What would alternate, alien forms of life look like?
All life as we know it relies on carbon and water. But researchers speculate this doesn't have to be the case.
- Life on Earth (and therefore all life we know) relies on carbon and water.
- Carbon and water make for excellent ingredients when making life, but many other elements could serve in their place under the right conditions.
- What are these alternative forms of life and under what conditions could they flourish?
All life on Earth, and thus, all life we've ever observed in the universe, shares a few basic characteristics. Its molecular structures are built using carbon, it relies on water to act as a solvent and facilitate chemical reactions, and it uses DNA or RNA as its blueprints.
These qualities seem so ubiquitous that most any compound we can find that contains carbon is called an organic compound. Carbon works very well as the basis for the chemistry of life. It can bond with many molecules, building structures large enough to be biologically relevant, and its bonds are strong and stable. Using water and DNA/RNA are also seemingly fine-tuned to enable life to exist.
But just because these properties of life are true on Earth doesn't mean they are true everywhere. In fact, we can readily imagine different environments where alternative forms of life can exist. Here are some of the major ways we think that life can vary from the standard we see on Earth.
Lei Chen and Yan Liang (BeautyOfScience.com) for Caltech
An artists' rendering of organosilicon-based life. Organosilicon compounds contain carbon-silicon bonds.
The same stuff that constitutes computer chips and electrical circuits may also constitute life somewhere in the universe. Carbon can form bonds with up to four other atoms at once, bind to oxygen, and form polymer chains, all of which make it ideal for the complex chemistry of life. Silicon, which lies just beneath carbon on the table of elements, also shares these characteristics.
Despite these qualities, silicon is still quite limited as a basis for life. It can only form stable bonds with a limited number of other elements; its polymers would be very monotonous, limiting its ability to form the complex compounds needed for life to occur; and silicon chemistry is not stable in aqueous, or watery, environments. Another issue is that when carbon oxidizes, it forms carbon dioxide, an easily expellable gas. When silicon oxidizes, it forms silicon dioxide, also known as silica, quartz, or sand. This solid waste would pose some serious mechanical challenges for any silicon-based life. Such a hypothetical lifeform would excrete bricks of sand every time it took a breath, which would make vacationing at the beach somewhat more horrifying.
Under certain conditions, silicon-based chemistry might be more favorable for life than carbon-based. Silicon chemistry would also be much more amenable to life in oceans of cold elements that we don't usually associate with life, such as liquid nitrogen, methane, ethane, neon, and argon. Places like these exist in the universe, notably in our own solar system: One of the major features of Saturn's largest moon, Titan, is its lakes of liquid ethane and methane.
An artist's depiction of a world with ammonia-based life. Ittiz [CC BY-SA 3.0]
Most of the chemical reactions that life relies on take place within a watery environment. Water dissolves many different molecules — it is a solvent, and having a good solvent is a prerequisite for the kind of chemistry that brings about life.
Like water, ammonia is also common throughout the galaxy. It's also capable of dissolving organic compounds like water, and, unlike water, it can also dissolve some metallic ones, opening up the possibility for some more interesting chemistry to be used in living things.
However, ammonia is also flammable in the presence of oxygen; has much lower surface tension than water, making it difficult to hold prebiotic molecules together for very long; and its melting and boiling points are much lower than water, at –78°C and –33.15°C, respectively. Thus, the chemistry of ammonia-based life would occur much more slowly, and commensurately, its metabolism and evolution would also be slower. An important caveat, though, is that these are the melting and boiling points that occur at Earth's atmospheric pressure. Under higher pressures, these values would rise.
One of the exciting features of ammonia-based life is that it could exist outside of the so-called habitability zone, or the range where liquid water can exist. Titan, for instance, may hold oceans of ammonia beneath its surface, and although it lies outside of our solar system's habitable zone, it could for this reason host life. Astrobiologists often point to Titan as a possible site of alternative life forms within our own solar system.
Just as a person can be left-handed or right-handed, so too can organic molecules. These molecules are mirror images of one another, but life, for whatever reason, wound up using one side or the other, which is called chirality. Amino acids, for instance, are "left-handed," while the sugars in RNA and DNA are "right-handed." For these molecules to interact with one another, they have to be of the correct kind of chirality; if protein chains are made with mixed-chirality amino acids, they simply don't work. But a protein chain constructed from right-handed amino acids, the opposite of what life on Earth uses, would work perfectly fine.
All of Earth's ecology depends on this convention. In order to eat, we need to consume food of the appropriate chirality. We can be infected and defend against infections of the appropriate chirality. Everything on Earth has the appropriate chirality, so this works just fine.
