By Brenna Henn
<img loading="lazy" decoding="async" class="size-full wp-image-750" style="border: 0pt none;" title="maasihut_sat" src="https://blog-api.23andme.com/wp-content/uploads/2008/08/maasihut_sat.jpg" alt="" width="314" height="234" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/08/maasihut_sat.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/08/maasihut_sat-300x225.jpg 300w" sizes="auto, (max-width: 314px) 100vw, 314px" />A Nilotic-speaking pastoralist from Tanzania / Sarah A. Tishkoff
Genes are just one component that children inherit from their parents. Throughout much of human history, especially when populations consisted of small hunter-gatherer groups, the language and lifestyle of a people were also inherited from generation to generation.
This is why genetic patterns and cultural traits are often correlated. So, when scientists see cultural similarities between two populations, they can ask whether there are genetic similarities between the two groups as well.
For many cultural traits, such as pastoralism and agriculture there is still a debate: did people actually migrate into new regions, bringing their genes and culture with them, or did the language and lifestyle simply spread by word of mouth to new lands?
<h6>Pastoralism</h6>
In this week&#8217;s <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.0801184105" target="_blank" rel="noopener noreferrer">Proceedings of the National Academy of Sciences</a>, scientists from Stanford University (several of whom are also associated with 23andMe, including myself) have used the principle of genetic and cultural exchange to find the first genetic evidence of a prehistoric migration of people from Tanzania to southern Africa. We discovered a mutation (aka &#8216;SNP&#8217;) on the Y-chromosome that originated about 10,000 years ago in eastern Africa and is now most common among people from two regions: Tanzania and southern Africa.
Pastoralists (people who rely heavily on animal husbandry for food) such as the Datog and Burunge of northern Tanzania carry the newly discovered SNP. In fact, it is present among 30-40% of men from these populations. Unexpectedly, the click-speaking Kxoe of southern Africa carry the same SNP at similar levels to the Tanzanian populations, indicating that these people are closely related to the Tanzanian pastoralists. The evidence indicates that men from southern and eastern Africa shared very recent common ancestors between about 1,200 and 2,700 years ago.
<h6>Genetic Exchange</h6>
With this genetic evidence in hand, we then turned to archaeologists to see if the fossil record indicated an ancient migration around this time.
As it turns out, the current thinking among archaeologists is slightly different than what this new genetic evidence has revealed. Archaeologists currently favor a model in which the cultural practice of pastoralism spread from an unknown eastern African group into southern Africa about 2,000 years ago, perhaps without any sort of movement of people (i.e. genetic exchange).
Our new genetic study<img loading="lazy" decoding="async" class="size-full wp-image-751 alignright" title="donkeycart" src="https://blog-api.23andme.com/wp-content/uploads/2008/08/donkeycart.jpg" alt="" width="268" height="400" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/08/donkeycart.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/08/donkeycart-200x300.jpg 200w" sizes="auto, (max-width: 268px) 100vw, 268px" />, while still supporting the archaeological record for the timing and place of the origins of pastoralism in sub-Saharan Africa, puts a new twist on the current thinking. It suggests that a small group of men actually migrated into southern Africa about 2,000 years ago. These men probably married into local hunter-gatherer populations, contributing their livestock and cultural knowledge of pastoralism. These migrants were probably closely related to the modern day Datog and Burunge groups of Tanzania.
<h6>Nama of Nambia</h6>
A shift to pastoralism was a fundamental change for the hunter-gatherers of southern Africa during the last couple thousand years. It caused a dramatic change in the culture and belief systems of these people. As pastoralism became more widespread in southern Africa, so did the beginnings of a sense of ownership of animals and the emergence of chieftans.
These changes can still be seen today in the practices of people throughout Namibia, Botswana and South Africa. For example, the Nama of Namibia began practicing pastoralism not long after its arrival in southern Africa and continue to do so today.
The question of whether the shift from hunting and gathering to agriculture was the result of cultural exchange or actual migrations between groups is one of the most important debates among archaeologists and geneticists. With this new genetic evidence, we think we have answered this question, at least in southern Africa.
Future studies will further examine the relationhip between genes and culture, and how this relationship has influenced the genetic and cultural makeup of modern African populations.
&nbsp;
 Brenna Henn is a doctoral student in Stanford University&#8217;s Department of Anthropology and a 23andMe consultant. Brenna studies human evolution using genetic information. Her interests include the origin of modern humans, migration patterns among African groups, and genetic models of demography.

