Genetics and Race

Credit Angie Wang

In 1942, the anthropologist Ashley Montagu published “Man’s Most Dangerous Myth: The Fallacy of Race,” an influential book that argued that race is a social concept with no genetic basis. A classic example often cited is the inconsistent definition of “black.” In the United States, historically, a person is “black” if he has any sub-Saharan African ancestry; in Brazil, a person is not “black” if he is known to have any European ancestry. If “black” refers to different people in different contexts, how can there be any genetic basis to it?

Beginning in 1972, genetic findings began to be incorporated into this argument. That year, the geneticist Richard Lewontin published an important study of variation in protein types in blood. He grouped the human populations he analyzed into seven “races” — West Eurasians, Africans, East Asians, South Asians, Native Americans, Oceanians and Australians — and found that around 85 percent of variation in the protein types could be accounted for by variation within populations and “races,” and only 15 percent by variation across them. To the extent that there was variation among humans, he concluded, most of it was because of “differences between individuals.”

In this way, a consensus was established that among human populations there are no differences large enough to support the concept of “biological race.” Instead, it was argued, race is a “social construct,” a way of categorizing people that changes over time and across countries.

It is true that race is a social construct. It is also true, as Dr. Lewontin wrote, that human populations “are remarkably similar to each other” from a genetic point of view.

But over the years this consensus has morphed, seemingly without questioning, into an orthodoxy. The orthodoxy maintains that the average genetic differences among people grouped according to today’s racial terms are so trivial when it comes to any meaningful biological traits that those differences can be ignored.

The orthodoxy goes further, holding that we should be anxious about any research into genetic differences among populations. The concern is that such research, no matter how well-intentioned, is located on a slippery slope that leads to the kinds of pseudoscientific arguments about biological difference that were used in the past to try to justify the slave trade, the eugenics movement and the Nazis’ murder of six million Jews.

I have deep sympathy for the concern that genetic discoveries could be misused to justify racism. But as a geneticist I also know that it is simply no longer possible to ignore average genetic differences among “races.”

Groundbreaking advances in DNA sequencing technology have been made over the last two decades. These advances enable us to measure with exquisite accuracy what fraction of an individual’s genetic ancestry traces back to, say, West Africa 500 years ago — before the mixing in the Americas of the West African and European gene pools that were almost completely isolated for the last 70,000 years. With the help of these tools, we are learning that while race may be a social construct, differences in genetic ancestry that happen to correlate to many of today’s racial constructs are real.

Recent genetic studies have demonstrated differences across populations not just in the genetic determinants of simple traits such as skin color, but also in more complex traits like bodily dimensions and susceptibility to diseases. For example, we now know that genetic factors help explain why northern Europeans are taller on average than southern Europeans, why multiple sclerosis is more common in European-Americans than in African-Americans, and why the reverse is true for end-stage kidney disease.

I am worried that well-meaning people who deny the possibility of substantial biological differences among human populations are digging themselves into an indefensible position, one that will not survive the onslaught of science. I am also worried that whatever discoveries are made — and we truly have no idea yet what they will be — will be cited as “scientific proof” that racist prejudices and agendas have been correct all along, and that those well-meaning people will not understand the science well enough to push back against these claims.

This is why it is important, even urgent, that we develop a candid and scientifically up-to-date way of discussing any such differences, instead of sticking our heads in the sand and being caught unprepared when they are found.

To get a sense of what modern genetic research into average biological differences across populations looks like, consider an example from my own work. Beginning around 2003, I began exploring whether the population mixture that has occurred in the last few hundred years in the Americas could be leveraged to find risk factors for prostate cancer, a disease that occurs 1.7 times more often in self-identified African-Americans than in self-identified European-Americans. This disparity had not been possible to explain based on dietary and environmental differences, suggesting that genetic factors might play a role.

Self-identified African-Americans turn out to derive, on average, about 80 percent of their genetic ancestry from enslaved Africans brought to America between the 16th and 19th centuries. My colleagues and I searched, in 1,597 African-American men with prostate cancer, for locations in the genome where the fraction of genes contributed by West African ancestors was larger than it was elsewhere in the genome. In 2006, we found exactly what we were looking for: a location in the genome with about 2.8 percent more African ancestry than the average.

When we looked in more detail, we found that this region contained at least seven independent risk factors for prostate cancer, all more common in West Africans. Our findings could fully account for the higher rate of prostate cancer in African-Americans than in European-Americans. We could conclude this because African-Americans who happen to have entirely European ancestry in this small section of their genomes had about the same risk for prostate cancer as random Europeans.

