The new findings raise questions about when (and where) life began
By Dirk Schulze-Makuch | Published: 2025-02-03 20:27:00 | Source: Hard Science – Big Think
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In Menoya A paper published last year in Nature ecology and evolutionEdward Moody and co-authors describe a deep genetic analysis that led them to delay the estimated lifespan of “Last common universal ancestor“(LUCA) of all terrestrial life to a time between 4.09 and 4.33 billion years ago – which is several hundred million years earlier than previous estimates based on the fossil record alone. If this finding is correct, it would corroborate an earlier study by Elizabeth Bell, who He claimed to have found carbon from life in a 4.1 billion year old mineral.
Just a few years ago, most of the scientific community was saying that life did not appear on Earth until after the so-called.Late heavy bombardment“, the intense fallout of asteroids and comets that occurred between 4.1 and 3.8 billion years ago (based on lunar impacts dated during the Apollo Moon missions). This bombardment was assumed to have completely sterilized the Earth’s youth surface So that life doesn’t have a chance until the beating is over. While scholars have recently wondered whether such heavy bombardment actually occurred – and… How far the early biosphere would have been sterilized – Most of them still believe that The first solid evidence of life on our planet is between 3.5 and 3.8 billion years old.
The origin story of life
This new study may change that. While the exact date of LUCA may seem unimportant to many readers, what is a few hundred million years in the grand scheme of things? – Timing has far-reaching implications. If Moody and his colleagues are right, this means that life arose very quickly, almost as soon as our planet became habitable.
According to our current knowledge, the Earth formed about 4.56 billion years ago, and the Moon formed (violently) about 100 million years later. This leaves a very short time period, perhaps only 200 million years or so, before the first living cells appeared. Moody’s team also found that this early life was indeed very complex, encoding about 2,600 proteins, compared to modern bacteria. It even had a rudimentary immune system that defended it against viruses.
Could the emergence of life really be so rapid, like the inflationary phase of the universe immediately after the Big Bang? This is certainly faster than most of us previously thought. If it happened so quickly, shouldn’t it be relatively easy to decipher the steps life took to evolve?
However, we still cannot get a real handle on how all the functional components are put together. We don’t even know for sure in what kind of environment life arose. It may have been near the “Black Chimney” hydrothermal vent, but it could also be there Ponds, tidal flats or other sites. We don’t know.
Mass squandering
The astonishing speed at which life emerged on Earth opens the door to another intriguing possibility known as “panspermia” — the idea that life originated on another planet and arrived here inside meteorites. It’s an old idea, and one that’s often dismissed because it seems so statistically improbable. I agree with this assessment if the next meteorite came from outside our solar system: eons of interstellar space travel would likely sterilize any life form due to harsh radiation. Furthermore, any object arriving from a great distance would be more likely to fall into the Sun or Jupiter due to their much stronger gravitational pull.
But it’s different if a life-sowing meteorite comes from Mars. It is entirely plausible that life could have arisen on the Red Planet independently. The two worlds formed at about the same time, but Mars cooled much faster than Earth, and the geological record suggests that soon after its formation, the planet was habitable with abundant water. Without a large moon violently interrupting its early years, the window for the onset of life on Mars was actually longer than it was on Earth. Because Mars’ gravity is lower, rocks that are blown off its surface by asteroid impacts escape the planet more easily and are propelled into the inner solar system, toward Earth. The hundreds of Martian meteorites already discovered on Earth are proof of this.
Could primitive organisms survive the journey from Mars? The interior of the famous Martian meteorite ALH 84001 (featuring David McKay and colleagues) He claimed to have found fossilized Martian life in the 1990s) Never heated above 40°C. Whether or not there were actually fossils in that rock, as McKay claimed, it is theoretically possible that organisms could have survived the journey to Earth.
As long as we are speculating, we might also consider another theory known as “guided”. Panspermia.” Over 50 years ago, Nobel Prize winners Francis Crick (one of the discoverers of DNA) and Leslie Orgill It has been suggested that a highly advanced extraterrestrial civilization could have intentionally seeded the EarthThis exposes our planet to the first primitive cellular life, which, after gaining a foothold, will evolve to become more complex and even intelligent. While this may sound like science fiction, we could probably do it ourselves if we chose. Simply send the inert beings inside a protected capsule to a habitable planet and open the hatch after arriving. (Whether this is ethical is another matter. For now, we’re just wondering if aliens would have done it.)
Although the pan-seeding hypothesis may be interesting, indications still point to life beginning here on Earth, considering, for example, the similarity of primitive Earth’s oceans to the inside of microbial cells in terms of elemental abundance (cells are basically bags filled with salt water!). However, if life has already begun elsewhere and It arrives Instead of appearing on Earth, we still don’t know how it happened. Perhaps studying Mars alongside our planet will provide the evidence we need to solve this issue.
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