Brenna Henn

The Origins of Pastoralism in Africa: What do the Genes Say

<img loading="lazy" decoding="async" class="alignright alignnone size-medium wp-image-164 alignright" style="float: right;" title="brainmaze" src="https://blog-api.23andme.com/wp-content/uploads/2008/03/istock_000005152907xsmall.jpg" alt="" width="277" height="300" />
Even as the genetic studies on schizophrenia released this week illustrate our progress toward the ultimate goal of personalized medicine, they also bring to mind the challenges that still lie ahead.
All three studies focus on identifying the genetic bases of schizophrenia, a mental disorder <a href="http://www.nimh.nih.gov/health/publications/schizophrenia/what-is-schizophrenia.shtml" target="_blank" rel="noopener noreferrer">characterized</a> by hallucinations, <a href="http://www.tv.com/criminal-minds/derailed/episode/509889/summary.html" target="_blank" rel="noopener noreferrer">delusions</a> and the decreased ability to plan and organize. These symptoms typically manifest during a patient’s late teens or early 20s.
One <a href="https://www.nature.com/ng/journal/vaop/ncurrent/abs/ng.201.html" target="_blank" rel="noopener noreferrer">study</a> led by Cardiff University researcher Michael O’Donovan identified single nucleotide gene variants (SNPs) associated with schizophrenia. As detailed in the journal Nature Genetics, the researchers started with 12 variants, narrowed the list to six after replicating the tests on several thousand study participants and finally identified three SNPs associated with the disease.
The variant with the strongest association has a small effect — only increasing the chances of schizophrenia by only about 12 percent among people who have the higher risk version – that it offers limited information.
The other studies – <a href="https://www.nature.com/nature/journal/vaop/ncurrent/full/nature07239.html" target="_blank" rel="noopener noreferrer">one</a> from the International Schizophrenic Consortium and <a href="https://www.nature.com/nature/journal/vaop/ncurrent/full/nature07229.html" target="_blank" rel="noopener noreferrer">one</a> from deCODE and the SGENE Consortium – which appear in the journal Nature opted to look for genetic associations by checking copy number variants, DNA segments with deletions or duplications that can be inherited.
One group found three deletions – one on chromosome 1 and two on chromosome 15 – that showed up in a few dozen people out of thousands sampled and were more common among people with schizophrenia. The other group identified two of those three deletions. They also found that people with schizophrenia tend to have more rare copy number variants – both duplications and deletions – in their genomes compared to people without the disease.
“This work opens up an entirely new way to think about schizophrenia and eventually will suggest new avenues for researching effective therapies for the sake of patients and families suffering from this terrible disorder,” said International Schizophrenic Consortium member and study co-author Pamela Sklar in a statement.
One of the frustrations schizophrenia researchers have encountered is that while the disease is fairly common – affecting one percent of Americans – the genetic basis of schizophrenia has been difficult to pinpoint. One as-yet unsolved mystery is how the disease, which has a high degree of heritability, is as prevalent as it is when correlated with the fact that people who have schizophrenia and other similar mental disorders have fewer offspring.
These studies suggest that very rare gene mutations might play more of a role in the disease than had previously been supposed. That’s valuable information for scientists, and may explain why the genetics of schizophrenia have been so difficult to figure out. But it also suggests that it will take much more research to understand the genetic risk factors underlying schizophrenia than many other diseases.

23andMe Blog

23andMe Blog Team

Needles in a Haystack

This guest post is by Roy King, who is a professor of psychiatry at Stanford University and a research colleague of Stanford geneticist and 23andMe scientific adviser Peter Underhill. Roy and Peter have been using genetics to trace the spread of agriculture from the Near East to Europe.
<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/germanvineyard.jpg" alt="" title="germanvineyard" class="alignright size-full wp-image-564" width="350" height="260" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/germanvineyard.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/07/germanvineyard-300x223.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
The question of how agriculture first arose and spread in Europe has perplexed archaeologists and geneticists alike for decades. Evidence for farming communities in Greece, Crete, the Balkans, Southern Italy, and Mediterranean France and Spain first appears in the archaeological record eight to nine thousand years ago with the appearance of domesticated wheat, barley, sheep, goats and cows, and a related culture featuring pottery and anthropomorphic figurines. Before this period, most of the indigenous people of Europe fished, hunted small game or foraged for their livelihood.
But how did farming get to Europe in the first place? We know that 2,000 years before agriculture hit Europe, just after the end of the Ice Age, people living in the Near East had already developed farming, with the domestication of wild species of grasses, goats and cattle likely beginning in the fertile river valleys in present-day northern Iraq, Syria and southeastern Turkey. Near Eastern farmers also settled in villages and produced pottery and ceramic human figurines similar to the ones later found across Mediterranean Europe.
So did the first farmers of the Near East hop into boats with their domesticated plants, animals and artistic motifs and colonize Mediterranean Europe? Or did native Europeans learn about farming through trade with the Near East and decide to adopt this agricultural economy too? 
 