Did this research rely on terms like “African-American” and “European-American” that are socially constructed, and did it label segments of the genome as being probably “West African” or “European” in origin? Yes. Did this research identify real risk factors for disease that differ in frequency across those populations, leading to discoveries with the potential to improve health and save lives? Yes.

While most people will agree that finding a genetic explanation for an elevated rate of disease is important, they often draw the line there. Finding genetic influences on a propensity for disease is one thing, they argue, but looking for such influences on behavior and cognition is another.

But whether we like it or not, that line has already been crossed. A recent study led by the economist Daniel Benjamin compiled information on the number of years of education from more than 400,000 people, almost all of whom were of European ancestry. After controlling for differences in socioeconomic background, he and his colleagues identified 74 genetic variations that are over-represented in genes known to be important in neurological development, each of which is incontrovertibly more common in Europeans with more years of education than in Europeans with fewer years of education.

It is not yet clear how these genetic variations operate. A follow-up study of Icelanders led by the geneticist Augustine Kong showed that these genetic variations also nudge people who carry them to delay having children. So these variations may be explaining longer times at school by affecting a behavior that has nothing to do with intelligence.

This study has been joined by others finding genetic predictors of behavior. One of these, led by the geneticist Danielle Posthuma, studied more than 70,000 people and found genetic variations in more than 20 genes that were predictive of performance on intelligence tests.

Is performance on an intelligence test or the number of years of school a person attends shaped by the way a person is brought up? Of course. But does it measure something having to do with some aspect of behavior or cognition? Almost certainly. And since all traits influenced by genetics are expected to differ across populations (because the frequencies of genetic variations are rarely exactly the same across populations), the genetic influences on behavior and cognition will differ across populations, too.

You will sometimes hear that any biological differences among populations are likely to be small, because humans have diverged too recently from common ancestors for substantial differences to have arisen under the pressure of natural selection. This is not true. The ancestors of East Asians, Europeans, West Africans and Australians were, until recently, almost completely isolated from one another for 40,000 years or longer, which is more than sufficient time for the forces of evolution to work. Indeed, the study led by Dr. Kong showed that in Iceland, there has been measurable genetic selection against the genetic variations that predict more years of education in that population just within the last century.

To understand why it is so dangerous for geneticists and anthropologists to simply repeat the old consensus about human population differences, consider what kinds of voices are filling the void that our silence is creating. Nicholas Wade, a longtime science journalist for The New York Times, rightly notes in his 2014 book, “A Troublesome Inheritance: Genes, Race and Human History,” that modern research is challenging our thinking about the nature of human population differences. But he goes on to make the unfounded and irresponsible claim that this research is suggesting that genetic factors explain traditional stereotypes.

One of Mr. Wade’s key sources, for example, is the anthropologist Henry Harpending, who has asserted that people of sub-Saharan African ancestry have no propensity to work when they don’t have to because, he claims, they did not go through the type of natural selection for hard work in the last thousands of years that some Eurasians did. There is simply no scientific evidence to support this statement. Indeed, as 139 geneticists (including myself) pointed out in a letter to The New York Times about Mr. Wade’s book, there is no genetic evidence to back up any of the racist stereotypes he promotes.

Another high-profile example is James Watson, the scientist who in 1953 co-discovered the structure of DNA, and who was forced to retire as head of the Cold Spring Harbor Laboratories in 2007 after he stated in an interview — without any scientific evidence — that research has suggested that genetic factors contribute to lower intelligence in Africans than in Europeans.

At a meeting a few years later, Dr. Watson said to me and my fellow geneticist Beth Shapiro something to the effect of “When are you guys going to figure out why it is that you Jews are so much smarter than everyone else?” He asserted that Jews were high achievers because of genetic advantages conferred by thousands of years of natural selection to be scholars, and that East Asian students tended to be conformist because of selection for conformity in ancient Chinese society. (Contacted recently, Dr. Watson denied having made these statements, maintaining that they do not represent his views; Dr. Shapiro said that her recollection matched mine.)

What makes Dr. Watson’s and Mr. Wade’s statements so insidious is that they start with the accurate observation that many academics are implausibly denying the possibility of average genetic differences among human populations, and then end with a claim — backed by no evidence — that they know what those differences are and that they correspond to racist stereotypes. They use the reluctance of the academic community to openly discuss these fraught issues to provide rhetorical cover for hateful ideas and old racist canards.

This is why knowledgeable scientists must speak out. If we abstain from laying out a rational framework for discussing differences among populations, we risk losing the trust of the public and we actively contribute to the distrust of expertise that is now so prevalent. We leave a vacuum that gets filled by pseudoscience, an outcome that is far worse than anything we could achieve by talking openly.

