Here's my weekly column, which will also run Monday on the cover of the Philadelphia Inquirer's Health and Science section:

There was no hanky-panky involved when a fairy-tale white foal was born to two brown Standardbreds at the Four Winds Farm in New Jersey. DNA tests confirm that the snowy foal, born May 6, is a mutant, but that’s nothing to be ashamed of. So are most humans, according to a new analysis.

Geneticists and veterinarians say this unusual foal’s lack of color comes from a spontaneous or “de novo” mutation — a spelling error in the DNA carried in either the sperm or egg from which he was conceived.

 “De novo mutations are the fuel of evolutionary change,” said Joshua Akey, a geneticist from the University of Washington. He’s been studying de novo mutations in humans, and found hundreds of them. Most of these new mutations haven’t caused anything as dramatic as this foal’s white coat, but Akey says they are probably influencing our susceptibility to diseases.

 There are no exact numbers for the frequency of white foals, but experts say it’s extremely rare to see one crop up spontaneously. Most horses that appear white are really pale gray, said Hannah Galantino-Homer, a veterinarian and researcher with the Penn Veterinary School’s New Bolton Center. Gray horses tend to fade as they age. (That may explain why there are both a pale horse and a white horse ridden by the four horsemen of the apocalypse — they truly are different colors.)

Think you're smarter than a doctor? If you get this right, you are way ahead of the curve when it comes to medically relevant statistics.

Toxicologist Dave Cragin sent me this question after we had been discussing risk, probabilities and the controversy over PSA testing for prostate cancer. 

It's a question he poses to his students. I was relieved to find I'd gotten it right, since it's part of my job to communicate health information. According to an article in Science, 23 out of 24 doctors get it wrong:

For the Hemoccult-Test for colon cancer:  The probability that a 50-year-old man without symptoms has colon cancer is 0.3%. If he has cancer, the probability of him having a positive test is 50%. If he does not have cancer, the probability of him receiving a positive test result anyway is 3%.

What is the probability that a patient has colon cancer based on a positive Hemoccult test?

I'm starting to see what it takes to get a science story on the breaking news column of Philly.com. This exciting bigfoot story is from AP, and somewhere I think something was misconstrued. It’s possible the AP writer is in on the joke and trying to be funny too, but it’s hard to tell: 

"If the Yeti is real and somebody has found bits of their hair, you should be able to tell from the DNA in the hair if this is actually a Yeti," said Mark Thomas, a professor of evolutionary genetics at University College London. He is not connected to the Bigfoot project.

But Thomas was unsure how likely it was anyone might have actual Yeti hairs. Some scientists theorize Yetis are either a distinct hominid species, or a mix between homo sapiens and Neanderthals or other species. There is already evidence of interbreeding between homo sapiens and Neanderthals.

"If Yetis have survived for the last 30,000 years, they have probably had a pretty miserable existence and are a small population vulnerable to extinction," Thomas said. "It's not as insane an idea as many might think, but the chances are pretty small."

Oh you Brits and your naughty sense of humour! How will you identify Yeti DNA? Would you compare it to the OxBridge Yeti DNA database? You all deserve a spanking - especially Mark Thomas.

The mystery quote in yesterday’s post was from the incomparable writer H.L. Mencken. Below is the complete quote, which is part of a series being posted on the blog Why Evolution is True. In this particular passage, Mencken refers to Robert Millikan, a famous physicist who constructed a clever experiment to measure the charge of the electron for the first time.

Millikan was also a devout Christian and apparently too much of a church lady for the taste of H.L. Menken, who argued that the pious can’t be real scientists. Mencken used the dismissive term “technicians” to describe religious scientists.  

Here’s Mencken:

The effort to reconcile science and religion is almost always made, not by theologians, but by scientists unable to shake off altogether the piety absorbed with their mothers’ milk. The theologians, with no such dualism addling their wits, are smart enough to see that the two things are implacably and eternally antagonistic, and that any attempt to thrust them into one bag is bound to result in one swallowing the other. The scientists who undertake this miscegenation always end by succumbing to religion; after a Millikan* has been discoursing five minutes it becomes apparent that he is speaking in the character of a Christian Sunday-school scholar, not of a scientist. The essence of science is that it is always willing to abandon a given idea, however fundamental it may seem to be, for a better one; the essence of theology is that it holds its truths to be eternal and immutable. To be sure, theology is

always yielding a little to the progress of knowledge, and only a Holy Roller in the mountains of Tennessee would dare to preach today what the popes preached in the Thirteenth Century, but this yielding is always done grudgingly, and thus lingers a good while behind the event. So far as I am aware even the most liberal theologian of today still gags at scientific concepts that were already commonplaces in my schooldays.

It’s not all that easy to encapsulate the essence of science in a sound bite. Physicist Richard Feynman appears to do it in the little clip of a lecture attached to this post. The late great Feynman describes science as a comparison between ideas and observations or experiments. If your idea doesn’t agree with experiment, you’re wrong.

