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[...] For Danny Glavin, a senior sample scientist, he wanted to solve a relentless mystery in his life's work: Why are all known living things only based on the left-handed forms of amino acids, the molecules that build proteins?
His moment arrived nearly a decade later. Glavin and a team of researchers probed the grit from Bennu, a carbon-rich asteroid made of loosely bound boulders, but what they found threw them a curveball. Rather than supporting one of the leading hypotheses — that the early solar system favored the left-handed variety and brought those ingredients to primitive Earth — it showed no favoritism at all.
[...] Many amino acids, whether they're used in biology or not, come in two mirror-image forms. Each molecule has a central carbon atom with other atom groups attached, oriented in one direction or the reverse. This property, called chirality, is like a left and right hand: They're similar, but if you stacked them, the thumbs would be hitchhiking opposite ways.
In Earth life, the amino acids are always "left-handed," and sugars, which partly make up the backbone of DNA, are always right-handed, giving the double helix its signature twist to the right. The homogeneity found among both is especially confounding to scientists because the left and right-handed versions of all these molecules are equally available in nonliving chemical mixes.
Practically speaking, if all biological molecules took the reverse form, that might work just fine. So if life could have taken the other path, why didn't it? Is uniform "handedness" a secret ingredient in the recipe for life, and more specifically, did it have to turn left? Did the bias toward left-handed amino acids begin in the cosmos, or did it happen later on this planet?
"A fundamental question for all of us is whether life had to be the way it is," said Iris Chen, professor of chemical and biomolecular engineering at UCLA, who wasn't involved in the asteroid study. "Is the universe predisposed to our kind of life, or is our biology the result of accidents and chance?"
Scientists knew early on they would use the material collected by NASA's $800 million OSIRIS-Rex mission, short for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer, to analyze the "handedness" of individual amino acids. Bennu's mineral fragments could be older than the 4.6 billion-year-old solar system. These grains of stardust could have come from dying stars or supernovas that eventually led to the creation of the sun and planets.
To do their study, they brewed a sort of "Bennu tea," boiling a small amount of the rocks and dust in water and acids to extract organic compounds. Then they used mass spectrometry techniques to identify organic molecules, including 14 of the 20 amino acids life uses to build proteins, which carry out genetic instructions. Some of the latest findings were published this week in the journal Nature Astronomy.
Over the past few decades, researchers have found that meteorites — rocks that have traveled space and crash-landed on Earth — have had a higher concentration of left-handed amino acids than right-handed ones, in the neighborhood of 60 percent more. Perhaps space rocks delivered the compounds that then underwent chemical reactions near Earth's deep-sea vents to form the first cells. The rest is evolution, perhaps.
Those results, coupled with the knowledge that space rocks have bombarded the planet for eons, have led scientists to believe ancient asteroids, the solar system's time capsules, would also reveal more left-handed amino acids. If the solar system indeed harbors more lefties, perhaps polarized light in space was the culprit. A slight favoritism in the environment could turn into a larger disparity over time.
But the Bennu researchers found lefties and righties comingling equally. Now Glavin wonders if the previous studies on meteorites are invalid, perhaps contaminated with Earth proteins when they fell to the ground. Jason Dworkin, project scientist for the OSIRIS-Rex mission, thinks there may be a different reason for Bennu bucking the trend.
"Bennu is an example of one type of future meteorite which is too fragile to survive landing on Earth, and so it's not really in our collections," Dworkin said.
Maybe the reality is that life's design was determined by a coin flip. Once a successful pattern was established, the template continued through evolution. Proteins and enzymes, tiny drivers inside cells, fit together like a jigsaw puzzle. If life emerged with left-handed amino acids, switching to right-handed amino acids later might have stopped everything from working. There are vast advantages to uniformity: If people were based on right-handed amino acids, they wouldn't be able to eat and digest plants or animal products based on left-handed amino acids.
Researchers have made mirror versions of biological proteins with right-handed amino acids in a lab. They function similarly, but they're much harder to destroy. Enzymes that would typically break them down are rendered useless. Like your hair dryer on an international vacation, the tool won't work if the plug and outlet don't match.
Some scientists considering the implications of this problem have expressed concerns about the future development of mirror cells in laboratories. If people became infected with harmful mirror bacteria, their immune systems might be defenseless, unable to wage any sort of counterattack. A group of biologists recently wrote an extensive paper on the risks, as reported by The New York Times.
