Science-- there's something for everyone

Friday, September 28, 2012

Don’t give young children alcohol

It may seem obvious that children under age ten should not be given alcohol. However, many parents believe that allowing children to taste alcohol when the adults around them are imbibing will actually inoculate them from future alcohol abuse. Some version of this belief was held by up to 40% of parents in a recent study conducted by Christine Jackson and her colleagues from RTI International the University of North Carolina at Chapel Hill.

Over a thousand mother and 3rd grade child pairs were recruited and interviewed about alcohol use in the home. Women were asked whether they allowed their own children to sip alcohol and whether they considered this to be an acceptable practice for all children. They were also asked whether there should be an age limit for the practice.

Many of the mothers chose to indulge children who requested a sip of alcohol. One of the top reasons given was the hope that by nonchalantly allowing children to taste alcohol, the drinks would lose their forbidden fruit appeal. Mothers also cited the expectation that, upon finding they disliked the taste, their children would choose to forgo alcohol in the future. Finally, some mothers expressed the belief that by allowing their children to sip drinks in the home, they were teaching their children how to be responsible drinkers.

Unfortunately, the drinking behavior of teens, when associating with other kids, bears little resemblance to the drinking norms practiced in the home. In fact, previous studies have shown that one of the factors most often associated with alcohol use by age fourteen is having tasted alcohol before age ten. In other words, if parents allow their children to sip alcohol in an effort to stave off underage usage, that intention is likely to backfire.

Christine Jackson, Susan Ennett, Denise Dickinson, & Michael Bowling (2012). Letting Children Sip Understanding Why Parents Allow Alcohol Use by Elementary School–aged Children Arch Pediatr Adolesc Med. DOI: 10.1001/archpediatrics.2012.1198. 

Donovan JE, & Molina BS (2011). Childhood risk factors for early-onset drinking. Journal of studies on alcohol and drugs, 72 (5), 741-51 PMID: 21906502.

Thursday, September 27, 2012

Huntington disease gene carriers have quicker minds

Good news and bad news for people who carry the Huntington’s disease (HD) gene. The good news is that they apparently can learn more quickly than noncarriers. The bad news is that they have HD. Okay, I admit that’s not much of a trade-off. My apologies to anyone suffering from this fatal disease.

HD is caused by a dominant gene mutation. Thus, if one of your parents has the disease, you have a 50/50 chance of having it yourself. Nowadays, there is a genetic test that can tell whether a person has the mutation. Needless to say, choosing whether to get tested for an illness that is both inevitable and incurable is not an easy decision.

Christian Beste and his colleagues from Ruhr-Universitat Bochum and Leibniz Research Centre recruited participants who had made the choice to be tested. The researchers gave ‘pre-manifest’ HD gene mutation carriers (people who were as yet symptom free) and healthy controls a set of perception tests. The subjects were asked to detect changes in the brightness of bars on a screen. After the initial test, participants were given the opportunity to passively observe changes in brightness, a training method known to increase visual discrimination, and then retested. HD carriers improved as much with only 20 minutes of training as controls did after 40 minutes of training.

I’d like to delve into the world of utter speculation now. One reason that HD is as common as it is, affecting one of out every 10-20,000 people, is that most people have already reproduced by the time they realize they have the disease. Perhaps another reason is that being an HD carrier confers some cognitive advantage during the pre-symptomatic stage. Again, not much comfort to the unfortunates who will succumb to this illness, though this new knowledge may be of some use to people with other kinds of cognitive defects.

hristian Beste, Edmund Wascher, Hubert Dinse, & Carsten Saft (2012). Faster Perceptual Learning through Excitotoxic Neurodegeneration Current Biology DOI: 10.1016/j.cub.2012.08.012

Wednesday, September 26, 2012

Tuesday, September 25, 2012

Viruses may be the fourth domain of life

While people still debate whether or not viruses can be considered life forms, some scientists, like University of Illinois researchers Arshan Nasir, Kyung Mo Kim and Gustavo Caetano-Anolles, propose that viruses get their own cherished spot on the tree of life. According to them, viruses deserve their own domain along with Archaea, Bacteria and Eukarya.

Just as archaeons have a different evolutionary history and biochemistry than bacteria (leading to them getting their own domain separate from bacteria) viruses also have a distinct history. In fact, the researchers suggest that viruses arose from a lineage that predated or coexisted with the earliest non-viral life forms on Earth. Much of this conclusion is based on studies of giant viruses. To be fair, not everyone agrees with the methodology used to make the case for a fourth domain. No doubt it will be debated for some time.

