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Can I get 1% of my one of my great great grandparents genes?

Can I get 1% of my one of my great great grandparents genes?



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I basically took a 23andme test and found out genetically I was 1% African. The weird part though is that family records shows that my father's mother's grandmother was African, making me 1/16 African. Shouldn't it be closer to 6%?


The science behind "being X % from a certain place" based on genetic analyses is… approximative at best. It relies on the assumption that some genetic traits are only found in certain (narrow) regions of the planet - which for most of them, is not really true.

Additionally, did your test provide any confidence metric for this result? If not, it may mean that it may be derived from a statistically unsignificant number of traits (and the number could therefore mean anything) or maybe it's simply something like 1% with a confidence interval of several points, in which case the result could be a compatibe the mathematical truth. Genomes are large and have complex dynamics, it it probably difficult to get a precise estimate.

On a side note, there is more genetic diversity in native African populations than on any other continent (for reasons pertaining to Homo sapiens history) so "African" does not describe a homogeneous population.

Source: https://www.nature.com/articles/nature13997 doi:10.1038/nature13997


Cerebral palsy: It can be in your genes

An international research group led by a team at the University of Adelaide has made what they believe could be the biggest discovery into cerebral palsy in 20 years.

It has long been the belief that cerebral palsy occurs when a child experiences a lack of oxygen during pregnancy or at birth. However, the Australian Collaborative Cerebral Palsy Research Group, based at the University of Adelaide's Robinson Research Institute, has found at least 14% of cerebral palsy cases are likely caused by a genetic mutation.

The findings of this research are published in the Nature journal, Molecular Psychiatry.

The Head of the Cerebral Palsy Research Group, Emeritus Professor Alastair MacLennan, says prior to this research it was believed that as little as 1% of cerebral palsy cases had a genetic cause.

"Cerebral palsy is a major neurodevelopmental disorder, which disrupts movement control, and it occurs in 1 in 400 children," Emeritus Professor MacLennan says.

"While we have long suspected that genes may play a role in the development of cerebral palsy, it wasn't until our research group mapped the DNA from cerebral palsy families that we could show genetic mutations are the likely cause of the condition in at least 14% of cases," he says.

Professor Jozef Gecz, University of Adelaide genetic scientist, says because cerebral palsy is at least partly genetic in origin there will be significant changes in the approach to diagnosis, management and treatment of the condition.

"Our findings of genetic diversity in cerebral palsy are similar to the genetic architecture of other neurological disabilities, such as intellectual disabilities, epilepsies, autisms and schizophrenias," Professor Gecz says.

"Our research will lead to early diagnosis of some cerebral palsies and aid preventative genetic techniques in the future. It should also reduce inappropriate litigation against obstetric medics -- who at times are blamed for causing the condition -- which has led to defensive obstetrics and unnecessarily high caesarean delivery rates," he says.

University of Adelaide PhD student and lead author, Gai McMichael, who was supervised by Professors MacLennan and Gecz, says this dramatic research finding will change how people think about cerebral palsy. "These results will make many rethink assumptions about the causes of cerebral palsy, which can be devastating for all concerned and costs Australia billions of dollars each year," says Ms McMichael.

With the help of collaborators around Australia and in Houston, Texas, and with funding from the National Health and Medical Research Council and the Cerebral Palsy and Tenix Foundations, the University of Adelaide-based research group has gathered a unique DNA and clinical data cerebral palsy biobank, which is attracting international attention and further research collaboration.

This work has been the result of 20 years of research by the group. The team is continuing to seek further mutations in cerebral palsy cases, which will add to the percentage of cases with a genetic basis.


‘It made me question my ancestry’: does DNA home testing really understand race?

L ast year, I did what 12 million people from all over the world have done and surrendered my spit to a home DNA-testing company. I hoped a MyHeritage test would bring me the peace I needed my Irish mother had never been able to give me any information about my biological father. Raised by her and my white dad, I’d always longed for a country to attribute my blackness to, or for help answering the ubiquitous “Where are you from?” question. I’d spent years making up exotic-sounding combinations to justify my appearance (some days Jamaican-Spanish-Swedish other days half Brazilian, or half Iranian). But, at 24, I was done with occupying a box of black ambiguity. Could I finally get a clear answer?

The results arrived by email on a summer’s day last year. I clicked on the “ethnicity estimate” link, which offers an analysis of DNA by country, my heart pounding as I scanned the digital map.

The test showed that my blackness comes from Nigeria 43% of my DNA, in fact. Then there’s 1% from Kenya, and the rest from Great Britain and Ireland (55%), as well as eastern Europe (1%). I’d often been told I looked east African, or mixed with multiple countries, so I was surprised by what was nearly a 50:50 split.

I had no cultural knowledge of Nigeria should I now start claiming it as my own? Did the results mean my very distant ancestors were Nigerian, or that my biological father was probably from there? Why did my features not resemble a typical west African? I felt more confused than ever.

This wasn’t quite what the adverts had promised. Targeted marketing for home-testing kits shows smiling (often mixed-race) models under the banner “find out your ethnicity”, or urges people to book holidays based on their “DNA story”. It’s estimated the industry will be worth a staggering £7.7bn by 2022 in the last year alone, market leader AncestryDNA pulled in $1bn in revenue.