Genetic studies are starting to provide answers to this enduring question. Not only do genetic studies of sheep, goats, cows and wheat demonstrate that the European varieties are subtypes of the species found in the Near East, but data from the human Y chromosome suggest that people currently living in Southern Europe are descended in large part (at least through the paternal line) from the Near East. This suggests, at least for the Mediterranean areas of Europe, that the most probable scenario is that Near Eastern farmers did actually move into Europe, bringing farming with them.
23andMe has a Y chromosome marker on its custom chip, rs34126399, which captures the spread of agriculture from the Near East to Europe. The G state at rs34126399 is found in most individuals carrying paternal haplogroup J2a, whose origin can ultimately be traced to Turkey 15,000 to 20,000 years ago. Southern Turkey is the likeliest source for the initial domestication of wheat.
<img loading="lazy" decoding="async" class="aligncenter size-medium wp-image-559" title="rs34126399" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/rs34126399.png" alt="" width="222" height="172" />
In the millennia after its appearance in Turkey, rs34126399G then experienced a population growth and spread westward into the eastern Mediterranean and eastward into Mesopotamia, Iran and northern Egypt. The map to the right shows the present-day distribution of rs34126399G in Europe and the Middle East.
In addition to its high frequency in the Near East, rs34126399G is present in 10 to 25% of the population of southern Greece and Italy, Crete, Sicily, Bulgaria and Romania. The concentration is an indication of the early spread of farming to these regions, where the climate of wet winters and hot dry summers suited the varieties of winter wheat that were first domesticated.
Since the initial movement of people associated with the origins of agriculture nearly 10,000 years ago, there has been persistent contact and trade throughout the Mediterranean. Just think of the Mediterranean diet – rich in olive oil, goat cheese, and red wine – all of whose origins can be traced to these regions. One archaeologist described the Mediterranean Sea figuratively as a giant bathtub that for millennia has permitted easy seafaring transit from one area to another. The genetic evidence appears to support that analogy.