But alien life might evolve to use the opposite chirality as Earth. This life would be fundamentally quite similar to life on Earth — using carbon as its backbone and water as its solvent — but it would interact with us in one of two possible ways. First, it wouldn't be able to interact at all. Even if microbial life tried eat some other microbial life, the "reverse" sugars would be indigestible, and viruses wouldn't be able to bind to host cells. This would probably be a good thing, since we don't want to be infected with any alien diseases.
But there are critters on Earth that don't eat chiral nutrients, such as cyanobacteria. A comparable alien microbe would be able to eat as much as it wants, reproduce indefinitely, and would never be kept in check by predators since it itself would be of the wrong chirality. This would dramatically disrupt the food chain on an apocalyptic scale.
These alternative forms of life aren't the only ones that exist, but they're among the most likely. A lot of what we know about chemistry suggests that carbon- and water-based life will be the most common among the universe, but we've only ever had a sample of one to study: our own planet. If we find life on other worlds, we'll gain even greater insight into how living things come about.
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What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.
- Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
- Eventually, scientists hope to print patient-specific organs that can be transplanted safely into the human body.
- Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
The Flynn effect shows people have gotten smarter, but some research claims those IQ gains are regressing. Can both be right?
- Many countries made incredible gains in IQ scores during the 20th century, averaging three IQ points per decade.
- Studies out of Europe have shown a reversal of this trend.
- Such declines are not universal, and researchers remain unsure of what is causing them.
They'll reportedly last for thousands of years. This technology may someday power spacecraft, satellites, high-flying drones, and pacemakers.
Nuclear energy is carbon free, which makes it an attractive and practical alternative to fossil fuels, as it doesn't contribute to global warming. We also have the infrastructure for it already in place. It's nuclear waste that makes fission bad for the environment. And it lasts for so long, some isotopes for thousands of years. Nuclear fuel is comprised of ceramic pellets of uranium-235 placed within metal rods. After fission takes place, two radioactive isotopes are left over: cesium-137 and strontium-90.
New research shows that a healthy supply of locally-sourced beer helped maintain Wari civilization for 500 years.
- A new analysis of an ancient Wari brewery suggests chicha helped maintain the civilization's social capital for hundreds of years.
- Civilizations throughout the ancient world used alcoholic drinks to signify kinship, hospitality, and social cohesion.
- The researchers hope their findings will remind us of the importance in reaffirming social institutions and sharing cultural practices — even if over coffee or tea.
Beer is history's happiest accident. Though the discovery probably happened much earlier, our earliest evidence for beer dates back roughly 13,000 years ago. Around this time, the people of the Fertile Crescent had begun to gather grains as a food source and learned that if they moistened them, they could release their sweetness to create a gruel much tastier than the grains themselves.
One day a curious — or perhaps tightfisted — hunter-gatherer hid his gruel away for a safekeeping. When he returned, he found the bowl giving off a tangy odor. Not one to waste a meal, he ate it anyway and enjoyed an unexpected, though not unpleasant, sensation of ease. By pure happenstance, this ancestor stumbled upon brewing.
That's one possible origin story, but we know that our ancestors learned to control the process, and beer took a central role in Fertile Crescent civilizations — so central that Professor Patrick McGovern, a biomolecular archaeologist at the University of Pennsylvania, argues that beer, not bread, incentivized hunter-gatherers to relinquish their nomadic ways.
Beer may also be proof of a God who wants us to be happy (Dionysus?), because the beverage* would be independently rediscovered by peoples across the ancient world, including those in China and South America.
One such peoples, the pre-Inca Wari Civilization, made beer, specifically chicha de molle, a critical component in their religious and cultural ceremonies. In fact, a study published in Sustainability in April argues that the role was so important that beer helped keep Wari civilization intact for 500 years.
Brewing social capital
Twenty years ago, a team of archaeologists with the Field Museum of Natural History, Chicago, discovered a brewery in Cerro Baúl, a mesa in southern Peru that served as an ancient Wari outpost. The brewery contained original equipment, clay storage vessels, and compartments for milling, boiling, and fermentation.
The team recently analyzed these on-site vessels to uncover the secrets of the Wari brewing process. Removing tiny amounts of material found in the spaces between the clay, they were able to reconstruct the molecules of the thousand-year-old drink. They then worked alongside Peruvian brewers to recreate the original brewing process.**
Their molecular analysis revealed several key features of the beer: The clay used to make the vessels came from a nearby site; many of the beer's ingredients, such as molle berries, are drought resistant; and though alcoholic, the beer only kept for about a week.