While DNA home tests are more popular than ever, people are starting to raise questions about what happens after the results land. Concerns about the storage of sensitive genetic information were highlighted recently, when an open-source DNA testing site, GEDmatch, was used by the police to identify California’s Golden State Killer. As well as privacy concerns, there’s the emotional fallout of receiving confusing or life-changing results. Identities that have been cherished by families for generations can be dismantled overnight.

A yshah Blackman, in her 50s, is of Caribbean descent and lives in London. She had always known two things about her family: that they had Indian heritage, and that her father had another daughter he wasn’t in touch with. Last year, with his permission, she set about trying to track down her half-sister through the UKTV show The Secrets In My Family.

Blackman was encouraged to take the AncestryDNA test as part of the programme, and thrilled to eventually connect with her long-lost sibling, living on the other side of London. But she was shocked by the details of the results according to the test, Ayshah had no Indian DNA at all. “It made me question my ancestry, the fact that I might not be what I thought I was. I began to think that my grandmother had had an affair, that my mother had an affair. My imagination ran riot,” she tells me.

Blackman’s AncestryDNA test traced her roots to west Africa. “That wasn’t a surprise,” she says, recalling the mix of Benin, Togo and other parts of west Africa that made up 43% of her DNA. She was also 13% Scandinavian, and parts Native American and British. “But Indian wasn’t on my chart – I spent months agonising about it,” she says.

For people of African descent, whose individual and collective histories are blurred by the legacies of colonialism, slavery and rape, what they know about their identities is particularly important. Blackman felt that one of the narratives woven through her family had been broken.

“That little thing of not having any Indian ancestry is now sitting on my shoulder – I may not be as much a part of this tribe as I thought I was,” she says. “If I had to do it again, I wouldn’t.”

Y ouTube is full of videos of people revealing their DNA results, often with “click me” headlines such as What Am I? and I Was Lied To – My Shocking Results. They film themselves “unboxing” test kits like a new toy and taking cheek swabs, and then cut to footage in which they analyse their results. Many seem astonished by what they find, and begin to question whether their parents have been unfaithful, or whether they have been misled about their heritage some clips are heartbreakingly difficult to watch.

Shana Dennis, 34, decided to make a YouTube video after taking her test. She was born in India but adopted at six weeks by a family in Australia. Wanting to find out more about her racial mix, she took a test from AncestryDNA, which analysed her as mainly central Asian in origin (44%), with links to Afghanistan, Azerbaijan, Kazakhstan, Kyrgyzstan and Uzbekistan. Dennis uploaded a video going through the geographical breakdown of her results. When commenters suggested she try other DNA companies to verify the findings, she decided to do just that like several others, AncestryDNA’s website allows you to access your “raw DNA file” and send it to different companies for analysis.

Each site has produced wildly different results. DNA.Land suggests Dennis’s biggest country match is China, with 29%. WeGene puts that figure at closer to 58%, while MyHeritage suggests that most of her DNA comes from Mongolia, a 21% match. “The results caused even more confusion,” Dennis says. “Most think I’m Nepalese. Others have argued I’m not.”

Rachel Nye, 30, from London, was also left without a clear answer. Nye’s mother has a black mother and a white father, but Nye has never known exactly where her grandmother was born.

“My nana died in 2008 but was always very vague about where she came from. She often gave different answers,” Nye says. “Some days she was British-born, other days she was from Barbados, some days she was African. I remember seeing two passports – one of them was Kenyan – but the names and dates of birth were different.”

Nye’s 23andMe test analysed her as 76.9% European, offering a breakdown that included the UK, France and Scandinavia. Her black heritage was less detailed she’s 21.9% sub-Saharan African – 13.9% west African, 5.1% east African and 0.4% “African hunter-gatherer”.

Nye says she was frustrated by the lack of country breakdown within Africa despite the fact the vast majority of the world’s genetic variation comes from the continent, DNA testing companies often have very few samples from Africa.

23andMe has launched a number of initiatives to redress this. In 2016, the company launched the African Genetics Project, offering free DNA kits to people with all four grandparents born in the same African country, or from the same ethnic or tribal group. Now it has launched the Populations Collaborations Program, which encourages researchers studying remote populations to submit their data to the website.

But questions have been raised about the ethics of European and American scientists harvesting genetic information from Africans and African scientists for economic gain. 23andMe has announced plans to share the test results of five million customers with GlaxoSmithKline, the drugs giant, in order to facilitate the design of new drugs. (Users are asked if they want to participate in scientific research when they sign up.)

Privacy is a major concern for everyone using these sites, but perhaps more so for those from minority backgrounds. For those who are already discriminated against, having their genome used against them – for example, in the criminal justice system – could have serious implications. AncestryDNA’s privacy agreement states it can only share a customer’s DNA with research partners with explicit consent but it could disclose personal information to law enforcement if requested. (An internal report revealed that in 2017, AncestryDNA received 34 law enforcement requests, and provided information to 31.) MyHeritage asks customers to email if they want their sample removed from its database, though a representative tells me that the company does not sell or share DNA data with third parties. “We would need the explicit permission of our users – we do not own anyone’s DNA”, I am told on the phone. In 2010, to illustrate the privacy risks, researchers from the Whitehead Institute for Biomedical Research in Massachusetts identified nearly 50 people who had participated in an anonymous genomic study, based on publicly accessible information.

T here are many scientific limitations to the home DNA test. “These companies aren’t actually testing your ancestry at all,” says Mark Thomas, professor of evolutionary genetics at University College London. “They’re problematic in their claims to be able to infer an individual’s ancestry.”