So what are giant viruses? As the name implies, these are extra large viruses that were first discovered two decades ago. How large? A typical giant virus has a genome with over a million bases and close to a thousand genes. ‘Regular’ viruses are far smaller. The influenza virus genome has between 12,000 and 15,000 bases and the HIV virus genome is less than ten thousand bases long. Meanwhile, one of the smallest bacteria, Mycoplasma genitalium, has a genome of less than 600,000 base pairs and only 521 genes. I should point out that no one disputes that tiny M. genitalium is alive. Intriguingly, some giant viruses have their own satellite viruses that act like parasites on the larger virus.

Megavirus particle.
Thin section, electron microscopy by Chantal Abergel, 10/10/2011.

If you’re interested, the Giant Virus website maintains a top 100 list with the hundred largest viruses known to date. Currently holding the top position is Megavirus chilensis with a whopping 1.25 million bases and 1120 genes.

Arshan Nasir, Kyung Mo Kim, & Gustavo Caetano-Anolles (2012). Giant viruses coexisted with the cellular ancestors and represent a distinct supergroup along with superkingdoms Archaea, Bacteria and Eukarya BMC Evolutionary Biology DOI: 10.1186/1471-2148-12-156

Monday, September 24, 2012

Optimized tumor treatment through starvation

There’s good news and bad news about brain cancer treatment. The good news is that Fernando Safdie of the University of Southern California and his colleagues may have found a way to boost the effects of chemotherapy and radiotherapy without damaging healthy cells. The bad news is that the method involves starvation.

The most common type of brain cancer is glioma. Treatment usually includes surgery, radiation and chemotherapy, but even with all that the five-year survival rate is less than 3%. The standard chemotherapy drug for this type of cancer is Temozolomide (TMZ) but it can only temporarily halt the growth of brain tumors. Meanwhile, these treatments damage healthy tissue as well as cancerous cells. Obviously, any approach that can improve these odds is worth investigating. 

Why pursue fasting as a treatment? Unlike normal cells, under times of duress, cancer cells don’t transfer scant resources from growth to maintenance functions. Thus, the tumor cells are particularly vulnerable to starvation. The researchers hope that fasting can cause these toxic therapies (chemotherapy and radiotherapy) to preferentially attack tumors rather than healthy tissues.

‘Short-term starvation’ was tested both in vitro, with glioma cell cultures, and in mice. In both cases, tumor cells but not normal cells were sensitized to TMZ. In fact, starvation alone slowed tumor growth as much as chemotherapy alone, though the greatest benefit was seen with fasting and chemotherapy. Mice that fasted and got TMZ had the smallest tumors and survived the longest. The same pattern held for radiotherapy. Mice that had been deprived of food had the best outcomes.

I’d like to point out that each enforced fast lasted 48 hours, and the mice underwent two cycles of fasting during their treatment. In other words, this treatment will have to have an amazing success rate before any humans are willing to try it. That doesn’t seem to be the case yet. Although the fasting mice fared better, all but one eventually succumbed to their tumors. To be fair, the fasting mice did not appear to suffer from their deprivations. Judging by their activity and general interest in their surroundings, they felt better than their non-fasting cohorts, possibly because the chemotherapy was not devastating their healthy tissues to the same extent. 

Safdie F, Brandhorst S, Wei M, Wang W, Lee C, Hwang S, Conti PS, Chen TC, & Longo VD (2012). Fasting enhances the response of glioma to chemo- and radiotherapy. PloS one, 7 (9) PMID: 22984531

Friday, September 21, 2012

Build your own lab equipment

What do you get when you combine free and open-source software with 3D printing? Anything you want! Joshua Pearce of Michigan Technological University wrote a piece in Science explaining the wonders of do-it-yourself lab equipment construction.

Michigan Tech's Joshua Pearce with a second-generation, open-source, 3D printer called a Mendel RepRap. The machine is made up of parts available in any local hardware store, open-source electronics available online, and parts that it can make for itself--all the red, white and blue components. Pearce has saved thousands of dollars by building his own lab equipment with this machine and others like it.
Credit: Sarah Bird/Michigan Tech.

To make your own lab supplies, the first thing you’ll need is a 3D printer. As the name implies, this is a device that prints solid objects. Instead of using ink, these printers build up a series of sub-millimeter thick layers of plastic or metal until they create the desired object. Pearce recommends the RepRap, which is not only under $1000, but can halfway replicate itself. This means that by adding a few components, you’ll soon have as many RepRaps as you need. 

