<img loading="lazy" decoding="async" class="alignright size-full wp-image-2073" title="studentdna" src="https://blog-api.23andme.com/wp-content/uploads/2008/11/studentdna.jpg" alt="studentdna" width="350" height="233" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/11/studentdna.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/11/studentdna-300x200.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
It&#8217;s not enough to teach genetics, says Michael Dougherty, director of education for the American Society for Human Genetics.   It has to be taught in the right way.
&#8220;Current teaching practices may be producing a public that is unprepared to participate effectively as medical consumers in a world where personalized medicine will rely increasingly on genetic testing, risk assessment, predispositions, and ranges of treatment options that include biological and behavioral components,&#8221; writes Dougherty in an opinion piece published online today in the <a href="http://www.cell.com/AJHG/abstract/S0002-9297(09)00208-0" target="_blank" rel="noopener noreferrer">American Journal of Human Genetics</a>.
Dougherty calls for curriculum reform at all levels, from middle school all the way up through undergraduate education. The key, he says, is for students to understand that the genetics of most human traits and conditions are complex and, with only rare exceptions, not deterministic.
Dougherty suggests a new genetics curriculum that begins with lessons on traits that show continuous variation, such as height and weight, and focuses on how multiple inherited and environmental factors can affect these traits.   Teachers could then move on to discussions of genes and the molecular details of how they are passed from generation to generation.   Only here, in the later stages of their genetics education, would students learn about the rare single gene diseases, such as <a href="https://www.23andme.com/topics/carrier/cystic-fibrosis/">cystic fibrosis</a> and <a href="https://www.23andme.com/topics/carrier/phenylketonuria">PKU</a>, that make up the bulk of today&#8217;s genetics lessons.
&#8220;Our incompleteness of understanding and the messiness of complex-trait examples are poor arguments for maintaining the status quo in our genetics classrooms.   We know on theoretical grounds that the entirety of phenotype is defined by genes and environment, and substantial uncertainty still characterizes both.   To pretend such uncertainty does not exist is to deprive students of an appreciation of both modern genetics and the nature of science.&#8221;
Dougherty points to the Genes, Environment and Human Behavior module, funded by the Department of Energy and available from BSCS, as an example of the kind of lesson that could help correct the misconceptions that students already have.   The National Human Genome Research Institute also has available a <a href="https://www.genome.gov/10001551" target="_blank" rel="noopener noreferrer">Human Genetic Variation curriculum supplement</a>.   And of course, you can always check out the <a href="https://www.23andme.com/gen101/" target="_blank" rel="noopener noreferrer">Genetics 101</a> section of the 23andMe website for a basic introduction to genetics.

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23andMe Blog Team

Curriculum Reform Needed For An Informed Public When It Comes To Genetics, Expert Says

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New research says that malaria, a robust evolutionary pressure in humans, has also shaped the baboon genome.
<h2>Impact of Malaria</h2>
Each year, at least 350 million people around the world are infected by malaria parasites.   More than one million people, mainly young children, succumb to the disease.
But these numbers would be even higher if not for genetic adaptations that have evolved in populations living in areas where malaria is a common threat.
For example, populations in Africa, Papua New Guinea, and Brazil carry variations in the DARC gene that protect them from infection by the P.vivax malaria parasite.   DARC encodes the Duffy antigen, a protein exploited by P.vivax to enter red blood cells.
<h2>Protective Genetic Variants</h2>
The protective variations prevent the DARC gene from expressing the Duffy antigen, leaving the parasite without a mode of entry to establish an infection.
Wild baboons are not usually infected by P.vivax or other malarial parasites that affect humans, but they are vulnerable to several closely related species.
In a new report, Duke University researchers show that, like some humans, groups of yellow baboons from Kenya&#8217;s Amboseli National Park carry variants affecting DARC gene expression that provide protection against malaria. These findings, published in the journal Nature this week, mark the first time that a genetic variation has been linked to complex traits in a wild non-human primate population.
<h2>Malaria Resistance</h2>
While the genetic variations that produce P. vivax malaria resistance in humans turn off the DARC gene, the variations that protect baboons from malaria actually increase the amount of protein made from the gene.
This suggests the mechanisms of resistance to malaria infection differ between the two species.   Researchers, however, are still impressed with the parallel nature of these evolutionary adaptations.
&#8220;It&#8217;s a nice example of how — in the vastness of the genome — the same gene was modified in the same way in two different species to produce the same kind of resistance,&#8221; Greg Wray, senior author of the report, said.   &#8220;That&#8217;s remarkable when you think of all the different ways malaria resistance might have evolved.&#8221;
Gathering the data for this study was no easy feat.
Graduate student Jenny Tung, the lead author of the report, spent three summers in the East African savanna collecting DNA-laden baboon feces and darting animals to take blood samples.
Wray says that the success of her work shows the power of combining fieldwork and genomic analysis.   According to him, the next challenge will be understanding how genetic variation contributes to complex behavioral traits like social status and aggression in wild primates.

