One Common Ancestor? Why Not Many?

We have all heard the theory that life on Earth, as we know it, all derived from one common ancestor. In biology, this ancestor is called LUA, the Last Universal Ancestor, or the cenancestor, which is the most recent organism from which all organisms now living on Earth descend.

In the words of Darwin, "Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed."

How did it get here? How did life arise on Earth? One is that they came from meteorites. Another is that they were created at deep-sea vents. A third is that they were synthesized by lightning in a reducing atmosphere, although it is not clear if Earth had such an atmosphere.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I am proposing the idea that life, or at least the building blocks for life, DID come from space, not from one, but from MANY asteroids, resulting in the vast, vast amount of biodiversity current found on Earth. I am proposing the idea that perhaps life didn't all start from the ocean, but that maybe ocean life started from one meteorite that landing in the ocean, and land creatures arose from the organic material of another meteorite that crashed on land.

Is this idea too far fetched? I realize that our DNA points to ONE ancestor, but is it possible that there were many different ancestors that just so happened to have some similar batch of material that resulted in DNA? Maybe the exposure to Earth's geography and atmosphere created the reason for such similarities, like people of all nationalities finding their way to the pool and all of them getting sunburned?

What if some life came from meteorites and some from biogenesis? What if life can be created from a variety of conditions?

I agree. Im a big fan of panspermia so why not?

pretty much every animal shares the same basic construction so while life could of come from an asteroid/marvin the martian deciding to seed the planet/what ever its certain that the basic dna that's survived has done so since its been the best at surviving so while its possible that other life types could of existed its possible that they couldn't handle the environment and so got sent to the dustbin and given we look for life as we expect it we may easily miss the evidence in the rocks since it doesn't seem like life as we know it

reply to post by SubPop79


Because everything else died

Its like a Giagantic tree where all the branches that dont dont make it get trimmed off. and sometimes the whole bottem of teh tree is lost and one branch falls off and sticks in the mud while the rest of the tree burns to ashes. That little stick become the tree and it goes on like that forever.

Life branches and evolves... that which doesnt make it is possibly physicaly erased from history if not properly preserved.

If you want to believe in panspermia ( very likely) then you just have to imagine a tree of life twig flying through space and sticking into teh mud on earth where it grows a new tree.

reply to post by Wertdagf


Why can't there be multiple trees of life? If life came from one meteorite, why can't other life come from other meteors? Why couldn't life manifest in different places at the same time?

Multiple common ancestors would probably point to creation instead of a natural occurrence causing an electrical charge or something to that effect.

Just speculation. I'm no scientist.

Originally posted by Anonymous404
Multiple common ancestors would probably point to creation instead of a natural occurrence causing an electrical charge or something to that effect.

Just speculation. I'm no scientist.

How does that point to creation? Evolution posits that life descended from from one organism, the common ancestor. The organism was somehow assembled, became alive, creating the first cell or cells, which in turn evolved into multicellular organism, which in turn evolved into the many creatures we see today.

I'm offering the idea that maybe this started in many ways. Maybe there were multiple "first cells" which all evolved into various organisms.

I don't know what you are seeing, but I don't see how god has to fit into the equation. On the other hand, I guess you could call evolution "creation" if the first living thing was assembled from non-living material.

reply to post by SubPop79



I like your idea, is just that for example, if multiple meteorites started the life.. then why do all animals have same features... like an Eye, Limb, A symmetric shape.. why is it so similar... Why is a head important or a Body important.. its hard for us to think that because we already have that engraved in our head that a creature can;t exist without a "head"

If there is an animal with a sphere body and 3 tentacles coming out and eats thru its skin, you know a whole different make up that snot "humanoid", then i would believe but saying all meteorites coincidentally produced creatures with similar traits like eyes, limbs, a head, a body...

reply to post by SubPop79


As I said...it was speculation.

Maybe I should have said it could have been misconstrued as such.

I don't believe in any god, so I was just rambling.

reply to post by SubPop79


Well it could happen at the same time in multiple places... although we havent found another tree yet.

What we do think we have is fragments from an exploded tree from another planet. THE DNA on earth points to common anscestry.

Maybe another form of life on another planet has its own tree,,, or maybe we all belonged to to the same one.

Originally posted by SubPop79
reply to post by Wertdagf

 

Why can't there be multiple trees of life? If life came from one meteorite, why can't other life come from other meteors? Why couldn't life manifest in different places at the same time?

While possible, based especially on ribosomal RNA sequences (the 'machines' that translate the genetic code similarly in all known cellular organisms), it sure looks like all contemporary species from the three known domains of life, archaea, bacteria, and eukarya (which are really chimeras of bacteria and archaea), share a common ancestor. The chances of these ribosomal RNAs having evolved independently similarly multiple times are astronomical.

Nowadays it's possible to isolate and sequence total DNA from basically any environment. These metagenome sequence sets have not revealed anything that breaks the pattern, although about a year ago there was a paper about the possible 4th domain of life, which some researcher might have recognized from the Sargasso sea metagenome set. If proven to exist (which I personally doubt in this particular case), it was still part of the same tree.

Of course it's possible that e.g. cellular life began twice (archaea and bacteria), and then one acquired ribosomes from the other. However, the chances of cellular life rising multiple times seem quite distant to me, although it needs to be noted that archaea and bacteria have quite different kinds of cellular membranes..

reply to post by SubPop79


I think you are missing some points or have a lack of information regarding the subject you are covering.