You can see a 3D printer in action below (vastly speeded up):

Next, you’ll need an Arduino. This is a microcontroller that can run either your 3D printer, or the items you end up fabricating. There are specific Arduino programs for running oscilloscopes, ph meters, Geiger counters and even DNA amplifiers. You can pick up an Arduino for about $30.

Finally, you’ll need to input a design or blueprint. Luckily, you can find free digital designs for everything from test tube racks to centrifuge rotors at Thingiverse. Just perusing the examples of things people can fabricate with their 3D printers is fascinating.

Obviously, we have a ways to go before labs can manufacture everything they need, especially complex or sensitive electronic machinery. In the meantime, labs with these 3D printers can save money while never running out of pipette tips or Petri dishes again. If you add in the fact that you can modify designs to create precisely what you need, you have a real winner.

Thursday, September 20, 2012

If you have cold feet, you may want to think twice about marrying

Pre-wedding jitters, sometimes referred to as ‘cold feet’ are not uncommon. On the other hand, they aren’t universal either. Justin Lavner, Benjamin Karney and Thomas Bradbury from the University of California, Los Angeles wondered whether these feelings of anxiety could have any predictive power about the longevity of the ensuing marriage. For better or worse, women’s negative prenuptial feelings do correlate with a higher divorce rate.

Both spouses from 232 newlywed couples were invited to participate in a study. Each couple had been married for less than six months at the time of recruitment and no one in the study had been married before or had children. Each person filled out questionnaires and was interviewed every six months for the next four years.

At the initial interview, each spouse was asked, “Were you ever uncertain or hesitant about getting married?” and asked to rate their engagement period as ‘smooth’ or ‘difficult and turbulent’. In subsequent interviews, subjects were asked to rate their marital satisfaction.

Overall, 47% of husbands and 38% of wives had had some hesitancy or uncertainty about getting married. Premarital doubts did not correlate with age, income, education, premarital cohabitation, length of pre-marriage relationship or parental divorce. For men only, uncertainty did go along with having a higher level of neuroticism.

By the end of the four-year study, 27 couples had divorced. Whether or not men had entered a marriage with trepidation did not predict whether the couple would soon divorce. On the other hand, women who had had cold feet were two and a half times more likely to end the marriage than women who had not had any doubts.

I have a couple of comments about this. First, even though more than a third of women had pre-wedding jitters, only 11% of the couples went on to divorce. Clearly, having cold feet need not spell doom for a marriage. Also, this study does not address the nature of the doubts. Do worries about raising future children together spell doom more often than commitment fears? Finally, four years is a pretty short time frame in which to assess a marriage. I’d be interested to know how many marriages that began with at least one partner feeling some doubts survived to celebrate a 25th anniversary. 

Justin Lavner, Benjamin Karney, & Thomas Bradbury (2012). Do Cold Feet Warn of Trouble Ahead? Premarital Uncertainty and Four-Year Marital Outcomes Journal of Family Psychology DOI: 10.1037/a0029912

Wednesday, September 19, 2012

Just for fun: Planarian regneration

Planarians have an incredible ability to regenerate, even when chopped in pieces. A word of warning, if you don't speak Japanese, and maybe even if you do, you may want to watch this with the sound off.

By the way, if anyone can provide an English translation for this clip, please send it to me.

Tuesday, September 18, 2012

Ibuprofen makes you say what?

Sharon Curhan of Brigham and Women’s Hospital, Boston and her colleagues tested whether common over-the-counter analgesics can increase the risk of hearing loss. Unfortunately, they found that they do.

The scientists conducted two studies, an older study of men and a newer study including only women. In each study, some tens of thousands of adults were followed for over two decades. Participants filled out questionnaires every two years detailing their use of three categories of pain medicines (ibuprofen, acetaminophen and aspirin) and any onset of hearing loss.

For men, the overall risk of developing hearing loss increased significantly if they were frequent analgesic users. The risk was the greatest for men under fifty years old. For them, taking ibuprofen two or more times per week increased their risk of hearing loss by 61% percent, and taking acetaminophen increased it by 99%! Aspirin usage led to a 33% higher risk of hearing loss in men under 50.

The picture for women was similar, if not so severe. Again, younger women were hit the hardest. Overall, women had a 17% greater risk of hearing loss if they used ibuprofen at least twice a week, and a 9% greater risk with acetaminophen. Interestingly, women who used acetaminophen more than five times a week had a slightly lower risk than those who used it four or five times per week (11% versus 21%). The authors aren’t sure what to make of this, and neither am I. It almost seems as if once you’ve hit your fifth dose of the week, you should make it a clean sweep.