But that doesn’t explain what makes a scientifically valid observation or experiment, or how we can be sure we’re properly interpreting what we observe. Feynman expands on all this in the rest of the lecture. I’m not sure his aim was to define science in a sound bite. His attention-getting witticisms and wry observations punctuate his lectures in a way that keeps the students riveted. The verbal spice is best enjoyed and understood as part of the whole lecture.

Here’s another famous person’s nutshell account of science. I clipped this quote from biologist Jerry Coyne’s blog Why Evolution is True:  

The essence of science is that it is always willing to abandon a given idea, however fundamental it may seem to be, for a better one; the essence of theology is that it holds its truths to be eternal and immutable.

Anyone want to venture a guess who said this? (Answer revealed tomorrow)

It’s become a kind of mantra that scientists are failing at explaining science to regular people. But I don’t think this is the real problem. Some scientists excel in theoretical work, others at designing experiments, and still others at teaching. If there’s any problem with scientists, it’s that the scientific community tends to revere research and not give enough respect to great teaching.  

I would give University of the Sciences chemistry professor Fred Schaefer an A+ in science explanation. He not only enjoys teaching students, he volunteers a serious chunk of his time to demonstrate chemistry to kids of all ages. The demos happen every month at a restaurant/brewery in Germantown with the memorable name Earth, Bread and Brewery. (Disclaimer: This post might be biased because Fred is a fellow Laser sailor and always brings a growler of some incredible “Earth” invention to drink when we’re finished racing.)

I acted as his assistant during the Science Festival last month, when he spent hours demonstrating the magic of reality - sending electrical currents through gases, using dry ice and indicators to create dramatic color changes, and performing various reactions that foamed, bubbled or occasionally exploded. The best part was seeing the astonishment and wonder on the faces of the little kids. May they never lose that natural curiosity.  

The show starts at 6 and runs until about 9 pm. The brewery also has a great tradition of experimentation. Fred informs me they never brew the exact same beer twice. Read more about Earth, Bread and Brewery here.

(photo credit: University of the Sciences/Scott Hewitt Photography)

Last week, scientists announced an intriguing discovery - bacteria that are slowly eking out a living deep beneath the ocean floor. The researchers raise the possibility that the organisms are more than a million years old. Since the findings were published in the journal Science, many people wrote about it, but the clearest and most engaging story I saw appeared in the Washington Post. You can read the whole story here.

Call it survival of the slowest: Extraordinarily old, bizarrely low-key bacteria have been found in sediments 100 feet below the sea floor of the Pacific Ocean, far removed from sunlight, fresh nutrients and what humans would consider anything interesting to do.

Some of these organisms, scientists say, could be at least 1,000 years old. Or maybe millions of years.

Their strategy for staying alive is to be barely alive at all. Their metabolism is dialed down to almost nothing, an adaptive advantage in a place with so few resources. The bacteria that survive are the ones that can satisfy themselves with minute traces of oxygen and a parsimonious diet of organic material laid down millions of years ago.

I love the use of the term “parsimonious diet”. Here’s a quote from the lead researcher, Hans Roy, a biologist at Aarhus University:

It's always fun for me to report these columns because I learn so much. This was one of the most interesting for me to research. It will appear in Monday's Health and Science section of the Philadelphia Inquirer:

From the inside of our heads, it feels like colors are intrinsic aspects of the outside world and our eyes are beautifully designed to see them. But we humans are merely sampling the possible ways of sensing the spectrum of light. Most of us see more colors than dogs but miss millions of colors that make up the world for birds, reptiles and insects.

Why do we see the colors we do?

Last week’s column explained how some of it goes back to the types of color-absorbing pigments that we inherited from bacteria more than a billion years ago. The specific colors we see are, in part, an artifact of bacterial needs.

These ancient color sensing pigments are tuned to two different wavelengths – shorter ones that correspond to blue and longer ones that go with yellows or reds.

A reader sent me this interesting blog post from NPR’s Robert Krulwich. He comments on a snippet of a 1964 lecture by physicist Richard Feynman:

Think about what he's saying. Science is our way of describing — as best we can — how the world works. The world, it is presumed, works perfectly well without us. Our thinking about it makes no important difference. It is out there, being the world. We are locked in, busy in our minds. And when our minds make a guess about what's happening out there, if we put our guess to the test, and we don't get the results we expect, as Feynman says, there can be only one conclusion: we're wrong

That makes it sound easy, but how do you define a valid experiment or observation of nature? A few readers informed me recently that there are hundreds of papers describing cold fusion and showing that it works. There are also quite a few showing that it doesn’t work. I'd put my money with the naysayers.

And scientists have to be careful to distinguish whether an idea is wrong or the experiment that appeared to contradict the idea is what’s wrong. Some overly eager physicists starting talking about proving Einstein's relativity wrong last fall when they thought they’d observed a beam of particles travel faster than the speed of light. That would contradict Einstein if that’s what they saw. But it wasn’t.   

The right take-away message from Feynman is that in an ideal world, scientists should try not to prove their ideas right but to prove them wrong. But that, too, is easier said than done, scientists being human and subject to wishes, desires and self-delusion. That’s why it’s so important to have lots of independent confirmation.