If scientists can be confident of anything, it is that whatever we currently believe about the genetic nature of differences among populations is most likely wrong. For example, my laboratory discovered in 2016, based on our sequencing of ancient human genomes, that “whites” are not derived from a population that existed from time immemorial, as some people believe. Instead, “whites” represent a mixture of four ancient populations that lived 10,000 years ago and were each as different from one another as Europeans and East Asians are today.

So how should we prepare for the likelihood that in the coming years, genetic studies will show that many traits are influenced by genetic variations, and that these traits will differ on average across human populations? It will be impossible — indeed, anti-scientific, foolish and absurd — to deny those differences.

For me, a natural response to the challenge is to learn from the example of the biological differences that exist between males and females. The differences between the sexes are far more profound than those that exist among human populations, reflecting more than 100 million years of evolution and adaptation. Males and females differ by huge tracts of genetic material — a Y chromosome that males have and that females don’t, and a second X chromosome that females have and males don’t.

Most everyone accepts that the biological differences between males and females are profound. In addition to anatomical differences, men and women exhibit average differences in size and physical strength. (There are also average differences in temperament and behavior, though there are important unresolved questions about the extent to which these differences are influenced by social expectations and upbringing.)

How do we accommodate the biological differences between men and women? I think the answer is obvious: We should both recognize that genetic differences between males and females exist and we should accord each sex the same freedoms and opportunities regardless of those differences.

It is clear from the inequities that persist between women and men in our society that fulfilling these aspirations in practice is a challenge. Yet conceptually it is straightforward. And if this is the case with men and women, then it is surely the case with whatever differences we may find among human populations, the great majority of which will be far less profound.

An abiding challenge for our civilization is to treat each human being as an individual and to empower all people, regardless of what hand they are dealt from the deck of life. Compared with the enormous differences that exist among individuals, differences among populations are on average many times smaller, so it should be only a modest challenge to accommodate a reality in which the average genetic contributions to human traits differ.

It is important to face whatever science will reveal without prejudging the outcome and with the confidence that we can be mature enough to handle any findings. Arguing that no substantial differences among human populations are possible will only invite the racist misuse of genetics that we wish to avoid.

Race and DNA

DNA Tests, and Sometimes Surprising Results

Students at West Chester University in Pennsylvania have volunteered to take part in ancestry DNA testing. Anita Foeman, a communications professor, says she has found that conversations around race are “complicated and jagged.” CreditWest Chester University

Race and identity in many ways define who we think we are, while modern genetics can challenge those notions. To delve into these issues, I am involved with a communications studies project at West Chester University in Pennsylvania that explores narratives at the intersection of race and identity.

For the last decade, I have invited hundreds of people to be part of ancestry DNA tests. But first I ask people how they identify themselves racially. It has been very interesting to explore their feelings about the differences between how they define themselves and what their DNA makeup shows when the test results come in.

Biologically, our ancestral differences reflect only a 0.1 percent difference in DNA. Yet we often cling to those differences — both in unity with our fellow people of origin and, at times, in divisiveness.

Over all, the experiment has provided a special opportunity to explore the lines of race. I found that as human beings, our strategies for survival are the same, and our similarities far outweigh our differences.

But inside each comment was a longing to find out more. And a long-term, ever-deepening conversation began.

What started out as a curiosity turned into a study. My colleague Bessie Lee Lawton and I began our collaboration in 2012, and a more rigorous protocol was established. Statistical analysis was done to look for patterns not easily gleaned from individual stories.

Speaking in generalities, we found that women were more flexible about their racial identity than men; that people of color expected diversity in their backgrounds more than people of European ancestry; and that younger people were more open to diversity than older ones. People of European background tended to have more anxiety, before and after the test.

Keep in mind that analyzing a person’s ancestry through DNA, means looking back hundreds of years. People receive only half of their DNA from each parent, and therefore the race or identity of either parent may be too diluted to show up in these tests.

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Participants in the research study were asked to predict their ancestral backgrounds before test results come in.CreditWest Chester University

As a black girl growing up in the 1960s, I often felt race undermined me. I was expected to love Motown, but not ballet. I was praised for speaking standard English, but my interest in the sciences was never appreciated and certainly not cultivated. Random doors opened; others closed.

It took me 10 years before I tested myself. What I found both confirmed and shook my perspective. My background included African heritage from the Gold Coast, including Nigeria and Ghana, intermingled with British and Scandinavian. I suspect this reflects the impact of the brutal Viking Age and later the English in the slave trade.

I have a smattering of Asian genes, most likely from indigenous Americans crossing the Bering Strait. For Americans, about 4 percent of our ancestry traced to Asia may actually reflect Native American roots.

