Today we learn about how doppelgangers can share similar DNA, a recent discovery of a lost lineage in Indonesia, and recent advancements in finding out what causes Alzheimer’s.
Today we learn about how doppelgangers can share similar DNA, a recent discovery of a lost lineage in Indonesia, and recent advancements in finding out what causes Alzheimer’s.
DNA & Lookalikes
Extinct Lineage Found
Alzheimer’s Viruses
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Find episode transcripts here: https://curiosity-daily-4e53644e.simplecast.com/episodes/dna-lookalikes-extinct-lineage-found-alzheimers-viruses
[SFX: INTRO MUSIC/WHOOSH]
NATE: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from Discovery. Time flies when you’re learnin’ super cool stuff. I’m Nate.
CALLI: And I’m Calli. If you’re dropping in for the first time, welcome to Curiosity, where we aim to blow your mind by helping you to grow your mind. If you’re a loyal listener, welcome back!
NATE: Today we are gonna learn about how doppelgangers can share similar DNA, discovering a lost lineage in Indonesia, and recent advancements in finding out what causes Alzheimer’s.
CALLI: Without further ado, let’s satisfy some curiosity!
[SFX: WHOOSH]
CALLI: Nate, you know how people in our lives have a tendency to come up and tell us how much we look like somebody else they know?
NATE: It happens to me more often than I care to admit. 9 times out of 10, it’s just another skinny white dude with facial hair that doesn’t ACTUALLY look like me, though. It doesn’t stop people from saying we look like we could be brothers.
CALLI: Well, it’s funny you brought that up because a recent study has shown that people who have strong facial similarity have remarkably similar DNA - so similar in fact that it’s actually shocking that they’re not related!
NATE: How did they figure this out?
CALLI: So, for a bit of background: a Canadian artist started a photography project where he took photos of people with their unrelated doppelgängers and posted them on social media. This caused scientists to wonder about the genetic relationship between people who are lookalikes but don’t share any blood relation.
NATE: And when you say lookalikes… how do you even measure that?
CALLI: Well, to be considered for the project, the duos had to have incredibly similar features. They needed to be objectively almost-identical. And when I say objectively, I mean the resemblances are actually uncanny. Like, same nose, same hair, same arch above the lip, you name it. Researchers took the photographs of the 32 couples and used three different facial recognition algorithms to cement their resemblance. They wanted to see how these similarities are represented on a molecular level.
NATE: So it’s like a study of twins that aren’t actually twins?
CALLI: Pretty much. The algorithm said that half of the 32 duos shared common physical traits, and that 9 of those have REMARKABLY similar genes, despite being unrelated.
NATE: Wow, that’s pretty interesting.
CALLI: What they also found is that, along with the obvious physical traits, their behavioral traits were also super alike. Things like whether someone went to college or if they smoke cigarettes often showed up the same within those pairs. So, this means that similar DNA not only tells us about how people look but also what their habits are and how they behave.
NATE: I think I understand but I’m just confused as to how DNA can predict behavior. It’s not like if I just started smoking cigarettes and took up tap dance and I met my doppelgänger they would be into the same thing, right?
CALLI: Yeah, it’s not that simple. It would be more like, you meet your lookalike and, based on this research, they would be more likely to be a vegetarian, for example, than someone who looks completely different to you.
NATE: So, if my math is right, they would have about a nine-in-sixteen chance to share that behavior.
CALLI: In theory. But 9/16 is not that much, right? Because the study is so small, you have to take the data with a grain of salt. HOWEVER, if expanded on, these findings could really affect research in different fields like biomedicine, evolution, and forensics. For instance, forensic scientists could, in theory, reconstruct a criminal’s face from DNA alone or be able to look at someone’s face and determine which genome they have.
NATE: That sounds like the plot to some kind of early 2000s sci-fi movie.
CALLI: Totally! It’s pretty wild to think about because, as we know, forensics are always evolving and there are some ethical implications here that are definitely concerning.
NATE: Yeah, I can see how this use of this kind of research could fuel certain biases or be problematic, especially when it comes to traits like race, ethnicity and gender.
CALLI: That’s definitely something on the researchers’ minds, too. They admit that they’ve already seen how existing facial algorithms have been used to reinforce outdated racial bias in things like housing, job hiring and criminal profiling. They acknowledge that the study, “raises a lot of important ethical considerations.”
