standing schism between science and the Catholic faith.
Catholicism let go of the idea that the Earth is the center of the universe and accepts that evolution happened, but it still views mankind as having a special place in the cosmos, shaped partly by evolution and partly by the divine endowment of a soul. The Catholic scientists also see mankind - or some rational being - as part of the purpose of evolution.
Catholics "cannot accept evolution as we scientists accept it - as an unguided, materialistic process with no goal or direction," said University of Chicago biologist Jerry Coyne, who writes about science and religion in his blog, "Why Evolution Is True."
All agree there is order and majesty in nature. But they disagree over how it got here.
Many religious people see life as a symphony, all the notes carefully written by a divine composer. Nonreligious scientists see it more as an improvisational riff - or a comedy improv - with creativity emerging organically from within, free of any outside scriptwriter.
And like any improv act, chance comes into play. The late paleontologist Stephen Jay Gould wrote that if the clock were wound back to the age of the dinosaurs and evolution was again allowed to take its course, the process would lead to a completely different mix of living things - a mix unlikely to include us.
Some Catholic scientists, such as University of Pennsylvania paleontologist Peter Dodson, say Gould may be right. "Perhaps we'd get intelligent penguins" the second time around, he said.
Dodson points out that the previous pope, John Paul II, was clear that when talking about the human body, we should listen to science. Catholicism, he said, deals more with the spiritual part of man's existence.
Or, as Brown's Miller puts it, "What makes us truly special is our ability to reason."
Miller acted as an expert witness for those opposing the teaching of creationism in the famous 2005 Dover, Pa. trial. There, the form of creationism at stake wasn't a literal interpretation of the Adam and Eve story, but so-called Intelligent Design (ID).
ID proponents concede that evolution happened but argue that certain biological structures are too complex to have arisen without the intervention of an "intelligent designer." One often-cited such example is the flagellum - a taillike projection that certain bacteria use to propel themselves.
Miller says he rejects the ID position because it makes erroneous claims about biology. Evolution, he said, explains many of the structures that ID theory cites as proof of a "designer's" intervention," including the flagellum.
And in Catholicism, he said, God wouldn't micromanage that way. "Surely he can set things up without having to violate his own laws."
In Miller's view, God created the whole process of evolution. "We're here because a creator God created a universe in which it was possible for beings like us to arise."
Miller and other Catholic scientists say that even though they believe we were created by a creator, they are not creationists - a term they reserve for the official Intelligent Design movement and biblical literalism.
Others aren't so sure.
"I think that [Pope] Benedict was trying to find, like so many other religious people, a middle ground between creationism and evolution," said Scott Gilbert, a biologist at Swarthmore College.
"And, like so many others, he does it by proposing a divinely ordained evolutionary process, at least as far as the mind is concerned." Gilbert, who has studied comparative religion, has gone to the Vatican to take part in scientific advisory panels on stem cells and evolution.
Many biologists are not religious, and few see any evidence that the human mind is any less a product of evolution than anything else, said Chicago's Coyne. Other animals have traits that set them apart, he said. A skunk has a special ability to squirt a caustic-smelling chemical from its anal glands.
Our special thing, in contrast, is intelligence, he said, and it came about through the same mechanism as the skunk's odoriferous defense.
The other problem with the pope's words is that there really is randomness inherent in the natural world, said Drexel University physicist Leonard Finegold, who teaches a course in science and religion. And that is hard to square with a universe moving along some divinely directed course.
Such a universe might leave room for a view called Deism, he said, where God set up the laws of physics and some starting conditions and then took early retirement.
Catholic scientists say they are not Deists. "God is always present, not only as a creator but also a sustainer," said Harvard biologist Martin Nowak, who is Catholic.
Physicist Stephen Barr of the University of Delaware says it is possible to believe simultaneously in a world that is shaped by chance and one following a divine plan. "God is in charge and there's a lot of accident," said Barr, also a Catholic. "It's all part of a plan. . . . God may have known where every molecule was going to move."
There are quite a few molecules to keep track of, though he is God, after all.
This brings up some thorny issues with disease, natural disasters, and other sources of suffering. As one of Woody Allen's characters put it, if God is in charge, it's a wonder everyone doesn't file a class-action lawsuit.
Contact staff writer Faye Flam at 215-854-4977 or email@example.com.
Go online to discuss evolution with Faye Flam at www.philly.com/evolution