However, my grandfather shared with me years ago that in his birthplace of Mobile, Ala., his earliest memories were of Chinese merchants living alongside poor black folks like him. So who knows?

Today I look at faces, even my own, with new recognition. I see that people regularly share narratives that miss something their physical features suggest, and sometimes we find ancestry that we would not have imagined. It is a new twist on an old narrative made possible by cutting-edge science.

The conversation is complicated and jagged, and it mercifully undermines neat, simplistic stories.

Over the last 11 years, more than 2,000 people have taken part in our DNA ancestry project. Below are the stories from a handful of them.

Anita Foeman, professor of communications studies

Source: New York Times

Medical Monday

DNA SNAPSHOT

 

Already genetic sleuths can determine a suspect’s eye and hair color fairly accurately. It is also possible, or might soon be, to predict skin color, freckling, baldness, hair curliness, tooth shape and age.

 

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DNA Discovery

Genetically Speaking, Americans Really Are a Melting Pot of Diversity

 

A new genetic study shows that the U.S. really is a great melting pot. (Wikimedia Commons)

In the outstanding science fiction novel, Lathe of Heaven, racism is solved by turning everyone’s skin color to the same light gray shade. It turns out that if we peel away the skin and pay attention to just the DNA, we might not need this magical solution. At the DNA level, people in the U.S. are more similar than their outward appearance might suggest.

That is the conclusion of a new study that used genetics to trace the ancestry of over 160,000 U.S. customers of 23andMe, a personal genomics company located in Mountain View, CA. The researchers found that most people who self-identified as European-American, Latino or African -American actually had DNA from the one or both of the other groups as well.

For example, people who self-identify as African-American had, on average, 24% European and 0.8% Native American ancestry. And people who self-identify as Latino had, on average, 6.2% African, 18% Native American and 65% European ancestry. Although the numbers were not as large for those who report themselves to be European-American, they still had on average around 0.2% African and 0.2% Native American heritage.

We are all way more similar than our cultural labels might imply.

This doesn’t sound like a lot but if we extrapolate the results with European Americans to the U.S. population, it means that more than 6 million of these folks carry some African ancestry and over 5 million carry some Native American ancestry. We are all way more similar than our cultural labels might imply.

Of course, this doesn’t mean the labels are totally wrong. Another finding is that self-reporting lined up very well with the majority of people’s ancestry. For example, if you are mostly of African ancestry, odds are you have self-identified as such.

This last result does not change the fact that scientists can see in people’s DNA there has been a whole lot of mixing since Europeans and Africans came to the U.S. The U.S. really has been and still is a great melting pot.

Moms Not Dads

Scientists are able to tease out how much of a certain ancestry came from mom’s side of the family and how much from dad’s by comparing a person’s X chromosome with his or her other chromosomes. Remember, men have an X and a Y chromosome and women have two X’s.

By doing such an analysis, the scientists in this study concluded that the non-European ancestry tended to come more from mom’s side of the family. For example, European-Americans might have ten times as many female Native American ancestors as male ones. And African-Americans have four times as many.

There are a couple of possible explanations for this. One obvious one is exploitation. European men may have taken advantage of Native American women meaning that Native American ancestry would flow in from the maternal side of the family.

Another possible explanation has to do with there being more men than women on the frontier. In that situation, many of these men needed to turn to Native American women if they wanted a partner. We can see the results of their successful searches in modern DNA.

Digging Deeper

As companies like 23andMe and AncestryDNA amass more and more genomes in their database, they will be able to parse out everyone’s genomes more and more precisely. For example, in this study the researchers were able to see that the European part of the ancestry of Latinos tended to come from Spain and Portugal as we might expect.

They were also able to see that most of the mixing we see in the U.S. population happened over the last 500 years or so. They are not seeing some ancient mixing of African and European populations back in the Old World. No, they are seeing the results of everyone coming together in the New World.

There is lots more in this study too that you can peruse at your leisure (it is open access which means anyone can read it.) And these sorts of studies are just a start. I can’t wait to learn even more about our ancestry in the future.

 

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The Truth about DNA

Geneticists Just Discovered a Shocking Truth About Race in White People’s DNA

As it turns out, many white people may not be so “white” after all.

In fact, millions of Americans who consider themselves white actually have mixed-race roots. A study offers yet more evidence that race is no more than a social construct.

Our “hidden” African ancestries. Population genetics scientists from institutions including Harvard University analyzed DNA from thousands of Americans who described themselves as being part of a singular racial group. The results, published in the American Journal of Human Genetics, revealed that almost 4% of participants who identify as white have “hidden” African ancestry.

