from the world's big
Could Earth have a 'shadow' biosphere?
Some scientists think there may be a hidden, second form of life living right under our noses.
- All life on Earth shares some basic characteristics, such as being carbon-based; using DNA, RNA, and proteins to function; and so on.
- Many of these characteristics are simply the only ones that could work in Earth's environment, but there are also a surprising number of seemingly arbitrary features of life.
- Under the shadow biosphere theory, some scientists argue that alternative forms of life exist right here on Earth, undetected simply because we don't know to look for them.
In 2009, a NASA researcher isolated a peculiar bacteria from Mono Lake in California. Mono Lake is hypersaline and rich in arsenic, making it a difficult place for life to eke out an existence with the exception of some hard-scrabbling brine shrimp, the migratory birds that feed upon them, and some very interesting extremophile bacteria.
The researcher believed that this particular bacteria, dubbed GFAJ-1, was capable of an incredible trick. All life on Earth — and consequentially, all life that humans know of — uses phosphorus in its DNA. But when GFAJ-1 had no phosphorus, it seemed able to grow using just arsenic. The closest analogy would be to say that the researchers had just discovered alien life right on Earth.
There was a flurry of excitement and activity amongst the scientific community, but it was unfortunately short-lived; further research failed to replicate the experiment, and it appeared that GFAJ-1 was simply remarkably resistant to arsenic and had been surviving on trace amounts of phosphorus that had contaminated the culture.
This episode raises a question that bothers molecular biologists and astrobiologists alike; why is life the way it is? Why couldn't GFAJ-1 have used that arsenic molecule in place of the standard phosphorus molecule? There are plenty of hypothetical forms of life that simply couldn't exist under the conditions on Earth, such as silicon-based life rather than our carbon-based one, but there are also many, many variations on Earth's carbon-based life that should do fine.
These questions lead to another: What if there are indeed other forms of microbial life on Earth, unnoticed but existing in parallel with our own? This hypothetical scenario is referred to as the shadow biosphere.
Mysterious co-inhabitants of Earth
Mono Lake and GFAJ-1 (inset).
If Earth hosted not one, but two fundamentally different forms of life, it would substantially increase the odds of alien life existing out in the universe. If a shadow biosphere existed, then it would stand to reason that when a planet exists under the right conditions, life doesn't just have a shot at emerging, it's practically guaranteed.
But then again, this idea also seems extremely far-fetched. If a second form of life existed in parallel alongside our own, one would expect that we would have detected it by now. To that point, proponents argue that our techniques for detecting life are based on our current understanding of it. Hypothetical, alternate microbial life forms could go undetected.
It is important to note that the majority of biologists do not endorse the idea of a shadow biosphere. There is little evidence to suggest that such a biosphere exists, and it is extremely difficult to prove a negative, so we are left with assuming that ours is the only format that life takes. Still, contemplating the shadow biosphere is a useful exercise, as it may help us understand alien life. Not to mention that the shadow biosphere may in fact be real.
What would the shadow biosphere look like?
All life relies on DNA, RNA, and proteins to function. DNA and RNA are composed of 5 nucleobases in total, and proteins are composed of 20 amino acids. The problem is that these 5 nucleobases and 20 amino acids seem arbitrary — there are plenty of other nucleobases and hundreds of naturally occurring and abundant amino acids. Meteorites have even landed on Earth loaded with these apparently extraneous amino acids and nucleobases. It's plausible that alternate forms of life could use different combinations of these building blocks.
Another possible candidate for the shadow biosphere would be RNA-based life. Both DNA and RNA carry genetic information, and life on Earth uses both to function. Unlike DNA, RNA only has a single strand, uses the nucleobase uracil rather than thymine, and directly codes for amino acids.
Because RNA is structurally simpler than DNA, some scientists argue that predominantly RNA-based life evolved first on Earth, often referred to as the "RNA World." Under a shadow biosphere, such life would have persisted, branching off from what would eventually become DNA-based life.