Malaria Drove Evolution in Humans And Baboons

<img loading="lazy" decoding="async" class="alignright size-full wp-image-3853" title="starry_night" src="https://blog-api.23andme.com/wp-content/uploads/2009/06/starry_night.jpg" alt="starry_night" width="350" height="260" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/06/starry_night.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2009/06/starry_night-300x223.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
Genomewide association studies have had <a href="https://blog.23andme.com/2008/08/18/snpwatch-snps-in-ion-channel-genes-are-associated-with-type-2-diabetes-and-bipolar-disorder/" target="_blank" rel="noopener">some success</a> in finding DNA variants associated with increased risk for bipolar disorder.   But researchers from the MRC Centre for Neuropsychiatric Genetics and Genomics at Cardiff University in England have taken these studies a step further by looking for common functional themes running through the GWAS data. Their results, published online this month in the <a href="http://www.cell.com/AJHG/abstract/S0002-9297(09)00209-2" target="_blank" rel="noopener">American Journal of Human Genetics</a>, implicate some of the most basic biological pathways in the genesis of bipolar disorder.
Starting with the idea that the genetic variations increasing risk for a disorder are probably not randomly distributed throughout the genome, but instead are in one or more sets of related genes, Holmans et al. re-analyzed the SNP data from four previous studies that included a total of 4,387 cases of bipolar disorder and 6,209 controls. Researchers at the Children&#8217;s Hospital of Philadelphia recently took a similar approach (although the technical details of the analysis differ) for a study of <a href="https://blog.23andme.com/2009/02/26/researchers-make-progress-in-understanding-crohn%E2%80%99s-disease-by-looking-at-the-big-picture/" target="_blank" rel="noopener">Crohn&#8217;s disease</a>.
The bipolar disorder researchers found that biological pathways involved in broad control of cellular activity were overrepresented in the genetic variations association with bipolar disorder.   Two of the pathways, hormone activity and cellular self-digestion, are known to be impacted by lithium, the major medication used to treat bipolar disorder. As always, more research will be needed to substantiate these findings, as well as to understand how they can be used to help the more millions of people worldwide dealing with bipolar disorder.

Researchers Look For Common Themes In Bipolar Disorder Genetics

<img loading="lazy" decoding="async" class="alignright size-full wp-image-3837" title="DNA code analysis" src="https://blog-api.23andme.com/wp-content/uploads/2009/06/atcg.jpg" alt="DNA code analysis" width="425" height="282" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/06/atcg.jpg 425w, https://blogcms.23andme.com/wp-content/uploads/2009/06/atcg-300x199.jpg 300w" sizes="auto, (max-width: 425px) 100vw, 425px" />
Each one of us carries in our cells the vital genetic data, compliments of our parents, that code for many of our traits and attributes. &nbsp;Whether it&#8217;s our eye color, height or the ability to consume dairy products, the variations in our genes contribute to making us &#8216;one of a kind&#8217;. &nbsp;Unfortunately, these variations can also lead to the onset of disorders that aren&#8217;t so unique.
Technology now allows scientists to tap into our DNA as they attempt to unlock the underlying genetic causes of diseases that afflict so many of us. &nbsp;These studies, often called Genome-Wide Association Studies (GWAS) because of their comprehensive design, are producing some very compelling results. Under the present research model, individuals who are asked to consent to participating in these studies typically donate a blood or saliva sample and provide access to information about their particular disease (or drug response, in the case of pharmacogenetic studies) through their health records or through diagnostic interviews. &nbsp;Scientists then look for genetic correlations that can help direct the development of diagnostics and therapeutics.

