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DNA says you’re related to a Viking, a medieval German Jew or a 1700s enslaved African? What a genetic match really means

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DNA says you're related to a Viking, a medieval German Jew or a 1700s enslaved African? What a genetic match really means

A genetic match to an ancient person doesn't mean you're more related genealogically.
Mark Edward Atkinson/Tetra Images via Getty Images

Shai Carmi, Hebrew University of Jerusalem and Harald Ringbauer, Max Planck Institute for Evolutionary Anthropology

In 2022, we reported the DNA sequences of 33 medieval people buried in a Jewish cemetery in Germany. Not long after we made the data publicly available, people started comparing their own DNA with that of the 14th-century German Jews, finding many “matches.” These medieval individuals had DNA fragments shared with thousands of people who have uploaded their DNA sequence to an online database, the same way you share DNA fragments with your relatives.

But what type of a relationship with a medieval person does a shared DNA fragment imply?

It turns out, not too much that will with your roots research.

We are population geneticists who work with ancient DNA. We understand how exciting it can be to find a genetic link to particular people who lived many generations ago. But these DNA matches aren't the tight ties you may be imagining. Here's how it works.

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Sequencing DNA from those who lived long ago

Ancient DNA is a new and rapidly growing field, with a Nobel Prize awarded in 2022 to Svante Pääbo for his foundational work.

Using samples taken from skull bones or teeth, aDNA researchers can sequence the DNA of people who lived as far back as 100,000 years ago. More than 10,000 ancient DNA sequences, or genomes, are currently available. These genomes, which from all corners of the world, have dramatically revolutionized scientists' understanding of human origins.

A new trend in ancient DNA is sequencing the genomes of “historical” individuals: those who have lived during the past millennium.

Examples include genomes from Sweden, Norway, Denmark, Iceland, Poland, Southeastern Europe, and London, Cambridge and Norwich in the U.K. Outside Europe, scientists have sequenced historical genomes from East Asia, the Swahili coast, South Africa, the Canary Islands, Lebanon, Machu Picchu, the Caribbean and the San Francisco Bay area. Genomes of enslaved Africans from Delaware, Maryland, South Carolina and St. Helena are also available.

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Some historical genomes belong to named individuals, Ludwig van Beethoven, the family of the last Russian czar, medieval Hungarian royals, the Lakota Sioux leader Sitting Bull and King Richard III of England.

horse-drawn wagon with two black-clad people in front, pulling coffin marked 'Richard III, 1452-1485'
The remains of King Richard III were reinterred in 2015.
Christopher Furlong via Getty Images News

How could you compare your own DNA with that of these historical people?

Several direct-to-consumer genetic testing companies, such as 23andMe, MyHeritage or Ancestry, make reading your own genome sequence simple and affordable. They compare your DNA with that of their other customers. They identify relatives who share with you long, continuous stretches of identical DNA and to you these matches – from the closest to the more distant.

After initial deliberation, 23andMe now lets customers compare their genomes with historical people. Other genetic testing companies don't yet, but passionate genealogists can take matters into their own hands. For example, the service GEDmatch lets users upload their own DNA data, along with published DNA sequences of any historical people. Once uploaded, GEDmatch will identify any user with whom you share genetic material.

two lines representing chromosomes with green, yellow and red bands along their length
A comparison of one chromosome's DNA sequence between a 14th-century German Jew and two living people who uploaded their DNA to GEDmatch. Each thin vertical bar represents one letter in the DNA sequence and is color-coded based on whether it is a match. A shared DNA fragment appears between living person 1 and the medieval person.
GEDMatch

So, what does a genetic match with a medieval person mean for your genealogy?

Surprisingly, very little.

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Where genealogy and genetics diverge

The first thing to understand is how many ancestors you have in each past generation. One generation back, you have two ancestors. Two generations back, that doubles to four. Then eight, and 16. By 30 generations ago, around the 12th century, you have over one ancestors.