These details suggest that Cerro Baúl maintained a steady supply of chicha, limited by neither trade nor fair weather, and became a central hub for anyone wishing to partake. The Wari would likely make such trips during times of festivals and religious ceremonies. Social elites would consume chicha in vessels shaped like Wari gods and leaders as part of rituals attesting to social norms and a shared cultural mythology and heritage.
"People would have come into this site, in these festive moments, in order to recreate and reaffirm their affiliation with these Wari lords and maybe bring tribute and pledge loyalty to the Wari state," Ryan Williams, lead author and head of anthropology at the Field Museum, said in a release. "We think these institutions of brewing and then serving the beer really formed a unity among these populations. It kept people together."
The Wari civilization was spread over a vast area of rain forests and highlands. In a time when news traveled at the speed of a llama, such distinct and distant geography could easily have fractured the Wari civilization into competing locales.
Instead, the researchers argue, these festive gatherings (aided by the promise of beer) strengthened social capital enough to maintain a healthy national unity. This helped the Wari civilization last from 600 to 1100 CE, an impressive run for a historic civilization.
Bringing people together (since 10,000 BCE)
A Mesopotamian cylinder seal shows people drinking beer through long reed straws. Image source: Metropolitan Museum of Art.
Of course, the Wari weren't the first civilization to use beer to reaffirm bonds and maintain their social fabric. Returning to the Fertile Crescent, Sumerians regarded beer as a hallmark of their civilization.
The Sumerian Epic of Gilgamesh tells of the adventures of the titular hero and his friend Enkidu. Enkidu beings as a savage living in the wilderness, but a young woman introduces him to the ways of civilization. That orientation begins with food and beer:
"They placed food in front of him,
They placed beer in front of him,
Enkidu knew nothing about eating bread for food,
And of drinking beer he had not been taught.
The young woman spoke Enkidu, saying:
"Eat the food, Enkidu, it is the way one lives.
Drink the beer, as is the custom of the land."
Enkidu ate the food until he was sated,
He drank the beer — seven jugs! — and became expansive
and sang with joy.
He was elated and his face glowed.
He splashed his shaggy body with water
and rubbed himself with oil, and turned into a human."
Tom Standage, who recounts this scene in his History of the World in 6 Glasses, writes: "The Mesopotamians regarded the consumption of bread and beer as one of the things that distinguished them from savages and made them fully human." Such civilized staples not only demarcated their orderly life from that of hunter-gatherers, they also served a key role in their culture's unifying mythology.
Furthermore, Standage notes, Sumerian iconography often shows two people sipping from waist-high jars through reed straws. The earliest beers were consumed in a similar fashion because technological limitations prevented baking individual cups or filtering the beverage. But the Sumerians had the pottery skills to make such cups and filter the dregs. That they kept the tradition suggests that they valued the camaraderie brought by the experience, a sign of communal hospitality and kinship.
The ancient Greek's similarly used alcohol as a means of maintaining social and political relationships — though their drink of choice was wine.
During symposiums, upper-class Greek men would gather for a night of drinking, entertainment, and social bonding. In Alcohol: A history, Rod Phillips notes that symposiums were serious affairs where art, politics, and philosophy were discussed throughout the night and could serve as rites of passage for young men. (Though, music, drinking games, and sex with prostitutes may also be found on the itinerary.)
Of course, we can amass social capital without resorting to alcohol, which has been known to damage social relationships as much as improve them.
In the 17th century, London's coffeehouses stimulated the minds of thinkers with their caffeine-laden drinks, but also served as social hubs. Unlike the examples we've explored already, these coffeehouses brought together people of different backgrounds and expertise, unifying them in their pursuit of ideas and truths. Thus, coffeehouses can be seen as the nurseries of the Enlightenment.
Relearning ancient lessons
The Field Museum archaeologists hope their research can help remind us the importance social institutions and cultural practices have in creating our common bonds, whether such institutions are BYOB or not.
"This research is important because it helps us understand how institutions create the binds that tie together people from very diverse constituencies and very different backgrounds," Williams said. "Without them, large political entities begin to fragment and break up into much smaller things. Brexit is an example of this fragmentation in the European Union today. We need to understand the social constructs that underpin these unifying features if we want to be able to maintain political unity in society."
So, grab a beer or coffee or tea, spend some time together, and raise a glass. Just try not focus too much on whether your friend ordered Budweiser's swill or an overpriced, virtue-signaling microbrew IPA.
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