The Origin of Farming in Europe: A View from the Y Chromosome

<img loading="lazy" decoding="async" class="alignleft wp-image-577 size-full" style="float: left;" title="mckusick" src="http://35.88.189.111/wp-content/uploads/2008/07/mckusick.jpg" alt="" width="232" height="350" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/mckusick.jpg 232w, https://blogcms.23andme.com/wp-content/uploads/2008/07/mckusick-199x300.jpg 199w" sizes="auto, (max-width: 232px) 100vw, 232px" />
&#8220;Sometimes I feel like Sir James Murray must have felt while he was grubbing away at writing the Oxford English Dictionary,&#8221; the Washington Post once quoted Victor McKusick as saying. &#8220;He managed to complete the first 17 letters before he died.&#8221;
When McKusick, University Professor of Medical Genetics at Johns Hopkins University School of Medicine, the so-called &#8220;Father of Genetic Medicine&#8221; and a key architect of the Human Genome project died on July 22, his own magnum opus, the online Mendelian Inheritance in Man (OMIM) <a href="https://www.ncbi.nlm.nih.gov/sites/entrez?db=omim" target="_blank" rel="noopener noreferrer">database,</a> had nearly 19,000 entries.
The man who wrote the bible of medical genetics attended Tufts University and then entered Johns Hopkins Medical School without finishing college.
&#8220;Part of my reverse snobbery is that I was a college dropout, that I don&#8217;t have a bachelor&#8217;s degree,&#8221; McKusick observed during a 2001 interview. &#8220;I have twenty-one honorary doctorates in addition to my M.D., but no bachelor&#8217;s degree.&#8221;
Once he got into Johns Hopkins in 1943, McKusick never left. He started his medical career as a cardiologist because, he said, medical genetics didn’t exist as a field then.
&#8220;The problems presented by hereditary disorders were intellectually tremendously challenging, and that was part of the reason I was interested in them,&#8221; he said during a 2001 interview. &#8220;It was obviously necessary to get at root causes in the terms of biochemical defects and, eventually, DNA defects.&#8221;
His interest in genetic disorders such as Marfan Syndrome led to studies involving the Old Amish in Pennsylvania, and eventually fostered a need to compile not just an annual review of genetic research done thus far, but to provide &#8220;a comprehensive compendium of all the information up to a given point.&#8221;
That compendium was the Mendelian Inheritance of Man or MIM, which went through 12 editions in print before the sheer number of entries rendered volumes unwieldy. In 1987, the online MIM, which McKusick and his colleagues continued to edit on a daily basis, became available to the public. By 2000, OMIM had <a href="https://www.nature.com/ng/journal/v25/n1/full/ng0500_11.html" target="_blank" rel="noopener noreferrer">1,000 gene entries</a> where at least one version of a gene had been linked with a human phenotype.
In 1968, McKusick published a Proceedings of the National Academy of Sciences <a href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&amp;pubmedid=5246559" target="_blank" rel="noopener noreferrer">paper</a> in which he mapped the Duffy blood group locus to chromosome 1. The following year he began campaigning for a map of the human genome, and saw the full DNA sequence completed in 2001.
McKusick received the 1997 Albert Lasker Award for Special Achievement in Medical Science and the 2001 National Medal of Science. Earlier this year he was awarded the Japan Prize in medical genomics and genetics from the Science and Technology Foundation of Japan. And for nearly 50 years he was co-director of the Short Course in Medical and Experimental Mammalian Genetics, a two-week summer course held at The Jackson Laboratory in Bar Harbor, Maine.
He also foresaw the promise of genome-based medical care. “On the traditional turf of clinical medicine diagnosis will become more specific and precise, and treatment also more specific and safer,” McKusick wrote in a 2001 JAMA <a href="https://www.ncbi.nlm.nih.gov/pubmed/11710895?dopt=Abstract" target="_blank" rel="noopener noreferrer">paper</a>. &#8220;Better understanding of individual genomic constitutions should permit drug therapy to get away from the one-size-fits-all approach. It should allow selection of drugs likely to be more effective in the treatment of a given disorder in a given individual.&#8221;
At the end of an <a href="http://www.socgen.ucla.edu/hgp/mckusick.html" target="_blank" rel="noopener noreferrer">interview</a> for the Oral History of Human Genetics Project, McKusick talked about the opportunities he’d had to work on so many intriguing topics, ultimately comparing the scope of his work to that of Sir Isaac Newton.
&#8220;Of course, to compare my career with that of Isaac Newton is absurd,&#8221; he noted, &#8220;but he [Newton] says that he feels like a small boy playing on the beach and picking up an occasional pebble that is smoother and brighter in color than the rest while all the great mysteries of the ocean go unexplored. He&#8217;s just picking up a little stone here and there. So I feel like an unabashed dilettante, as well as a chauvinist and opportunist.&#8221;
Image from: Johns Hopkins Medicine

Victor McKusick: 1921-2008

<img loading="lazy" decoding="async" class="alignright size-full wp-image-546" title="muscleache" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/muscleache.jpg" alt="" width="350" height="233" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/muscleache.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/07/muscleache-300x200.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
By lowering blood levels of “bad cholesterol,” or LDL, statins can lower the risk of heart attack and stroke. But the drugs are not without side effects – about one patient out of 10,000 experiences a form of muscle pain and/or weakness known as myopathy.
<h2>The SEARCH Collaborative Group</h2>
A report published yesterday in the <a href="https://dx.doi.org/10.1056/NEJMoa0801936" target="_blank" rel="noopener noreferrer">New England Journal of Medicine </a>suggests that a variation in a gene previously linked to how the body processes statins may be partially to blame.
The SEARCH Collaborative Group, a large consortium of scientists studying the use of high simvastatin (Zocor/Lipex) doses in British patients who have previously had heart attacks, found a genetic variant associated with an increased risk of myopathy.
<h2>Simvastatin</h2>
Out of about 6,000 people taking 80 mg daily of simvastatin (the usual dose is 20-40 mg), researchers identified 85 who either had myopathy or whose bloodwork suggested they were on the verge of developing it.
When these people were compared to 90 people who were on high-dose simvastatin but had no signs of muscle problems, the researchers found that one version of the variant increased a person’s odds of myopathy 4.9 times and two variants increased the odds 16.9 times.
The researchers also found an association between one variant and myopathy in the Heart Protection Study. That study compared 10,200 people taking 40 mg of simvastatin with a similar number of people taking a placebo. In this case, however, the effect of the variant was much smaller, increasing the odds of myopathy by only 2.6 times. Only 23 of the simvastatin-taking patients in this study had myopathy.
<h2>More Serious Side Effects</h2>
The myopathy experienced by both patients in the New England Journal of Medicine report was mild and reversible. There is, however, a potentially fatal (but even more rare) form of muscle breakdown called rhabdomyolysis that has also been linked to statins. More research will be needed to investigate whether rs4149056 is also associated with rhabdomyolysis.
In addition to simvastatin, five other statins are available in the United States: lovastatin (Mevacor/Altocor), pravastatin (Pravachol/Selektine/Lipostat), fluvastatin (Lescol), atorvastatin, (Lipitor/Torvast), and rosuvastatin (Crestor). The authors of the study say that their findings likely apply to those drugs as well &#8212; myopathy is known to be a side-effect of all statins and variants in the gene where rs41419056 is found are known to affect blood levels of several statins.
Sixty percent of the myopathy cases observed in the study of patients taking 80 mg of simvastatin could be attributed to the C version of rs4149056. This suggests that avoiding giving high doses of statins to people who carry this version of the SNP could significantly reduce the incidence of myopathy, wrote Yusuke Nakamura in an editorial accompanying the study. However, he added, “Further investigation is required to identify the optimal therapeutic approach.”

