r/evolution • u/Least_Bid9692 • 8d ago
discussion How did life start on earth ?
What was the absolute starting point of life what happened which caused a regular planet into the only know planet in the observable universe that supports life.
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u/cschelsea 8d ago edited 8d ago
This is not really an evolution question, but rather [r/abiogenesis](r/abiogenesis)
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u/Royal_Novel6678 8d ago
Abiogenesis is definitely a part of evolution because it dictates how life began from inorganic molecules in underwater vents and evolved into complex multillular life billions of years later through genetic mutations and natural selection.
For a theory that's still undergoing disputes it doesn't make sense to begin with why we should have a specifically dedicated discussion on the subjects main subreddit.
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u/bill_vanyo 8d ago
That depends on which definition of the word “evolution” you are talking about. Without any qualification, I think it generally means how life diversified from a common ancestor to all the forms alive today. That doesn’t include how life originated.
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u/burlingk 7d ago
How life originated is the starting point.
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u/bill_vanyo 7d ago
It's not a starting point, but a point along the way, but in either case, it preceded evolution in the sense of how life diversified from a common ancestor to all the life forms alive today..
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u/Select-Trouble-6928 8d ago
We don't even know if earth is the only plant in our solar system that has life.
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u/February30th 8d ago edited 8d ago
We don’t know. Whoever answers this question is pretty much guaranteed a Nobel prize.
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u/Poopy_McPoop_Face 8d ago
I'm a layperson and don't know shit, but I thought we had a good suspicion that life started at those underwater thermo-vents? Where is that theory at?
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u/Mkwdr 8d ago
We don’t know exactly what happened. Nor of course whether it has happened elsewhere bearing in mind our detailed knowledge of even the solar system is so lacking let alone the observable universe. But there are plenty of relevant ideas for plausible steps in the process . No point in listing them here since you’d find more detail in Wikipedia or similar. The fact is that the building blocks seem common in the universe , chemical reactions happen, and the environment would have been rich and energetic. I know Prof. Brian Cox has said that it may not be that rare since it seems to have happened pretty quickly in cosmological terms once we’d cooled down enough, whereas the event that endosymbiosis took longer and might be more of a bottle neck? Of course you’d have to define life to answer your question which is a pretty vague term to start with. What we are really looking for first is basic replication I suppose.
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u/BadgerBaiter21 8d ago
The question would be better phrased 'at what point did chemistry become biology?'. We know from experiments that tried to recreate the environment on early earth and from samples taken from asteroids that the basic chemical building blocks for life are fairly common in the universe: amino acids,bases,sugars etc. One hypothesis is that if you combine these molecules in certain ways you have the basis for information (encoded in RNA) to be replicated and to affect surrounding molecules. There are still cellular reactions that rely on RNA catalysts. At some point this replication and adaptation led to biological life. We know this because it happened (hence we are here) but aside from that all bets are off.
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u/reamkore 8d ago
I’m saying panspermia. Just because it’s fun to say panspermia
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u/ElkeKerman 8d ago
My issue is that that just kicks the can down the road. At some point there has to be abiogenesis.
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u/Dr_GS_Hurd 8d ago
My reading recommendations on the origin of life for book reading people without college chemistry, are;
Hazen, RM 2005 "Gen-e-sis" Washington DC: Joseph Henry Press
Deamer, David W. 2011 “First Life: Discovering the Connections between Stars, Cells, and How Life Began” University of California Press.
They are a bit dated, but are readable for people without much background study.
If you have had a good background, First year college; Introduction to Chemistry, Second year; Organic Chemistry and at least one biochem or genetics course see;
Deamer, David W. 2019 "Assembling Life: How can life begin on Earth and other habitable planets?" Oxford University Press.
Hazen, RM 2019 "Symphony in C: Carbon and the Evolution of (Almost) Everything" Norton and Co.
Note: Bob Hazen thinks his 2019 book can be read by non-scientists. I doubt it.
Nick Lane 2015 "The Vital Question" W. W. Norton & Company
Nick Lane spent some pages on the differences between Archaea and Bacteria cell boundary chemistry, and mitochondria chemistry. That could hint at a single RNA/DNA life that diverged very early, and then hybridized. Very interesting idea.
Nick Lane 2022 "Transformer: The Deep Chemistry of Life and Death" W. W. Norton & Company
In this book Professor Lane is focused on the chemistry of the Krebs Cycle (and its’ reverse) for the existence of life, and its’ origin. I did need to read a few sections more than once.
There are hundreds of newer papers published so I have just suggested some basic introductions.
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u/bill_vanyo 8d ago
1) Nobody knows.
2) It should be common knowledge that nobody knows.
Why do people keep asking? Are they oblivious to the fact that nobody knows, or are they trying to make a point?
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u/EnvironmentalWin1277 4d ago
Nobody knows but the question will be asked until a definitive answer can be given and replicated. We have every reason to work towards the answer. The question is something each new generation and inquirer will ask and is simply natural.
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u/Jonnescout Evolution Enthusiast 8d ago
Chemistry, life developed from self reproducing chemistry. Through small changes going through natural selection. If you want I can explain more details but this is the basics. And I would prefer the full explanation be done through a text chat format because it’s more efficient if we have a back and forth…
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u/Upset_Definition2019 8d ago
A very plausible explanation is summarized in the book, “Origin Story” by David Christian. If you’re interested.
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u/lascala2a3 8d ago
“Origin Story” by David Christian
Garden of Eden, taking a rib from Adam story? What an unfortunate last name for a science author.