“For a generation, historians have been writing books about how race is culturally constructed,” said Claudio Saunt, a University of Georgia historian, commenting on the study. “This article uses another tool, DNA analysis, to get at the same question.”

The study: Thousands of customers of 23andMe, a genotyping company, submitted saliva samples for DNA analysis and answered questionnaires about their racial and ethnic identifications. One questionnaire asked participants about geographic ancestral origins while another asked about racial affiliation. Only customers who said they identified with a single racial or ethnic group were included.

The study included 150,000 white participants and several thousand Latinos and African-Americans. They collectively hailed from 48 states. Researchers used participants’ DNA samples to render their genetic profiles and compared the results to their self-reported ancestries.

There’s a link between racial identity and geography. The frequency with which self-identified white participants had African ancestry varied significantly by region. And ancestry patterns appeared to mirror major population shifts tied to historical events in American history.

For example, researchers found white people with African ancestry at much higher rates in southern states. As much as 12% of self-described European Americans from South Carolina and Louisiana had African ancestry. And in other parts of the South, it was about 1 in 10. Researchers estimated that this interracial mixing, which geneticists call “admixture,” started about six generations ago (roughly 180 years) — before African-Americans migrated to the northern states.

Oklahoma, the study revealed, has the highest proportion of self-identified African-Americans with Native American genes. Oklahoma also happens to be where Native Americans and African-Americans first crossed paths, so to speak, when Native Americans walked the Trail of Tears in the 1830s after being forced out of the South.

How people describe themselves, it increasingly seems, has less to do with genetic makeup than the influence of social norms.

“Many Americans claim ancestry they don’t have or don’t claim ancestry that they do,” said Saunt. “In my own state of Georgia, for example, where I teach Native American history, numerous students tell me they have Cherokee ancestry, but in fact whites from Georgia have less indigenous ancestry than whites from just about any other state.”

The study is not without controversy: Personal genotyping companies like 23andMe have come under fire for cherry-picking the genes they analyze (millions out of billions) for participants’ DNA profiles. But, 23andMe codes for genes that are pretty well-established in tracing ancestry, according to a company representative.

And while there’s potentially bias in studying only 23andMe customers, both study authors and other experts in the field said it would be hard for a single research institution, or even a government agency, to perform a study of this magnitude and complexity.

“We needed many, many people,” said lead study author Kasia Bryc, “so it wasn’t possible just a short time ago. 23andMe was the first source that could offer this kind of data.”

Overall, and perhaps most importantly, the findings speak to the thorny relationship between biology and identity.

“Individuals who self-identify as white will respond in diverse ways to genetic testing showing that they have recent African ancestry,” said Saunt. “Some will embrace the findings, and others will deny them, even in the face of the evidence. The insistence on racial purity is part of a long American tradition.  Even before DNA analysis, families repudiated relatives they knew were theirs. That tradition is waning, but it is, unfortunately, far from extinguished.”

Source: ScienceMic

Medical Monday

Photo

A 7,700-year-old skeleton of a woman found in Hungary has yielded DNA. Scientists have found that she belonged to a wave of early farmers who moved into Europe from the Near East. Credit Ron Pinhasi

 

About 50,000 years ago, humans from Africa first set foot in Europe. They hunted woolly mammoths and other big game — sometimes to extinction. Eventually, they began grazing livestock and raising crops.

They chopped down forests and drained swamps, turning villages into towns, then cities and capitals of empires. But even as they altered the Continent, Europeans changed, too.

Their skin and hair grew lighter. They gained genetic traits particular to the regions in which they lived: Northern Europeans, for example, grew taller than Southern Europeans.

Up till now, scientists have learned about evolution on the Continent mostly by looking at living Europeans. But advances in biotechnology have made it possible to begin extracting entire DNA from the bones of ancestors who lived thousands of years ago. Their genomes are like time machines, allowing scientists to see bits of European history playing out over thousands of years.

Recently David Reich, a geneticist at Harvard Medical School, and his colleagues analyzed the genomes of nine ancient Europeans. Eight belonged to hunter-gatherers who lived about 8,000 years ago, seven in what is now Sweden and one in Luxembourg. The ninth came from a farmer who lived 7,000 years ago in present-day Germany.

The scientists compared these genomes with those of living Europeans. As they reported last month in Nature, the study revealed something scientists never knew: Europeans today have genes from three very different populations.

The oldest of these populations were the first Europeans, who appear to have lived as hunter-gatherers. The second were farmers who expanded into Europe about 8,500 years ago from the Near East.

