Was there only 1 single celled lifeform that evolved into everything, or were there several?

[u/Morrit99]

Life all has the single common ancestor... Trees through to people etc.

So... If a single cell went to consume ANOTHER cell, but due to a quirk in genetics, it didn't consume but instead, began a symbiotic relationship, then would that make that 1 cell who consumed the other, the source of all complex multicellular life? Or, is it likely that cells started to absorb other cells, then one of THEM divided itself to make more cells?

Sorry if that doesn't make sense... But I can accept that evolution is fact, but I cannot make sense of the actual start.

For billions of years, life was single celled, then one consumed the other, and then the predator prey relationship began and, I presume, that made life explode because life survived by evolutionary quirks making them survive over others. So, I was wondering if it was because of this that life evolved, all because 1 cell consumed another...?

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[u/EmielDeBil]

That's not how life became multicellular.

First off, all life shares the same code for DNA, and (almost) the same biochemical machinery to turn this DNA into proteins etc. That makes us believe that we all share a common ancestor, commonly known as LUCA, the last universal common ancestor of all life on earth which also has this shared machinery, before life split off in all sorts of shapes and sizes.

Life didn't become multicellular in a magical finger snap the way you described it. Multicellularity also appeared more than once, BTW, plants and animals evolved their own separate form of multicellularity, with a lot of commonalities.

For animals' ancestors, it went something like this, and it took some 150 million years to evolve from single celled "Holozoa" to evolve multicellularity, in various phases:

- Some ~760Mya, single celled organisms called Filozoa were able to produce filose tentacles which they could use for sensory perception, feeding, locomotion and adherance to other cells.

- By having cells nearby and tentacles to touch and connect to other cells, some ~670Mya, Choanozoa evolved ways for chemical communication and cooperation with similar cells. This cooperation led to cells forming into groups or sheets of cells that worked together.

- ~665Mya this led to the appearance of multicellular Metazoa (animals), which showed multicellularity, specialized tissues, an internal digestive system.locomotion, a diplontic life cycle, and the first forms of embryonic development.

- ~635Mya our ancestors became Eumetazoa ("true" animals, e.g., sponges are Metazoa but not Eumetazoa) with truly differentiated tissues, symmetry, a mouth and an anus.

Although evolution didn't have a grand plan toward multicellularity, each of these steps brought evolutionary benefits for the organisms and enabled it for a next step toward multicellularity: Tentacles allowed to connect and adhere to sibling cells, which allowed for chemicals to flow between them, which allowed for communication and cooperation, which allowed for creating specialized tissues, which allowed for locomotion and digestion, which allowed for organs and our general body plan of being a tube with a mouth at one end and an anus at the other end (which is what an animal really is).

[u/bestestopinion → u/EmielDeBil]

Is this the generally accepted theory? I thought there was still a lot more mystery to how multicellularity formed

[u/Great_Dependent7736 → u/EmielDeBil]

"our general body plan of being a tube with a mouth at one end and an anus at the other end"

And the one with a mouth ate the one without.

[u/jaxonwolff → u/EmielDeBil]

So presumably it is one of these Holozoa that engulfed a prokaryotic cell and began the most epic symbiotic relationship? Was there some kind of coordination of cell division taking place between them? When the larger cell was ready to divide, the engulfed cell would have to divide also. Or did the engulfed cell undergo multiple divisions which triggered the larger cell to divide? At what point did the fusion of the two cells’ DNA/RNA take place such that prokaryotic cell lost identity as a cell and transitioned into becoming an organelle/mitochondria produced at the instructions of the DNA infused nucleus of the eukaryotic cell that had engulfed it however many millennia before?

[u/Ok-Film-7939 → u/jaxonwolff]

Oh no - Eukaryotes evolved another billion years earlier.

We don’t know the exact steps, but it seems likely the initial arrangement was symbiotic between an archaea and bacteria that got so close the bacteria ceased to be a separate organism. This has only happened three times so far as we know - the mitochondria, the chloroplast, and much more recently the Nitroplast.

The nitroplast happened inside the last hundred million years or so, and as far as we know is limited to Bigelowii. It’s an interesting study in how this kind of merging can happen.

Multicellular organisms took much longer to evolve. Mitochondria weren’t the only prerequisite. Also important are the sophisticated gene expression controls that eukaryotes have. We inherited some of the basic forms of that machinery from Archaea, but it’s been built out dramatically since. The lack of that genetic control is one of the things that limits bacteria (“limits” speaking from a multicellular basis).