Gene Variant May Increase Risk for Rare Side Effect of Cholesterol-Lowering Drugs

<img loading="lazy" decoding="async" class="alignright alignnone size-medium wp-image-413" style="float: right;" title="Election - Young Voter Thumbsup" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/girlvote-200x300.jpg" alt="" width="200" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/girlvote-200x300.jpg 200w, https://blogcms.23andme.com/wp-content/uploads/2008/07/girlvote.jpg 283w" sizes="auto, (max-width: 200px) 100vw, 200px" />On the heels of his previous <a href="https://blog.23andme.com/2008/07/15/the-true-value-of-two-for-one-deals/" target="_self" rel="noopener noreferrer">paper</a> finding that participating in political activities such as voting is influenced in part by genes, political scientist James Fowler and his graduate student Christopher Dawes announced that they’ve identified two genes that are associated with voting itself.
In the current issue of The Journal of Politics, Fowler and Dawes <a href="http://media-newswire.com/release_1068548.html" target="_blank" rel="noopener noreferrer">identify</a> particular variants of the MAOA and 5HTT genes, both of which are part of the biological pathway that influences mood, emotion and judgment, as being &#8220;significantly associated with the decision to vote.&#8221;
Based on the description above, it&#8217;s easy to see how the serotonin pathway can affect social behaviors. <a href="http://www.madewithmolecules.com/serotoninnecklace.html" target="_blank" rel="noopener noreferrer">Serotonin</a> is a chemical in the brain that can induce feelings of happiness. Studies have shown that MAOA and 5HTT have different functions on the pathway, and variants of each gene have been linked to particular behaviors.
For example, the version of 5HTT with a slightly shorter genetic sequence has been associated with producing low levels of serotonin. Studies indicate that the &#8220;short&#8221; version of the gene has been linked to conditions such as <a href="http://hum-molgen.org/NewsGen/03-2005/000019.html" target="_blank" rel="noopener noreferrer">alcohol dependence</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/9832193?ordinalpos=3&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">bipolar depression</a>.
On the other hand, the &#8220;long&#8221; version has been linked to more positive traits such as <a href="https://www.ncbi.nlm.nih.gov/pubmed/16095668?ordinalpos=36&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">longevity</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/17642369?ordinalpos=16&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">competitiveness in athletes</a>.
Similarly, MAOA has high- and low-activity versions. The high-activity version has been linked with <a href="https://www.ncbi.nlm.nih.gov/pubmed/12136060?ordinalpos=8&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">restless legs syndrome</a> while the low-activity version, which is also associated with producing low serotonin levels, has been linked to <a href="https://www.ncbi.nlm.nih.gov/pubmed/17969463?ordinalpos=19&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">increased sleep apnea</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/18361446?ordinalpos=21&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">more severe symptoms of autism</a>.
Because the &#8220;long&#8221; version of 5HTT and the &#8220;high&#8221; version of MAOA have been correlated with social behaviors, Fowler and Dawes proposed these as candidate genes for voting participation. They then looked at population data from the National Longitudinal Study of Adolescent Health to find confirmation of their theory.
Known as Add Health, the study itself consists of data collected from more than 15,000 young adults who the researchers tracked for seven years between 1994 and 2001. Among the questions the now 18-26 year-old participants answered for the researchers toward the end of the study were how often they&#8217;d attended church services in the past year and whether or not they voted in the 2000 presidential election.
Fowler and Dawes based their conclusions on the data collected from a subset of 2,300 Add Health participants because information for six genetic markers, including 5HTT and MAOA, were also collected from them. They correlated the genetic information with the answers from the surveys to find out if their candidate genes would turn out to play a role in voter turnout.
Turns out they found a couple of links. &#8220;Having a high MAOA allele,&#8221; Fowler and Dawes wrote in their paper, &#8220;raises the likelihood of voting by about 5%. Among people active in their religious organizations, having a long 5HTT allele raises the likelihood of voting by about 10%.&#8221;
Given the age range of the study participants, and the timing, it&#8217;s worth asking some questions about these conclusions. Fowler and Dawes themselves note that the young adults might have been voting for the first time during the 2000 election; the historic significance of that contest might have been a motivator along with theoretically being genetically inclined towards pro-social behavior. Having older participants in the study might have been able to provide the researchers with a more constant voting behavior perspective.
What Fowler and Dawes don&#8217;t discuss, though, is the role of religion during the 2000 election. One <a href="http://apr.sagepub.com/cgi/content/abstract/35/6/846" target="_blank" rel="noopener noreferrer">study</a> published last year found that 25 percent of the public said their voting decisions for the 2000 election were influenced by the religious media. Another study found that members of evangelical Protestant churches form tight social networks that promote civic involvement such as political participation within these communities.
In short, the correlation between the long 5HTT version, religious involvement and voting might be a little more complicated than Fowler and Dawes contend.

