If Earth instantaneously reverted back to when the only organisms were small microscopic creatures in the sea, would evolution happen the same exact way creating the same animals and species? Was chance a factor in the world as it is today? How drastic could that change be?
The first thing that it's important to understand is that evolution is a by-product of natural selection, not the driver of it. That is to say, every change introduced by DNA combinations and mutations over time is (more or less) random, although the selection of which will become more common over time is not.
Ultimately, the most important factor in the evolutionary development of life on Earth is the environment in which that life exists. We know that life has gone through several mass extinctions in the past, and that the environment of the earth has been very different at different geological periods. Some periods have been warmer than now, some colder, some have had atmospheres with higher oxygen concentrations... The list goes on.
If life on this earth started over tomorrow, the selection of traits via natural selection would be based on today's environment, not the one in which early life formed. In the billions of years that life could potentially survive on the earth, its environment will change to be unrecogniseable from the former environment many times. As such, it's highly unlikely that life would evolve along similar lines to the past.
For one thing, early life had to survive in an environment where oxygen didn't exist as a freely available atmospheric gas. It was a form of life (probably cyanobacteria) that triggered the Great Oxygenation Event that made more conventional life possible at all. That step wouldn't be required the second time around meaning that the forms of life that allowed this to happen aren't necessary, so the divergence of species is starting from a completely different trunk to begin with, in a different environment that is going to 'reward' different traits.
I wouldn't say we are what we are today by 'chance', but it's clear that we could have evolved down a completely different path had environmental factors been even slightly different in certain quarters. The path to us leading from the past is clear, albeit fragile. If life was to begin that path again, it would take a different route because the starting conditions are different.
Add to that environmental factors that cannot be controlled directly by life on the earth (like the meteorite impact of the late Cretaceous) as massive disruptions to the status quo, and the probability of parallel development falls to so close to zero as to be certain not to have happened.
If you restart evolution, you would end up with new species. But some of their features may be very similar to what we know in our world.
The Nobel Prize winner Jacques Monod said that evolution is based on chance and necessity. According to him, there is no final causality that would lead evolution towards a specific goal (like creating Humans or sapient species).
Chance is the random part of the equation, that will bring you different results every time you roll the dice. During a long period of time, Life throws so many dice, so many times, that there is no chance that you could end up with the exact same results.
But necessity is what causes natural selection, and under the same conditions, similar features may be selected. This process leads to "convergent evolution". It means that different species may develop analogous structures independently from each other (in a sense that they don't inherit that feature from a common ancestor).
To get a good example of this process, you can compare the anatomy of dolphins, sharks and ichthyosaurs. They are very similar, even if dolphins are mammals, sharks are fishes and ichthyosaurs were reptiles. But life in similar aquatic environment gave them similar shapes.
So, if you restart evolution, you will get very different species, but some of them may look familiar.
It is extremely unlikely that starting over the evolutionary path we might end up in the very same situation we have today.
Evolution is determined by the interaction of the organisms with the surrounding environment, and though I have no data to support my affirmation, I am convinced that this is a chaotic system, meaning that small differences in the initial conditions would lead to dramatic differences in the evolution of the system itself.
Think, just as an example, at how can you have evolution of mammals in a world where the dinosaurs don't go extinct because there is no massive volcanic eruptions and meteorite strike.
It depends on what you mean by "reset".
If you can somehow reset it perfectly so that all elementary particles are exactly the same as they were at some point in the past, and all input (cosmic radiation) happens exactly the same again, and so on and so forth, then you have a chance of having thing work out exactly the same again.
But if anything is different then Chaos will take over and who knows what you'll get.
Not to get crude (or personal), but if a different one of the thousands of sperm had made it to the egg first, you wouldn't exist. If you go back before someones birth and change even the smallest thing, the chance of them being born is vanishingly small. Some baby might be born, and might even get the same name, but it wouldn't be the same person.
Genetic mutation is a product of quantum (e.g. true) randomness.
DNA mutations happen at the molecular level, making them subject to quantum mechanics. Thus, evolution couldn't possibly happen the same way, because it's wired into the only true source of randomness in the universe. In my humble opinion, evolution is, in a way, one of the great manifestations of quantum randomness at the macro level. But here's some research:
Duke University researchers have witnessed DNA bases making the slightest of changes -- shifting a single atom from one spot to another or simply getting rid of it altogether -- to temporarily mimic the shape of a different base. These "quantum jitters” are exceedingly rare and only flicker into existence for a thousandth of a second, and yet have far-reaching consequences.The study, which appears March 12 journal Nature, indicates that these jitters appear at about the same frequency that the DNA copying machinery makes mistakes, which might make them the basis of random genetic changes that drive evolution and diseases like cancer.
See my own question here: As a time traveler, how would I see quantum randomness change history?
This is secretly a physics question, and the answer is we don't know. A lot of quantum physics seems to suggest that the laws of nature are probabilistic at core, but deterministic "hidden variable" or pilot wave theories are still kicking, if unfashionable in the wake of Bell's theorem. In fact, NASA's proposed EM-drive propulsion system seems to depend on a pilot wave theory. (Unfortunately, independent testing has implicated the Earth's magnetic field, and not quantum weirdness, as the source of observed thrust in EM-drive tests.) Most physicists, however, will assure you that the laws of nature are fundamentally probabilistic and therefore in a scenario like this you could expect evolution to take a different course rather than unfolding exactly the same way as in the first trial.