This model is fairly steeped in tradition and protocol. &nbsp;Once your sample and information are collected, researchers go out of their way to break the link back to you, with the mindset that it&#8217;s a necessary measure to protect your privacy – and, frankly, minimize their liability to deliver and explain the data. The genetic information derived from your DNA is often &#8220;de-identified&#8221; or &#8220;anonymized&#8221; so that it can&#8217;t be traced back to you. &nbsp;As a &#8220;human subject&#8221; in a study such as this, you are not offered access to this very personal data. &nbsp;Yet it could be very important for you to know. Now that we have more knowledge about how our genes impact our lives, thanks to these very studies, shouldn&#8217;t you be given access to the data if you want it? Even if there&#8217;s little you can do to alter the course of your genetic predispositions – which are often not definitive – we&#8217;re seeing overwhelming evidence that a lot of people would like this information.
At 23andMe, we believe it&#8217;s time for a research revolution, where the people involved – let&#8217;s no longer call them human subjects – can play a more active role and contribute more directly to studies of most interest to them and their families. &nbsp;And if any individual would like access to his or her data, he or she should be granted that request.
In this spirit, 23andMe is proud to support www.HealthDataRights.org and the Declaration of Health Data Rights. &nbsp;We believe genetic data are an integral part of your health information, and you should have access if you so choose.

It’s Your Data … Shouldn’t You Have Access To It?

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Only 250 miles separates the island of Madagascar from the southeast coast of Africa.   The short distance between the two land masses traditionally led the outside world to assume that the native inhabitants of Madagascar &#8211; known as the Malagasy &#8211; originally came from the west, probably from the present day southeast African nation of Mozambique.   Yet upon closer examination of the Malagasy&#8217;s language and their physical features, many scholars began to question this notion.   The Malagasy of the central plateau of Madagascar, known as the Highlanders, had light skin and facial features more akin to Southeast Asia or Indonesia.   They also practiced a rice culture that was not unlike the rice cultures of Asia.   And yet the coastal Malagasy, known as the CÃ´tiers, seemed just the opposite.   They had darker skin and curly hair that was more similar to modern day Africans.
But both the Highlanders and the CÃ´tiers speak the same language, which shares 90% of its vocabulary with a language spoken today in Southeast Borneo, and which has been officially classified as a branch of the Austronesian language family called West Malayo-Polynesian.   So how could a significant portion of Malagasy seem to share more in common with a region 5,000 miles away than they do with mainland Africa?   Trying to find the answers to these questions has vexed archaeologists, historians and linguists for generations.   Over the past several years, geneticists have entered the fray to try and unravel the mysterious origins of the Malagasy.   Their most recent effort appears this week in Molecular Biology and Evolution.
 