There are a few reasons for this. First, the genetic information these DNA testing companies hold is based on living populations. When you send your spit off in a little tube, it is specific snippets, or markers, in your genome (the total collection of DNA that resides in your cells) that are being analysed, and then compared to the markers of others who are good representatives for distinct regions or ethnicities around the world. But as Thomas notes, the companies are only looking at very recent samples, from a relatively small group, in one specific database. “They are just saying: ‘If I wanted to make your genome, I could pull bits of your DNA from people all over the world who are around today. And this is just one way I could do it,’” he says.

The databases are skewed towards different parts of the world, too. “23andMe has more American customers, and AncestryDNA has more British and Australian,” Thomas explains. “And none of these companies asks: ‘What do we know about the genetics of the past, and which of those past inferred genetic clusters do we get our ancestry from?’ They are giving us what the market wants, not what the genetics tells us.”

There’s also the question of just how much information is passed down through a person’s DNA. Thomas explains that we probably inherit very few genes from our ancestors DNA is inherited in “chunks” that break up the further back in time you go. “You start with two parents, then four grandparents, then eight great-grandparents, it goes to 16, 32 and so on. And by the time you go 10 generations back, there are ancestors from whom you inherit no DNA.”

I ask Dr Yaniv Erlich, who works for MyHeritage, how the company’s “ethnicity estimate” is created. He says they define good DNA “representatives” for English people as having “at least all of their eight great-grandparents born in England”. He believes you can “estimate that present-day individuals probably reflect populations from about 200 to 300 years ago, as they never got DNA of any other ethnicity. Evolution is not acting fast enough to create any substantial changes.”

But as the American academic Sheldon Krimsky and journalist David Cay Johnston explain in their online consumer guide, Ancestry DNA Testing And Privacy, markers maketh the result. “Today’s markers do not necessarily match the markers of 400 years ago, during the African colonisation and enslavement period,” they write. In other words, markers are inconsistent sometimes they’re passed on and sometimes they’re not. There might be a lot of genetic markers Nigerians share, for example, but that are not necessarily exclusive to them.

Thomas tells me it is very possible that my birth father could be from anywhere, but have parents or grandparents who are Nigerian, or are from a “combination of countries with broad genetic similarities to Nigerians”.The bigger question is, how much should we connect geography and identity anyway? An individual’s “ethnicity” is largely based on their own perception of cultural and social traits, not which geopolitical borders they were born between. And there aren’t universal genetic traits within certain groups, Thomas points out.

“Let’s be honest, these companies are using ethnicity as a nice, polished euphemism for race, and they’re trying to define biological races using this genetic data. That in itself is shifty,” he says. “If genetics has taught us one thing over 30 years or so, it’s that there are no clearcut biological racial categories. Everyone in the world is racialised in some way. But rather than overturning these outdated notions of race, these companies are servicing them instead – presumably because they get better profits.”

When I ask the home-testing sites about linking the language of ethnicity to science, they offer varying responses. An AncestryDNA spokesperson told me that “analysing DNA to determine a person’s ethnic breakdown is at the cutting edge of science”, explaining that they have “thousands” of DNA samples from around the world. “Each is from a specific location and most are accompanied by a documented family tree indicating deep heritage in a particular region.” A 23andMe spokesperson tells me the company does “not refer to ethnicity” in its analysis, instead calling it an “ancestry composition”. Yaniv Erlich of MyHeritage says: “Ethnicity is not encoded in someone’s genes, but this human-made construct can be in correlation with genetic variations. We use this correlation to infer the ethnicity.”

After I got over the initial shock of my own test results, I began to explore the rest of the MyHeritage site. I was amazed to find that I could contact a fourth cousin on my biological father’s side – my first black relative – and that she lived in the same city as me. We plan to meet up, and my quest to find out more about my biology continues.

But I know that decoding my DNA is only one chapter of my history. Ancestry is a legacy, not a bloodline. Our genetic script may be one of the most valuable things we own, but it’s never the whole story.

This article was amended on 11 August 2018 to correct Golden Gate Killer to Golden State Killer and to include a missing “not” in the sentence: Why did my features not resemble a typical west African?

    Comments on this piece are premoderated to ensure the discussion remains on the topics raised by the article.


Can a genetic test predict my medical future?

Not entirely—its scope is limited. For starters, not all diseases are caused by genes. Plenty of conditions stem from environmental and lifestyle factors they may interact with your genes, but the external factors are the real trigger.

But even if a disease is caused solely by faulty instructions written in your genes, you won’t necessarily be able to test for it. That’s because genetic tests are mainly used for diseases that are “penetrant,” a term that scientists use to describe a strong connection between having a certain gene (or multiple genes) and getting a disease.

Genetic tests are surprisingly simple on the surface. All that’s required of you is a small sample of cells, like a blood sample or saliva (which doesn’t have DNA itself, but picks up cheek cells during its journey out of your mouth). It get sent to a lab where sequencing machines match up small pieces of synthetic DNA with your DNA to figure out the overall sequence.

Once they have your sequence, geneticists can compare it with “normal” or disease-causing sequences. In the end, they might give you a “yes” or “no” answer, or sometimes you’ll get a probability—a measure of how much your genes increase your risk of developing the disease. Then, it’s up to your doctor to figure out what these genes (in combination with your lifestyle, family history and other risk factors) mean for your health.

