A neurosurgeon who believes the human brain is too complex for anyone but God, an ophthalmologist who refuses to talk about the age of the earth, and a Harvard-trained lawyer beloved by creationists are running for president of the United States, raising the prospect of an election without science. Retired doctor Ben Carson joined Senator Rand Paul (the ophthalmologist) and Senator Ted Cruz (the Harvard alum) on the campaign trail on Monday, vying for the Republican nomination against each other and other confirmed and likely candidates including Senator Marco Rubio, former Florida governor Jeb Bush and Wisconsin Governor Scott Walker. But despite assorted elite educations and illustrious careers, none can apparently make up their minds about basics of modern science - that the earth is about 4.5 billion years old, that humans evolved from earlier primates over millions of years, and that people are making the world dangerously warm. "I think on issues like climate change and evolution it ends up being a proxy for identity politics," said Michael Halpern, of the Union of Concerned Scientists. "You're not actually talking about the science, you're talking about values." So far the candidates have mostly hemmed and hawed - save Carson, who outright rejected the theory of evolution when speaking to Faith & Liberty radio last year. "Carbon dating, all these things, really doesn't mean anything to a God who has the ability to create anything at any point in time," he said. "Dealing with the complexity of the human brain, and somebody says that came from a slime pit full of promiscuous biochemicals? I don't think so." Curiously, Carson did not reject natural selection - the engine that drives evolution - saying he "totally believe[s]" that useful genetic traits are more often passed on than less useful traits. But he could not draw the connection between that process acting over millennia and the human eye: "Give me a break. According to their scheme - boom, it had to occur overnight." Instead, he suggested an "intelligent creator" gave organisms the ability to adapt "so he doesn't have to start over every 50 years creating all over again". Cruz has courted the creationist camp with only a dab more subtlety - he announced his campaign at the evangelical Liberty University, which teaches creationism as science. Paul, Rubio and Walker have tried to duck the issue. In 2010 Paul refused to answer a Kentucky home school student's question whether the earth was only a few thousand years old, and in 2012 Rubio told GQ : "I'm not a scientist… I think parents should be able to teach their kids what their faith says, [and] what science says." In February 2015, Walker earned the ridicule of his British hosts by dodging a question about evolution. Only Bush has said that he believes in evolution - way back in 2005. But he also said schools should sort out curriculums on their own. On climate change, the candidates fare little better - almost uniformly saying they are "sceptics" and that while global warming may be real it might not be man-made. Rubio accepts it but denies its origin; Bush, Paul and Cruz toe the sceptic line; Walker and Carson prefer to talk about regulations and resources.