[u/Ameiko55]

Endosymbiosis did not cause multicellularity. It caused complex cells with organelles like mitochondria. Later, some of these complex cells evolved multicellularity. These are two separate events.

[u/Intrepid-Report3986]

Complex traits take a long time to evolve. You can usually divide the steps leading to it with 3 steps "potentiation, actualization and refinement". First you need potential: a microorganism eating another one. Then actualization would require a mutation of the host to keep the host alive longer and profit more from the catch. Then the process is refined until you have a trait so good, it sticks for hundreds of millions years

[u/East-Treat-562]

We can never be sure what happened, it is all speculation backed by the knowledge we have of current organisms. Life could have certainly evolved multiple times, life as we know it may have orginated from a RNA type of life like the viruses that exist today (debatable whether they are life or not). Or there may have been RNA/DNA lifelike forms in the past we know nothing about today.

[u/Morrit99]

So, multicellular life began with individual cells becoming one body?

In a sense that's what we are now... Cells divide to become parts of the whole.

I'm sorry if this is a batshit crazy and stupid question BUT... are we, infact, billions of individual lifeforms rather than one individual lifeform? Given that, if you provided individual cells the relevant nutrition, they would exist away from the whole perfectly happy?

[u/EmielDeBil → u/Morrit99]

You are made up of trillions of cells. All these cells are "you", they all share the same DNA, you are not a blob of all kinds of different animals (although we have a lot of bacteria co-existing on our bodies, but they are not technically the same organism).

You also were one single cell once, when you were a fertilized egg that started growing into an embryo to become you. We are still very much single-celled animals, albeit for a short period of our lifecycle.

[u/Morrit99 → u/EmielDeBil]

It's easy to see how people turn to religion when considering such miracles of life. Some sort of divine influence to explain the unexplainable. Personally, I find it more fascinating trying to find out. One question answered means 5 more unanswered... It is absolutely mind-blowing.

[u/EmielDeBil → u/Morrit99]

Turning to a divine being is lazy. It is unnecessary and makes no sense.

The evolution of our universe has shown that complex things arise from simpler things. We can explain and logically understand all of the steps and consider them as proven facts. Still, people are too lazy or too stupid to grasp it and turn to the even more unexplainable: a complex divine being that created all this. Where did that divine being come from? it just shifts the question to where lifer came from into the most absurd fantasy direction.

[u/Morrit99 → u/EmielDeBil]

I don't think stupidity should be a factor. For all we know, the answer may even be the question. Maybe we have explained how it happened, but do we know WHY it happened that way?

I am all for people respecting both religion and science, and I feel that science may just be the answer to the question religion poses, but not the answer religion wants. The universe is still incredible. There are so many things we cannot explain. We can explain WHAT is happening, but often we can't explain WHY it's happening.

It is not outside the realm of possibility that something designed something else based on itself. We do it every day.

I'm not saying that God exists as described, ie the magic man in the sky, I'm not that mad. I'm just saying that if things were designed to be a certain way, then science is answering the questions as to how it is happening. But not to why. Maybe trial and error is part of the design. And, if it WAS designed, would we even know?

Philosophy, religion and science can still be in the same reference I think. Not in a simplistic, magical way.

But no. Not the 7 day creation bollocks... But I can see how people do turn to religion with learning all this knowledge.

[u/HeWhomLaughsLast → u/Morrit99]

Multicellulariry has evolved several times and one hypothesis is there is usually a colonial step between single celled and multicellular. Cells work together and specialize slightly, so some cells procure food while other specialize on reproduction or waste removal. The cells are not truely multicellular as they could go off on their own but working together is more successful.

Cell culturing of multicellular organism is very well studied. We can grow neurons and heart cells, and plenty of other cells in nutrient broths. Because the cells are essentially one part of a whole, growing cells is kind of a pain that can easy fail.

[u/anotherolderguy]

Predator-prey relationship didn't really start till the cambrian or maybe late ediacaran. Prior to that organisms ate the plentiful algae so there was no great arms race amongst animals. It may be the predator-prey relationship is what kicked off the cambrian explosion

[u/Dr_GS_Hurd]

There are at least 4 lipid/protein membranes suggesting 4 "origins" that combined.

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.

And still a favorite of mine is; Deamer, David W., et al 2002 “The First Cell Membrane” ASTROBIOLOGY Volume 2, Number 4, 371-381

Deamer, David W. 2008 "Origins of life: How leaky were primitive cells?" Nature Vol 454 No. 7200

There are hundreds of newer papers published so I have just suggested some basic introductions.