How about aspirin? Unlike for men, taking aspirin had no significant effect on women’s hearing. This was true for both low-dose and regular dose aspirin. Again, it’s unclear why there should be this difference between the sexes. However, of the categories of pain killers studied, aspirin had the least effect in men, and all the analgesics had a smaller effect on women than men. Perhaps in women, the effect of taking aspirin is simply below the threshold of detection in this study.

There are a couple of possible mechanisms for how these medicines could affect hearing. They may reduce cochlear blood flow and/or they may reduce the level of chemicals that protect the cochlea from noise-induced damage. They may also induce damage in the hair cells within the ear.

Men: Sharon Curhan, Roland Eavey, Josef Shargorodsky, & Gary Curhan (2010). Analgesic Use and the Risk of Hearing Loss in Men American Journal of Medicine DOI: 10.1016/j.amjmed.2009.08.006 

Women: Sharon Curhan, Josep Shargorodsky, Roland Eavey, & Gary Curhan (2012). Analgesic Use and the Risk of Hearing Loss in Women American Journal of Epidemiology DOI: 10.1093/aje/kws146

Monday, September 17, 2012

Yes, you can spread the flu before you have symptoms

Once in a while, the conventional wisdom about an illness turns out to be correct. Remember hearing that you’re most contagious before you start showing symptoms? Well, if that illness is the flu and you’re a ferret, that’s absolutely true.

Doctors aren’t blind to the possibility that pre or asymptomatic people could be spreading disease. In fact, epidemiologists often assume that up to a third of disease transmissions originate in people with no obvious signs of illness. Kim Roberts and her colleagues from Imperial College London used ferrets to test whether this was so. Apparently, ferrets make good flu-patient models. They become feverish and sneezy just like we do. 

First, the researchers determined how quickly symptoms appeared during a normal bout of flu. They infected some unfortunate ferrets (donors) and monitored their temperatures and how much virus they shed in their nasal secretions over the next ten days. The peak for both virus and fever was on day two, with a secondary spike of viral secretions on day five. Ferrets stopped secreting virus on day seven. Fever was the earliest sign of illness and appeared between 38 and 45 hours post infection.

Next, the scientists conducted a series of experiments where they exposed healthy ferrets (sentinels) to the sick ones at various times. Sentinels that were housed with the sick donors from 16 to 20 hours post infection did not become infected, but ferrets that were placed with sick roommates from 24 to 28 hours post infection did become ill. Remember, this was at least ten hours before the earliest sign of disease appeared in the donors.

What about aerosol transmissions? The authors infected another set of ferrets and placed new sentinels in adjacent cages from either day 1 to 2 or day 5 to 6 post infection. Only the former group of sentinels became infected despite the fact that far more sneezing and coughing was going on during the latter time period.

Clearly, the sentinel ferrets were becoming infected before any outward sign of flu appeared in their fellows. If this translates to human epidemiology, it could be bad news for trying to contain a future pandemic. However, I want to point out a couple of caveats. For one thing, this was an extremely small study. Each phase included no more than four animals. And second, although the donors may have shown no demonstrable sign of flu (fever, coughing, etc), during the early infectious period, it’s impossible to know whether they felt completely well. If humans feel a bit ‘under the weather’ before any overt flu symptoms appear, they might take greater pains to avoid infecting other people.

Kim Roberts, Holly Shelton, Peter Stilwell, & Wendy Barclay (2012). Transmission of a 2009 H1N1 Pandemic Influenza Virus Occurs before Fever Is Detected, in the Ferret Model PLoS ONE DOI: 10.1371/journal.pone.0043303

Friday, September 14, 2012

Should restaurants change their music and lighting?

Does it serve a restaurant’s interests more to have soft music and lighting, or bright lights and loud music? People do eat faster in the more harsh conditions present in most fast food places, but do they also eat more and/or spend more?

Brian Wansink of Cornell University and Koert van Ittersum from the Georgia Institute of Technology used soundproof wall dividers, candles and soft jazz to transform part of a Hardee’s fast food restaurant into a fine dining experience. The rest of the restaurant maintained its usual d├ęcor (bright colors and loud music). Customers were randomly seated in one of the two sections. Unbeknownst to them, not only was their table time clocked, but their leftovers were weighed to calculate how many calories they had consumed. They were also asked to rate their dining experience.