This study, led by Sergio Tofanelli of the University of Pisa, built upon a <a id="t0-g" title="2005" href="http://www.cell.com/AJHG/retrieve/pii/S0002929707607368" target="_blank" rel="noopener">2005</a> study by Matt Hurles and colleagues that was the first genetic exploration of the Malagasy people.   But Tofanelli and his colleagues wanted to dig even deeper into the genetic history of the Malagasy.   So they took the data analyzed by Hurles in addition to new DNA samples that were collected from people across the island of Madagascar.
They focused on two regions of the human genome often used in genetic ancestry studies:   the mitochondrial DNA (mtDNA) and the Y chromosome.   Because the mtDNA is used to trace maternal ancestry, and the Y chromosome to trace paternal ancestry, analyzing both in the same study can give a more complete picture of a group&#8217;s genetic history.
Tofanelli and his research team examined the mtDNA and Y chromosomes of Malagasy individuals scattered across the island, from both the Highlander and CÃ´tiers groups.   They were searching for any clues that would give an exhaustive understanding of how and when the island of Madagascar was first settled, and by whom.
The researchers&#8217; analysis revealed a mixture of both African and Asian genetic ancestry, in both the Highlanders and the CÃ´tiers, which is perhaps contrary to the two groups&#8217; physical apperance.   So what does this mean?   That even the CÃ´tiers people, who often look more African in appearance, have an ancestry that traced back to Asia, specifically Borneo.   These results fit well with Hurles&#8217; study and with what linguists have been saying for years; that the Malagasy language &#8211; while clearly tracing back to Borneo &#8211; also has some African elements that are significant.
The results from these analyses then begged the next question &#8212; how and when did the earliest inhabitants of Madgascar arrive on the island?   Was it in two separate migrations &#8211; one from the east and one from the west &#8211; or did the Asian/African genetic make-up of the Malagasy exist prior to their first steps on Madagascar?   It is easy to assume that any intermarriage between Africans and Southeast Asians happened after each arrived on the island.   In fact, Tofanelli describes the genetic make-up of the Malagasy as a consequence of &#8220;the encounter of people surfing the extreme edges of two of the broadest historical waves of expansion&#8221; in human history.   He is referring to the sub-Saharan African Bantu expansions that began 5,000 years ago and swept across Africa from Cameroon to Mozambique and southern Africa, and the Austronesian expansions about 4,000 years ago when seafarers journeyed from Taiwan to Borneo and beyond.
But Tofanelli proposes an alternative hypothesis as well.   He argues for a long history of contact between Bantu-speaking Africans and seafarers from Borneo dating back thousands of years.   As evidence he cites banana cultivation in Cameroon and Uganda that can be traced back to Southeast Asia, as well as the introduction of humped cattle into Africa from Asia.   If the Southeast Asians and eastern Africans shared farming techniques, it stands to reason that they may have shared genes as well.   Thus the people of Madagascar may have not simply been Africans and Southeast Asians arriving on the island from opposite directions, but rather they represent a more complex genetic history of proto-Malagasy arriving on Madagascar about 2,300 years ago, already containing a mixture of Asian and African ancestry.
This hypothesis most certainly needs additional evidence and data before it can be supported, but it brings a new level of understanding to the mysterious origins of the Malagasy.

New Study Reveals Complex Origins of the Malagasy

It&#8217;s no secret that obesity rates are rising &#8212; quickly.   Between 2000 and 2005 the prevalence of obesity rose by 24%.   Extreme cases increased by more than 50%.   If current trends continue, more than half of all Americans will be clinically obese by the year 2030.
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Rapid changes in the prevalence of a disorder suggest that <a href="https://blog.23andme.com/2009/05/28/environment-not-genes-key-to-increasing-disease-rates/" target="_blank" rel="noopener noreferrer">environmental rather than genetic factors </a>are to blame. But scientists know from twin and adoption studies that body mass index (BMI) is highly heritable.  
So which is it: nature or nurture?
As with many aspects of human health, it&#8217;s both.   Some people have the bad luck to have inherited genetic variations that together with the modern environment — sedentary jobs and hobbies, easy access to calorie-dense foods — create the perfect storm for gaining weight.
Changing the environmental factors that lead to obesity in some people seems simple enough — more exercise, less food.  But public health campaigns touting these commonsense fixes have had little effect against the obesity epidemic. By understanding the genetic aspects of obesity, and how they interact with the environment, scientists may be able to develop more effective treatments and prevention strategies.
In the July issue of <a href="https://www.nature.com/nrg/journal/v10/n7/abs/nrg2594.html" target="_blank" rel="noopener noreferrer">Nature Reviews Genetics</a> Andrew J. Walley of Imperial College London and colleagues review the current state of obesity genetics research.   While much progress has been made, the authors make it clear that there is still a long way to go, as the genes identified thus far explain only a tiny fraction of the total genetic component.
One key to future advancements in obesity genetics research, say Walley et al., lies in improvements to current genomewide association study (GWAS) methods.
First, the authors recommend that researchers focus on recruiting extremely obese people for their studies to increase the likelihood of finding genes with large effects. They also suggest that scientists should stop using BMI as their primary measurement of obesity.   While simple and cheap, this method does not take fat distribution or the ratio of fat to muscle into account.   There are more sophisticated methods, such as CT scans, MRI scans and ultrasound imaging, as well as machines that use air displacement to measure body volume and weight and can calculate fat and fat-free body mass.   Technological advances that will reduce the costs associated with genotyping, and ultimately genetic sequencing, are also needed so that larger numbers of subjects can be studied.
Beyond these improvements to current GWAS methods, Walley et al. say studies of more than just common variations are needed.   They suggest that investigations of rare SNPs, copy number variations (duplications, insertions and deletions of DNA) and inherited changes that don&#8217;t affect the actual DNA sequence will be needed to fully understand the genetics of obesity.
There are several competing theories about the overall biological basis of obesity.   Some suggest that obesity is a disorder of energy balance in the body, while others think regulation of the growth of fat cells is the key.   Still others think obesity may be due to defects in the neurological control of appetite and food intake.   Continued advancements in understanding the genetics of obesity will help scientists tease these theories apart, and hopefully lead to a healthier future.<a href="https://blog.23andme.com/2008/05/04/snpwatch-mc4r-gene-associated-with-body-mass/" target="_blank" rel="noopener noreferrer"></a>

