In the original film, two astronauts are thrown forward thousands of years and land on Earth; sequels confused this (and I am not fully conversant in the series). But this is not a sequel to the original film, nor is it exactly a remake, but a new original story based on the original idea. It also contains at least four, and possibly six, trips through time. Let us recount these individually.
Time travel in this story is accomplished by accident; only once is it clear that the traveler intends to move through time, and in only one other case is it possible that time travel was recognized as a possible outcome of the actions taken. A phenomenon somewhere in space identified only as an electromagnetic storm is the conduit which carries travelers if not at random then at least without defined pattern to other points in time. No effort is made to explain this, but that it is a mysterious disturbance in space. We will identify the five trips in the order of departure.
The first two time trips occur seconds apart in the year 2029. Pericles, a genetically enhanced trained chimpanzee space pilot (yes, but they made the control panel simple for him) has disappeared into the magnetic storm, and Captain Leo Davison has taken a second pod to pursue him. At the moment he loses contact with their base station, Oberon, he sees the lost chimp; the chimp's pod then vanishes in a flash of light, ultimately, we learn, to arrive in or about 2675. Before Davison can even be certain that the pod is gone, a second flash engulfs his pod, and he begins a rough ride through the storm, bursting out and crashing in a pond on an unknown but lush planet. This proves also to be in or about 2675, a few days before Pericles' arrival. The bulk of the events of the movie take place thereafter.
The third trip is entirely speculation, but well considered speculation. It is eventually clear that Oberon ventures closer to the electromagnetic field in an effort to track and rescue the lost pilot. This is not seen in the film; however, it does appear that the phenomenon displaces its victims both temporally and spatially, that is, it is clear that Oberon is not anywhere near the planet of the apes (which we will henceforth call Apeland for lack of a better name). Each of the pods, as it enters the storm, is carried not merely through time but also through space to arrive near Apeland. There will be no homing beacon back in 2029, no signal onto which Oberon can latch to trace its lost pods. If it, too, is carried to that same planet, it must take the same path, through the storm. And there is every reason to believe that as Oberon is carried quite predictably through space it is also carried somewhat unpredictably through time. It is also most likely that Oberon has moved forward in time, toward the future. Note that of the four known trips, the two which went from Earth to Apeland went forward in time while the two which went from Apeland to Earth went backward. Davison somewhat irrationally relies on the assumption that the storm works that way. Thus it is reasonable to suppose that Oberon temporally shifts forward slightly as well. However, this is a considerably shorter trip, as Oberon reaches Apeland centuries before Davison.
The fourth trip carries not people but information; and again, this is speculation. Just after Davison vanishes, Oberon receives a distress call. It is garbled and distorted, but it ultimately appears to be a distress call from Oberon, received by Oberon. If, as we suggest, the Oberon has moved forward in time, the distress call must be carried back in time--a time trip of information. Even if Oberon is not carried forward in time, the distress call must still be carried back. It is possible that Oberon's trip is not forward in time but backward; in this case the distress call might not have traveled through time, but be a call from a temporally duplicated ship which having been thrown back in time happened to send a distress call out at this moment. Either the third or the fourth trip, as defined here, must exist; both might.
We see the fifth trip, as Davison leaves Pericles on Apeland and flies back into the storm to return to Earth. He reaches Earth in or about 2155, one and a quarter centuries after his departure, and the film ends there. However, it is clear that one more time trip from Apeland's future beyond the end of the film is made back to some point prior to 2155, possibly prior to 2029. It would seem that General Thane eventually left Apeland in some vessel and landed on Earth, where he altered history sufficiently to create our surprise ending. More on that later.
It has often been said on this site that time travel to the future does not, in itself, create any problems greater than travel to Boston. The difference between vanishing from timespace altogether for six hundred fifty years, spending that time in suspended animation, or being dead that long and then resurrected, is minimal. You aren't changing the future in this case, because the future has not yet been written and it is quite acceptable for it to be written without you. Travel to the future is only problematic if it is initiated from or caused by actions taken in the future, or if it is followed by travel to the past--but the former is because the action taken to pull something from the past is in essence a time trip from the future (like a hand reaching back and grabbing someone), and the latter not because of the leap to the future, but the return trip, which is no different from any other trip to the past. So when Pericles vanishes from time, no anomaly is created; and when Davison vanishes from time, there is still no anomaly. Even when Oberon jumps forward temporally this only means that it vanished for a while and then reappeared elsewhere--nothing happens to time itself. Even with three such trips, there is no problem, even though the arrival points in the future are not in the same sequence as the departure points in the past. But perhaps we should write the original timeline for clarity here.
Remember, our original timeline recounts those events which occur without any interference from travelers from the future. Neither Davison nor Thane can arrive in the past until the moment comes for them to depart from the future, and so there must be an original timeline which contains no such arrivals which will be altered by subsequent events.