[...] "Frankly, it actually might make the search for life easier in some respects because we don't have this risk potentially of a false positive," Glavin said. "We (could) believe that if there's an amplification of one or the other, that there may be biology behind it."
(Score: 2, Informative) by Gaaark on Sunday February 09 2025, @09:48PM (4 children)
Evolution?
I have no idea what i'm talking about.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. I have always been here. ---Gaaark 2.0 --
(Score: 2) by Gaaark on Monday February 10 2025, @12:33AM (2 children)
Off topic? How.
Maybe the "left-handed forms of amino acids" out evolved the right-handed.
I have no idea, but at least it's an idea. Maybe the off-topic person could come up with something better?
--- Please remind me if I haven't been civil to you: I'm channeling MDC. I have always been here. ---Gaaark 2.0 --
(Score: 2, Interesting) by khallow on Monday February 10 2025, @04:55AM (1 child)
Scenario one: all it takes is for a small region to unify on driving on one side of the road. Suddenly those drivers will fare better than the random drivers will and the choice will propagate as that initial population with their fixed choice spreads far and wide.
Scenario two: some driver evolves a vastly superior trait. They drive a tank while everyone else is driving small Yugos. Suddenly, being on the wrong side of the road makes you a pancake. Even that doesn't help in the long run. The tank drivers and their initial choice of road side propagate while everyone else eventually gets flattened.
In either case, there's a strong reinforcement mechanism. If the relatively rare mutation happens and a new driver ends up on the wrong side of the road? They'll quickly wreck and remove themselves from the driving population. Even though that will probably take out a normal, the established population will be much larger than the mutated population - easily accommodating the losses.
(Score: 0) by Anonymous Coward on Monday February 10 2025, @01:35PM
But, but, but, "isolated" populations do drive on the other side of the road...
https://www.statista.com/chart/9261/which-side-of-the-road-do-you-drive-on/ [statista.com]
(Score: 2) by mcgrew on Tuesday February 11 2025, @07:10PM
Evolution?
No, only life and its associations evolve, non-living things just change. Life has to begin before it can evolve.
If what I've read is correct, life on Earth consisted solely of single cell organisms for a billion years, 2/3 of the time life has existed here. That suggests that life didn't evolve at all for the first billion years. It also suggests that if we ever find life elsewhere, it will likely be single cells and not Vulcans.
What did you expect when you voted for a convicted felon, peace and rainbows?
(Score: 4, Interesting) by Azuma Hazuki on Monday February 10 2025, @01:36AM (1 child)
There may be -- and this would be huge news for physics -- a difference in total molecular bonding energy depending on which enantiomer of a given molecule is under consideration. What if the left-handed enantiomers have ever-so-slightly lower total embodied bonding energy in their structures than the right-handed analog, or vice versa?
I am "that girl" your mother warned you about...
(Score: 5, Informative) by PiMuNu on Monday February 10 2025, @04:11PM
Good idea but chemistry is driven by electromagnetic force which has been shown to be parity conserving to very high precision. If you do some electromagnetic things, then look at it in a mirror, you get the same things back. This has been demonstrated very conclusively for more than half a century (and particle physicists do think very hard about these things).
As an aside, the weak force has been shown very conclusively to violate parity symmetry (and also charge-parity symmetry) for 50 years. However weak force has negligible effect on chemistry, rather it turns up in beta decay and some higher energy stuff. The parity violation things come down to how spinning objects behave in a mirror (formally known as a parity operator).
* Consider a rocket flying into space. It has a velocity vector. That rocket flying into space *in a mirror* does what you expect.
* Consider a spinning top. We define a *pseudo* vector which is the axis along which the top spins. Now look at it in a mirror and the top looks like it is spinning in the opposite direction; i.e. the pseudo vector points in the opposite direction! It's an awesome thing.
So vector has even symmetry under parity operation and pseudo-vector has odd symmetry under parity operation.
It turns out that mathematically, the weak interaction can be modelled as a linear sum of a vector operator and a pseudo vector operator (I forgot Quantum Field Theory but someone else might be able to fill in this step better). So weak interaction in a mirror looks like a weird superposition of something that has even symmetry (stays the same) and odd symmetry (flips sign).