With penetrant diseases, there’s a “very, very high” ability to explain the disease, Rehm says. For example, the breast cancer-related gene BRCA1 can give you a 60 percent chance of getting breast cancer (in Jolie’s case, with her family history, the risk was 87 percent.)

This makes genetic tests better at detecting so-called “rare diseases,” says Steven Schrodi, associate research scientist at the Marshfield Clinic Research Institute’s Center for Human Genetics, but they’re less useful when it comes to more common diseases, like heart disease or diabetes. Genetics can increase your likelihood of getting these disease, but scientists still don’t know quite how much. Part of the problem is that there may be dozens or hundreds of genes responsible for these diseases, Schrodi says.

“We have an incomplete understanding of why people get diseases,” Schrodi says. “A large part of it hinges on how we define diseases. Perhaps physicians have inadvertently combined multiple diseases together into a single entity.”

Consumer genetic tests—the ones where you send in samples from home—sometimes claim to test for these more complex traits, but be careful: Their results might not be very medically relevant, Rehm says. If they tell you that your genes make you twice as likely to develop diabetes, for example, that’s a marginal increase that doesn’t significantly affect your risk, especially when you take into account lifestyle factors.


Mitochondrial Eve

On January 1, 1987, a paper was published in the journal Nature which rocked the world of anthropology.

Researchers Allan Wilson, Mark Stoneking, and Rebecca Cann used the then-new science of genetic analysis to analyze the DNA in human mitochondria.

What they found was evidence that humans on Earth can trace their ancestry back to a single woman who lived approximately 180,000 years ago.

Learn more about Mitochondrial Eve, the mother of everyone, on this episode of Everything Everywhere Daily.

This episode is sponsored by Audible.com.

My audiobook recommendation today is The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry by Bryan Sykes.

In 1994 Professor Bryan Sykes, a leading world authority on DNA and human evolution was called in to examine the frozen remains of a man trapped in glacial ice in northern Italy. News of both the Ice Man’s discovery and his age, which was put at over 5,000 years, fascinated scientists and newspapers throughout the world. But what made Sykes’s story particularly revelatory was his successful identification of a genetic descendant of the Ice Man, a woman living in Great Britain today

You can get a free one-month trial to Audible and 2 free audiobooks by going to audibletrial.com/EverythingEverywhere or clicking on the link in the show notes.

To start, we need a bit of background on how human genetics works.

Most of your genes are some combination of your mother and your father. What genes came from who can differ, so even siblings or fraternal twins can look very different, even though they have the same parents.

This mixing of genes is why sexual reproduction is so successful as an evolutionary strategy.

However, not all genes can be combined in such a manner. The mitochondria, which are the energy-producing center of our cells, have DNA that only comes from our mother.

That means that me, you, and everyone in the world will have that particular bit of DNA in common with our mothers. It isn’t something that is recombined with DNA from our fathers.

That means that the DNA in our mitochondria doesn’t change very much over time because it isn’t recombining during the process of reproduction.

However, it does change a little bit over time. These are mutations that occur naturally.

These mutations, statistically, occur at regular intervals. By determining the rate of mutation, you can create a type of Molecular clock and work backward to determine how long it was since different DNA diverged from the same DNA.

It was using this technique that the researchers determined how far back it was since we had our last common female ancestor.

What they determined is that it was a woman who lived about 180,000 years ago, give or take a few tens of thousands of years, and she lived in Africa.

She was dubbed Mitochondrial Eve.

There is one other thing we know about her. She must have had at least two daughters. Why? Because if she had zero, she couldn’t have passed along her mitochondrial DNA. If she had one, then that daughter would be our Mitochondrial Eve.

This technique has lead to some surprising conclusions and overturned many other theories in anthropology.

First, it lent a great deal of credibility to the “Out of Africa” hypothesis. This theory holds that humans developed in a single place in African and then left Africa in one or more migrations to populate the rest of the world, within the last 200,000 years or so.

This is the dominant theory today and it is supported by most evidence, especially genetic evidence.

Prior to the use of genetic evidence, the multiregional hypothesis had many adherents. This held that humans had a common ancestor about 2,000,000 years ago, they then spread around the world and evolved separately.

Secondly, it helped narrow down exactly where in Africa Mitochondrial Eve might have come from. Based on an analysis of the genes of current human populations, and based on 3,000-year-old remains, it is believed that Eve came from the region of what is today the Kalahari Desert in Southern Africa.

The term “Eve” obviously comes from the bible, and as such, there is some confusion over what the term Mitochondrial Eve means.

Mitochondrial Eve was not the first human or the first woman. She also wasn’t the only woman when she was alive. Other women alive when she was simply didn’t have female descendants who made it to today.

She is simply just the most recent common female ancestor that every human on Earth has today.

Moreover, and this is what really confuses many people, Mitochondrial Eve can change over time. As I just said, Mitochondrial Eve is defined to be the most recent female ancestor we all have in common, who we can identify via our mitochondrial DNA.

Over time, with increases in populations, people moving, and intermarrying, genetic populations become mixed and that person who is the most recent ancestor can change….but the fact still remains that we would still have a single recent ancestor which shares our mitochondrial DNA.

As I mentioned, only females can transmit mitochondrial DNA.

You might be wondering if there is an equivalent ancestor for males?

The male equivalent would be DNA passed in the Y chromosome. This is only passed from males to other males.

So, is there a Y Chromosome Adam who is the counterpart of the Mitochronial Eve?