But most living Europeans also carry genes from a third population, which appears to have arrived more recently. Dr. Reich and his colleagues found the closest match in DNA taken from a 24,000-year-old individual in Siberia, suggesting that the third wave of immigrants hailed from north Eurasia. The ancient Europeans that the scientists studied did not share this North Eurasian DNA. They concluded that this third wave must have moved into Europe after 7,000 years ago.

Last week, another team of scientists reported data from an even bigger haul of ancient European genomes — 13, all told. While Dr. Reich and his colleagues studied ancient Europeans separated by hundreds of miles, these scientists focused on just one region in Central Europe called the Great Hungarian Plain.

The people whose genomes the scientists retrieved lived on the plain at various times between 7,700 years ago and 2,800 years ago.

“What’s really exciting here is to have a transect through time,” said Johannes Krause, a co-director of the Max Planck Institute for History and the Sciences in Jena, Germany, who was not involved in the study. “It’s the first time that’s been done.”

Archaeological digs have revealed evidence of farming on the plain as long as 8,000 years ago. People there raised crops like barley, and raised cattle and other livestock. Shards of pottery show that they consumed milk.

The oldest genomes retrieved from human remains in the area — one from a man and one from a woman — date back to the dawn of agriculture on the plain. The woman’s DNA showed that she belonged to the ancient farming population documented by Dr. Reich and his colleagues.

The man, however, did not have the genes of a farmer. He belonged to the oldest population of hunter-gatherers.

“The archaeological information isn’t enough to say whether he was married to a local farmer,” said Ron Pinhasi, an archaeologist at University College Dublin and a co-author of the new study. It may even be that the man’s skull was a trophy of some sort, Dr. Pinhasi added.

Archaeologists have found that early farming culture didn’t change drastically for the next 3,700 years. But about 4,000 years ago, the Bronze Age arrived. People started using bronze tools, trading over longer networks and moving into fortified towns.

Dr. Pinhasi and his colleagues found that the era also brought a sudden shift in human DNA. A new population arrived on the Great Hungarian Plain, and Dr. Reich believes he knows who they were: the northern Eurasians.

“It’s very exciting,” he said. “It documents that by this time in Central Europe, this Eastern influence had already arrived.”

At the start of the Bronze Age, life settled down on the plain for a thousand years. But then came the Iron Age, bringing another shift in culture — and genes.

People began traveling across the plain by horse-drawn chariots and wagons, and the genomes from 2,800 years ago show that the people of the Bronze Age had begun to be supplanted by a new Iron Age population. These are the people most closely related to living Hungarians.

In the new study, Dr. Pinhasi and his colleagues also surveyed individual genes known to have changed over the course of European history.

Today, for example, people in Hungary tend to have light skin and light brown hair, and half of them carry a mutation that lets them digest milk as adults. It took thousands of years for the genes for these traits to appear on the Great Hungarian Plain, the scientists found.

The hunter-gatherer that lived 7,700 years ago, for example, probably had black hair and dark skin, along with blue eyes. His genes suggest that he also probably couldn’t digest milk — not surprising, since he came from a population that didn’t raise livestock.

The ancient farmer woman, on the other hand, probably had dark brown hair and brown eyes. But like the hunter-gatherers, she lacked the genetic mutation for digesting milk.

It is not until 6,400 years ago that the scientists find the first genetic evidence on the Great Hungarian Plain for light brown hair. And the milk mutation appeared even later, just 3,100 years ago.

It is possible that these new genes and others were brought to the plain by successive waves of immigrants. But natural selection probably played a role in making these genes pervasive.

Genetic mutations that enable people to drink milk as adults, for example, could have helped them survive famines. In cow-herding cultures, scientists have found, the milk-drinking mutation led to a 10 percent increase in the number of children.

If that’s true, then for 4,600 years people on the Great Hungarian Plain were milking cows but lacked the ability to digest milk. Dr. Pinhasi suggested that they only used milk at first to make cheese and yogurt, which would have been easier to digest.

Daniel G. Bradley, a geneticist at Trinity College Dublin and co-author of the new study, predicted more unexpected results would emerge as scientists gather more ancient DNA in Europe.

“The past is going to be a different country,” he said, “and it’s going to surprise us.”

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Medical Monday

New forensic tool detects ethnicity and gender in single hair

 

A cutting-edge technique to identify human hair could one day be helping to catch criminals according to a new study from researchers in Canada.

The tool produces results faster than current DNA analysis techniques used in law enforcement, and in early tests showed a 100% success rate at identifying gender and ethnicity.

The new tool is the work of Diane Beauchemin, a professor in the department of chemistry at Queen’s University in Kingston, Ontario, and MSc student Lily Huang. They describe their proof of concept study in the Journal of Analytical Atomic Spectrometry.