There could also be organisms with the opposite chirality to ours. Perhaps one of the most arbitrary characteristics that life on Earth exhibits is its chirality, or handedness. In molecular biology, the shape of a molecule plays a large part in its function, but some shapes are simply mirror images of the other, like our left hand is a mirror image of our right.
These molecules are functionally the same, they just need the right kind of molecular machinery to work. Life on Earth has somehow decided that left-handed amino acids make up proteins and right-handed sugars make up our DNA and RNA, but there's no reason why this couldn't be flipped. We may be exposed to molecular life with the opposite chirality to ours and not even know it; none of our cells could interact with a molecule using the "wrong" hand to ours.
Unfortunately, we will likely only be able to shut the book on the shadow biosphere if we find life that deviates from the formula that seems to work so well on Earth. Proving the absence of all other varieties of life on Earth is an impossible task, so we will likely be left to speculate. If, however, we do discover evidence of a shadow biosphere in some of Earth's stranger nooks and crannies, we will have to look at life in the universe from an entirely new point of view.
Sample Melbourne's best coffee without leaving an ecological footprint.
- The massive increase in single-use coffee pods has led to an environmental catastrophe.
- Plastic pods are notorious for their inability to break down in landfills.
- Thankfully, a new wave of eco-friendly compostable pods is coming to the market.
From gun control to immigration, Americans remain split on a handful of contentious issues.
- The data comes from a survey conducted by the Pew Research Center.
- Climate change, guns, and the environment ranked at the top of the list, which climate change representing the widest partisan gap.
- The survey also revealed some interesting splits along generational and gender lines.
Pew Research Center
1. Climate change<p>A majority of Americans say climate change should be a top priority for Congress and the president, marking a 14 percent increase from four years ago. But that concern is not bipartisan: 78 percent of Democrats called it a top policy priority in 2020, compared to just 21 percent of Republicans.<br></p><p>According to past Pew surveys, there's been no other year in which the two parties have been more divided on climate change, and it was the most divisive issue among the issues covered in the recent survey. So what explains the gap?</p><p>Some blame political messaging.</p><p>"Voters take cues on their policy preferences and overall positions," Dr. Riley Dunlap, a professor emeritus at Oklahoma State University, <a href="https://www.nytimes.com/interactive/2020/02/20/climate/climate-change-polls.html" target="_blank">told</a> The New York Times. "President Trump has, in the past, called climate change a hoax and all that. You get a similar message from many members of Congress on the Republican side. And most importantly, it's the message you get from the conservative media."</p><p>But among Republicans, concern about climate change is not spread equally among demographic groups. For example, a <a href="https://bigthink.com/politics-current-affairs/climate-change-poll-americans" target="_blank">recent poll</a> conducted by CBS News found that about 50 percent of Republicans under age 45 said climate change is a "crisis/serious problem," compared to 26 percent of those older than 45.</p>
2. Environmental protections<p>Environmentalism had bipartisan support when it emerged as a prominent political issue in the 1970s. Take, for example, this excerpt from a State of the Union address:<br></p><p style="margin-left: 20px;">"Shall we make peace with nature and begin to make reparations for the damage we have done to our land, to our air, and to our water? It has become a common cause of all people of this country, clean air, open spaces. These should once again be the birthright of every American."</p><p>That's a quote from former President Richard Nixon. But today, concern about the environment seems to be much more prominent among Democrats. Pew Research Center <a href="https://www.people-press.org/2020/02/13/as-economic-concerns-recede-environmental-protection-rises-on-the-publics-policy-agenda/" target="_blank">writes</a>:</p><p style="margin-left: 20px;">"Overall, 85% of Democrats say protecting the environment should be a top priority for the president and Congress, up 11 percentage points from the share who said this in 2019. Fewer than half as many Republicans (39%) rate environmental protection as a major priority; still, this is up 8 points since last year and is the largest share of Republicans saying this in Pew Research Center surveys over the past decade."