Again, yes. However, Y Chromosome Adam and Mitochondrial Eve were not hanging out in some genetic Garden of Eden. In fact, they didn’t even live remotely close to each other.

It is estimated that Y Chromosome Adam may have existed about 60,000 years ago, as opposed to Mitochondrial Eve who existed 180,000 years ago.

How is this possible? Shouldn’t they have been at least somewhat contemporary?

Well, no. It all has to do with reproductive potential.

Not even factoring in children surviving to adulthood, there is a limit to the number of children a woman can have in her lifetime. For example, an 18th-century Russian woman holds the known record for having given birth 27 times in her life, with several multiple births.

However, there are many examples of chiefs, kings, and emperors who have fathered hundreds of children.

Ghengis Khan, who lived only 800 years ago, may have fathered thousands of children. Genetic testing has shown that 8% of all men living in the former Mongol Empire are direct descendants of Ghengis Khan, which means that at least 1% of everyone in the world today is descended from this one man who only lived centuries ago.

These super fathers are why there is such a time difference between our genetic Adam’s and Eve’s.

And just like our Mitochrondial Eve might change, so too will our Y Chromosome Adam. In fact, in the future, it might very well become Ghengis Khan.

To top it all off, I’ve been very specific when talking about both of these genetic ancestors. I’ve only discussed the specific origins of specific DNA. That doesn’t mean that these are our most common recent ancestors.

If you do the math, the number of ancestors we have doubles every generation. You have 2 parents, 4 grandparents, 8 great-grandparents, etc.

Assuming you have 25 years between generations on average, you quickly get to a point where we have billions of ancestors, which is much larger than the number of humans which existed.

That means the most recent common ancestor might have existed only about 3,000 to 5,000 years ago. This person might have been male or female, and statistically would have probably lived in southern or eastern Asia.

It is hard to track this person genetically because as I mentioned above, genes get mixed, and we can’t track this as well as we can with mitochondrial DNA and Y chromosomes, which are only passed by a single sex.

The thing which really lowered the date for this most recent common ancestor was the expansion of Europeans to places like the Americas, Australia, and the Pacific several hundred years ago.

So, when you hear someone say that all of humanity is one family, it isn’t just some crunchy, granola, kumbaya slogan. It is a literal truth.

All of us, you, me, and everyone listening to my words are all very distant cousins of each other.

Executive Producer of Everything Everywhere Daily is James Mackala.

The associate producer is Thor Thomsen.

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Mom's Diet Counts

How the mother eats not only during their pregnancy but throughout their life can have an effect on their baby's health. "Babies live off the mother's body," Barker says. "And her body is the product of a lifetime of nutrition." In other words, mom's diet back in their own childhood can come back to either haunt -- or help -- their growing baby. He says mothers have to establish a lifetime of good nutrition, and not just eat a healthy diet while they're pregnant for it to make a difference to their children's health.

Kjersti Aagaard, MD, PhD, calls the first nine months in the womb -- as well as the child's first years out of the womb -- "programming for health." "There is no doubt that what happens in the first 1,000 days of life, from conception to 2 years of age, are fundamental influences not only on metabolism . but also on our developmental health and well-being," says the assistant professor of maternal and fetal medicine and obstetrics and gynecology at Baylor College of Medicine. "Kids [who are] given an optimal environment and optimal nutrition very early in life, that groundwork is laid."

Scientists are learning that the choices moms make during pregnancy not only directly affect their baby's health, they might even lead to changes in the baby's genes. A new field called epigenetics is looking at how nutrition and other factors in pregnancy might alter the way the baby's genes function. One study done in rats found that eating a poor diet during pregnancy affected a gene linked to the production of insulin in the young -- a change that scientists say could increase the offspring's risk of developing type 2 diabetes later in life. It's not yet clear if the same is true for people.

So what does all this new research mean for Mom? It means that their contribution is to provide the healthiest possible vessel for their baby, which includes eating a balanced diet and following good habits (such as not smoking) not only while they're pregnant, but throughout their life.

How Mom cares for their baby outside of the womb is also important. A number of studies have touted the benefits of breastfeeding, finding that it can boost children's brainpower and reduce their risk for obesity as they grow.

Once children start on solid foods, feeding them a healthy, well-balanced diet can prevent them from growing into obese adults and from developing diseases related to obesity, such as diabetes and high blood pressure. Mom also has the important task of instilling in their kids the good eating habits that will lead them into a healthy adulthood.


5. There Can Be Surprises

This is the most important thing to remember.

It's crucial to remember that DNA can lead to surprising results. Are you prepared if it shows that you have a half-sibling or an aunt or uncle that you didn't know about? What if your sibling's test is so different that it turns out you're only half-siblings (or not biologically related at all)? As Judy Russell pointed out, we simply must consider the ethics of genetic genealogy. We must consider informed consent before we have a relative take a test and we cannot bully people into communicating with us.


Can Schizophrenia Be Inherited?

The short answer is this: a person is 11 times more likely to develop schizophrenia if he or she has a relative with the disorder. It's important to understand what this number means. Many studies show that schizophrenia occurs in 0.2 to 1.1% of people who have no relatives with schizophrenia. People who have a relative with the disorder get it at a rate of 1.4 to 16.2%. In identical twins, if one sibling has schizophrenia, the other has a 31- 78% chance of having the disease. These numbers mean that there is a strong genetic part to schizophrenia.