Clearly, at this point, your ancestors include most people from your population who lived back then, excluding a small fraction who left no long-term descendants. This includes, if you have European origins, notable people such as Charlemagne or Edward I, but equally also people of every medieval social class. Your family tree reaches each of these ancestors through numerous lines.

a web of red lines getting denser and denser toward the top of the image, with generations marked 0 to 15 running vertically upwards
The red dot at generation 0 represents a present-day person in a simulated population of 100,000 people. Each tiny red dot represents one person, and the red lines connect people to their . Ancestors reached through multiple lines in the family tree are marked in black circles. The number of lines becomes so large so quickly that beyond 15 generations ago, most ancestors are reached by multiple lines.
Graham Coop

Mathematical research demonstrates the following surprising fact. In any given population, the number of lines in your family tree that reach any specific medieval person is about the same between you and everyone else who belongs to the same population you do. In other words, everyone alive is equally related, genealogically, to all medieval people from that population.

The next step is to understand how many ancestors you actually inherit DNA from. Surprisingly again, very few.

Despite your millions or more medieval ancestors, you inherit DNA from only a tiny fraction of them. So, we're sorry, you probably didn't inherit any DNA from Charlemagne or Edward I. For example, you have only about 2,000 genetic ancestors from the 12th century. In other words, your DNA sequence is a mosaic of approximately 2,000 “fragments,” each tracing back to a single 12th-century person.

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Who are the medieval people whose DNA you inherited? Each fragment of your DNA descends from a random line up your family tree – father's mother's mother's father and so on – at each generation in the past, selecting at random one of two parents. The more lines in your family tree that reach a certain medieval person, the more likely you are to inherit DNA from that person.

family tree
For someone alive today, the number of genealogical ancestors doubles each generation. But each DNA fragment (colored bars) is inherited through a random, zigzagging path up the family tree, meaning DNA is inherited only from a small fraction of one's ancestors.
Shai Carmi, CC BY-ND

But remember, the number of family lines that reach a medieval person is about the same for all present-day individuals from a given population. Therefore, all individuals inherit DNA from any medieval person with very similar probabilities. So, sharing genetic material with one particular medieval person or another is just a matter of , and everyone is playing the same .

Here's an analogy. Going to a casino and rolling a roulette ball onto 24 does not mean 24 is your special number. Anyone else might have rolled 24 as well. Similarly, sharing a DNA fragment with any one out of your millions of medieval genealogical ancestors does not mean any special relationship – beyond sharing a DNA fragment.

And if you don't have a shared segment, you just didn't get lucky. It doesn't mean you're any less genealogically related to that medieval person than anyone else from your population who does have a shared segment.

As a side note, a “population” is not always well defined, but these arguments hold generally for people with similar origins.

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How to interpret a historical DNA match

Consider again the medieval German Jews. Some present-day Ashkenazi (European) Jews will share DNA with one particular medieval Jew. Some will share with another. Some will share with none. It's a lottery draw. And given that most Ashkenazi Jews today are genealogically related in a very similar way to the medieval German Jews, seeing that shared DNA fragment does not imply any unique genealogical relatedness.

On the other hand, if you're willing to consider more recent ancestors, DNA matches can be informative. The same mathematical models show that the number of family lines reaching a particular historical person living around 200 or 300 years ago will be very different across present-day people. Therefore, a DNA match with an 18th-century person implies a more specific genealogical relationship, one that most other present-day indviduals do not have.

This pattern was demonstrated in a recent 23andMe study. Comparing the genomes of 18th-century enslaved Africans from Maryland to more than 9 million of their customers, 23andMe discovered over 41,000 living relatives, including a few nearly direct descendants.

3D models of enslaved African Americans: one a teenage boy, one a woman in her 30s
Facial reconstructions based on skeletal remains of enslaved African Americans who worked at Catoctin Furnace in Maryland, where scientists have also sequenced ancient DNA.
Katherine Frey/The Washington Post via Getty Images

How far back in time does a DNA match still have genealogical meaning? For example, are DNA matches informative in the period between the late Middle Ages and the 17th century? We don't know yet. Future research will be needed to clarify this question, as well as deviations from the simple model of a single, freely mixing population.

In the meantime, as scientists rapidly accumulate more and more historical genome sequences, keep the quirky behavior of human genealogies in mind when interpreting a DNA match.The Conversation

Shai Carmi, Associate Professor of Population and Statistical Genetics, Hebrew University of Jerusalem and Harald Ringbauer, Group Leader, Department of Archaeogenetics, Max Planck Institute for Evolutionary Anthropology

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Grizzly bear conservation is as much about human relationships as it is the animals

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theconversation.com – Alexander L. Metcalf, Associate Professor of Human Dimensions of Natural Resources, University of Montana – 2024-04-16 07:32:53
If the government takes grizzly bears off the Endangered Species List, some states will likely introduce a hunting season.
Wolfgang Kaehler/LightRocket via Getty Images

Alexander L. Metcalf, University of Montana

Montanans know spring has officially arrived when grizzly bears emerge from their dens. But unlike the bears, the contentious debate over their future never hibernates. New research from my lab reveals how people's social identities and the dynamics between social groups may play a larger role in these debates than even the animals themselves.