NATE: Well, at least they have that in mind. Because it leads me to another thought… DNA alone doesn’t really tell the whole story of humanity, right?
CALLI: Definitely. As tempting as it is to let this experiment solve the mystery of humanity, it only solves part of it. Our lived experiences, as well as those of our ancestors, influence which of our genes are switched on or off - or what scientists call our epigenomes. Those researchers found that while the doppelgängers’ genomes were similar, their epigenomes were different. Basically, the DNA affects the shared appearances way more than the behavioral similarities and those commonalities can be chalked up to coincidence.
NATE: So the next time someone tells me that I look exactly like someone they know, it’s either a skinny white dude OR it could be someone that I share my DNA with.
CALLI: Exactly.
NATE: Wow, I’m so excited to raise an army of Nates!
[SFX: WHOOSH]
NATE: Calli, today we are gonna talk a little bit about our lineage as humans.
CALLI: What do you mean? Like the history of the human race?
NATE: Kind of, but we are gonna go way back to a relatively unknown era of human development. There’s been a super exciting discovery on the Indonesian island of Sulawesi. Basically, scientists have found a set of human remains there and it’s the first time a mostly complete skeleton has been found near artifacts of the “Toalean” culture. The Toaleans were a mysterious group of hunter-gatherers who inhabited the area around 8,000 to 1,500 years ago.
CALLI: That’s incredible! I guess my question is, what does this tell us about human development?
NATE: So, researchers were able to analyze the DNA which was amazingly preserved within the inner ear bones of the deceased and what they found was that the body belonged to a woman who died around 7,000 years ago AND that she was a Denisovan. Have you ever heard of the Denisovans?
CALLI: I haven’t. Tell me everything.
NATE: So, let me break it down. Denisovans were a subspecies of humans that we thought went extinct about 50,000 years ago, similar to neanderthals. They are closely related to the first humans to reach Southeast Asia, Australia, and Oceania, and are distant relatives of modern day Aboriginal Australians and Melanesians.
CALLI: Well, if they were in that region of the world, it makes sense that her remains would be found there right?
NATE: Actually, not really! Based on everything we know, she shouldn’t have been there at all. She might have had some local ancestry there but that’s just a theory. What’s so interesting here is that the discovery has really affected what we knew about humans living in that region while she was alive.
CALLI: How so?
NATE: If we take a look at the DNA of ancient hunter-gatherers in Southeast Asia, they don’t share much ancestry with the Denisovans. This means that as a result of this research, we now can assume that Indonesia and its surrounding islands, an area known as Wallacea, was a meeting point for a major admixture event between the Denisovans and modern humans.
CALLI: Oh wow! So… what’s an admixture event?
NATE: Admixture is basically mating, but it’s when the mating results in the mixture of DNA which hasn’t been previously combined. Scientists found that this woman’s lineage doesn’t exist today which makes it, “A previously unknown divergent human lineage. To quote the researcher directly, the ancient woman has a genome, “That is unlike that of any modern people or groups that are known from the ancient past.” So basically, the researchers found no evidence that the modern people of Sulawesi descend
from the Toalean hunter-gatherers that I described earlier.
CALLI: So where exactly did she come from?
NATE: We really don’t know. All we know is that she was a Denisovan, her burial site was surrounded by Toalean artifacts, and that it looks like she was one of the last Denisovans alive during that time.
CALLI: So she really was one of the last of her species. That’s a bit of an existential crisis in the making.
NATE: Exactly.
CALLI: I think if I was the last human on Earth of my kind I’d probably post a tweet or something saying, “lol I’m the last one left” and die a little inside because nobody would be around to react to it.
[SFX: WHOOSH]
NATE: Okay, so I know this might seem a bit tasteless, but I promise I don’t mean it that way: whenever I forget little things like where I put my keys or what your name is, I’m constantly afraid that I’m developing Alzheimer’s
CALLI: I know what you mean. What makes that even worse is that nobody really knows how Alzheimer’s is caused, right?
NATE: Correct, but a recent study from Tufts University might be closer than ever to cracking the mystery behind Alzheimer’s. Researchers found that two common viruses may set in motion the early stages of the disease. So they found that the varicella zoster virus, or VZV…
CALLI: That’s what causes chicken pox and shingles?
NATE: Exactly. They found that having a VZV infection can activate a dormant secondary virus in the brain. Any idea which virus that one is?
