On This Week's Show

  • Ancient DNA Rewrites Settlement Story of the First Americans
  • A popular sugar additive may have fueled the spread of not one but two superbugs
  • The Climate Lounge

Science News with Sophie McManus and Nevena Hristozova

Ancient DNA Rewrites Settlement Story of the First Americans

Happy New Year!

So we start by going back in time – a few millenia back. This story concerns archaeology, the only job in which finding the remains of a baby constitutes a really good day….11,500 years ago, a baby girl sadly died and was buried in Alaska. In 2010 her remains were found and scientists have since been working to extract and sequence her genome (her genetic information) to learn more about early humankind. They succeeded in this last week and their work was published on January the 3rd in the journal Nature.

It turns out that the genetic material from this child is the second-oldest ever found in North America and that she belonged to a human lineage that hasn’t been seen before. It seems as though this group of people split off genetically from Native Americans around about their arrival time in North America. The infant whose genome they sequenced was more related to present-day Native Americans than any other humans alive today. Yet she still represents a different human lineage – the scientists have termed this the Ancient Beringian population.

“There has never been any ancient Native American DNA like it before,” said David Reich, a geneticist at Harvard Medical School (not one of the authors). It’s hard to study ancient human populations because remains are exceedingly rare. Not only were there not that many humans around that long ago, but they were rather more mobile than we are today (jogging notwithstanding), and naturally the perfect combination of conditions to preserve remains is an unlikely scenario. Finding ancient human remains is a rare scenario, and also an emotive one. For example, the Kennewick man – this 9000 year old man became the source of a pretty contentious battle. The scientists who found him wanted to analyse his genome, whereas local indigenous people preferred to give him a reburial. In this case there was no such dispute as scientists worked closely with the members of the local indigenous groups to ensure, essentially, that correct permission was given.

The discovery of this ancient population lends support to the theory that the Americas were originally settled by migrants from Siberia. Why?

Because this infant, an Ancient Berigian, was found in Alaska – yet her heritage would be Asian. The word Beringia actually refers to Alaska and the eastern tip of Siberia, as well as the land bridge that joined the two landmasses during the last ice age. This bridge between Siberia and present day Alaska came and went over millenia, successively submerged by sea, and it is thought that, throughout history, early humans could have walked across it from Asia, to reach the Americas. The discovery of this baby girl on Alaska, who is related to yet distinct from other early American populations, therefore supports the theory that this land bridge was a conduit for ancient people to migrate across the Earth.

Further work could well address some of the many mysteries of early human migration. However, while the authors of this study agree on the genetic findings – that this infant girl found represents a previously undiscovered human population – they disagree on the events that led to these people branching off from other early humans. How did they publish together, then?! They put two different models to explain how the Ancient Beringians originated. In one version, the Beringians are suggested to have split from the rest of the Native Americans before crossing the land bridge into North America, implying multiple waves of migration from Siberia. In the second, the group travelled across Beringia as one group, only splitting afterwards. As one question is answered, many more appear. It would help if there were more samples – in this case, the girl was found alongside other infants, but their genetic material was not preserved. Archaeologists therefore have to cross their fingers for more chance findings of ancient graves, though that may sound a bit grisly.

If you’d like to read more about this, apart from the original article in Nature, there are great articles on the story in Smithsonian and the New York Times.

Smithsonian Magazine, Live Science, New York Times

 

A popular sugar additive may have fueled the spread of not one but two superbugs

Here, we’re talking about a very unpleasant infection caused by the bacterium Clostridium difficile. It’s a naturally occuring bug around us and in our column. The problem with it arises when the bug becomes too populous in the gut for example after antibiotic treatment for another infection, when other bugs are killed off and the balance if the gut microbiome gets disturbed. Most often, the infection comes with diarrhea, fever, nausea, abdominal pain and other unpleasant feelings. If you are truly unlucky, it might end up killing you after it indices sepsis – your immune system goes in an overdrive and stops distinguishing between the cells of the pathogen and your own cells killing everything in sight – the ultimate form of physiological suicide.

