HOW MANY NEURONS IN THE HUMAN BRAIN? Here's an intriguing question about the origin of scientific truisms that may not be so true after all, thanks to a post by James Randerson at The Guardian's Notes & Theories. He tells of research by Brazilian neuroscientist Suzana Herculano-Houzel showing that adult men possess on average only 86 billion neurons, not the 100 billion so widely promulgated in the literature. He quotes her thus:
not one [of the brains] that we looked at so far has the 100bn. Even though it may sound like a small difference the 14bn neurons amount to pretty much the number of neurons that a baboon brain has or almost half the number of neurons in the gorilla brain. So that's a pretty large difference actually.
Randerson asks where the 100 billion estimate came from. I can't help him there, except to aver that it's been around for a long time. That's the number in the earliest reference from my personal neuroscience archive, a 1979 SciAm article by Charles Stevens, no source given.
That's also the number in Sandra Ackerman's Discovering the Brain (National Academy Press 1992). Based on a 1990 Institute of Medicine meeting, it's a solid reference for its time. Its time was, unfortunately, before we knew that adults grew new neurons. So the party line was that we are born with all the neurons we will ever have.
Ackerman says that 100 billion is the number of neurons in a newborn's brain, not an adult's. I don't know where that datum came from either, but, if true, it offers an easy explanation for why the new study seems to show so many fewer: brain cells are pruned heavily during childhood and somewhat thereafter. Even young adults have lost many of the brain cells they possessed at birth.
So, let me add my voice to Randerson's. At what point before 1979 was it decided that 100 billion neurons was a reasonable number for a human brain? And did it apply to a newborn's brain or an adult's? And who decided it?
Anybody know?
I also thank him for giving me an excuse for spending an enjoyable few hours hunting around in the neuroscience literature, ancient and modern. A particularly sophisticated form of Writing Avoidance.
Herculano-Houzel arrived at her figure by counting neurons in a sample of "soup" she made out of a brain — postmortem, you'll be relieved to learn. She then extrapolated to estimate the number of neurons in the entire brain the sample came from.
I can't resist pointing out (as does Herculano-Houzel herself) that this estimate is based on studying just four brains, all of them older than 50.
Also all from men.
Ahem.
ÖTZI NEWS: THE ICEMAN'S FULL GENOME COMETH. Speaking of men, check out Ed Yong's quite funny brief at Not Exactly Rocket Science describing publication of the nearly complete genome of Ötzi the Iceman, the 5300 year-old mummy found freeze-dried in the Alps some years ago.
The genome reveals that Otzi carried a large genomic region known as the ‘Y chromosome’, which significantly increases the risk of traipsing about in the a*se-end of nowhere with very little protective clothing, and getting shot by arrows.
Funny, yes, but a little harsh on the dignity of poor Ötzi, who was, after all, a murder victim, done in by a dastardly arrow in the back. Nor did Ötzi lack for clothing, Ed; he was warmly dressed, according to archaeologist Thomas Tartaron at the University of Pennsylvania. Find a video of Tartaron's talk at Dienekes' Anthropology Blog. (The sound vanishes near the beginning, but stick around, it resumes.)
Ötzi was lactose intolerant, not too surprising considering that the gene for lactase persistence is estimated to have arisen in Europeans only between 5000 and 10,000 years ago and is (of course) most strongly associated with milk-using populations. No sissy milk for Ötzi; he was a hunter and game-eater with with a genetic predisposition for coronary artery disease. Compared with present-day genomes, his is most similar to genomes in Sardinia. That could mean Ötzi's genome was a typical European's 5300 years ago. Sardinia is thought to have been (relatively) isolated genetically from the rest of Europe, where genomes have changed since 3288 BCE because of a constant influx of immigrants.
WOMEN'S MAGAZINES — AND EVERYBODY ELSE'S. Hillary Rosner has posted a soul-searing diatribe on trying to write science journalism for women's magazines at Tooth & Claw. Terrible experiences with editors, ranging from utter lack of interest in important issues to making up quotes.