Oberon is a human research vessel or station in space; two pods are launched from it into a magnetic storm. The first contains a chimp named Pericles; he vanishes from time. The second contains a pilot named Davison, who a moment later also vanishes. Neither of these are seen again for six and a half centuries.
It is important to note that the mayday received a moment later is not received in the original history. That is an effect of a cause still in the future, and until the moment arrives for that cause to be initiated that effect cannot occur. This should not affect Oberon's decision to look for its lost pilots (it ignores the distress beacon anyway), and as it does so it enters the storm. It, too, vanishes from time and space.
There is undoubtedly an immediate search for the lost ship; but not having the information to suggest that the ship entered the storm, humankind soon abandons hope of finding it. It is presumed destroyed. Some time later Oberon emerges from the storm and crashes on Apeland, but by this time no one is seeking it, and wouldn't be looking here even if they were. (The possibilities created if Oberon is not shifted forward in time are discussed below, under Temporal Hiccoughs.) The survivors make the best of things, until an intelligent chimpanzee named Semos leads a rebellion of the primates against the humans, and brings about the unlikely outcome that all are driven from the spaceship but sufficient populations of humans, gorillas, chimpanzees, and orangutans survive to breed future generations. Centuries pass, the apes advance at a remarkable rate and develop an incredibly high level of technology (metallurgy) in a relatively short time, and society falls into its established patterns. Meanwhile, on Earth, the story of Oberon is relegated to history books and humanity advances in its explorations.
Then, centuries later, Davison returns to existence and crashes in the pond. He is immediately captured by the apes, persuades one of the female chimps to help him, recovers some of his gear from the pod, and picks up the signal from Oberon. Not aware that he has traveled to the future, he assumes the ship tracked his homing beacon and came for him. He is very disappointed at the discovery that his fellow crewmen have been dead for centuries (and it is not clear whether he ever realizes that the humans who have been helping him are their descendants), but the events he has set in motion lead to a major battle between the humans and the primates, in which many are killed on both sides, but only one character that we know.
In the midst of the battle, Pericles arrives. His arrival seems to many of the apes first like the Second Coming of Christ and then like the proof that their faith has been a lie; but it ends the battle. Only General Thane is still fighting, and he is soon defeated and humiliated, but left alive.
And within hours after Pericles arrives, Davison gets into that pod and makes the first certain trip backward in time, from about 2675 to about 2159. But if you've been paying attention to these pages, you know that when someone travels to the past it creates an anomaly, and we must now construct the altered history.
In this analysis we've overlooked the transmission received; it, too, must represent at least one trip backwards in time, and it must create at least one anomaly. The difference is small, but should not be overlooked.
There is also the matter of all the other transmissions received. As Oberon approached the storm, it began receiving garbled communications, broadcast signals from throughout broadcasting history. It would be difficult in the extreme to determine whether any of those broadcasts were from the future; however, most of them are recognizable from our past, and Oberon has a few years more behind it, so it is reasonable to suggest that all of these are from the past. This might be the result of the time effects of the field; on the other hand, it might simply be a matter of electromagnetic radiation being caught in the whirls and eddies of the storm and coming back out constantly in drips and drabs. In the latter case, there is no time travel at all, just a natural analog recording system playing back the information captured. Yet even if every television transmission ever broadcast was carried to the future, this would not disrupt time in any way--because travel to the future does not create anomalies.
There are five possible explanations for how Oberon's as yet unsent distress message reached Oberon.
In any case, it is clear that the only differences any one of these scenarios will make are
The movie is not without some foolish ideas. The most glaring of these from a time travel point of view is the idea that digital clocks are somehow sensitive to time in a way that human bodies are not. It is first suggested when Oberon is studying the storm, and someone comments that all the digital clocks have stopped. Perhaps that might happen if all of the computers malfunctioned, as radiation and magnetism interfere with electrical flow in microcircuitry; but even this is unlikely. It is much worse when Davison flies the pod back through the anomaly and we watch the clock spin backwards through time from 2675 to 2159. There is no logic to this; if the clock should be so affected, so should the pilot and the ship, each of which should age six hundred fifty years when traveling forward and youthen five hundred fifteen years on the way back. No, the clock is a mistake; but it does help the viewer to understand events as it gives us at least rough fixed dates for them.