Researchers Look To The Future Of Obesity Genetics

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When it comes to fighting infections, it might seem like the more immune system firepower, the better. But in reality, the body&#8217;s response to bacteria and other invaders is a delicate balancing act. If the response is too little or too late, an infection can become unbeatable. But if the immune system comes on too strong, it may end up doing more harm than good.
New research suggests a genetic variation that arose in the first inhabitants of Europe may have helped them and their descendants hit the immune response sweet spot. These results, published online this week in <a href="https://dx.doi.org/10.1073/pnas.0811273106" target="_blank" rel="noopener">Proceedings of the National Academy of Sciences</a>, may also help scientists better understand sepsis, a state of whole-body inflammation in response to infection that is the <a href="http://content.nejm.org/cgi/content/full/348/16/1546" target="_blank" rel="noopener">tenth leading cause of death</a> in the United States, with an annual cost of nearly $17 billion.
Studies have shown that people who have one copy of a T at in the TIRAP gene are less susceptible to infection with <a href="https://www.ncbi.nlm.nih.gov/pubmed/17322885?ordinalpos=3&amp;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum" target="_blank" rel="noopener">malaria, tuberculosis, bacteremia and pneumococcal disease</a>. Scientists know that the TIRAP gene encodes a protein involved in helping the body recognize and destroy a broad range of pathogenic bacteria. But what they haven&#8217;t known until now is how might affect this process.
To investigate, Bart Ferwerda of the Nijmegen Institute for Infectious Inflammation and Immunity in the Netherlands and an international team of collaborators infused volunteers with LPS, a toxin found in the outer membranes of some bacteria.   They found that the variant was associated with the release of more pro-inflammatory signaling molecules into the bloodstream in response. The variant occurs at much higher frequencies in people with European ancestry than either Africans or Asians.   According to the authors, this suggests that the mutation didn&#8217;t arise until after the ancestors of East Asians and Europeans had split apart — sometime after the out-of-Africa migration but before the first people moved into Europe about 40,000 years ago.
Traditional thinking is that a person who ends up with high levels of pro-inflammatory signaling molecules in response to an infection is in trouble, because over-inflammation can lead to shock and death. But the authors suggest this may be true only in people who are already suffering from sepsis.   In the initial stages of infection, high levels of pro-inflammatory molecules could actually be very beneficial.
Their theory is that in the harsh environment the ancestors of modern Europeans encountered, those with the variant were more resistant to infections.   But if an infection did set in, their immune responses weren&#8217;t so overzealous that they were at risk for septic shock.