Evolution is a sequence of random changes that best allowed a life form to survive in a specific kind of environment.
Your question is also ill-posed: nothing happens in 'the next second' unless the destruction was caused by an impact of such magnitude as to delete life at all. There will be always something in the scale of insects, if not small scavengers as well, that will survive the event.
After that, it's all pure speculation. One thing for sure, life will not be what preceded the event
Evolution is highly noisy and stochastic and also chaotic in the sense that slight change in the initial conditions might lead to a very different results. It is an interesting question whether there are bifurcation points in this process. It is very unlikely that the evolution would take the same course it has taken even if condition would be almost the same (They can't be exactly the same ). Having said that, due to scale separation it might happen that certain things would evolve to be the same. Due to the fact that there is no theoretical exact solvable model to this problem, and there is also no capability at the moment to simulate this, it cannot be answered to a greater certainty.
In short: probably not
Even if this question can be answered only with some wild speculation, it is probably safe to assume that life forms as we know today will not evolve the same way: maybe there will still be mammals but not the one we know today.
Probably though, whatever life form present will tend to evolve to the same ending point we know (but maybe not).
For example there is some speculation about the fact that if the dinosaurs had not died out (for whatever reason) they may have evolved into a humanoid form instead of us, since the mammals would never had the chance given them by the disappearance of the dinosaurs.
But these are, as said, speculations: there is no way to prove them and there is no way to know what will happen if for some reason the time will be reset to 4.5 billion years ago
Since you commented:
Well no, reverting back as in going back to that time.
There may actually be a chance. In the end it boils down to how (if) time-travel works in our universe.
If it turns out that we live in a truly deterministic universe (so all things, even those that look random to us, are pre-determined or follow some logic), then yes, after reverting to that time, everything would play out exactly the same again. In essence the universe would just be a videotape which you rewind and watch again.
However, it seems more likely from our knowledge of quantum physics that the universe is inherently probabilistic, i.e quantum phenomena are truly and fundamentally random. In this case evolution would not play out exactly the same way, because the primary way species develop is through random mutations of DNA, some of which get selected for. These mutations are for example caused by radiotion and the interaction of ionizing radiation and matter is a quantum phenomenon. After that, add everything said in the other answers.
If you could find only microscopic organisms then they are protozoans. According to your question if the earth is instantaneously reverted back then the atmospheric conditions will remain the same and the same species will be evolved. But if the earth is destroyed completely and there is no life forms , then if there is evolution ,the species evolved depends on the natural selection , how the genetic material DNA is formed , so the evolution will be different and new species would be formed.
The evolution from bacteria to humans can be deterministic. Life works like a heat engine. 4 billion years ago, the temperature of the Cosmic Background Radiation was higher, that the temperature difference between Earth's surface and CBR was very low. Now it is nearly 225 degrees Kelvin. The evolution from simple to complex would have happened incrementally with the gradual increase in the temperature difference that make heat engines more efficient, or life more efficient. If we were introduced 4 billion years ago, our brains would be of no use because it will not be able to process anything given the smaller temperature difference. Similarly if primitive life is introduced now, it may not survive. So a going back in terms of expansion of universe will once again bring humans back. Chance has a negative role, it may sometime disrupt this with some unseen events.
One of Stephen Jay Gould's best-known works, "Wonderful Life: The Burgess Shale and the Nature of History" addressed this question in an interesting way. He talked about "replaying life's tape" rather than reverting it back and restarting. His conclusion is fairly quotable (and has been often quoted):
any replay of the tape would lead evolution down a pathway radically different from the road actually taken.
Gould's thesis has not won universal assent, but the book is a good read and has direct bearing on your question.
No, but exactly why it is a no depends on what you mean by "reset". For example, let's say just life resets. It would be different to some degree, due to mutations being completely random, but similar mutations would tend to thrive, e.g. wings, because the environment would be almost, (except for stuff caused by photosynthesis in the atmosphere,) completely the same. Let's say the earth as a whole reset. Then it would be completely different, because the natural selection would be different, due to the environment being reset.
Absolutely not. For example mammals like us developed due dinosaurs extinction. As we know it, that huge and far more powerful species was erased from Earth by asteroid impact (~160.000.000 years ago). This good example proves that most species we have on Earth in current form is mostly a matter of chance.
I don't see any answer that mentions abiogenesis.
Evolution is defined in terms of change, so you have to have life before it can supposedly evolve, and that's where abiogenesis comes in. So the start of an answer to the evolution question must depend on a similar question about abiogenesis.
But no one has come up with a plausible theory for how abiogenesis occurred, if it indeed occurred. There are a number of interdependent complex molecular machine molecules which are needed for even simple life. These include polymerase enzymes, DNA Helicase, and ribsomes. These are all encoded in DNA, but they require the molecular machines themselves to synthesize themselves--the original and ultimate chicken and egg problem, which confounds the answer.
On top of the complexity, there's the question of the origin of building blocks: amino acids and nucleotides. Some argue that they've been produced external to life, but they would have to all be produced in sufficient quantity and concentration to enable the original organisms to be built.
So the answer to the original question seems certain to be no.