As long as we're on the subject of mistakes, we should perhaps mention the horses. The planet on which they have crashed is rich with flora; whether upon arrival they planted everything they had in the hope that they might establish a stable agriculture and environment or they happened to hit a rare planet on which plant life had already reached this state (and perhaps as fortunately had a chemistry consistent with earth dietary needs), this is a suitable environment. But there do not seem to be any animals at all, apart from the primates and the humans--no birds, no beasts, not even rats in the city that we see. Yet there are horses. Either those horses had to have appeared independently on Apeland, or they had to have been brought in the Oberon. To have evolved independently they would have had to have conditions very similar to those of Earth, including a rich fauna with many predators. Size in a horse is thought to be a survival response to small predators (the horse is too big to be taken seriously as prey, and longer legs provide greater speed to outrun attackers), so the absence of any other life on this planet would mitigate against the idea that large horses would have evolved here. We thus must consider whether these were on Oberon when it crashed. Again, this seems unlikely. Horseback riding is not a very practical form of recreation on a spaceship, and Oberon's mission and design did not suggest frequent planetary stops. If they were there, it would have been for experimental purposes. But horses are not very close to the top of the list in animal experimentation. Mice, rats, pigs, groundhogs, and several other animals are more similar to humans in specific ways that make medical testing on these practical. If there were horses on board for experimental purposes (not at all suggested at any time), there must also have been many other creatures, probably in greater abundance. There is no reason to think the horses--and only the horses--would have survived.
But let us set these things aside and look at the time trip itself.
Whenever anyone travels back in time, to borrow a phrase from another movie, time travels with him, at least in a sense. We have identified an original timeline in which Davison vanished in 2029 and reappeared in 2675; in this timeline, he did not exist in 2159. now he appears in 2159, and changes history. The important question is whether he has changed history in any way that will change his own (sequential) past--that is, is it possible that his appearance here will prevent him from making any of his time trips, or in some way change who he is?
It is first to be noted that the scene at the end of the movie is not representative of this timeline. In order for Thane to have changed things on Earth, Thane must have left Apeland in the future; but that moment has not yet arrived, and cannot arrive until after this history is rewritten and time is allowed to move forward again. No, the Earth to which Davison returns is a human Earth, and he will live out the rest of his life there (unless for some crazy reason he tries to go back to Apeland).
Second, note that Oberon vanished over one hundred twenty years ago. Nothing Davison does will prevent Pericles or him from making those trips to the future, or will prevent Oberon from vanishing. Historians may be interested in what happened to that space station, but they undoubtedly ceased searching for it a hundred years ago. Davison might get them interested in the subject again, but given that he seems completely unaware that, like himself, Oberon must have moved forward in time at least a bit, there will be no rescue mission for astronauts dead long ago.
However, there are two points that might be significant; either of these changes in history could impact events in a decisive way.
First, Davison brings news that suggests the high probability that right now, on a planet somewhere else in the galaxy, intelligent life is evolving and building society. If there's a way to observe it happening in the present, it's likely that someone will attempt to do so. The possibility exists that sometime in the next five centuries humans will travel to Apeland from Earth, perhaps to observe; there may even be a movement on Earth pressing governments to do something on behalf of the oppressed humans on Apeland. Any such action will change the events of Davison's visit, and so change him. It may prevent his return to the past. If it does so, it will create an infinity loop, as his trip to the past undoes itself. However, while this is a strong possibility, there are factors which mitigate against it. For one thing, no one on earth actually has any clue where Apeland is. It may be particularly odd that the pods contained digital clocks capable of somehow determining real time in the universe and converting it to our system of measurement but did not have a simple star tracking program that could work out the relative positions of major stars and so fix coordinates in space--but in fact it seems Davison has no idea where he is when he's on Apeland or when he leaves it. There's a good chance that Apeland is more than two hundred light years away--it may even be in another galaxy (which would explain why the star tracking program the pod should have had could not fix its position), so even if the faint homing beacon of the ship were detectable through the background radiation of the universe at that distance, it won't arrive for some time yet. As much as these scientists or these activists may want to rush out to Apeland to see what's happening, they don't really know where it is.
But this raises the second possibly significant point. Up to this time, the only thing that has been known about the magnetic storm in space is probably that two pods and a major space station vanished into it without a trace. Perhaps unmanned probes have been fired through it since, but perhaps nothing more has been learned. Suddenly someone has come out of that storm who went into it over a century ago, and this provides significant new information. He knows that there are temporal effects connected to it, as well as spatial displacement; he will undoubtedly spark interest in examining it more carefully. And now it becomes possible that someone examining the storm will wind up on the planet some time before Davison. Again, this creates the possibility that the history of Apeland will change in ways that will affect Davison's experience there. Again we have the possibility of an infinity loop.
And it is disturbing that the storm seems to be rather fixed in its position in space. We don't know where it is or how it moves, but we do know that it is in the neighborhood of earth in 2029 and again in 2159, and that it is near Apeland at three distinct points in time: once for over a day around the time when Davison and Pericles arrive, once centuries before when Oberon crashes, and once again within the lifetime of Thane. Thus the anomaly is either always near the same place, or it is moving such that it is frequently in the area, or it is moving slowly enough that earth scientists should be able to locate it. The very availability of the storm makes it a potential subject for study.