Both groups ordered the same amount of food, and thus spent the same amount of money. Not surprisingly, the people in the fine dining section stayed a bit longer than those in the fast food section. Despite this, the fine dining patrons actually ate less than their fast food cohorts, mainly because they left more food on their plates. I’d suggest that lingering too long over a fast food meal makes you lose your appetite, except that this group also rated the experience and the food higher, even though it was the exact same food.

Softer music and lighting sounds like a win for the customers, who consumed fewer calories and enjoyed the meal more. Meanwhile, the restaurant didn’t lose anything in this scenario, since people spent the same amount of money.

I actually think the benefit is greater than that shown in this study. Because all the test subjects entered the Hardee’s anticipating a fast food meal, they only stayed 4.7% longer in the fine dining area than in the fast food area. If you assume that the average person eats a fast food meal in under fifteen minutes, that translates to less than a minute longer. Not really long enough to order dessert. In a real sit down restaurant, the difference between a jarring, unpleasant ambiance and one where you can comfortably hear your tablemates may very well translate into higher expenditure.

That said, if a restaurant relies heavily on rapid turn-over, they should probably stick to bright lights and loud music.

Thursday, September 13, 2012

Introducing ENCODE

A huge international project called the ‘Encyclopedia of DNA Elements’ (ENCODE) is now ready for prime time. This week, some thirty papers have been published explaining what it is and what it might mean. For a far more comprehensive discussion than I can give here, you can’t go wrong with Ed Yong’s tour de force at Not Exactly Rocket Science.

In a nutshell, ENCODE is an enormous manual for the human genome. Now that we’ve sequenced all those stretches of Gs, Ts, As and Cs, what exactly are they doing? The ENCODE analyses are as interesting for what they disprove as they are for what they demonstrate.

For example, have you heard that over 95% of the human genome is ‘junk DNA’, not really of any use to us? Wrong! It turns out that nearly every part of our genomes might serve some function. That doesn’t mean the number of genes was grossly underestimated. We still think that only a few percent of our DNA codes for proteins. It’s just that lots of non-coding sections of DNA are used either to make regulatory RNAs, or simply as landing zones for RNAs and proteins. 

Another thing ENCODE tackles is the problem of how and why our myriad cell types differ from each other. You’re not going to get very far in figuring out why we aren’t chimps if you can’t even say why we aren’t just giant livers rather than being composed of more than a thousand distinct cell types.

For a summary from some of the lead researchers, see below:

And for a more visual explanation, leave it to Ian Sample of The Guardian:

Obviously, much more data is going to come out of this immense collaboration. In the meantime, you can look over the results yourself at the ENCODE website.

Wednesday, September 12, 2012

Just for fun: Time lapse vines

Who doesn't love timelapse photography, especially when it involves twining vines?

This sort of twisting motion is called 'nutation'. It's not well understood, although it does rely on unequal growth rates on different sides of the plant tissue. These images were taken at 10 minute intervals.

Tuesday, September 11, 2012

A binary star system

It’s not enough anymore to simply announce the finding of a new exoplanet. We’ve found so many in the past few years (thousands to date) that they’re almost commonplace. Now, the new planets have to have something unusual about them to make them noteworthy. Case in point, a pair of planets orbiting the binary star system Kepler-47.

Circumbinary (orbiting two stars rather than just one) planets have been discovered before. However, this time, it’s a whole star system going around the pair of stars. Granted, that system only has two known stars, but more may yet be found.

The planets were discovered by Jerome Orosz of San Diego State University and more than three dozen collaborators who shared authorship. They had to observe the two stars eclipsing each other, as well as the planets transitting (passing in front of) the stars. Each of these events had to be observed multiple times in order to confirm the data. Luckily, the two stars orbit each other every seven and a half days and the inner planet orbits both stars in just under 50 days. Thus, it didn’t take that long to see several transits. At a little over 300 days, the outer planet has a year almost as long as ours. Cosmologists have only observed three transits of this planet.

An artist's depiction of the Kepler-47 system. Kepler-47c is the large planet on the left; Kepler
47-b appears as the small blue crescent to the right of the two stars.
Image courtesy of NASA/JPL-Caltech/T. Pyle.

What about habitability? Although one of the stars is similar in size to that of our sun (the other is about a third as big), neither of the planets is expected to be Earth-like. While the outer planet does technically reside in the habitable (liquid water zone), it’s about four and a half times as big as the Earth. The inner planet is also three times the size of the Earth and not even in the habitable zone.