The main point you are missing is that there is a root source (that as previous posters have said is yet to be categorically established as starting on Earth or even how it started), even if valid hypothesis exist.

The primal source is how cellular life and DNA has evolved and looking on why certain choices, over alternative paths have been "made". (There is a lot of interesting papers about this some things are even simple to understand like how sugars are processed and how choices have been taken because of environmental imperatives (like UV radiation).

Then the other root is multi-cellular organisms, there is a common root to that, as one looks into this stuff one has to keep in mind that each step is an exponential increase in complexity (more pieces must be in place so life can "evolve"), note also that evolution is a path that takes place if there is a benefit to it, but also implies random mutations and freak accidents.

Now regarding you proposal of multiple contributors across branches of the species (as someone previously explained). There is also other factors that I think are most offten dismissed and my have a real impact on evolution. Virus and Food.

Virus are interesting because their are a "specific" type of life, but they can move genetic code across species and have always done that, as they mutate they incorporate their hosts DNA and add to it, most of the time without any specific effect but across generations these alterations may become activated, as an example one would expect that as virus move across, lets say from dogs or cats, into people and vice versa some parts of the DNA is becoming replicated across those species.

Food is also interesting, you are ultimately what you eat, food may also be a vector for genetic alterations and not only to adaptations necessary to improve what one takes from it but even across all the fauna that lives with us.

So while there is a root to each step of evolution, branches can "cross-pollinate" and converge...

Subpop79-Although alien origin is not my forte, I agree that multiple origin points is quite possible. I remember that my Cell Biology lecturer included a timeline upon which there was the tic-mark “spontaneous generation of life stops” based on environmental changes. That diagram certainly proposes that even the earth itself had a long time period for life to generate life and for it to only happen once when the time slot was… oh I don’t remember but likely at least a few million years…a single ancestor is unlikely. At worst there were likely many very similar ancestors (similar enough to be a “species”). And with the way that bacteria tend to swap genes around, it possible that after lots of swapping and extinction events, we ended up with a set organisms which appear to be the same things and end up being the “single common ancestor.”

Lucciddream: Convergent evolution. The Cephalod eye, the chordate eye, the annelid eye and the arthropod are all unique evolved structures. This is even ignoring more primitive adaptations such as the eye spots on euglena (protest algae). The reason organism tend to have features with similar structures is that we all live in the same reality. Seeing is good for hunting and avoiding danger. So many organisms are better able to survive as seeing instruments evolve. The idea that a series of bacterial ancestors from space came to earth and evolved similar traits is a legitimate idea based on this logic.

Originally posted by SubPop79
reply to post by Wertdagf

 

Why can't there be multiple trees of life? If life came from one meteorite, why can't other life come from other meteors? Why couldn't life manifest in different places at the same time?

But they did, they're genetically called animals.

Lifeforms coming from different meteorites would have different DNA wouldn't they? For a life form to have the same DNA wouldn't they have to have come from one common ancestor?

reply to post by SubPop79


Oh ! But what about it 's ancesters ? Where did they come from ? And what about their ancestors ?

why is it that people today are smarter for not believing in god, and dumber for not?
I was watching a documentary on human evolution and when you look at the 100s of different skulls and bones of different "evolutionary Man", why is Man, the only species that has evolved? What about dogs, cats, and if we came from a breed of ape or chimpanzee then why are chimpanzee still here, if we evolved from them wouldn't that make them extinct just as the other 100s of skeletons? I don't believe in evolution, I believe in divide and conquer, the way the world works today has worked forever. Humans have killed off every species on this planet forever, we are doing it today, and we will do it tomorrow, hell, my dog eats my cats food even though he can't digest it, he just wants it to starve. The buffalo were almost wiped off the continent to starve off the native americans, so who's to say there weren't 500 species of "man" or human, and we killed them off too, basically evolution is methodical genecid. Always has been always will be. For some reason today the Ethiopians and Haitians drew the shortest straw, I even read somewhere that red haired people will be extinct in a few hundred years due to social bias.
I like the thought of history, but I know there is no such thing, its always been and always be. Evoloution is a story, just like every story it has a happy ending.."us". Because the victors write it. Like life after death, if there is, then what is "this", a pit stop?
Please understand I know nothing of DNA, microbes,or scientific theories, I am looking at it from the dark, with a fresh perspective, unedjumikated yes, but aware of cycles and methods I am . If you see it and it doesn't make sense the way it is explained, then believe your eyes. Like the phrase, "What are you going to believe? What you see or what I tell you?" Yes you can make 2+2=5, by square rooting the derivative to the 47 power and multiplying the denominator with x, but I will know it is 4, we have always been here in this form.

reply to post by PlayOnwards

Of course other species evolved. Where on earth did you get that idea?

Originally posted by john_bmth
reply to post by PlayOnwards

 

Of course other species evolved. Where on earth did you get that idea?

Probably the same place from which he heard that humans evolved from chimps. It's easy not to believe the creationist version of the theory of evolution..

reply to post by rhinoceros


It never ceases to amaze me how people can qualify their opinions with things like "please understand I know nothing of DNA, microbes,or scientific theories" yet proceed to dismiss entire branches of science that they admittedly know nothing about The level of ignorance is truly staggering.

reply to post by john_bmth

It's the equivalent of me asking why fundamentalist Christians are so anti gay although Jesus was a homosexual..