Selected to Elect?

Last week in the Blog we reported on a new study that identified an interesting genetic trade-off – a genetic variant known that has one effect on a person&#8217;s vulnerability to malaria, and the opposite on susceptibility to HIV infection. The &#8220;Duffy negative&#8221; version of the gene, which is common among Africans and African Americans, appears to protect a person against malaria but increases vulnerability to infection by HIV. As it turns out, Duffy is not the only example of a genetic trade-off in humans.   There are many instances of genetic variation throughout the human genome that offer both genetic advantages and disadvantages to their carriers.  
<h6> Sickle Cell Anemia vs. Malaria</h6>
<a href="https://www.23andme.com/topics/carrier/sickle-cell-anemia">Sickle cell anemia</a> is caused by a genetic mutation that alters the shape of an individual’s red blood cells.   This mutation, called Hbs, causes red blood cells to take on a sickle-shape, as opposed to the normal round shape.   The sickle-shaped cells then get stuck in the veins and arteries, causing tremendous pain and discomfort.   Sickle cell anemia is recessively inherited, meaning that someone must inherit the Hbs mutation from both parents in order to have the disease. Malaria is a disease that kills between 1 and 3 million people worldwide each year, mainly in the tropics.   After scientists noticed similarities between the geographic distribution of sickle cell anemia and malaria, they began to wonder if there was some sort of connection between the two.
Experiments soon confirmed that sickle cell anemia is a sort of genetic Faustian bargain. Recall that individuals with two copies of Hbs suffer from sickle cell anemia, but people with only one copy of the mutation do not.   They do however, display a resistance to malaria compared with people who have no copies of Hbs.   Occasionally, a pair of malaria-resistant parents will both pass Hbs – and thus sickle cell anemia – to their child. But overall, having only one copy improved the survival rate in human history so much that the Hbs mutation continues to exist in in spite of the disease burden it causes.
<h6>Hereditary Hemochromatosis vs. Iron Deficiency</h6>
Hereditary hemochromatosis (HH) is a genetic condition in which the body absorbs too much iron from the diet.   This leads to the toxic build-up of iron in the tissues of major organs such as the liver and heart.   Without treatment, HH can lead to organ failure. Genetic studies have found that HH, like sickle-cell, is a recessive trait. It appears to have evolved about 1,400 years ago, probably in western Europe, at a time when people ate mostly cereal grains – which are very low in iron. Because having some amount of iron in the diet is essential to maintain normal body functions, this was a serious problem.   During this time period, the ability to store extra iron in the body would have been helpful.   Individuals with HH could take iron from foods when it was available, and then store it in the organ tissues, dipping into those reserves when the supply of iron-rich foods was low.   Today, however, iron is much more abundant. It is an excess of iron, not a lack of it, that threatens the health of people with HH.
<h6>The Paleolithic Diet vs. Obesity</h6>
Why is it that humans crave the very foods that are unhealthy?   Why do we prefer donuts and candy to celery and spinach?   Like hereditary hemochromatosis, the source of this cruel irony lies in the history of our species. The human brain is a very expensive organ to maintain.   It requires a lot of energy to keep all the synapses working correctly, and simply feasting on celery would not do the trick.   Hundreds of thousands of years ago, our ancestors began eating meat as a way to get the required energy their brains needed.   Meat is high in the energy that humans needed to survive, and also in long-chain polyunsaturated fats, which are essential to maintenance of brain tissue.   Bone marrow, the fatty substance inside long bones, is also high in fat and calories, and was thus another prized item in our ancestors’ early diet.   Because foods high in fat and calories were so important to our ancestors, they would have searched them out and evolved a natural preference for them.   Their bodies would have evolved to store any excess fat, in case there were was a long hiatus until the next piece of meat or bone marrow came their way.   This ‘thrifty’ metabolic approach to fat has persisted to the present day, despite drastic changes in the way we feed ourselves.   Now, instead of searching constantly for food we have seemingly unlimited access to Twinkies, beer and other high-calorie delights.   But our bodies are still storing the excess fat. The genetics of obesity are complicated, and by no means can they be fully explained by our ancestors’ diet. But the dramatic change in the human diet since the Stone Age does help explain our cravings from an evolutionary perspective. Variations in the human genome are full of examples such as these: genetic mutations that are beneficial in some ways but harmful in others, or that used to be beneficial, but now result in an increased waistline.   Understanding these genetic ‘trade-offs’ is helpful to understanding the history of the human genome, and could be helpful in tackling conditions such as sickle-cell anemia, hereditary hemochromatosis, obesity and many others.