So neither of these new planets is going to be a New Earth. We’ll have to keep looking for the place to evacuate our citizenry when our sun becomes a white dwarf. The good news is that we now know that planets can be found in the habitable zone of binary star systems as well as single star systems.

ResearchBlogging.orgOrosz JA, Welsh WF, Carter JA, Fabrycky DC, Cochran WD, Endl M, Ford EB, Haghighipour N, Macqueen PJ, Mazeh T, Sanchis-Ojeda R, Short DR, Torres G, Agol E, Buchhave LA, Doyle LR, Isaacson H, Lissauer JJ, Marcy GW, Shporer A, Windmiller G, Barclay T, Boss AP, Clarke BD, Fortney J, Geary JC, Holman MJ, Huber D, Jenkins JM, Kinemuchi K, Kruse E, Ragozzine D, Sasselov D, Still M, Tenenbaum P, Uddin K, Winn JN, Koch DG, & Borucki WJ (2012). Kepler-47: A Transiting Circumbinary Multiplanet System. Science (New York, N.Y.) PMID: 22933522

Monday, September 10, 2012

Good news for tigers

Species are going extinct at a prodigious rate, often because their habitats have been eradicated by human encroachment. Tigers are a prime example of a creature not expected to last into the next century. But that needn’t be the case. Neil Carter from Michigan State University and his colleagues have found that humans and tigers can coexist successfully.

First, let’s be clear about what’s being discussed. No one is suggesting that tigers and humans can happily occupy the same suburban neighborhoods. This study simply shows that human usage of a specific site in a forest does not prevent tigers from using that same site at a later time. In other words, the activities of humans need not drive tigers out of an area.

The study was conducted in and around Nepal’s Chitwan National Park. This region is home to over 25 breeding female tigers and is also visited regularly both by tourists and researchers and by local residents collecting forest resources such as firewood (though the latter operate outside the park boundaries).

The scientists found that over a two-year period, both people and tigers were using the same locations of the forest, as evidenced by camera traps. Even in areas of high human usage (both walking and driving), tigers were still observed. In fact, increasing human usage did not affect tiger density. The main concession the tigers seemed to make was to occupy the territory at night, leaving it to the humans during the daytime.

While this is somewhat encouraging, I think it will do little to prevent the eventual extinction of tigers or any other animals. It’s great that tigers don’t mind sharing their territories with humans, but I’m pretty sure most humans do mind sharing their territories with tigers.
Carter NH, Shrestha BK, Karki JB, Pradhan NM, & Liu J (2012). Coexistence between wildlife and humans at fine spatial scales. Proceedings of the National Academy of Sciences of the United States of America PMID: 22949642

Friday, September 7, 2012

Using teeth to determine handedness

ResearchBlogging.orgClose to 90% of Neandethals were right-handed. Much of this data comes from comparing the muscularity of their arms, which show clear differences. However, arms aren’t the only way you can tell a lefty from a righty. You can also look at that individual’s teeth.

How often have you used your teeth as a tool to hold, pull or tear something? Neanderthals, with their much stronger jaws, presumably made even more use of their teeth. Wear patterns on their enamel confirm this. A right-handed person who routinely uses his mouth as a vise grip will not wear down the same sides of his teeth as a left-handed person. You can try this yourself (though hopefully not to the point of damaging your enamel). Thus, by looking at the scratches on fossilized teeth, you can tell whether that individual was right or left-handed.

Virginie Volpato of the Senckenberg Research Institute Frankfurt and her colleagues examined the teeth and skeleton of one particular Neanderthal specimen (Regourdou 1). They found that using his teeth to determine his handedness yielded the same result as using his arm asymmetry. This strengthens the idea that you can distinguish right from left-handed Neanderthals and also confirms that most of them were in fact righties.
Labial scratches on Regourdou 1’s anterior teeth.

I think the authors go a bit off the rails with their suggestion that the preponderance of right-handedness amongst the Neanderthals indicates that they had language (which is predominantly a function of the left brain). I don’t doubt that Neanderthals did have language, but this seems like a tenuous connection. For one thing, couldn’t there be some other reason most Neanderthals are right-handed? And for another, left-handed people also have language. Perhaps someone with more training in neurology and/or paleontology could set me straight.

Virginie Volpato, Roberto Macchiarelli, Debbie Guatelli-Steinberg, Ivana Fiore, Luca Bondioli, & David W. Frayer (2012). Hand to Mouth in a Neandertal: Right-Handedness in Regourdou 1 PLoS ONE DOI: 10.1371/journal.pone.0043949.g004