Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
We know how evolution and extinction happens, and how the original single celled forms evolved to what we see today. What we don't know is how the leap was made from non-life to life (what you call the "very beginning of life"). It's not the same process at all, and it's not at all clear which of the many hypotheses that have been put forward (the latest last year) is closest to the mark.
I'm not so certain there was a "leap" from non-life to life. It depends on how long the leap was. I think the process from one to the other was probably a very gradual change over a long period of time with life slowly emerging from small changes in non-life. Over a long period of time, with enough of those small changes over time it all begins to make a difference. While we can talk about the evolutionary process of life, I think it's fair to say that evolution had been going on long before life emerged, starting with the origin of the universe. In a way, maybe it is the same process after all, but just that evolution, doing what it does, is a series of changes that can result in various outcomes. In this case, the outcome was life emerging from non-life. I do agree that it was not necessarily an inevitable outcome to have happened, but that the conditions were apparently sufficient enough to enable it to happen.
If we are the only life in the universe it sure is a ridiculous waste of space.
Just sayin....
Why would it be a waste of space? Maybe it's just a lot of extra elbow room. The thing is that we live in the era of stars. If the universe continues to expand at an accelerated rate, stars will eventually run out of fuel and die, which in turn will mean the end of galaxies as well, and the end of life as we know it. That'd be several billion years off in the future. Presumably, the universe itself will have a long way to go before it too will eventually cease to exist. Here in the stellar period of the universe, it may be that there is life elsewhere, but we have no idea if there is any life anywhere else. So far, there's there's no evidence, and considering that the galaxy and the rest of the universe is mostly space that is vastly huge, it's hard to guess if we'll ever really know if there is or isn't any life elsewhere. While it's certainly possible there's life elsewhere, maybe abundantly, it's also possible we're it. It's also possible that we might be the first or at least among the first forms of life to emerge in the universe. We just don't know.
I'm not so certain there was a "leap" from non-life to life. It depends on how long the leap was. I think the process from one to the other was probably a very gradual change over a long period of time with life slowly emerging from small changes in non-life. Over a long period of time, with enough of those small changes over time it all begins to make a difference. While we can talk about the evolutionary process of life, I think it's fair to say that evolution had been going on long before life emerged, starting with the origin of the universe. In a way, maybe it is the same process after all, but just that evolution, doing what it does, is a series of changes that can result in various outcomes. In this case, the outcome was life emerging from non-life. I do agree that it was not necessarily an inevitable outcome to have happened, but that the conditions were apparently sufficient enough to enable it to happen.
Yes, there was most likely RNA life before DNA life, and the developmepnt of a cellular membrane was another step and so on. Natural selection was involved in the process. So I wasn't intending to imply life suddenly arose out of raw chemicals.
What we don't know is what those conditions were, and whether Earth is relatively unique in posessing those conditions. We know now that there's a wide variety of planets out there, but (for example) we haven't found another system like Earth-Moon, where there's a huge moon and big tides. And we have no idea how often you'll run across continental drift and the hot undersea vents that go along with it. So for example if life requires big tides (as in some models) or black undersea smokers to arise and those are relatively rare, then l suspect life would be relatively rare in the cosmos.
Yes, there was most likely RNA life before DNA life, and the developmepnt of a cellular membrane was another step and so on. Natural selection was involved in the process. So I wasn't intending to imply life suddenly arose out of raw chemicals.
What we don't know is what those conditions were, and whether Earth is relatively unique in posessing those conditions. We know now that there's a wide variety of planets out there, but (for example) we haven't found another system like Earth-Moon, where there's a huge moon and big tides. And we have no idea how often you'll run across continental drift and the hot undersea vents that go along with it. So for example if life requires big tides (as in some models) or black undersea smokers to arise and those are relatively rare, then l suspect life would be relatively rare in the cosmos.
I know you didn't mean to imply that life suddenly arose just like that, but the term "leap" (from non-life to life) needed some clarification as it's often misunderstood and used by some people to mean just that. You are quite right that over long periods of time there are countless changes with tiny bits and pieces that gradually end up as an end result which only leads to more changes that can be successful or unsuccessful.
Ultimately, the molecules and ingredients for life exist in the solar system, the galaxy and the universe. And we know from looking around the solar system that hydrocarbons, water, chemicals, etc., have been deposited not only on Earth, but other bodies around the solar system as well. I agree that we don't really know if the conditions you mentioned are essential requirements for the potential of life to emerge or not. But even with those conditions, I don't think that guarantees that life will always emerge. A lot of it has to do with the circumstances of chance. But once it got started on Earth, the rest is history, but even that could've just as easily failed. For example, if the dinosaurs had continued to survive, early mammals during that reign might not have evolved into the variety we see today. Not all dinosaurs perished though, as birds are thought to have descended from them.
I know you didn't mean to imply that life suddenly arose just like that, but the term "leap" (from non-life to life) needed some clarification as it's often misunderstood and used by some people to mean just that. You are quite right that over long periods of time there are countless changes with tiny bits and pieces that gradually end up as an end result which only leads to more changes that can be successful or unsuccessful.
What I meant to imply by "leap" was that the transition was a long and involved one, which we only partially understand at this point in time. To go back to the OP, if we can get to the point where we can specify the conditions needed to make that long drawn out transition, we'll be in a better position to take data from Kepler and its descendants and make a best guess as to which of the planets we find are the best candidates ... for life as we know it.