The fact that this disease has a strong genetic component doesn't necessarily mean that someone with schizophrenia will pass it down to his or her children. There are several ways in which people inherit disease. Huntington's disease, a movement disorder with many psychiatric symptoms, is caused by an error with a single gene that causes the disease in everyone who has the defective gene (in medical jargon, this is called autosomal dominant inheritance). Family members with the disorder can get a blood test to find out if they will get it or not. Schizophrenia is not like this. No specific gene that causes schizophrenia has been isolated and no blood test will prove whether or not a person will develop the condition or pass it down to their children. Researchers believe schizophrenia is a disease in which many genes conspire to cause symptoms. This is not a clear-cut situation, and unfortunately, represents the case for many diseases.

The question of whether schizophrenia puts relatives of patients at higher risk for other psychiatric disorders is a complicated one. There is some consensus that substance dependence and anxiety disorders are not specifically increased in relatives of people with schizophrenia. Recent evidence has suggested that depression is increased in relatives of people with schizophrenia. Definitive studies on these issues have yet to be done.

From my personal experience working with patients, schizophrenia presents itself in all families from all walks of life. The first psychotic break for a patient is often a time of fear and confusion for many family members. Despite the fact that schizophrenia has a strong genetic component, when it occurs, it usually does so as the result of random chance. Even if there are relatives in a family with the disorder, there's no way to predict whether a child will grow up to have schizophrenia, and there is little that can be done to prevent the disorder for emerging. Early detection and proper treatment, however, can have a substantial impact on quality of life. There are many types of schizophrenia and the disease occurs with varying severity. I will discuss these subtypes in a future article.


Charlemagne’s DNA and Our Universal Royalty

Nobody in my past was hugely famous, at least that I know of. I vaguely recall that an ancestor of mine who shipped over on the Mayflower distinguished himself by falling out of the ship and having to get fished out of the water. He might be notable, I guess, but hardly famous. It is much more fun to think that I am a bloodline descendant of Charlemagne. And in 1999, Joseph Chang gave me permission to think that way.

Chang was not a genealogist who had decided to make me his personal project. Instead, he is a statistician at Yale who likes to think of genealogy as a mathematical problem. When you draw your genealogy, you make two lines from yourself back to each of your parents. Then you have to draw two lines for each of them, back to your four grandparents. And then eight great-grandparents, sixteen great-great-grandparents, and so on. But not so on for very long. If you go back to the time of Charlemagne, forty generations or so, you should get to a generation of a trillion ancestors. That’s about two thousand times more people than existed on Earth when Charlemagne was alive.

The only way out of this paradox is to assume that our ancestors are not independent of one another. That is, if you trace their ancestry back, you loop back to a common ancestor. We’re not talking about first-cousin stuff here–more like twentieth-cousin. This means that instead of drawing a tree that fans out exponentially, we need to draw a web-like tapestry.

In a paper he published in 1999 [pdf], Chang analyzed this tapestry mathematically. If you look at the ancestry of a living population of people, he concluded, you’ll eventually find a common ancestor of all of them. That’s not to say that a single mythical woman somehow produced every European by magically laying a clutch of eggs. All this means is that as you move back through time, sooner or later some of the lines in the genealogy will cross, meeting at a single person.

As you go back further in time, more of those lines cross as you encounter more common ancestors of the living population. And then something really interesting happens. There comes a point at which, Chang wrote, “all individuals who have any descendants among the present-day individuals are actually ancestors of all present-day individuals.”

In 2002, the journalist Steven Olson wrote an article in the Atlantic about Chang’s work. To put some empirical meat on the abstract bones of Chang’s research, Olson considered a group of real people–living Europeans.

The most recent common ancestor of every European today (except for recent immigrants to the Continent) was someone who lived in Europe in the surprisingly recent past—only about 600 years ago. In other words, all Europeans alive today have among their ancestors the same man or woman who lived around 1400. Before that date, according to Chang’s model, the number of ancestors common to all Europeans today increased, until, about a thousand years ago, a peculiar situation prevailed: 20 percent of the adult Europeans alive in 1000 would turn out to be the ancestors of no one living today (that is, they had no children or all their descendants eventually died childless) each of the remaining 80 percent would turn out to be a direct ancestor of every European living today.

Suddenly, my pedigree looked classier: I am a descendant of Charlemagne. Of course, so is every other European. By the way, I’m also a descendant of Nefertiti. And so are you, and everyone else on Earth today. Chang figured that out by expanding his model from living Europeans to living humans, and getting an estimate of 3400 years instead of a thousand for the all-ancestor generation.

Things have changed a lot in the fourteen years since Chang published his first paper on ancestry. Scientists have amassed huge databases of genetic information about people all over the world. These may not be the same thing as a complete genealogy of the human race, but geneticists can still use them to tackle some of the same questions that intrigued Chang.

Recently, two geneticists, Peter Ralph of the University of Southern California and Graham Coop of the University of California at Davis, decided to look at the ancestry of Europe. They took advantage of a compilation of information about 2257 people from across the continent. Scientists had examined half a million sites in each person’s DNA, creating a distinctive list of genetic markers for each of them.

You can use this kind of genetic information to make some genealogical inferences, but you have to know what you’re dealing with. Your DNA is not a carbon copy of your parents’. Each time they made eggs or sperm, they shuffled the two copies of each of their chromosomes and put one in the cell. Just as a new deck gets more scrambled the more times you shuffle it, chromosomes get more shuffled from one generation to the next.