Social scientists like me work to understand the human dimensions behind wildlife conservation and management. There's a cliché among wildlife biologists that wildlife management is really people management, and they're right. My research seeks to understand the psychological and social factors that underlie pressing environmental challenges. It is from this perspective that my team sought to understand how Montanans think about grizzly bears.

To list or delist, that is the question

In 1975, the grizzly bear was listed as threatened under the Endangered Species Act decades of extermination efforts and habitat loss that severely constrained their range. At that time, there were 700-800 grizzly bears in the lower 48 states, down from a historic 50,000. Today, there are about 2,000 grizzly bears in this area, and sometime in 2024 the U.S. Fish and Wildlife Service will decide whether to maintain their protected status or begin the delisting .

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Listed species are managed by the federal government until they have recovered and management responsibility can return to the states. While listed, federal prevents hunting of the animal and destruction of grizzly bear habitat. If the animal is delisted, some states intend to implement a grizzly bear hunting season.

People on both sides of the delisting debate often use logic to try to convince others that their position is right. Proponents of delisting say that hunting grizzly bears can reduce conflict between grizzly bears and humans. Opponents of delisting counter that agencies cannot be trusted to responsibly manage grizzly bears.

But debates over wildlife might be more complex than these arguments imply.

Identity over facts

Humans have survived because of our evolved ability to cooperate. As a result, human brains are hardwired to favor people who are part of their social groups, even when those groups are randomly assigned and the group members are anonymous.

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Humans perceive reality through the lens of their social identities. People are more likely to see a foul committed by a rival team than one committed by the team they're rooting for. When randomly assigned to be part of a group, people will even overlook subconscious racial biases to favor their fellow group members.

Your social identities influence how you interpret your own reality.

can leverage social identities to inspire cooperation and collective action. For example, during the pandemic, people with strong national identities were more likely to physically distance and public health policies.

But the forces of social identity have a dark side, too. For example, when people think that another “out-group” is threatening their group, they tend to assume members of the other group hold more extreme positions than they really do. Polarization between groups can worsen when people convince themselves that their group's positions are inherently right and the other group's are wrong. In extreme instances, group members can use these beliefs to justify immoral treatment of out-group members.

Empathy reserved for in-group members

These group dynamics help explain people's attitudes toward grizzly bears in Montana. Although property damage from grizzly bears is extremely rare, affecting far less than 1% of Montanans each year, grizzly bears have been known to break into garages to access food, prey on free-range livestock and sometimes even maul or kill people.

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People who hunt tend to have more negative experiences with grizzly bears than nonhunters – usually because hunters are more often living near and moving through grizzly bear habitat.

Two mean wearing jackets and holding shotguns as they walk across a grassy field with a dog.
When hunters hear grizzly bear conflict stories from other hunters, they might favor grizzlies less, even if they've never had a negative experience with one themselves.
Karl Weatherly/DigitalVision via Getty Images

In a large survey of Montana residents, my team found that one of the most important factors associated with negative attitudes toward grizzly bears was whether someone had heard stories of grizzly bears causing other people property damage. We called this “vicarious property damage.” These negative feelings toward grizzly bears are highly correlated with the belief that there are too many grizzly bears in Montana already.

But we also found an interesting wrinkle in the data. Although hunters extended empathy to other hunters whose properties had been damaged by grizzly bears, nonhunters didn't show the same courtesy. Because property damage from grizzly bears was far more likely to affect hunters, only other hunters were able to put themselves in their shoes. They felt as though other hunters' experiences may as well have happened to them, and their attitudes toward grizzly bears were more negative as a result.

For nonhunters, hearing stories about grizzly bears causing damage to hunters' property did not affect their attitudes toward the animals.

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Identity-informed conservation

Recognizing that social identities can play a major role in wildlife conservation debates helps untangle and perhaps prevent some of the conflict. For those wishing to build consensus, there are many psychology-informed strategies for improving relationships between groups.

