The changes of mind that gave philosophers and scientists new insights
They are the intellectual elite, the brains the rest of us rely on to make sense of the universe and answer the big questions. But in a refreshing show of new year humility, the world's best thinkers have admitted that from time to time even they are forced to change their minds.
When tackling subjects as diverse as human evolution, the laws of physics and sexual politics, scientists and philosophers, including Steven Pinker, Daniel Dennett, Paul Davies and Richard Wrangham, all confessed yesterday to a change of heart.
The display of scientific modesty was brought about by the annual new year's question posed by the website edge.org, which drew responses from more than 120 of the world's greatest thinkers.
Edge's publisher, John Brockman, asked the intellectual cream what they had changed their mind about and why. "Science is based on evidence. What happens when the data change? How have scientific findings or arguments changed your mind?" said the brief.
A common theme in the responses is that what distinguishes science from other forms of knowledge and from faith is that new ideas can rapidly overturn old ones as new evidence emerges. So there's nothing to be ashamed about in admitting an intellectual switch. Some responses, such as Dennett's change of heart on how the mind works, resist paraphrasing in 100 words, but here is a selection of the rest.
What was the turning point in human evolution?
Richard Wrangham, British anthropologist who studied under Jane Goodall. Now at Harvard University, his research includes primate behaviour and human evolution.
"I used to think that human origins were explained by meat-eating. After all, the idea that meat-eating launched humanity has been the textbook evolutionary story for decades, mooted even before Darwin was born.
"But in a rethinking of conventional wisdom I now think that cooking was the major advance that turned ape into human ... Cooked food is the signature feature of human diet. It not only makes our food safe and easy to eat, but it also grants us large amounts of energy compared to a raw diet, obviating the need to ingest big meals. Cooking softens food too, thereby making eating so speedy that as eaters of cooked food, we are granted many extra hours of free time every day."
Why do men dominate society?
Helena Cronin, philosopher at the London School of Economics and director of Darwin@LSE, a research group devoted to what Darwinism can tell us about human nature.
"I used to think that patterns of sex differences resulted mainly from average differences between men and women in innate talents, tastes and temperaments ... Add to this some bias and barriers - a sexist attitude here, a lack of childcare there - and the sex differences are explained. Or so I thought ... But they alone don't fully explain the differences ... Females are much of a muchness, clustering round the mean. But, among males, the variance - the difference between the most and the least, the best and the worst - can be vast.
"So males are almost bound to be over-represented both at the bottom and at the top. I think of this as 'more dumbbells but more Nobels'... Unfortunately, however, this is not the prevailing perspective in current debates, particularly where policy is concerned."
Are there genetic differences between "races"?
Mark Pagel, evolutionary biologist at Reading University. His research includes work on language and cultural evolution.
"Flawed as the old ideas about race are, modern genomic studies reveal a surprising, compelling and different picture of human genetic diversity. We are on average about 99.5% similar to each other genetically. This is a new figure, down from the previous estimate of 99.9%. To put what may seem like minuscule differences in perspective, we are somewhere around 98.5% similar, maybe more, to chimpanzees, our nearest evolutionary relatives.
"The new figure for us, then, is significant. It derives from among other things, many small genetic differences that have emerged from studies that compare human populations ... Like it or not, there may be many genetic differences among human populations - including differences that may even correspond to old categories of "race" - that are real differences in the sense of making one group better than another at responding to some particular environmental problem.
"This in no way says one group is in general "superior" to another ... But it warns us that we must be prepared to discuss genetic differences among human populations.
Are humans still evolving?
Steven Pinker, leading psychologist and language expert at Harvard University. Author of The Language Instinct and The Blank Slate.
"I've had to question the overall assumption that human evolution pretty much stopped by the time of the agricultural revolution ... New [laboratory] results have suggested that thousands of genes, perhaps as much as 10% of the human genome, have been under strong recent selection, and the selection may even have accelerated during the past several thousand years ... If these results hold up, and apply to psychologically relevant brain function ... then the field of evolutionary psychology might have to reconsider the simplifying assumption that biological evolution was pretty much over and done with 10-000-50,000 years ago."
Is the universe flat?
Laurence Krauss, physicist at Case Western Reserve University and prominent opponent of the Intelligent Design movement. His books include The Physics of Star Trek.
"I was relatively certain that there was precisely enough matter in the universe to make it geometrically flat ... according to general relativity [geometrically flat] means there is a precise balance between the positive kinetic energy associated with the expansion of space, and the negative potential energy associated with the gravitational attraction of matter in the universe so that the total energy is precisely zero ... We are now pretty sure that the dominant energy-stuff in our universe isn't normal matter, and isn't dark matter, but rather is associated with empty space! And what is worse (or better, depending upon your viewpoint) is that our whole picture of the possible future of the universe has changed. An accelerating universe will carry away almost everything we now see, so that in the far future our galaxy will exist alone in a dark, and seemingly endless void. And that is what I find so satisfying about science ... that the whole community could throw out a cherished notion, and so quickly! That is what makes science different than religion."
Should we use brain-boosting drugs?
Philip Campbell, editor-in-chief of the leading scientific journal Nature
"I've changed my mind about the use of enhancement drugs by healthy people. A year ago, if asked, I'd have been against the idea, whereas now I think there's much to be said for it. The ultimate test of such a change of mind is how I'd feel if my offspring (both adults) went down that road, and my answer is that with tolerable risks of side effects and zero risk of addiction, then I'd feel OK if there was an appropriate purpose to it ... Research and societal discussions are necessary before cognitive enhancement drugs should be made legally available for the healthy, but I now believe that that is the right direction in which to head.
Does God exist?
Alan Alda, perhaps best-known as Hawkeye in the 70s series MASH. He now hosts Scientific American Frontiers on US television.
"Until I was 20 I was sure there was a being who could see everything I did and who didn't like most of it. He seemed to care about minute aspects of my life, like on what day of the week I ate a piece of meat. And yet, he let earthquakes and mudslides take out whole communities, apparently ignoring the saints among them who ate their meat on the assigned days. Eventually, I realised that I didn't believe there was such a being ... I still don't like the word agnostic. It's too fancy. I'm simply not a believer."