This means that if you compare two people’s DNA, you will find some chunks that are identical in sequence. The more closely related people are, the bigger the chunks you’ll find. This diagram shows how two first cousins share a piece of DNA that’s identical by descent (IBD for short).

Ralph and Coop identified 1.9 million of these long shared segments of DNA shared by at least two people in their study. They then used the length of each segment to estimate how long ago it arose from a common ancestor of the living Europeans.

Their results, published today in PLOS Biology, both confirm Chang’s mathematical approach and enrich it. Even within the past thousand years, Ralph and Coop found, people on opposite sides of the continent share a lot of segments in common–so many, in fact, that it’s statistically impossible for them to have gotten them all from a single ancestor. Instead, someone in Turkey and someone in England have to share a lot of ancestors. In fact, as Chang suspected, the only way to explain the DNA is to conclude that everyone who lived a thousand years ago who has any descendants today is an ancestor of every European. Charlemagne for everyone!

If you compare two people in Turkey, you’ll find bigger shared segments of DNA, which isn’t surprising. Since they live in the same country, chances are they have more recent ancestors, and more of them. But there is a rich, intriguing pattern to the number of shared segments among Europeans. People across Eastern Europe, for example, have a larger set of shared segments than people from within single countries in Western Europe. That difference may be the signature of a big expansion of the Slavs.

Ralph and Coop’s study may provide a new tool for reconstructing the history of humans on every continent, not just Europe. It will also probably keep people puzzling over the complexities of genealogy. If Europeans today share the same ancestors a thousand years ago, for example, why don’t they all look the same?

Fortunately, Ralph and Coop have written up a helpful FAQ for their paper, which you can find here.

Update: Adjusted the estimated generations since Charlemagne to thirty. Corrected Ralph’s affiliation.


The Toxins That Affected Your Great-Grandparents Could Be In Your Genes

Michael Skinner’s biggest discovery began, as often happens in science stories like this one, with a brilliant failure. Back in 2005, when he was still a traditional developmental biologist and the accolades and attacks were still in the future, a distraught research fellow went to his office to apologize for taking an experiment one step too far. In his laboratories at Washington State University, she and Skinner had exposed pregnant rats to an endocrine disruptor—a chemical known to interfere with fetal development—in the hope of disturbing (and thereby gaining more insight into) the process by which an unborn fetus becomes either male or female. But the chemical they used, an agricultural fungicide called vinclozolin, had not affected sexual differentiation after all. The scientists did find lower sperm counts and decreased fertility when the male offspring reached adulthood, but that was no surprise. The study seemed like a bust.

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“Conflicts with individuals solve very little,” skinner says. “The best way to handle these things is to let the science speak for itself.” (Brian Smale) Skinner has traded hunting for fly-fishing. (Brian Smale)

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By accident, though, Skinner’s colleague had bred the grandchildren of those exposed rats, creating a fourth generation, or the great-grandchildren of the original subjects. “It’s OK,” Skinner told her. “You might as well analyze them.” If nothing else, he thought, the exercise might take her mind off her mistake. So she went ahead and studied the rats’ testes under a microscope.

What they found would not only change the direction of Skinner’s research but also challenge a bedrock principle of modern biology. And Skinner would become the forerunner of a new way of thinking about the possible long-term health consequences of exposure to environmental chemicals.

His discoveries touch on the basic question of how biological instructions are transmitted from one generation to the next. For half a century it has been common knowledge that the genetic material DNA controls this process the “letters” in the DNA strand spell out messages that are passed from parent to offspring and so on. The messages come in the form of genes, the molecular equivalent of sentences, but they are not permanent. A change in a letter, a result of a random mutation, for example, can alter a gene’s message. The altered message can then be transmitted instead.

The strange thing about Skinner’s lab rats was that three generations after the pregnant mothers were exposed to the fungicide, the animals had abnormally low sperm counts—but not because of a change in their inherited DNA sequence. Puzzled, Skinner and his team repeated the experiments—once, twice, 15 times—and found the same sperm defects. So they bred more rats, and tested more chemicals, including substances that lead to diseases in the prostate, kidney, ovaries and immune system. Again and again, these diseases also showed up in the fourth- and fifth-generation offspring of mothers exposed to a chemical.

“In essence,” Skinner explains, “what your great-grandmother was exposed to could cause disease in you and your grandchildren.”

And, startlingly, whatever disease pathway a chemical was opening in the rats’ fur-covered bodies, it did not begin or end at a mutation in the genetic code. Skinner and his team found instead that as the toxins flooded in, they altered the pattern of simple molecules called methyl groups that latch onto DNA in the fetus’ germ-line cells, which would eventually become its eggs or sperm. Like burrs stuck to a knit sweater, these methyl molecules interfered with the functioning of the DNA and rode it down through future generations, opening each new one to the same diseases. These burrs, known to be involved in development, persisted for generations. The phenomenon was so unexpected that it has given rise to a new field, with Skinner an acknowledged leader, named transgenerational epigenetics, or the study of inherited changes that can’t be explained by traditional genetics.

A study by Skinner and colleagues published last year in the journal PLOS One has upped the ante considerably. The burrs were not just haphazardly attached, Skinner found. Instead, they fastened themselves in particular arrangements. When he bathed the insides of his pregnant rats in bug spray, jet fuel and BPA, the plastics component recently banned from baby bottles, each exposure left a distinct pattern of methyl group attachments that persisted in the great-grandchildren of exposed rats.