Prof. Beauchemin says her first “foray into forensic chemistry was developing a method of identifying paint that could help solve hit and run cases.” Applying a similar approach to hair analysis was Ms. Huang’s idea, she adds, so they started working on it last year.

Blood samples recovered at a crime scene are often used to identify gender and ethnicity, but blood deteriorates quickly and is prone to contamination.

However, hair is very stable. The reason it is a promising avenue for forensics is because of the unique mix of elements it contains, which varies according to diet, ethnicity, gender the environment and working conditions. They get into the hair from sweat secretions.

The team found they could identify gender from the elements magnesium, sulfur, strontium and zinc. And to discriminate ethnicity they used lithium, molybdenum, sulfur, strontium, chromium, potassium, nickel, zinc and lead.

The process takes just 85 seconds to complete. First they grind up the hair sample, burn it (using a method called electrothermal vaporization), and then analyze the vapor it produces (using inductively coupled plasma optical emission spectrometry).

Current forensic methods used to analyze hair are time-consuming and use corrosive solvents and reagents, Prof. Beauchemin told Chemistry World.

Method is robust and can be used universally

Ms. Huang says the method is “very robust and can be used universally. One of our samples even included dyed hair and the test was 100% accurate. The test was able to distinguish East Asians, Caucasians and South Asians.”

a hand picking a strand of hair from a hairbrush
Current forensic methods used to analyze hair are time-consuming and use corrosive solvents and reagents.

The team is already talking to law enforcement agencies about the next step in using the new method.

And the researchers are also planning to develop the method so it can pinpoint exactly where in the world a hair sample is from, as well as add more ethnicities and age to the repertoire.

To extend the repertoire of variables the method can identify means measuring more elements, but Prof. Beauchemin says this would not take more time, because their detection is simultaneous.

In 2010, Medical News Today learned how researchers are working on a method of forensic identification using hand bacteria. The method uses the fact that when we handle objects we leave behind bacterial communities that are uniquely identifiable.

Source: Medical News Today

Medical Monday

 

DNA TESTING

All his life, Neil Schwartzman searched for his biological family. He was adopted in 1960 at 10 days old, and he never knew where he came from. At first, he looked for answers by going to social services in his hometown of Montreal, Quebec, and trying to access adoption records. “There was nothing in the file,” he said. “Everything I did ended up being a dead end.” As he approached middle age, in 2008, he had just about given up. That’s when he heard about the direct-to-consumer genetic testing service 23andMe.

Unlike previous inquiries about his origins, this one occurred at the molecular level. He spit in a tube and sent it off to 23andMe’s California headquarters for analysis. For about $100, they sent back information about his genealogy (biological relatives), ancestry (lineage and geographic origins), and — this was before a 2013 Food and Drug Administration crackdown — his health, including genetic predispositions for various diseases and behavioral traits. Schwartzman said he didn’t expect much from his foray into personal DNA testing. He just signed up “as a last-ditch effort to try to get some medical information for myself.”

In early May 2011, several years after enrolling, he was pleasantly surprised: an email arrived from another anonymous 23andMe user saying she thought Schwartzman might be a half-brother.

The 23andMe website prompted him with a question about whether he wanted to find out more about the nature of their DNA relationship. He consented. Soon, he said, “We began to realize that my mother had a baby that she never disclosed to anyone.” That baby was Schwartzman. “The whole thing was swept under the rug until — fast forward 50, 51 years ahead — and there I am.”

Because of this “technological magic,” as Schwartzman put it, he was reunited with his family with more ease than any other search he had undertaken. He was able to fulfill that deep, universal longing we all have to understand our origins.

“It was nice to finally share this commonality with the rest of the world. It was very emotionally satisfying.”

Within a few weeks, he flew to California to meet his older sister, Jolie Pearl. They had their first meeting in a crowded restaurant in San Francisco’s theater district. They were the first ones at the restaurant, and they talked until the place closed. During that same visit, on an emotional day he will never forget, he was reunited with his biological mother in Oakland, California. On the way there, he asked his sister what kind of flower his mom would like. They decided on a potted orchid.

His mother, who was already confused with dementia, gave Schwartzman a book, “a random gift she pulled up at last minute,” he said. “It certainly wasn’t a typical reunion you see on TV, where the music swells up and everyone is carried away on gossamer wings.” Still, he said, “It was the welcome completion of a quest I had had for 50 years. It confirmed that I wasn’t placed on the earth by aliens, that I had a mother.”  

The reunion went well enough that the family met again, once in California and once in Montreal. “It was nice to finally share this commonality with the rest of the world,” Schwartzman said. “It was very emotionally satisfying.”