But it got me thinking about some of my own dismaying experiences with magazines not aimed specifically at women. The time, for example, I tried to interest a major science-y magazine in a piece about the genetics of alcoholism. In novels you read about people turning pale when alarmed, but that's the only time I've seen it in real life: the blood actually drained from the editor's face, he stammered and quickly changed the subject. I was bewildered until I flipped through the magazine and realized it was full of liquor ads.
Many science writers can tell tales like these. It set me to wondering how much worse women's mags are compared with other mass-market media. Glossy magazines certainly. And think of television, particularly local TV news, with its unabashed plugs for dubious practitioners of this and that, complete with flattering footage from said practitioners. There seems to be a kind of Gresham's Law for the media, and no one has yet invented a way to stop it.
NEW RULES FOR STATIN PRESCRIPTIONS. Several takes on the FDA's new rulings on statins. The agency notes, for example, a potential for the cognitive problems that keep being reported even though they don't seem to show up in clinical trials. Scott Hensley sums things up at the NPR health blog Shots.
Docs are mad for statins, so it's not too surprising that Howard LeWine, MD, takes an upbeat view at the Harvard Health Blog. At In the Pipeline, a pharma blog, Derek Lowe is worried that the warnings — especially about potential memory loss — may cause people to stop taking statins, to the detriment of public health. Michael Todd, at Miller-McCune's By the Way, took the opportunity to recap the pub's previous skeptical inquiries into statin use and overuse.
HEARTSICK ABOUT THE HEARTLAND EMAIL SCANDAL. I have said this tale has staying power, and it sure does. But I'm not sure I do. Unless there's a truly ramifying development, this post is going to be it for a while.
Given that a focus of this blog is science journalism, I'm bringing to your attention a long Observatory post by Curtis Brainard at the Columbia Journalism Review. The topic is the ethical and legal issues surrounding deceptive tactics in journalism with particular reference to Peter Gleick's use of them in obtaining documents from Heartland.
I find myself not caring deeply about either the ethics or legality of what Gleick did. All I can think about is what an incredibly dumb public relations move it was. Here we have a poll showing, at last and in this same damn week, that US citizens are inching toward accepting global warming as real and dangerous and that it's caused by human practices that can be altered and stopped. Which opinions might eventually force policymakers to Do Something. At last, at last. And just as the opinion tide seems to be turning, someone who presumably cares deeply about warming presents the professional deniers with such a powerful propaganda weapon. [Sound of weeping and gnashing of teeth.]
OPEN SESAME FOR OPEN ACCESS. Legislation that would have prevented US government agencies from requiring that their taxpayer-funded grantees make their papers freely available has been abandoned. The turning point seems to have come when thousands of scientists threatened to boycott journals published by Elsevier, the giant journal-monger, which was backing the legislation. Publishers of Science and the Nature journals were also enthusiasts.
Jocelyn Kaiser summarizes at ScienceInsider. At Tree of Life, Jonathan Eisen does the happy dance. Another evolutionary biologizing Eisen brother, Michael, one of the boycott fomenters, points out at It is NOT Junk that defeating the legislation was just a single battle in an ongoing war. He urges open-access advocates not to relax for a moment.
Tim Gowers, who launched the boycott, says he thinks it forced Elsevier to drop its opposition and links to the company's statements reliquishing the field. For the moment. At his Denialism Blog, Mark Hoofnagle restates a basic argument for open access:
While publishing is a capitalist enterprise and they should make money, their compensation should be proportionate to the effort and investment they put into the manuscript. The reality is, their contribution is vanishingly small compared to the efforts of scientists and costs to taxpayers.
OTOH, at The Scholarly Kitchen, Kent Anderson wrings his hands over the debacle, which he attributes to "a terrible misreading of the political winds" and tries to correct what he terms misunderstandings of commercial journal publishing
Fair and balanced, that's us.
.png)
