IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. The drinking water problems in Flint, Michigan continue. While workers work to replace damaged pipes, and many residents continue to avoid using the water that comes from their home taps, this week, the director of Michigan’s Department of Health and Human Services was charged with involuntary manslaughter for actions related to the water crisis. Joining me now to talk about those charges and other stories from this week in science is Rachel Feltman, Science Editor at “Popular Science,” here back in our New York studios. Welcome back, Rachel.

Thanks Thanks for having me, Ira.

IRA FLATOW: Let’s recap the Flint case. This started a few years ago when the city decided to switch its sources of water. It switched, a cost-saving measure. The new water was more corrosive. Tell us what happened there.

RACHEL FELTMAN: Right, so they switched from getting their water from Detroit to getting it from the Flint River to save money. Unfortunately, to save even more money, they didn’t add an anti-corrosive agent to the water system. The Flint River water was especially corrosive. It caused the pipes to start to break down.

And as most people know, that meant there was a high level of lead in the water. There still is. A lot of people still do not have access to safe water from their faucets in Flint. But what some people don’t know is that it also led to the release of a lot of iron, which is what the bacteria that causes Legionnaires’ disease feeds on. So, in fact, there was a Legionnaires’ outbreak in Flint. And some people did die. And so that is the cause of the involuntary manslaughter charge.

And it’s very rare. I was trying to find hard numbers on this. But it’s very rare for a public official to get charged with involuntary manslaughter for something like this.

IRA FLATOW: And there were several other government officials charged as well?

RACHEL FELTMAN: You know, I think right now it’s just this the director of health from Michigan.

IRA FLATOW: Moving on, let’s talk about you have a story this week about the strange genetic makeup of a salamander.

RACHEL FELTMAN: Yes. So, the study is about a really cool hybrid salamander. This genus of salamander has one line of all females. It’s this lineage like five million years long. And they just only have daughters. And they do need sperm to make this happen.

And some animals make that work by just using the sperm– long story short, it has to penetrate the egg to get the process going, but then they don’t use any genetic material. These salamanders make it even more complicated. They can collect sperm from multiple males and then can use any combination, or lack thereof, of their genetic material.

So these female salamanders sometimes have as many as five copies of salamander genomes in their DNA from males of these different species. It’s really interesting. And scientists already knew about their ability to do this, but have been trying to figure out exactly how it works because it’s incredible that they’ve existed for millions of years doing something that’s so unusual.

IRA FLATOW: Yeah, you wonder why they– what evolutionary key here– why would you do this if you were a salamander?

RACHEL FELTMAN: Right, and scientists really aren’t sure. But in this new study, they wanted to figure out– basically, once a daughter is given some certain assortment of genomes from her mother, does she use all of those genes equally? Because usually in hybrids, there will be one genome that they’re using preferentially, and most of the other genes are basically inactive. But they found, at least in the one they studied, she was using all of those genes pretty much equally.

So they think that that might suggest that this is just kind of a system of incredible genetic flexibility and redundancy that helps them be really adaptive. But there’s still a lot left to learn about them.

IRA FLATOW: Hm, makes dating a problem.

[LAUGHTER]

Sorry. There was news this week about the sun. And now this is something we have talked about for years in science fiction. People have said, there’s a sun somewhere else. It has a twin.

RACHEL FELTMAN: Right. So there has been this idea for a while that the sun has a twin, which some scientists have called Nemesis because there’s a theory that it pulled the asteroid that killed the dinosaurs into our atmosphere. But this new study– this all comes down to a longstanding belief that stars of the age, and composition, and size of our sun tend to be born in pairs or triplets. And in this new study, researchers just did some new crunching of the latest data. And in their computer simulations, they think it really is likely that our son did have a twin when it was born and that that second sun obviously left us a long time ago.

We have no idea where it is. We certainly haven’t located it. But this is just kind of one more piece in that puzzle.

IRA FLATOW: So we don’t know. This is just a theory, because it’s probably more probabilistic we had a sun than didn’t have a sun.

RACHEL FELTMAN: Right, it’s more likely that our sun was a twin than that it was born alone. But we have no idea where that other star is.

IRA FLATOW: I know where it is.

RACHEL FELTMAN: Where?

IRA FLATOW: It’s there with Planet Nine.

RACHEL FELTMAN: Yep, they’re just hanging out.

IRA FLATOW: They’re just hanging out still looking for that one also. Finally, you have some important French fry news that has been getting a lot of attention this week.

RACHEL FELTMAN: Yeah, we have a big correction to make to the French fry record. So this study has been going around that a lot of outlets have been reporting as meaning that French fry is double your risk of death, which first of all is very confusing because everyone has a 100% chance of death. But also, it is actually not really a conclusion you can run with. And I’ll explain why.

So, as with a lot of nutritional studies, this isn’t really a conclusion that you can broadly apply as advice for people. This study– the dataset kind of came from somewhere weird. It was from another study looking at osteoarthritis. So it’s not really a good random subset of the population.

IRA FLATOW: In other words, they didn’t set out to decide whether French fries were bad for you or not.

RACHEL FELTMAN: Exactly. And they had a bunch of nutritional information from these people. And first of all, they found that eating potatoes a certain number a week did nothing to increase the likelihood that you would die over the course of the study, which is what we mean by “double your chance of death.” But they found that if you looked at just eating fried potatoes three times a week, that doubled the subjects likelihood of dying while the researchers were still collecting data on them.

The problem with that is that it’s kind of a classic correlation does not imply causation. You have to imagine that people who eat fried potato products at least three times a week have other–

IRA FLATOW: –issues.

RACHEL FELTMAN: –issues– are making other poor health choices. And so you really can’t say, oh, French fries double your rate of death. Obviously we all know French fries are not great for you. But you shouldn’t take this study as a reason to never eat them again if they are part of your moderate healthy diet.

IRA FLATOW: Well it’s good to have you here to set the record straight, Rachel.

RACHEL FELTMAN: Thanks, Ira.

IRA FLATOW: Rachel Feltman, Science Editor at “Popular Science”–

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