Some skeptics of evolutionary theory say it fails to explain how something as complex and abstract as the human mind could have evolved.
A century and a half after Charles Darwin published his theory of evolution, some still doubt its ability to explain the emergence of human beings and other forms of life.
These days, some Darwin skeptics are focusing on the human brain. They say a higher power must be involved; otherwise, how could a bunch of cells produce such complicated mental processes as consciousness or subjective experiences? How could something like free will be the result of evolution?
While Darwin skeptics have homed in on this mind-brain problem, most brain scientists say there's plenty of evidence that mental actions such as consciousness have evolved along with the brain.
Steven Novella, a neurologist at Yale University, studies the mind-brain connection. His work points to a mind that depends on the brain.
"If you change the brain, you change the mind. If you damage the brain, you damage the mind. If you turn off the brain, you turn off the mind," he says.
"And now with more sophisticated tools, when we're looking at brain function with functional MRI, for example, we can see that brain activity precedes mental activities — and that makes sense, because causes come before their effects."
The evidence that the brain causes the mind is "overwhelming," says Novella, but science isn't exactly sure how. And there's a real debate about how science needs to further explore that question, he says.
Belief In A Divine Hand
This is where the Darwin doubters come in. One of them is neurosurgeon Michael Egnor from the State University of New York, Stony Brook.
"I'm a neurosurgeon. I realize how closely the mind and the brain are related," Egnor says. "But the question is, is there something else, in addition to the material properties of the brain, that we need to invoke to have an adequate explanation for the mind? And I think there is."
Egnor says that an intelligent designer was involved in producing not only the brain but all living things and certain features of the universe. Without this designer, the brain would be just a meat computer made up of brain cells, he says.
"There is nothing about neurons that scientifically would lead you to infer consciousness from them. They're masses of gelatinous carbon and hydrogen and nitrogen and oxygen, just like other kinds of flesh. And why would flesh have first-person experience? So, even logically, it doesn't hang together."
Egnor and Novella have been arguing about the mind-brain debate on dueling blogs for months now.
Egnor writes for a blog called Evolution News & Views, hosted by the Discovery Institute, a think tank that's the hub of the intelligent design movement and that rejects Darwinian evolution.
Novella writes for a blog called Neurologica, hosted by the New England Skeptical Society, an organization he co-founded.
Neither has much respect for the other's ideas.
"The brain uses energy, it can hold information, it can communicate, it can receive sensory input. It can even activate itself and create a loop of ongoing activity," Novella says in response to Egnor's contention that brain cells alone can't cause the mind.
The brain "can do things that can plausibly cause consciousness and self-awareness, so the argument really just falls on its face."
Novella also says Egnor is really a creationist who's recycling the religious arguments once used to attack evolution and the idea that natural selection could have produced our genetic code.
Egnor counters, "Whether it's the DNA code or the mind that understands the DNA code, both require an explanation that transcends what we know of matter."
And he says he's not a creationist: "My personal view is that we have souls and that they're created by God. But you don't have to hold that view to recognize what I think is the evidence that the mind is not entirely material."
Beliefs In Action
Not surprisingly, Egnor and Novella have very different views on the Terri Schiavo case. Schiavo was the woman in Florida who had severe brain damage and was taken off life support after a legal battle that lasted seven years.
Novella says the court was right to assume that Schiavo's mind was determined by her physical brain.
"She had significant enough brain damage that it was incompatible with somebody being conscious in any significant way. And it's reasonable to base medical decisions on that scientific evidence," says Novella.
"If you also want to bring moral or ethical things into the picture, that's slightly different. You know, science doesn't make moral decisions for us. It just informs our moral decisions."
Egnor says the court was wrong because there's no scientific test that can detect the presence of a mind.
Also, anecdotal evidence suggests even when the brain stops working, the mind can persist, he says. These anecdotes usually involve a person who has nearly died.
"The person was able to have mental processes during a time when they were in cardiac arrest, in cardiac standstill, and sometimes even absent EEG waves," Egnor says. "So I think there is very real scientific evidence that the mind in some circumstances can exist without a functioning brain."
Darwinist brain scientists say in these cases the brain is still functioning, even if its electrical signals are hard to detect.
For the record, Egnor and Novella do agree about one thing: The outcome of the mind-brain debate will have a profound impact on everything from what students learn in high school to how decisions are made at the end of life.