Genetic Variation May Help Immune System Put Up Just The Right Amount Of Fight

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Science is dynamic and ever changing. As new research is published, theories get revised, and hypotheses retested. The field of genetic ancestry is no exception: The flurry of published research just in the last five years has been staggering, and we can now piece together the histories of many groups from nearly all parts of the globe. At the same time, a worldwide community of genealogists has seized upon this wealth of published research, combining it with their own genetic data to produce an even richer, more detailed human history.
We want our customers to have the most current information possible, so our scientists and engineers have spent the last several months updating the paternal lineages, or haplogroups, for all of our (<a id="lhsl" title="male" href="https://blog.23andme.com/articles/whose-y-to-use-paternal-ancestry-for-ladies">male</a>) customers. This has been quite a task, involving many layers of analysis and quality control to meet our standards of precision and accuracy.   The end result is a more detailed understanding of paternal ancestry for our customers.

<h6>The New Tree</h6>
Customers can find the 23andMe paternal haplogroup tree on the paternal line feature page.   It lays out the specific haplogroups for populations around the world, how they are related to each other, and how all men alive today can trace their paternal ancestry back to one individual who we refer to as the PoP (Poppa of all Poppas).   The organization of this tree is derived from more than 2,000 variable genetic markers, known as SNPs, on the Y chromosome. The particular combination of SNPs a man has determines which haplogroup his Y chromosome belongs to.
<h6>Finding the Right Tree</h6>
Over time enough additional SNPs are discovered, and there are enough revisions to the organization of other researchers&#8217; Y haplogroup trees, that we must give our own a face lift to keep up. We used a variety of sources as a basis as we developed our new paternal haplogroup tree. We examined the published literature and spoke with experts in the field of Y chromosome genetic ancestry.   Perhaps most importantly, we used the wealth of information gathered from the International Society of Genetic Genealogy (also known as ISOGG).   This non-profit organization is run by genealogy enthusiasts who are passionate about discovering their family history through genetics. These enthusiasts, many of them 23andMe customers, have sifted through mounds of genetic data, both from the published literature and their own genetic profiles. The fruits of their labor are collected and organized in a haplogroup tree that is regularly updated at a high level of detail. ISOGG exists and prospers because so many genealogists are working together for a common goal.
We have worked primarily with the December 2008 ISOGG paternal haplogroup tree as a basis for updating our own.   Even since then, some paternal haplogroups been updated significantly.   So for these rapidly evolving haplogroups, we used the May 2009 ISOGG paternal haplogroup tree as a reference. The end result is a very detailed and up-to-date paternal haplogroup assignment for each of our male customers.
<h6>Your Paternal Haplogroup</h6>
What does this update mean for our customers?   For many it means a change in their haplogroup assignment. That change may be slight, or it may be more substantial.   For other customers it means no change at all.   When examining your new paternal haplogroup, it is likely you will see one of the following differences:
1) A more specific assignment:   Because the new paternal haplogroup tree examines many more SNPs than the original, we are able to give our customers more precise assignments. As a result, it is possible that your new haplogroup assignment may be longer and more specific than the original.   For example, customers who were assigned haplogroup J2a1 will now be reassigned to haplogroup J2a1a.
2) A more specific and slightly different assignment:   This category of change is by far the most common affecting our customers, because the organization of the haplogroup tree has changed. Therefore someone&#8217;s new assignment may look similar to their old one, but it will be longer and/or slightly different. For example, a customer who was assigned to R1b1c may now be reassigned to R1b1b2.
3) A completely new letter assignment: This is the rarest of the changes that will likely occur, and is also due to a reorganization of the paternal haplogroup tree over the past few years. For example a customer currently classified as K2 will now be reassigned to haplogroup T.
It is important to note that your ancestry has not changed. It&#8217;s only your haplogroup assignment that&#8217;s changed. This update has allowed us to define many more haplogroups than we had originally. This means we can give even more specific information about our customers&#8217; paternal ancestry.   We will continue to update the summary pages for our haplogroups with this additional genetic history.