</p><p>A 2019 Gallup poll found that Republicans' concern over the quality of the environment and their desire for government step in to protect dropped both during the Bush and Trump administrations. Gallup <a href="https://news.gallup.com/opinion/gallup/248294/partisan-polarization-environment-grows-trump.aspx" target="_blank">said</a> the trends reveal three key points:</p><ul><li>First, as we entered the new millennium, there was already substantial partisan polarization on both measures of environmental concern, with Democrats expressing substantially higher levels of worry about environmental quality and belief that not enough was being done to protect it.</li><li>Second, these gaps persisted with only modest variation until the Trump era.</li><li>Third, for both items, the partisan gap has become enormous under the Trump administration.</li></ul>
3. Guns<p>The recent Pew survey shows that Democrats are more likely to say that gun control should be a top priority, by about 40 percentage points (66% vs. 25%). Gun control wasn't the most partisan issue, but it was the most divisive issue between the genders: women were 20 percent more likely than men to say it should be a top priority.</p>
Pew Research Center<p>A separate Pew <a href="https://www.pewresearch.org/fact-tank/2019/10/16/share-of-americans-who-favor-stricter-gun-laws-has-increased-since-2017/" target="_blank">survey</a> conducted in September 2019 found that support for gun control has gained modest support since 2017. The results showed that 71 percent of Americans favor banning high-capacity magazines, compared to 65 percent two years ago.</p>
4. Military<p>Republicans are more likely than Democrats to want to strengthen the military (66 percent versus 30 percent). What's more, no other issue revealed a bigger chasm between the generations: Older Americans (65+) are 30 percent more likely than younger generations (19 to 29) to support bolstering the armed forces. Perhaps unsurprisingly, older Americans are also much more likely to support strengthening Social Security, while protecting the environment is a more important issue among young Americans.</p>
Pew Research Center
5. Immigration<p>More than <a href="https://www.pewresearch.org/fact-tank/2019/06/17/key-findings-about-u-s-immigrants/" target="_blank">1 million immigrants</a> enter the U.S each year, mainly from India, Mexico, Cuba, and China. According to a 2019 Pew survey, about two-thirds of Americans have positive views on immigrants, saying they <a href="https://www.pewresearch.org/fact-tank/2019/01/31/majority-of-americans-continue-to-say-immigrants-strengthen-the-u-s/" target="_blank">strengthen the country</a> "because of their hard work and talents." But in the recent Pew survey, Republicans were far more likely than Democrats to say dealing with immigration should be a top priority (73 percent compared to 40 percent). Men are also more likely than women to prioritize immigration (59 percent to 51 percent).</p>
6. Education<p>Overall, Americans ranked improving education in the top three most policy issues, with 67 percent support, according to the recent Pew survey. But only about half of Republicans said education is a top priority, compared to 80 percent of Democrats. Younger Americans are especially concerned about education, showing 74 percent support. It's worth noting that this partisan gap has widened by <a href="https://www.people-press.org/2019/01/24/publics-2019-priorities-economy-health-care-education-and-security-all-near-top-of-list/" target="_blank">10 percentage points</a> in just a year, according to Pew data.</p>
7. Health care costs<p>The U.S. spends more than $<a href="https://time.com/5785945/health-care-problems-america/" target="_blank">10,000 per person</a> on health care each year, making it the most expensive system in the world. Although a majority of Americans want to reduce the cost of health care, Democrats prioritize this issue higher than Republicans (80 percent to 52 percent support). Women also rank this issue higher than men, by 10 percentage points. Generationally, there wasn't a huge gap in support for reducing health care costs, though the oldest generation did express the highest support (73 percent).<br></p>
Workers are adjusting to their new employment reality on couches and kitchen tables across the nation.
A new study suggests that an old tuberculosis vaccine may reduce the severity of coronavirus cases.
- A new study finds a country's tuberculosis BCG vaccination is linked to its COVID-19 mortality rate.
- More BCG vaccinations is connected to fewer severe coronavirus cases in a country.
- The study is preliminary and more research is needed to support the findings.
Professor Luis Escobar.
Credit: Virginia Tech