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Dremmer
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Wouldn't that suggest that life is a rare event in the universe? If it were common, shouldn't we expect it to have developed more than once on Earth?
Dremmer said:Wouldn't that suggest that life is a rare event in the universe? If it were common, shouldn't we expect it to have developed more than once on Earth?
For starters, practically every biologist since Darwin, who wrote in Origin of Species that "all the organic beings which have ever lived on this Earth have descended from some one primordial form."berkeman said:Can you cite the scientific reference for your claim in the thread title?
Oldfart said:The assumption here seems to be that life originated on earth. Why? Is it not more probable that life originated much earlier on one of millions of planets in our galaxy, and spead through our galaxy over many more millions of years as a result of collisions that released little bits of resilient life into space?
I actually don't know how to calculate the odds of this, but giving millions of planets instead of just one the chance to start life outwardly appears to improve the bet.
This is a legit propsal known as "cenancestor'. This only speaks of modern life forms though. Basically the suggestion is that it is much more probable that all life on Earth has come from a single common ancestor, instead of from multiple. This does not mean that there was a single original life form. Life could have formed multiple times one after the other, all at the same time, all over the place. Until eventually one (our common ancestor) was able to somehow get a stronger foothold (probably some sort of special protein developed) and probably out competed other life.D H said:For starters, practically every biologist since Darwin, who wrote in Origin of Species that "all the organic beings which have ever lived on this Earth have descended from some one primordial form."
More recently, there is the May 13 2010 article in Nature by Douglas Theobald, A formal test of the theory of universal common ancestry. Abstract here: http://www.nature.com/nature/journal/v465/n7295/abs/nature09014.html. Theobald calculates that a universal common ancestor is at least 102,860 times more probable than having multiple ancestors. You can find full copies of the paper on the 'net, but I'm not publishing those links as I don't know if they are legit.
Precisely.That all existing life has a universal common ancestor does not necessarily mean that the origin of life is extremely rare. It could just mean that once life did originate, it locked out any independent subsequent formation of life. If life did formed independently after life originated, that new life may well have just been a new (but fleeting) food source to the already existing life.
Pythagorean said:But was it a single organism or multiple instances of a single species that arose at abiogenesis?
That is, were the conditions pervasive across Earth or only occurred in "hot spots"?
Pythagorean said:But was it a single organism or multiple instances of a single species that arose at abiogenesis?
That is, were the conditions pervasive across Earth or only occurred in "hot spots"?
Would you like to define what you consider a species at the time of abiogenesis?
Ken Natton said:I think it is broadly accepted that prokaryotes came first and eukaryotes were an early piece of evolution.
Pythagorean said:Semantics are not particularly important as long as you can describe the process. I'll give my picture that has developed so far from lectures, skimming abstracts, and water-cooler talk. Maybe we can look work it from the other direction (correcting mistakes or unreasonable belief):
Say we have a "soup" (i.e. in a Miller-Urey fashion, we have a self organized set of organic tools). There's a lot of crazy reactions going on Ribozymes and amino acids being key players:
Q1: are these reactions already happening without lipid membranes containing them, just free-floating? Or do they require lipid membranes to have any kind of mentionable lifetime?
Ken Natton said:Pythagorean, may I just ask you, just out of interest… when you talk of lectures, abstracts and water-cooler talk, is this an area of actual professional (or perhaps academic) involvement for you, rather than just interest, however intense?
I’m really not sure how much serious scientific research goes on into understanding the origin of life. If you are involved in serious work in this regard, have you not come across this guy Tibor Ganti.? His work, as I understand it and again, I have to acknowledge the limits to my understanding, centres around this whole question of at what point does a chemical process become ‘life’. I’m interested in what you know of this.
Edit: Some links to demonstrate that I am not talking about some crackpot.
http://en.wikipedia.org/wiki/Chemoton
http://www.amazon.com/dp/0306477858/?tag=pfamazon01-20
http://www.amazon.com/dp/0198507267/?tag=pfamazon01-20
http://home.wxs.nl/~gkorthof/korthof66.htm
ryan_m_b said:As we currently understand it lipid vesicles can spontaneously form under a variety of conditions. These lipids would be very good at keeping large molecules out but small molecules such as nucleotide monomers could diffuse in, these monomers can then polymerise which prevents them leaving. Lipid vesicles grow due to absorption of lipids from other vesicles what is very cool is that large polymers inside a vesicle will increase the membrane pressure which will increase the strength at which the membrane can absorb lipids from smaller vesicles! The larger the vesicles grow the more chance there is that they will split into smaller vesicles a bit like when a soap bubble get's to big. At that point polymers will be divided up into different vesicles, what is really cool is that now selection can occur because the polymers that polymerise faster (thanks to sequence, structure and enzymatic activity) will increase their size increase the membrane pressure increase the vesicle growth speed at the expense of others and increase it's replication rate. It's all very interesting stuff.
Pythagorean said:Wow, video was awesome, very explicit.
ryan_m_b said:Annoyingly someone has chosen to put an unnecessary classical track over the top so you may want to mute.
Ken Natton said:I've just had an opportunity to watch the video, excellent stuff. I had trouble keeping up with the words and the animations simultaneously, so I might need to watch it a few more times. I dare say you know this Ryan but the 'unnecessary classical track' is the famous fourth movement of Beethoven's Choral Symphony - I think it is actually an abridged version of it to fit the video. In any case, for sure mute it if you don't like it, but we are talking about one of the most influential compositions ever written and I thought it did quite a good job of underlining the epic enormity of some of the things the video portrays. In any case, thanks for the link, well worth watching.
Yeah, but if you close the direct youtube link before it's through, then the embedded link is still playing in the thread, and because I'm obsessive, I can't just pause the video, I have to leave the thread and then return so it actually stops playing. I like the option, call me lazy.Ygggdrasil said:Evo, after you click play on the embeded youtube video, you can click on it again to open the video in youtube (plus it starts off where you left off).
There are several lines of evidence that support this idea. First, all living organisms share a common genetic code, suggesting a single origin of life. Additionally, the fossil record shows a gradual increase in complexity and diversity of life over time, rather than multiple independent origins. Finally, the presence of universal biomolecules, such as DNA and RNA, in all living organisms also supports the idea of a single origin of life.
While it is possible, there is no evidence to support the idea of multiple origins of life on Earth. The conditions necessary for life to arise are extremely specific and the likelihood of these conditions occurring in multiple locations on Earth is very low. Additionally, the fact that all living organisms share a common genetic code suggests a single origin of life.
The exact timing of when life first developed on Earth is still a topic of debate among scientists. However, the oldest known fossil evidence of life dates back to approximately 3.5 billion years ago. It is believed that life may have originated even earlier, possibly as far back as 4.1 billion years ago.
While it is theoretically possible for life to develop more than once on Earth, the likelihood of this happening is very low. The conditions necessary for life to arise are highly specific and the chances of these conditions occurring in multiple locations on Earth are slim. Additionally, the presence of existing life forms would make it difficult for new forms of life to emerge and thrive.
Yes, the idea of life only developing once on Earth has significant implications for the search for extraterrestrial life. It suggests that the conditions necessary for life to arise may be very rare and that the search for life on other planets may be more challenging than previously thought. It also raises questions about the possibility of life existing elsewhere in the universe, as the conditions on Earth may not be representative of other planets.