CALLI: No clue.
NATE: Well, it’s the herpes simplex, or HSV-1, which is also insanely common. So, someone would catch chicken pox and will get itchy, then that virus lays dormant in the body to the point you might not even know you still have it. If you then get HSV-1, that virus becomes activated and it’s this set of events that might be what sets in motion the early stages of Alzheimer’s.
CALLI: Oh, weird! So it’s like your brain is under attack by two viruses at once that create… not quite a supervirus, but a sort of super viral effect?
NATE: Exactly. Normally, HSV-1, which is the most common variant of the virus, lies dormant within the brain, but once it’s activated, it leads to the growth of proteins that leads to a loss of brain function… all of which are signature features found in Alzheimer’s patients.
CALLI: Wow. So they’ve kind of cracked the code then right?
NATE: Mmmm, not quite. Researchers say that this is only ONE pathway to Alzheimer’s but they think that it’s possible that other inflammatory events could occur in the brain that can cause the disease.
CALLI: If there’s a link between HSV-1 and Alzheimer’s, that also means that anybody developing Alzheimer’s from HSV-1 might see some kind of treatment soon for that initial virus, right?
NATE: It’s possible! According to the World Health Organization, around 3.7 billion people under the age of 50 have been infected with HSV-1 -- which, again, causes oral herpes. So that means roughly HALF the earth’s population has the virus. Before you freak out, in most cases HSV-1 is asymptomatic, but it is still pretty crazy the amount of people that could be at risk for Alzheimer’s. VZV can remain in the body and find its way to the nerve cells before it becomes dormant. Later in life, it can be reactivated and cause shingles, which is said to occur in one out of three people.
CALLI: So these numbers are massive, but both viruses are typically dormant. Can you walk me through how researchers got to this discovery? Give me some specifics on this experiment.
NATE: I absolutely can, it’s very cool how they found this. The researchers essentially made a fake brain using sponges, silk protein and collagen. The model was only 6-millimeters wide and 6 millimeters is tiny, less than a quarter of an inch. They filled those sponges with stem cells related to the nervous system. These little cells eventually grow and become functional neurons like we have in our brains and they’re able to pass signals and information to each other in a network.
CALLI: So what happened?
NATE: When they infected those neurons with VZV, they didn’t see anything Alzheimer’s related and everything was functioning normally. BUT, when the model already had the dormant HSV-1 virus and they were exposed to VZV, the HSV-1 virus was reactivated AND led to an increase in Alzheimer’s proteins. So, basically dormant HSV plus new VZV equals potential Alzheimer’s, or as one of the researchers succinctly put it: “they could cause trouble.”
CALLI: Wow, so if someone were to get the chicken pox vaccine, would that help?
NATE: According to research, probably. The VZV vaccine has been shown to hugely reduce the risk of dementia because the key is helping to stop the cycle of reactivation once the virus is already in the body. So hopefully with these new findings we can help stop Alzheimer’s before it starts!
CALLI: And if researchers are finding one cause of Alzheimer’s it means that others can present themselves soon!
NATE: Yep!
CALLI: So long story short… is this all your covert way of making sure we all get VZV vaccines?
NATE: You read me like a book, Calli. You, me, and everybody listening should make sure we have all our relevant vaccines. Even if this isn’t the ONLY cause for Alzheimer’s, being properly vaccinated could help prevent it from activating in our brains!
[SFX: WHOOSH]
NATE: Let’s recap what we learned today to wrap up.
CALLI: Researchers teamed up with a Canadian artist who takes photos of doppelgängers and discovered that unrelated strangers who resemble one another actually share remarkably similar genotypes. What’s even more unusual is that there are behavioral similarities between the lookalikes as well, which scientists are working to explore further.
NATE: There was a breakthrough genetic finding through studying the DNA of an ancient woman’s remains that were uncovered in 2015 on the Indonesian island of Sulawesi. Scientists found that she is one of the last members of the Denisovans, who were a subspecies of humans that existed tens of thousands of years ago. This paints a better picture of how modern humans developed in Oceania.
CALLI: A new development in Alzheimer’s research has been explored, showing that common viruses can cause a reaction in the brain that leads to Alzheimer’s. The good news is that there are vaccines that prevent one of the viruses in the first place, which will lead to better numbers of Alzheimer patients.