For example, conversations between members of different groups can help people realize they have shared values. Hearing about a member of your group helping a member of another group can inspire people to extend empathy to out-group members.

Conservation groups and wildlife managers should take care when developing interventions based on social identity to prevent them from backfiring when applied to wildlife conservation issues. Bringing up social identities can sometimes cause unintended division. For example, partisan politics can unnecessarily divide people on environmental issues.

Wildlife professionals can reach their audience more effectively by matching their message and messengers to the social identities of their audience. Some conservation groups have seen uniting community members who might otherwise be divided around a shared identity associated with their love of a particular place. The conservation group Swan Valley Connections has used this strategy in Montana's Swan Valley to reduce conflict between grizzly bears and local residents.

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Group dynamics can foster cooperation or create division, and the debate over grizzly bear management in Montana is no exception. Who people are and who they care about drives their reactions to this large carnivore. Grizzly bear conservation efforts that unite people around shared identities are far more likely to succeed than those that remind them of their divisions.The Conversation

Alexander L. Metcalf, Associate Professor of Human Dimensions of Natural Resources, University of Montana

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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In the age of cancel culture, shaming can be healthy for online communities – a political scientist explains when and how

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theconversation.com – Jennifer Forestal, Assistant Professor of Political Science, Loyola Chicago – 2024-04-16 07:32:06
Public shaming can uphold online community norms.
bo feng/iStock via Getty Images

Jennifer Forestal, Loyola University Chicago

“Cancel culture” has a bad reputation. There is growing anxiety over this practice of publicly shaming people online for violating social norms ranging from inappropriate jokes to controversial business practices.

Online shaming can be a wildly disproportionate response that violates the privacy of the shamed while offering them no good way to defend themselves. These consequences lead some critics to claim that online shaming creates a “hate storm” that destroys lives and reputations, leaves targets with “permanent digital baggage” and threatens the fundamental right to publicly express yourself in a democracy. As a result, some scholars have declared that online shaming is a “moral wrong and social ill.”

But is online public shaming necessarily negative? I'm a political scientist who studies the relationship between digital technologies and democracy. In my research, I show how public shaming can be a valuable tool for democratic accountability. However, it is more likely to these positive effects within a clearly defined community whose members have many overlapping connections.

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When shaming helps

Public shaming is a “horizontal” form of social sanctioning, in which people hold one another responsible for violating social norms, rather than appealing to higher authorities to do so. This makes it especially useful in democratic societies, as well as in cases where the shamers face power imbalances or lack access to formal authorities that could hold the shamed accountable.

For example, public shaming can be an effective strategy for challenging corporate power and behavior or maintaining journalistic norms in the face of plagiarism. By harnessing social pressure, public shaming can both motivate people to change their behavior and deter future violations by others.

Public shaming has a long history.

But public shaming generally needs to occur in a specific social context to have these positive effects. First, everyone involved must recognize shared social norms and the shamer's authority to sanction violations of them. Second, the shamed must care about their reputation. And third, the shaming must be accompanied by the possibility of reintegration, allowing the shamed to and be welcomed back into the fold.

This means that public shaming is more likely to deliver accountability in clearly defined communities where members have many overlapping connections, such as schools where all the parents know one another.

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In communal spaces where people frequently into each other, like workplaces, it is more likely that they understand shared social norms and the obligations to follow them. In these environments, it is more likely that people care about what others think of them, and that they know how to apologize when needed so that they can be reintegrated in the community.

Communities that connect

Most online shamings, however, do not take place in this kind of positive social context. On the social platform X, previously known as Twitter, which hosts many high-profile public shamings, users generally lack many shared connections with one another. There is no singular “X community” with universally shared norms, so it is difficult for users to collectively sanction norm violations on the platform.

Moreover, reintegration for targets of shamings on X is nearly impossible, since it is not clear to what community they should apologize, or how they should do so. It should not be surprising, then, that most highly publicized X shamings – like those of PR executive Justine Sacco, who was shamed for a racist tweet in 2013, and Amy Cooper, the “Central Park Karen” – tend to degenerate into campaigns of harassment and stigmatization.

