This is not an “eat dirt for your health and happiness” study. You don’t need to shovel soil in your mouth. Just go outside.

Biologist Dorothy Matthews and company wanted to test a particular bacteria, Mycobacterium vaccae. It’s found commonly in the soil and carried widely through the air, so if you take a walk in the park you’ll probably breathe it in. Previous studies have shown that the bacterium increases serotonin in the brain, and have even suggested that the bacterium has antidepressant qualities. Since the neurotransmitter serotonin is also involved in cognition, the team wanted to see if the bacterium could have a direct effect on learning. Indeed it did, Matthews’ team announced at the General Meeting of the American Society for Microbiology in San Diego.

In a classic test of learning ability, Matthews gave mice a treat – white bread with peanut butter – as a reward to encourage them to learn to run through a maze. When she laced the treat with a tiny bit of Mycobacterium vaccae, she found that the mice ran through the maze twice as fast as mice that were given plain peanut butter [New Scientist].

The uptick in learning ability lasted as long as the researchers kept giving their mice the laced peanut butter.

But here’s a caveat: When they tested bacteria-fed mice three weeks after removing the single-cell organisms from their diet they found that these mice were still faster than the mice who never received the bacteria. The difference, however, was not significant. So the results are temporary [Scientific American].

And this is just a mouse model, too, so take that for what you will. But the least it’s another blow struck for the good name of bacteria, for the hygiene hypothesis, and for going outside, Matthews says.

“It just shows that we evolved with dirt as hunter-gatherers,” she says. “So turn off your TV and go work in your garden, or walk in the woods” [New Scientist].

Related Content:
DISCOVER: Is Dirt the New Prozac?
80beats: Special Seaweed-Chomping Bacteria Found in the Guts of Japanese Diners
80beats: Scientists Sequence DNA from the Teeming Bacterial Universe in Your Gut
80beats: Let Kids Eat Dirt: Over-Cleanliness Linked to Heart Disease
Discoblog: Let Them Eat Dirt! It Contains Essential Worms

Image: iStockphoto

This is a guest post from Vanessa Woods, author of the new book, Bonobo Handshake. Vanessa is a Research Scientist in Evolutionary Anthropology at Duke University and studies the cognition of chimpanzees and bonobos in Congo. When I wake up this morning, someone might try to kill me. I live 10 minutes from a small town called Durham, NC, where according to the last statistics, 22 people were killed, 76 women were raped, and there were 682 cases of aggravated assault. When a chimpanzee wakes up in the morning, they probably have the same thought. In fact, if you're a male chimpanzee, you're more likely to be killed by another chimpanzee than anything else. If you're a female chimpanzee, expect to be beaten by every adolescent male who is making his way up through the ranks. People often ask me why humans are so intelligent, as in, what is it other apes lack that makes us so unique. I'll tell you this: I would swap every gadget I own - my car, my laptop, the potential to fly to the moon - if I could wake up as a bonobo. No bonobo has ever been seen to kill another bonobo. There is very ...

I'm pleased to announce that beginning today and running for a week at the Intersection, we will have daily guest posts from Vanessa Woods, author of the new book, Bonobo Handshake. Vanessa is a Research Scientist in Evolutionary Anthropology at Duke University and studies the cognition of chimpanzees and bonobos in Congo, and her posts will be about her new book. I've already seen the content, and it is spectacular....so, let bonobo week begin! The first post appears later today.

A new paper is out which drills down a bit on the genetic substructure in Spain. Genetic Structure of the Spanish Population:

Background
Genetic admixture is a common caveat for genetic association analysis. Therefore, it is important to characterize the genetic structure of the population under study to control for this kind of potential bias.

Results
In this study we have sampled over 800 unrelated individuals from the population of Spain, and have genotyped them with a genome-wide coverage. We have carried out linkage disequilibrium, haplotype, population structure and copy-number variation (CNV) analyses, and have compared these estimates of the Spanish population with existing data from similar efforts.

Conclusions
In general, the Spanish population is similar to the Western and Northern Europeans, but has a more diverse haplotypic structure. Moreover, the Spanish population is also largely homogeneous within itself, although patterns of micro-structure may be able to predict locations of origin from distant regions. Finally, we also present the first characterization of a CNV map of the Spanish population. These results and original data are made available to the scientific community.

They used a 160 K SNP-chip for this, though for the PC charts below they were constrained to ~100,000 SNPs. Nothing too revolutionary in the paper. The fact that Spaniards have more haplotype diversity vis-a-vis the “CEU” sample in the HapMap, which consists of Utah Mormons, isn’t too surprising, since those individuals are Northern European and Northern Europeans tend to be a touch less diverse than Southern Europeans (more heterozygosity in Southern Europe than in the North). A common explanation for this is that Northern European populations emerged as subsets of Southern populations which expanded out of Ice Age “refugia” within the last ~10,000 years or so, and this migratory process would have induced some bottlenecks and so reduced their diversity. The findings in this paper are broadly consistent with the idea that Spain was a refugium, and so one of the sources of the population of Northern Europe. But, note that there are lots of controversies about recent European demographic history right now, so I wouldn’t take the aforementioned model as a given. Also, one major issue which sticks out is the lack of Basque populations in the sample, since that’s a group which has long been of interest, and some aspects of many demographic scenarios hinge on their nature. No surprise that Visigoths, Berbers and Arabs didn’t perturb these results too much. I believe that these groups did arrive in Iberia in large numbers, but on a relative scale their proportions were small and they probably didn’t alter Spain’s basically genetic character.

Below are some charts of note.

First, dimensions of genetic variation in the Spanish population using 100,000 SNPs by locality where the sample was collected.

If some of the localities were as obscure to you as me, here is the PC chart with a subset of them rotated and superimposed upon a map of Spain.

Finally, here are the Spanish samples plotted in relation to two HapMap populations, the CEU (American whites of Northern European ancestry) and TSI (Tuscans from Italy).

There are a few outliers here in relation to their putative population cluster, but in general the three groups are nicely separated as expected. Spain is bounded by water and a rather imposing mountain range. These serve as natural barriers to gene flow. But within the peninsula it’s dominated by a high plateau. I really don’t have an intuitive understanding of whether the spatial distribution of Spain’s people (which for ecological reasons probably can be extrapolated back to antiquity) should homogenize it through a circular pattern of gene flow, but perhaps that’s what these data are showing. I am a bit wary of saying that Spain is internally homogeneous without referencing other European populations of the same scale in detail. Perhaps what this group found is what you’d find on this scale with this chip; not much.

Cite: BMC Genomics 2010, 11:326doi:10.1186/1471-2164-11-326

H/T Dienekes