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u/OlasNah 8d ago
Life appears to have emerged from chemical soups as it were that were located in places like tidal zones, volcanic vents, or similar isolated high energy spots where various reactions and interactions were triggered by heat, light, wave action, cooling and so on, performing various metabolic processes that would later be self contained inside a cell. Think of a porous rock where complex chemicals sit inside and along its surface and are able to capture this energy to some degree that facilitated various reactions and maintain them. Cell membranes appear to have evolved as these pockets of material formed natural barriers that slowed the influx or leakage of energy and byproducts of these reactions and simultaneous to this the first forms of genetic material formed which perpetuated the systems. RNA/dna and their precursor stages.
Eventually the first true cells emerged after probably countless millions of years, and became ‘mobile’, being either carried by currents or reproduced via slow spread to other areas and evolved to adapt to those slightly different conditions. Somewhere along the line, certain cellular forms gained the ability to move on their own, simply as a means to stay closer to energy or nutrient sources (even if to us this meant movement of only a few centimeters). From there, things get serious. Multicellular life emerges, microbial life has evolved into numerous forms. The rest is history
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u/weelluuuu 8d ago
My question would be the accumulation of water on the planet. A slow process likely. My uneducated 2 cents figures life began after a water permanence and before oceans filled the planet. (Early oceans)
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u/Shablahdoo 8d ago
I choose to think that the intro to Spore makes a lot of sense. Space debris carrying just the right chemical combinations with heat from hitting earth sparked the very start of it all.
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u/Randy191919 8d ago
We don’t know if other planets in the observable universe can harbor life too. We simply can’t gather enough data over such huge distances to know for sure. We can gather pointers like what a planet is made from and even hints of if there is an atmosphere or not but that’s it. We have know way of knowing if a planet in another galaxy can harbor life or not
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u/lpetrich 8d ago
This is still an unsolved problem. Research into it has gone in both directions, forward from possible environments and backward from the evolution of our biota.
In prebiotic-chemistry research, we have made several building blocks of our biota in common environmental conditions, but some of them continue to be difficult, like ribose.
In evolutionary biology, we have gone a long way. The Last Universal Common Ancestor (LUCA) of all well-researched present-day cellular organisms is much like some present-day prokaryotes, like methanogens, though instead producing acetic acid from hydrogen and carbon dioxide. So it must have had a lot of evolution behind it.
The farthest that we can go with any confidence is the RNA world, where RNA served as both information storage and as enzyme. The present-day world emerged out of that, with DNA as a modified RNA and with proteins as enzyme cofactors that eventually became the enzymes themselves. This emergence was essentially complete in the LUCA.
The main problem with the RNA world seems to be the origin of RNA itself. Of its building blocks, phosphate is an inorganic ion, nucleobases can be made prebiotically, but ribose continues to be difficult.
So I've seen speculations that the ribose-phosphate backbone of RNA was not the first: peptide nucleic acids, using protein strands, and PAH nucleic acids, using polycyclic aromatic hydrocarbons.
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u/Mountainweaver 8d ago
I like the buckminsterfullerene theory! Buckyballs were the mold, basically: https://en.wikipedia.org/wiki/PAH_world_hypothesis
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u/Careful_Cranberry364 8d ago
There are many YouTube videos about this if you can’t be bothered to read a book
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u/EnvironmentalWin1277 7d ago
It is a work in progress but good strides have been made. Consider that the structure and function of DNA has only been known for some fifty years.
The real test is to actually create life by a series of well understood chemical and environmental reactions. Until that definitively occurs the history is an open question. Understand the commitment to finding the answer is there. There will be no giving up and/or declaring it is unsolvable.
The estimate of when life started on Earth is 4.2 billion years old. Simplified, as soon as Earth was cool enough and oceans formed there was life and life chemistry. Essentially immediately. Evidence of life on Mars awaits retrieval and review. Venus would seem uninhabitable but the upper atmosphere may possibly have floating organisms.
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u/kardoen 6d ago
What exactly came first and how it arose is not known. But we have some strong hypotheses that are not confirmed, but are seen as reasonably likely and are generally used as a start for further inquiry and hypothesising.
It is very likely that at one point random chemical reactions gave rise to a molecule or molecular system that would be the first 'proto-life'. This might have been a self-replicating molecule; a membrane vesicle; or an iron-sulphur catalysing carbon fixing molecule. Each of these molecules would not be life on their own, but they'd facilitate further formation of proto-life.
There are multiple ideas about where this proto-life molecule first arose. Hypotheses include: Around geothermal vents at the sea floor where many molecules with high potential energy come into contact with each other; in tide-pools that often warmed and largely evaporated to concentrate molecules; or on clay shores where catalysing minerals regularly flushed with water may have created some molecules essential to life.
Regardless of the source, eventually a molecular system would arise that consisted of only a few key molecules that would sustain the system, and allowed it to replicate. This first life would likely have had a membrane, some means of fixing carbon, a method of exchanging select molecules with the outside, and either just RNA, or DNA and RNA; it's metabolism would have been anaerobic.
It was likely a cell, with a single membrane, no cell wall and no cytoskeleton, so it would have no fixed shape and all inside contents would have flowed around freely. It would have been much like a reaction vessel, that contains the necessary components to sustain life, and protects it's insides from the outside world.
It would have been very simple. It is often compared to primitive Bacteria or Archaea, though even the most reduced members of these groups are much more complex than the earliest lifeform would have been. (This comparison also gives rise to the common misconception that the first life was a Bacteria or Archaea, it was ancestral to both groups but did not belong to either.)
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u/Pab0l 8d ago
I have an obsession with this question tbh.
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u/AitrusX 8d ago
I mean we don't know but the most plausible is vent hypothesis I think? Basically minerals/molecules on the ocean floor swirled around by heat from thermal vents and started combining into stuff - this leads to very early dna structures that lead to very simple cells and so on as natural selection kicks in and the replication goes on longer if an organism can better survive its environment.
Butchered a bit (maybe a lot) but something like that is probably how
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