23andMe’s New and Improved Paternal Haplogroups

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Just over 20 years ago, the first study using mitochondrial DNA (mtDNA) to trace prehistoric human migrations was published.
<h6>Your Mother&#8217;s Mother&#8217;s Mother&#8217;s, etc.</h6>
In this seminal <a href="https://www.ncbi.nlm.nih.gov/pubmed/3025745?ordinalpos=24&amp;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum" target="_blank" rel="noopener">study</a>, scientists managed to determine that all humans alive today can trace their maternal ancestry back to one woman who lived about 200,000 years ago in Africa.
The findings were revolutionary, and the idea that we could use genetics as a new tool to examine human prehistory was staggering.
One of the main reasons mtDNA was originally used was that it is passed down relatively intact, from mother to children, without recombining with any other bit of the human genome. And even more importantly, there was a small section of the mtDNA that did not code for any genes and was thus unaffected by natural selection.
Any changes in this bit of mtDNA over time had to be caused by random mutations, which were believed to occur at a regular, clock-like rate. By counting and analyzing the mutations distinguishing any two individuals &#8211; or any two groups of people &#8211; scientists reasoned they could discover when their most recent maternal ancestor lived.
<h6>Some Issues</h6>
But there were a few problems with this idea.
First, the small section of mtDNA scientists were analyzing, known as the Hyper-Variable Region (HVR), represents only about 2.5% of the entire mitochondrial genome. Some scientists argued that analyzing the genome in full would yield more accurate information about our past. Second, the idea that the mutations in our mtDNA accumulate like clockwork has been questioned continually.
Just last year, 23andMe scientists <a href="https://blog.23andme.com/2008/11/18/23andme-scientists-offer-solution-to-apparent-mutation-rate-discrepancy/" target="_blank" rel="noopener">reported</a> that the mtDNA mutation rate may have been accelerating since the end of the Last Ice Age about 15,000 years ago, when human populations around the world began to grow and diversify at much faster rates. It soon seemed that many of the time estimates scientists had been calculating for years had been less accurate than previously thought.
<h6>A New Method</h6>
So geneticists at the University of Leeds took decided to create a new method of calculation based on the best possible evidence. In the June 12 issue of the <a href="http://www.cell.com/AJHG/abstract/S0002-9297%2809%2900163-3" target="_blank" rel="noopener">American Journal of Human Genetics</a>, the team led by Pablo Soares and Martin Richards describes how they developed a way to estimate the maternal ancestry of the world&#8217;s people that is more accurate and precise.
The revised method used by these geneticists centered around the idea of natural selection. Up to now natural selection had not played a major role in calculating time estimates, mainly because scientists only used the HVR to make these calculations, which was thought to be immune from natural selection.
Natural selection, an evolutionary force first described by Charles Darwin, gradually removes harmful genetic mutations and does appear to act on much of the mitochondrial genome. Failing to account for this evolutuionary force, according to Soares, has led to inaccurate and imprecise time estimates.
&#8220;What we&#8217;ve done is work out a formula that corrects this effect,&#8221; says Soares.
Dating Migration
<h6>Using this newly developed mathematical formula, &#8220;we can [now] date any migration for which we have the available data.&#8221;</h6>
After developing this formula, Soares and his colleagues set about to test current theories on prehistoric human migrations patterns by comparing previous time estimates to those calculated using their new and improved formula. The results have already cleared up some problems with the previous estimates. Using their formula to calculate the time when humans first made their away across the Bering Strait to the Americas, they came up with a date of about 15,000 years, a full 2,000 years later than previous estimates. This new estimate can put to rest a longstanding discrepancy between genetic data and the archaeological record.
According to Richards, &#8220;We can settle the debate regarding mankind&#8217;s expansion through the Americas. Researchers have been estimating dates from mtDNA that are too old for the archaeological evidence, but our calculations confirm the date to be some 15,000 years ago, around the time of the first unequivocal archaeological remains.&#8221;
The 23andMe Maternal Line feature already puts that event at 15,000 years ago, because our scientists rely on both archaeological and genetic evidence when estimating the dates of past events.
Soares and colleagues found similar differences when recalculating the time estimates of other important prehistoric migration events, like the peopling of Polynesia just a few thousand years ago and the earliest migration of modern humans out of Africa nearly 70,000 years ago.
But if anything, these corrections bolster the use of mtDNA in dating prehistoric events. Contrary to what some scientists have long feared, this study reveals that the principle underlying the technique was always sound; it was the specific method scientists used to analyze mtDNA that required a bit of fine-tuning.

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