The Ultimate Trade-off:  Genes, Environment, and Why We Crave Twinkies

In a recent paper, Southern California researchers <a href="http://ucsdnews.ucsd.edu/newsrel/soc/06-08GenesAndPolitics.asp" target="_blank" rel="noopener noreferrer">announced</a> that political involvement has a genetic component.<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/twins-300x199.jpg" alt="" class="alignright size-medium wp-image-392" width="300" height="199" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/twins-300x199.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2008/07/twins.jpg 425w" sizes="auto, (max-width: 300px) 100vw, 300px" />
Though they stopped short of identifying a gene or genes at work, the researchers concluded that the decision to go out and vote was genetically determined by up to 50 percent. Genes, they also noted, were partially involved in other activities such as attending rallies, donating to a campaign, and even running for office.
UC San Diego professor James Fowler and his colleagues published their results in The American Political Science Review — not your typical genetics journal. They studied 396 same-sex twins, culled from a list of nearly four million registered voters in Los Angeles County, who had voted in eight state elections between 2000 and 2005. They then replicated their results using an independent twin population taken from the National Longitudinal Study of Adolescent Health.  
<h6 class="MsoNormal">Twin Study</h6>
Aside from finding identical twins more likely to vote the same way than fraternal twins, their data also suggested that genetics accounts for 53 percent of variance in going out to vote.
Fowler and his colleagues aren’t the only ones who use twin studies for their research. In a way, twins can provide researchers with perfectly matched test subjects and controls. Because identical twins have the same genetic information, for example, scientists can do one-on-one comparisons to find out why one is left-handed and the other right-handed, or why one has cancer but the other doesn’t. Such twin studies allow researchers to estimate how much of behavior is due to genes and how much can be attributed to environmental factors. They can also make such comparisons over larger groups of twins to look for a gene or genes that could explain these common traits.

Twin studies have indicated a genetic component underlying an amazing variety of traits, including:

<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal"><a href="http://www.sciencedaily.com/releases/2007/11/071114183244.htm" target="_blank" rel="noopener noreferrer">age-related hearing loss</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/18257946?ordinalpos=1&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">neophobia</a>, or aversion to new food;</li>
<li class="MsoNormal"><a href="http://www.sciencedaily.com/releases/2008/04/080408160636.htm" target="_blank" rel="noopener noreferrer">back pain</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/17804594?ordinalpos=20&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">chronic fatigue syndrome</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/17438154?ordinalpos=3&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">heart disease</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/sites/entrez" target="_blank" rel="noopener noreferrer">nearsightedness</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/18412099?ordinalpos=27&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">obsessive-compulsive disorder</a>;</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/15651931?ordinalpos=129&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">the size of one’s brain</a>; and,</li>
<li class="MsoNormal"><a href="https://www.ncbi.nlm.nih.gov/pubmed/18315789?ordinalpos=1&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">happiness</a>.</li>
</ul>

<h6>Not So Fast</h6>
But not all researchers are impressed.

&#8220;We suggest that no scientific purpose is served by the flood of heritability estimates generated by these studies,&#8221; psychologist Leon J. Kamin and economist Arthur S. Goldberger wrote in a 2002 paper.

Kamin and Goldberger looked at two population samples used as the basis for several twin studies. One twin population known as MISTRA (Minnesota Study of Twins Reared Apart) is composed of identical twins separated early in life. Researchers wishing to study behavioral differences who used this group might think that any similarities between the twins would be genetic (attributed to nature) and any differences would then be due to environmental influences (nurture). However, Kamin and Goldberger found some cases where statements the twins had given indicated they might have compared notes prior to being interviewed. Such interactions, they argued, could skew the results in studies using MISTRA twins.