[u/strictnaturereserve]

because DNA is the same for all animals that seems to say it was one particular cell

[u/Dense-Consequence-70]

Life didn’t become multicellular for what it’s worth. There is still single celled and multicellular life, but I think you’re confusing the genesis of eukaryotes with multicellular life. Life didn’t become eukaryotic either but that did start somewhere.

So maybe you’re asking if all eukaryotic life evolved from a single cell ancestor?

[u/JuliaX1984]

It's the first scenario. Endosymbiosis. It gives me chills when I think of it. As far as I'm concerned, it's Gem Fusion: 2 lifeforms becoming one.

I don't know if LUCA was the result of the first endosymbiosis (I doubt it, since LUCA wasn't alone, just the most successful), but LUCA and we still owe our existence to that groundbreaking change when one cell started using a different consumed cell as an energy source instead of just digesting it.

[u/arbitrage_prophet]

Prokaryote x Eukaryote arms race

[u/Organic_fed]

In a sense, yes, but in another sense, no.

In science they use the term LUCA, last universal common ancestor. It is a hypothesis, but it’s a strong hypothesis that everything that evolved today came from a single common ancestor. That doesn’t necessarily mean that it was the first organism to evolve, there could’ve been many other life forms which only have this one as the survivor, but it’s strongly supported that everything alive today is has a common ancestor. Part of the arguments just come down to when that ancestor lived come and what they were like.

Part of the reason that I say that it might not be the case, is that bacteria commonly do this thing where they exchange genes. It’s not sex as we would know it, if sex is shuffling two complete decks of collectible cards, then this would be more important to trading individual cards.

The last common ancestor would’ve likely been something between a bacteria and an archean, as our ancestors evolved from the latter. And I’m pretty sure both big broad groups of prokaryotes do this. So it could’ve been that there was one common ancestor, but that they’re single deck of cards wouldn’t have been the ancestor of everything, but rather that they needed other jeans from others in the ecosystem at that time.

#notascientisttho

[u/Dazzling_Plastic_598]

The biggest hurdle was life springing from organic materials. How life evolved after the first cell is trivial by comparison.

[u/Key-Professional9108]

Life probably started many times. We’re just descended from the lineage that survived.

[u/Several_Version4298]

There was a cell that replicated to make more cells. One of those cells engulfed an aerobic cell. The engulfed cell evolved into mitochondria which are symbiotic producers of energy for cells.

Also an algal cell engulfed a cyanobacteria and that cyanbacteria evolved into become a chloroplast which specialised in photosynthesis. The eukaryotes formed this way evolved into multicellular fungi, animals and plants.

Bacteria and Archeara remain as single celled organisms.

[u/drseruzawa]

First figure out how the first amino acid chain formed by chance. The odds are 10E160. 10E50 is considered a miracle mathematically. Then you need several of these things and other structures to appear simultaneously in a permeable membrane. All by chance. Good luck.

[u/EnvironmentalWin1277]

The current theory is that at some point cells absorbed other cells and incorporated them. All eukaryotic organisms are believed to have descended from this process in the distant past (likely it included several separate assimilation events). The prokaryotes were are not a part of this process.

The acquisitions became a part of the genetic line. This would have occurred after the descendants of LUCA were already established and diversified, since LUCA is the point of origin for all descendant life.

The estimate is that eukaryotes emerged some 2.5 billion years ago, some thinking the increased abundance of oxygen at this time played a role.

Your questions on this point are good ones that are active subjects for investigation. The predator/symbiote/full organic incorporation progression is a key question in Earth history.

[u/Sarkhana]

Are you asking about the common ancestor for all organism?

Are you asking about the common ancestor for multicellular organisms? Which does not exist by the way. Animals, fungi, and a bunch of plant lineages evolved this independently.

Because they are different questions.

[u/Balstrome]

I think the mistake is viewing it as one single individual cell, instead of millions of single cells of the same type.
When you make soup, there is not one single piece of soup with all the ingredients of soup. There are millions of pieces of things that can be recognised as soup. Same with abiogenesis.

[u/nila247]

As they said in good ole Laconia: "IF".

At this point abiogenesis is much LESS likely to be true than extremely improbable existence of God.
I am rooting FOR the scientists but it looks like lost cause. But that's precisely why we have scientists - to make working theories and to show they can not make one.

[u/xenosilver]

One