But we have a certain bias toward what we already know ... is life for example possible on Titan which is -350 degrees Fahrenheit at the surface (-179 Centigrade)? We don't know ... See:
But again, we don't know if the conditions on Titan were such that life could evolve independently there. But it's complicated by the fact that the panspermia hypothesis ... that life drifts from planet to planet, star to star ... has more credibility these days now that we've identified a number of Martian meteorites that have fallen here. Which is to say, life or its precursors could have drifted here from another star system, then from planet to planet. All it would take would be for life to evolve on one planet in a galaxy, and over billions of years, it might fill all habitable planets in the galaxy.
As we've identified more and more extremophiles here on Earth, we've also had to expand the limits of what seems to be possible. Life is living in some very strange places on our planet.
Quote:
For example, if the dinosaurs had continued to survive, early mammals during that reign might not have evolved into the variety we see today. Not all dinosaurs perished though, as birds are thought to have descended from them.
I think it's gone beyond the "thought to have" point ... it appears birds are just dinosaurs who have lost their forearms and teeth.
What I meant to imply by "leap" was that the transition was a long and involved one, which we only partially understand at this point in time. To go back to the OP, if we can get to the point where we can specify the conditions needed to make that long drawn out transition, we'll be in a better position to take data from Kepler and its descendants and make a best guess as to which of the planets we find are the best candidates ... for life as we know it.
But we have a certain bias toward what we already know ... is life for example possible on Titan which is -350 degrees Fahrenheit at the surface (-179 Centigrade)? We don't know ... See:
But again, we don't know if the conditions on Titan were such that life could evolve independently there. But it's complicated by the fact that the panspermia hypothesis ... that life drifts from planet to planet, star to star ... has more credibility these days now that we've identified a number of Martian meteorites that have fallen here. Which is to say, life or its precursors could have drifted here from another star system, then from planet to planet. All it would take would be for life to evolve on one planet in a galaxy, and over billions of years, it might fill all habitable planets in the galaxy.
As we've identified more and more extremophiles here on Earth, we've also had to expand the limits of what seems to be possible. Life is living in some very strange places on our planet.
I completely agree we'd need to specify the conditions, which would be a very long list indeed. The search for characteristics of other solar systems could potentially get us a little closer to determine the likelihood of habitability of life, but we're not quite at that point yet. Since it isn't likely any time in the near future to directly see the surface of any exoplanets, the next best thing would be to analyze the atmosphere of likely candidate planets. Currently, the search is for rocky planets with orbits in the habitable zone with respect to the host star. The zone is where the potential of water (if present) would likely be in a liquid state rather than being frozen solid or boiled away. Perhaps in the next generation of space satellites, we might be able to have a view good enough to at least determine the composition of the atmosphere of nearby exoplanets. The presence of methane in the atmosphere could be an indicator of life, but that can also be a chemical in nature. The solution would be to send a landing rover for a closer look from the surface.
You're right that we tend to have a bias with what we currently know, and Earth is the primary model for that. However, since we know the conditions of Earth are suitable for life, it's not an unreasonable model to start with. Titan's liquid seas appear to be liquid hydrocarbons. While that might work as a solvent for some kind of unknown form of life, that's little more than speculation. You're right, we don't know. I don't think I'd be placing any bets on finding any life on Titan though. It's not that it's impossible, just that I think it's extremely unlikely. The moons Europa (of Jupiter) and Enceladus (of Saturn) appear to have liquid oceans beneath frozen crusts that could potentially harbor life, although I don't think I'll be putting any bets on those either. Even if they do, the icy crusts are extremely thick which would make it a huge challenge to get through it with a probe. But there's probably enough tidal flexing with the planets that water temperatures could be relatively warm, even undersea vents. I would think if there's any other planet that has had primative life or the conditions for life in its distant past, or might even still contain microbial life, it'd be Mars. Mars is a lot easier to get to and explore than the moons of the outer planets or incredibly distant exoplanets.
Panspermia is a potential possibility that I don't think can be completely ruled out. It's possible microorganisms, like bacteria, could've hitched rides embedded in meteors and drifting for long periods of time until landing on Earth where it could survive and thrive. You're right that we have meteorites from Mars as well as the Moon that have been found on Earth. In any case, however life got started on the planet, this is the only planet we know of that has life. We currently have no conclusive evidence of life existing anywhere else.
If there is life elsewhere in the galaxy and the universe, my guess is that the most abundant would be microorganisms like bacteria, followed by complex but simple organisms - less common, then complex organisms - relatively rare, then highly complex organisms that are intelligent - extremely rare, and finally intelligent organisms that have technological capability - among the rarest of all life forms.
Quote:
Originally Posted by Vasily
I think it's gone beyond the "thought to have" point ... it appears birds are just dinosaurs who have lost their forearms and teeth.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
I know you didn't mean to imply that life suddenly arose just like that, but the term "leap" (from non-life to life) needed some clarification as it's often misunderstood and used by some people to mean just that. You are quite right that over long periods of time there are countless changes with tiny bits and pieces that gradually end up as an end result which only leads to more changes that can be successful or unsuccessful.