<h6 class="MsoNormal">Other Studies</h6>
A second twin population is known as SATSA (Swedish Adoption/Twin Study of Aging). This sample is composed of four groups of twins: identical twins separated in childhood; identical twins reared together; fraternal twins separated before the age of 11; and fraternal twins reared together.

Kamin and Goldberger questioned the definition of separation as in some cases the twins were raised within the same extended family though they didn’t live in the same house. The environmental influences would be too similar, they argued, and that again could skew any conclusions reached by those conducting studies using these twin populations.

One twin study where researchers seem to have been able to successfully separate and track twins and multiples for years was conducted between 1953 and 1997. Known as the Child Development Center’s Study of Twins Reared Apart, the data are part of the records donated by lead researcher Peter Neubauer to Yale University, with the stipulation that the information remain sealed until 2066. For those unwilling to wait, some tidbits may be gleaned from a book by two of the study’s unknowing participants, Elyse Schein and Paula Bernstein, in their book <a href="https://www.amazon.com/Identical-Strangers-Memoir-Separated-Reunited/dp/1400064961/ref=pd_bbs_sr_1?ie=UTF8&#038;s=books&#038;qid=1215550534&#038;sr=1-1" target="_blank" rel="noopener noreferrer">Identical Strangers</a>, as well as in Neubauer’s own book, <a href="https://www.amazon.com/Natures-Thumbprint-Peter-B-Neubauer/dp/0231104413/ref=sr_11_1?ie=UTF8&#038;qid=1215548664&#038;sr=11-1" target="_blank" rel="noopener noreferrer">Nature’s Thumbprint</a>.

The true value of two-for-one deals

<img loading="lazy" decoding="async" class="alignright alignnone size-medium wp-image-375" style="float: right;" title="bluescale" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/bluescale-300x222.jpg" alt="" width="300" height="222" />European researchers have identified variations in the PCSK1 gene that could influence obesity risk in both adults and children. The <a href="https://dx.doi.org/10.1038/ng.1077" target="_blank" rel="noopener noreferrer">results</a>, published online in Nature Genetics, are based on data collected from nearly 14,000 people in five European countries.
The team was led by David Meyre and Philippe Froguel of the Pasteur Institute in France, who have been studying the genetics of diabetes and obesity.
The researchers were inspired by the <a href="https://www.ncbi.nlm.nih.gov/pubmed/9207799?ordinalpos=4&#038;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank" rel="noopener noreferrer">earlier</a> research of British colleagues, who discovered a rare mutation in the <a href="http://obesitygene.pbrc.edu/cgi-bin/ace/gene/acedb?name=PCSK1" target="_blank" rel="noopener noreferrer">PCSK1</a> gene about a decade ago. That mutation causes obesity by preventing the production of an enzyme involved in metabolism. 
 
For this study, Meyre, Froguel and their colleagues started by examining genetic data from 1,045 obese and 1,265 non-obese French adults. They found six variants — or SNPs — in PCSK1 that showed a strong association with obesity. The researchers narrowed their list to just two SNPs that cause protein sequence changes: rs6232 and rs6234/rs6235. Because the latter two SNPs are linked, they were treated as one variation by the researchers. (23andMe customers should note that while our service does not currently offer information on rs6234 or rs6235, SNP rs10515237 can be used as a direct substitute for this variation.)
An association between obesity and the PCSK1 variants was also observed when the researchers sampled Danish adults, Swiss adults, French children and Swedish families. A sample of children from Germany found an association with SNP rs6232, but not rs6234/rs6235.
After compiling all their data, the researchers found that each copy of the riskier C version of rs6232 increased a person’s odds for obesity 1.34 times over the TT genotype. Each copy of the riskier G version of rs10515237 — which 23andMe uses instead of rs6234/rs6235 — increased odds for obesity 1.22 times over the AA genotype. 
In laboratory experiments, the researchers found that while the obesity-associated variants of PCSK1 found in this study do not interfere with production of the enzyme, rs6232 did reduce the enzymatic activity of the PCSK1 protein by 10%. Research in mice has shown that a change in the mouse PCSK1 gene very similar to the C version of rs6232 in humans <a href="http://hmg.oxfordjournals.org/cgi/content/abstract/15/11/1884" target="_blank" rel="noopener noreferrer">results</a> in increased fat accumulation and obesity.
In the following table, “Effect” is the increase in odds of developing obesity conferred by each copy of the riskier version of a SNP. SNPs where we are providing a proxy for the ones originally reported in the paper are marked with an asterisk. This information applies only to people with European ancestry.
&nbsp;

Latest Posts — Page 210