At the time, Schwartzman and Pearl were the poster children for 23andMe’s “DNA relatives” program. Their story — and a picture of them staring at each other at a fork in a railway track — is still featured on the company web page about adoptees. They were, it seemed, among the many now finding family and having joyful reunions as a result of personal genetic testing. “It was the start of a relationship,” 23andMe writes of Schwartzman’s discovery. Then, Schwartzman hailed 23andMe as “an example of the miracle of modern science.” Pearl called the reunion “the best thing.”

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Medical Monday

Single letter of DNA ‘defines hair color’


Changing just one letter of genetic code is enough to generate blonde hair in humans, according to a new analysis from researchers at the Howard Hughes Medical Institute in Chevy Chase, MD.

David Kingsley, of the Howard Hughes Medical Institute, has been studying the evolution of sticklebacks – the small fish that moved from the seas to colonize lakes and streams at the end of the last Ice Age – for the last 10 years.

Using the sticklebacks’ adaptive responses to different habitats as a case study, Kingsley and his colleagues have been able to identify molecular-level changes responsible for driving evolution. More recently, they have turned their attention to see how evolutions in the stickleback might apply to other species, such as humans.

The research that led Kingsley’s team to investigate the genetic code responsible for hair color initially concerned changes in stickleback pigmentation. As part of a 2007 study, they found that a change in the same gene had driven pigmentation changes in different populations of sticklebacks around the world.

Interestingly, they found that this genetic change was not unique to the stickleback.

Same gene in sticklebacks and humans controls pigmentation

“The very same gene that we found controlling skin color in fish showed one of the strongest signatures of selection in different human populations around the world,” Kingsley says.

magnifying glass and DNA
The genome “is littered with switches,” the researchers suspect.

Different versions of this gene – called “Kit ligand” – in humans are associated with differences in skin color. In both fish and humans, Kingsley found, the genetic changes thought to be responsible for pigmentation differences take place in regulatory elements of the genome.

“It looked like regulatory mutations in both fish and humans were changing pigment,” Kingsley says.

But tracking down specific regulatory elements in the whole genome is like finding a needle in the proverbial haystack. “We have to be kind of choosy about which regulatory elements we decide to zoom in on,” Kingsley acknowledges.

As well as encoding a protein that develops pigment-producing cells, however, Kit ligand has many other functions. For example, it influences the behaviors of blood stem cells, sperm or egg precursors and neurons in the intestine.

The team was interested in seeing whether they could isolate the regulatory changes in Kit ligand responsible for hair color without affecting any of the gene’s other functions.

‘Switching on’ Kit ligand’s hair color-determining powers

To do this, a research specialist in Kingsley’s team – Catherine Guenther – cut out segments of human DNA in the implicated region and linked each piece to a reporter gene. When these genes correctly “switch on,” they produce a distinctive blue color.

Next, Guenther introduced these pieces of switched-on DNA into mice. This allowed the team to further narrow the scope of their search until they had isolated a single piece of DNA that switched on the gene activity for developing hair follicles.

Further examining the DNA in that regulatory segment, the team found that it was just a single letter of genetic code that differed between people who have different hair colors.

The versions of this DNA associated with different hair colors were then each tested on the Kit ligand gene using cultured cells. The “blonde” switch reduced the activity of the gene by about 20%, which led the researchers to conclude they had identified a critical component of the DNA sequence.

Mice were then engineered to have a Kit ligand gene placed under either the genetic switches for blonde or brunette hair. Kingsley explains the results:

“Sure enough, when you look at them, that one base pair is enough to lighten the hair color of the animals, even though it is only a 20% difference in gene expression. This is a good example of how fine-tuned regulatory differences may be to produce different traits. The genetic mechanism that controls blonde hair doesn’t alter the biology of any other part of the body. It’s a good example of a trait that’s skin deep – and only skin deep.”

Their work with switching on different hair colors has led the team to suspect that the genome “is littered with switches.” Kingsley thinks that the various activities of Kit ligand, as well as other genes, may be adjusted by very subtle DNA tweaks.

As well as leading to a better understanding of the molecular mechanisms involved in human diversity, Kingsley hopes that this work may lead to improving human resistance to many common diseases.

“The trick is,” he says, is finding “which switches have changed to produce which traits.”

Source: Medical News Today

Medical Monday

 

DNA: The Basics

We each have 23 pairs of chromosomes. Each chromosome holds packages of DNA, which contains genes passed down from your parents and holds potential keys to everything from your hair color to your risks of certain illnesses. Within the DNA are many types of genetic variants, including one called single nucleotide polymorphisms, There are about 10 million SNPs in the human genome, and some have been found to predict risk of diseases or have a regulatory effect on a gene’s function.

Source: Prevention

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