But just because X shamings often turn pathological does not mean all online shamings do. On Threadless, an online community and e-commerce site for artists and designers, users effectively use public shaming to norms around intellectual property. Wikipedians' use of public “reverts” – reversals of edits to entries – has helped enforce the encylopedia's standards even with anonymous contributors. Likewise, Black Twitter has long used the practice of public shaming as an effective mechanism of accountability.

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What sets these cases apart is their community structure. Shamings in these contexts are more productive because they occur within clearly defined groups in which members have more shared connections.

Acknowledging these differences in social context helps clarify why, for example, when a Reddit user was shamed by his subcommunity for posting an inappropriate , he accepted the rebuke, apologized and was welcomed back into the community. In contrast, those shamed on X often issue vague apologies before disengaging entirely.

The scale and speed of social can change the dynamics of public shaming when it occurs online.

Crossing online borders

There are still very real consequences of moving public shaming online. Unlike in most offline contexts, online shamings often play out on a massive scale that makes it more difficult for users to understand their connections with one another. Moreover, by creating opportunities to expand and overlap networks, the internet can blur community boundaries in ways that complicate the practice of public shaming and make it more likely to turn pathological.

For example, although the Reddit user was reintegrated into his community, the shaming soon spread to other subreddits, as well as national outlets, which ultimately led him to delete his Reddit account altogether.

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This example suggests that online public shaming is not straightforward. While shaming on X is rarely productive, the practice on other platforms, and in offline spaces characterized by clearly defined communities such as college campuses, can provide important public .

Shaming, like other practices of a healthy democracy, is a tool whose value depends on how it's used.The Conversation

Jennifer Forestal, Assistant Professor of Political Science, Loyola University Chicago

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Deepfake detection improves when using algorithms that are more aware of demographic diversity

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theconversation.com – Siwei Lyu, Professor of Computer Science and Engineering; Director, UB Forensic Lab, at Buffalo – 2024-04-16 07:31:48
Deepfake detection software may unfairly target people from some groups.
JLco – Ana Suanes/iStock via Getty Images

Siwei Lyu, University at Buffalo and Yan Ju, University at Buffalo

Deepfakes – essentially putting words in someone else's mouth in a very believable way – are becoming more sophisticated by the day and increasingly hard to spot. Recent examples of deepfakes include Taylor Swift nude images, an audio recording of President Joe Biden telling New Hampshire not to vote, and a video of Ukrainian President Volodymyr Zelenskyy calling on his troops to lay down their arms.

Although companies have created detectors to spot deepfakes, studies have found that biases in the data used to train these tools can to certain demographic groups being unfairly targeted.

a hand holds a smartphone with text on it in front of a screen with a man in front of a lectern
A deepfake of Ukraine President Volodymyr Zelensky in 2022 purported to show him calling on his troops to lay down their arms.
Olivier Douliery/AFP via Getty Images

My team and I discovered new methods that improve both the fairness and the accuracy of the algorithms used to detect deepfakes.

To do so, we used a large dataset of facial forgeries that lets researchers like us train our deep-learning approaches. We built our work around the -of-the-art Xception detection algorithm, which is a widely used foundation for deepfake detection and can detect deepfakes with an accuracy of 91.5%.

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We created two separate deepfake detection methods intended to encourage fairness.

One was focused on making the algorithm more aware of demographic diversity by labeling datasets by gender and race to minimize errors among underrepresented groups.

The other aimed to improve fairness without relying on demographic labels by focusing instead on features not visible to the human eye.

It turns out the first method worked best. It increased accuracy rates from the 91.5% baseline to 94.17%, which was a bigger increase than our second method as well as several others we tested. Moreover, it increased accuracy while enhancing fairness, which was our main focus.

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We believe fairness and accuracy are crucial if the public is to accept artificial intelligence technology. When large language models like ChatGPT “hallucinate,” they can perpetuate erroneous information. This affects public trust and safety.

Likewise, deepfake images and can undermine the adoption of AI if they cannot be quickly and accurately detected. Improving the fairness of these detection algorithms so that certain demographic groups aren't disproportionately harmed by them is a key aspect to this.

Our research addresses deepfake detection algorithms' fairness, rather than just attempting to balance the data. It offers a new approach to algorithm design that considers demographic fairness as a core aspect.The Conversation

Siwei Lyu, Professor of Computer Science and Engineering; Director, UB Media Forensic Lab, University at Buffalo and Yan Ju, Ph.D. Candidate in Computer Science and Engineering, University at Buffalo

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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