Not only is your great-grandmother’s environment affecting your health, Skinner concluded, but the chemicals she was exposed to may have left a fingerprint that scientists can actually trace.

The findings point to potentially new medical diagnostics. In the future, you may even go to your doctor’s office to have your methylation patterns screened. Exposure of lab rats to the chemical DDT can lead to obesity in subsequent generations—a link Skinner’s team reported in October. Hypothetically, a doctor might someday look at your methylation patterns early in life to determine your risk for obesity later. What’s more, toxicologists may need to reconsider how they study chemical exposures, especially those occurring during pregnancy. The work raises implications for monitoring the environment, for determining the safety of certain chemicals, perhaps even for establishing liability in legal cases involving health risks of chemical exposure.

These possibilities have not been lost on regulators, industries, scientists and others who have a stake in such matters. “There are two forces working against me,” Skinner says. “On one side, you have moneyed interests refusing to accept data that might force stronger regulations of their most profitable chemicals. On the other side, you have genetic determinists clinging to an old paradigm.”

Michael Skinner wears a gray Stetson with a tan strap, and leans back easily in his chair in his office on the Pullman campus. His fly-fishing rod stands in the corner, and a colossal northern pike is mounted on the wall. An avid fly fisherman, Skinner, age 57, was born and raised on the Umatilla Indian Reservation in eastern Oregon. The Skinners are not of Indian descent, but his parents owned a family farm there—“a good cultural experience,” he says. His father worked in insurance, and he and his four brothers grew up just as five generations of Skinners had before them—hunting and fishing and cowboying, learning a way of life that would sustain them into adulthood.

He loved the outdoors, and his fascination with how nature worked prompted a school guidance counselor’s suggestion that a career in science might be just the thing. He was about 12, and true to form he stuck with it. In high school and then at Reed College he wrestled competitively, and today his supporters and critics alike may detect a bit of his old grappling self in how he approaches a problem—head-on. “It probably taught me how to confront, rather than avoid challenges,” he says now. The sport also led him to his future wife, Roberta McMaster, or Bobbie, who served as his high-school wrestling team’s scorekeeper. “I was fascinated that someone so young knew exactly what he wanted to do with his life,” Bobbie recalls. He proposed marriage before heading for college, and the two have been together ever since and have two grown children.

He attended Washington State University for his PhD in biochemistry, and during that time he and Bobbie often lived on game that he’d hunted. It was not unheard of to find a freshly killed deer hanging in the carport of their student housing. “They were lean years,” Bobbie says. “But they were good ones.”

After positions at Vanderbilt and the University of California, San Francisco, Skinner returned to Washington State University. “I wanted a big research college in a rural town,” he says. He spent the next decade studying how genes turn on and off in ovaries and testes, and how those organs’ cells interact. He wasn’t aiming to take on the central idea in biology for much of the 20th century: genetic determinism, the belief that DNA is the sole blueprint for traits from hair and eye color to athletic ability, personality type and disease risk.

In some sense this interpretation of genetic determinism was always oversimplified. Scientists have long understood that environments shape us in mysterious ways, that nature and nurture are not opposing forces so much as collaborators in the great art of human-making. The environment, for example, can ramp up and pull back on gene activity through methyl groups, as well as a host of other molecules that modify and mark up a person’s full complement of DNA, called the genome. But only changes in the DNA sequence itself were normally passed to offspring.

So certain was everyone of this basic principle that President Bill Clinton praised the effort to complete the first full reading of the human genome, saying in June 2000 that this achievement would “revolutionize the diagnosis, prevention and treatment of most, if not all human diseases.” When stacked against such enthusiasm, Skinner’s findings have felt like heresy. And for a while, at least, he was criticized accordingly.

Critics of the Skinner-led research pointed out that the doses of vinclozolin in his rat studies were way too high to be relevant to human exposure, and injecting the rats as opposed to administering the toxins through their food exaggerated the effects. “What he’s doing doesn’t have any real obvious implications for the risk assessments on the chemical,” EPA toxicologist L. Earl Gray was quoted telling Pacific Standard magazine back in 2009. Until the results are replicated, “I’m not sure they even demonstrate basic science principles.”

Skinner responds to assaults on his data by saying that risk assessment, of the type that toxicologists do, has not been his goal. Rather, he’s interested in uncovering new biological mechanisms that control growth, development and inheritance. “My approach is basically to hit it with a hammer and see what kind of response we get,” he says. He remains calm, even when called on to defend that approach. “Conflicts with individuals solve very little,” he says. “The best way to handle these things is to let the science speak for itself.”

That science has received a lot of attention (the vinclozolin study has been cited in the scientific literature more than 800 times). Recently, the journal Nature Reviews Genetics asked five leading researchers to share their views on the importance of epigenetic inheritance. A “mixture of excitement and caution,” is how the editors described the responses, with one researcher arguing that the phenomenon was “the best candidate” for explaining at least some transgenerational effects, and another noting that it might, if fully documented, have “profound implications for how we consider inheritance, for mechanisms underlying diseases and for phenotypes that are regulated by gene-environment interactions.”

Though most of Skinner’s critics have been reassured by new data from his lab and others, he says he still feels embattled. “I really try to be a scientist first and foremost,” he says. “I’m not a toxicologist, or even an environmentalist. I didn’t come to this as an advocate for or against any particular chemical or policy. I found something in the data, and I pursued it along a logical path, the way any basic researcher would.”