Some recent studies covered in the LA Times and the news-page of the chemistry world dot com, discuss the correlation between the increased frequent use of a sugar called trehalose as a food additive and the spike in infections caused by the Clostridium difficile. Trehalose is a naturally occuring sugar, formed by two glucose molecules linked together – so basically nothing really fancy – it’s synthesised by many plants. It became a popular food additive since it’s more stable than glucose and sucrose at high temperatures. This pretty much means that you can heat treat your preparation without it caramelising and changing the looks, texture and flavour of the food. Few of the Clostridium difficile strains feed on trehalose if it has access to it in the gut and does so with gusto! In fact many bacteria grow better on trehalose than glucose or other sugars.

The study in question showed that with the higher use of trehalose in the food, not all is absorbed by the human gut and thus more of it remains available in the part of the gut where the clostridium spores live. This makes the environment for the spike of the number of the clostridium cell counts in the gut and causing the infection of the intestine. The study went further to find out if these two strains were the ones which caused recent outbreaks of the Clostridium difficile infection in the western world in the past decade. They also showed that these two strains in particular are happier with trehalose due to two very different mutations. Things are a lil complex here. One has a mutation in the suppressor protein for trehalose metabolism which has much lower threshold than the rest of the strains. Basically imagine that the high jump bar is much lower than it is now – much more people would be able to make it over it. In the other case, the second strain picked up few entirely new genes coding for proteins of the trehalose metabolism making it much more active in using up the sugar. This finding means that the two strains became sort of super bacteria in terms of being better prepared to live off the conditions of the environment independently.

LA Times, Chemistry World


The Climate Lounge

“It’s cold… global warming is fake.” said people who are wrong.

It’s cold on the East Coast of the United States, and since, little known fact, the East Coast of the US, which includes NYC, Boston, Philadelphia, and Washington DC, actually represents the entire world (sarcasm), some folks (including certain popular vote losers) have declared Global Warming fake because it’s cold, in winter, in one part of the globe.
Annoyingly, this happens every winter because it gets cold in winter. And if that sounds dumb, you’re right. It is dumb. And I’m tired of it too. But alas, let’s talk about why it’s just so freaking stupid.

First off, I’d be remiss if I didn’t say that the cold that the eastern/central US is experiencing is pretty impressive. In some ways, it’s a bit comforting to know that we can get cold air outbreaks like this still even with a warm climate.

But onto the stupid, for the thousandth time, weather is not climate. Weather is what we are experiencing. Climate is what you expect. If you like sports, think of it this way. Climate is the well diagrammed play. Weather is how that play actually turns out. So picking out one day and one location that seemingly goes against the warming trend doesn’t really mean anything. And that’s because…

If we for once take a non-US centric look at the world, we’d notice that while the central/eastern US has been colder than average, the rest of the world is running a fever. So overall, the globe was warmer than average. And even for the United States, if we take a look at the daily temperature records, hot records easily outpaced cold records.

So why is it so cold? All that cold air should be in the Arctic but due to a wavy jet stream, that cold air was allowed to spill south as if someone left the refrigerator door open. This can happen anywhere in the northern hemisphere. This time the eastern US was the victim. Now there is some research that suggests that wavier jet streams will become more common place in the future due to global warming and a decrease in temperature difference between the poles and tropics but this is still a hotly debated concept. If true, it would mean that cold air outbreaks might increase in some sense even while the planet as a whole warms at the surface. This would be potentially one of those counterintuitive impacts from climate change.

But contrarian listeners might be thinking, “Hey if he says cold doesn’t mean global warming isn’t real then why can he talk about heat waves in the summer”. I’ve seen this a bit from folks who try to do “both siderisms” as some sort of faux middle ground. So let’s nip this in the bud. Highlighting events which are consistent with the overall warming trend is not the same as cherry picking an outlier that goes against it. Not all events explain the warming trend equally. Also, when highlighting heat waves, one aspect of the communication is to educate on how events like that will be more commonplace in the future. We focus on heat waves because they act as harbingers of what’s to come as well as evidence of what we are already doing (in fact scientists have attributed climate change’s impacts on heat waves already). At no point did scientists ever say that it won’t get cold in winter occasionally. So let’s not pretend “both sides do it” is a reasonable argument.

Because global warming is real, it’s happening now, it’s hurting people now and it will hurt plenty more people in the future. Let’s do something about it!

Mashable, New York Times, Earther


In Closing

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