(Score: 2) by hendrikboom on Monday February 10 2025, @01:41AM
Maybe it was just genetic drift in the early years when there were still few instances of any kind of prelife.
(Score: 1, Funny) by Anonymous Coward on Monday February 10 2025, @02:43AM (1 child)
It was God's fault. That boy ain't right.
(Score: 0) by Anonymous Coward on Monday February 10 2025, @01:36PM
Correct, she's left.
(Score: 1, Funny) by Anonymous Coward on Monday February 10 2025, @02:50AM (1 child)
Well, reality does have a liberal bias...
If it turned right, everything would be anti-matter, and we don't have much of that around, do we?
(Score: 2) by gnuman on Monday February 10 2025, @09:54PM
This has nothing to do with anti-matter. This is about bond handedness and it's called Chirality. It's something that people should have learned in High School, or at least been told about it.
https://en.wikipedia.org/wiki/Chirality#Biology [wikipedia.org]
https://en.wikipedia.org/wiki/Homochirality#In_biology [wikipedia.org]
(Score: 3, Informative) by NotSanguine on Monday February 10 2025, @09:45AM (1 child)
FYI..These results were discussed here [soylentnews.org] in December, 2024.
It is fascinating that life here on Earth is *solely* of "left" chirality.
The how and why will likely remain a mystery, but really satisfying to hypothesize about!
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 0, Redundant) by rpnx on Monday February 10 2025, @05:46PM
It's not. Left handed evolved first, and having half your enzyme-material interactions fail because e.g. a left-handed sugar failed to interact with a right-handed sugar processing enzyme is a biological disadvantage. As an organism, you want to have all left handed or all right handed. Left handed simply evolved first, that's all. If you are all left handed, 100% of your enzymes are left handed, and 100% of the sugars are left handed, so 100% of the sugar-enzyme interactions are paired correctly and work. If you had 50% left handed sugars and 50% right handed sugars you'd need both left and right handed enzymes and 50% of the time they'd bump into the wrong chirality molecule.
For plants, this means producing only left handed sugars. For everything else, they only need to process left handed sugars because plants only make left handed sugars.
(Score: 1, Redundant) by rpnx on Monday February 10 2025, @05:42PM (3 children)
It was arbitrary. The molecules randomly happened to be left handed. It turns out that having both left and right handed amino acids is a disadvantage, so it's better to be all left or all right. There's no reason behind it being left handed, other than that left handed life evolved first.
(Score: 0) by Anonymous Coward on Tuesday February 11 2025, @03:57AM (2 children)
Except it didn't. The amino acids from Bennu coalesced before the Earth formed, so there were both left and right-handed amino acids before anything "evolved" on the Earth. And right-handed life may well have repeatedly started on Earth before and/or concurrently with left-handed life. In fact, during the Late, Heavy Bombardment [wikipedia.org] life (of the left and right-handed varieties) may well have started and been destroyed repeatedly.
From TFS. Not even TFA. it's right there in the summary:
We have absolutely no idea as to whether or not right-handed or left-handed life came first, only that left-handed life is what we have now. You're making assumptions about "which came first," without data to back up those assumptions. And we know what happens when one assumes [youtube.com], yes?
(Score: 2, Disagree) by rpnx on Tuesday February 11 2025, @05:52AM (1 child)
All other explanations have been ruled out.
Left handed life evolved first. Inorganically generated amino acids can form in either chirality, but organic ones form left handed because that's how plants and other life produce them.
Saying that life somehow formed right handed, went extinct, and we somehow also got left handed life genesis is so utterly absurd given how unlikely the initial formation of life is to begin with, that I refuse to take your argument seriously.
Do you understand how fundamental chirality is to our existing biological systems? There are fundamental chemical aspects of life that are shared by all of life on earth, descended from a single common ancestor, which was left handed. The notion there were multiple origins of life is utterly statistically absurd, and posing the idea that life could evolve to switch from one chirality to another shows that you have no basic understanding of even undergraduate level chemistry and biochemistry, or no common sense.
(Score: 1, Interesting) by Anonymous Coward on Tuesday February 11 2025, @10:48PM
[Citation Needed]
What other explanations? Who ruled them out? When? With what evidence?