But again, this is only a possibility. The effects of the storm are not well documented in the film. We know that it carried three spaceships from Earth to Apeland, and that at least two were thrown forward in time; we know that two were carried from Apeland to Earth and backward in time. We know that there seems no rhyme or reason to the temporal distance traveled. We have observed that travel from Earth to Apeland goes forward in time and travel from Apeland to Earth backward, but in truth our sample is too small--it is equally likely that travel before 2100 goes forward in time and travel after 2100 goes backward. Someone entering the storm in 2160 might come out anywhen. So again, this is a danger, but it is only a possibility not a certainty. An infinity loop might be created by events stemming from research into the storm, but it might not.
Thus this altered timeline is little different from the original. There is a fanfare for the man who returned from the storm, a note in the history books that the disappearance of Oberon was finally solved, knowledge of another inhabited world somewhere else in the universe, a slightly better understanding of the storm, and that's about it. Davison still lands on a planet ruled by primates who hunt and enslave humans, and still makes his trip home after Pericles' arrival ends the war.
Of Thane's anomaly, we know much less. But if you will permit me to attempt to reconstruct what we do know, you may discover it is more than you thought.
Thane was born a descendant of the great Semos; his father was keeper of some of the ancient lore, and was aware of the danger human technology posed in the hands of humans. He raised his son to hate and fear humans, and so son Thane was an aggressive oppressor of humanity. He became aware that Davison has arrived from space, and intends to discover what he can about that and then destroy him. He learns where Davison's space ship is hidden, and kills the only others in the world who know this at that time. But he is ultimately defeated and humiliated, in part by the arrival of Pericles and in part by the ingenuity of Davison. He is alone and disgraced, and has only the consolation that his father did not live to see this moment.
But Thane has become very much aware of the power of technology. His father warned him about it and showed him an ancient gun. He knows where the pod is. A working version of that gun was used against him, and he has it and knows in the most primitive sense what it does and how to make it do that; a working version of that pod allowed his worst enemy to escape to the stars. He has access to all the technology of Oberon, and the religious taboos that for centuries kept apes away from it have fallen. The computer onboard the other pod may have the same chance of finding the path back through the storm that Davison's pod has. As it was with the orangutan slave trader, a new world has opened up before Thane: technology.
What else is he going to do? He may be violent and petty, but he has never been stupid. He has every chance to figure out how these things work and to repair and relaunch that other pod. Will he not go after the man who pulled his family down from the most respected on Apeland to the most disgraced? He has been allowed to live; he must do something with his life. Exploring the possibilities of technology (something he understands better than anyone on the planet) is a good path. Eventually he, older certainly, makes his trip to the past.
Let us suppose that it is twenty years later that he leaves. It is nearly 2700. He travels back in time and arrives near Oberon, not far from Earth. For practical purposes, there are only two periods in time when he can arrive: significantly prior to the departures of the other time travelers, or some point between that and 2150.
If the arrival is moments before Oberon's departure, or any time thereafter, it changes nothing. Oberon enters the storm and vanishes, bound for Apeland. Thane makes it to Earth. However, it is possible that Thane might make it to earth early enough to disrupt Oberon's mission--to eliminate the possibility that Davison and Pericles are even in space at all, or that Oberon would be conducting research. This would, of course, create an infinity loop, as preventing the existence of Oberon undoes the existence of Thane, which permits the creation of Oberon which brings Thane back into being. That is a possible anomaly, but given that we have no information regarding Thane's arrival time on earth other than that it was before 2159, it is not a necessary one.
What Thane does on Earth clearly does alter history. There is a strong suggestion that he makes Earth his home, never attempting to get back to Apeland. If this is so, and if he has not arrived early enough to undo the existence of Oberon, he is not going to interfere with Davison's departure from Apeland, or with his own.
We might think that as the apes of Earth take over they might make some effort to contact their kin on Apeland; they must have known there were other apes in the universe, for their revered Thane was one of these. But the technology of the apes in Washington does not seem significantly beyond ours of today. By 2150 we might expect significant changes. After all, think of the difference between the vehicles driven in 1900 and those driven in 2000; and now remember that the rate of change in society is increasing. The rise of apes to power seems to have slowed development, such that they are not significantly advanced beyond what they had when Thane arrived (and perhaps less so--there were no fighter intercepts scrambled or missiles fired to destroy the incoming unidentified aircraft which threatened restricted airspace in Washington, D.C.). So it may be that Earth apes will not soon develop space travel sufficiently to visit Apeland. And again, they have no better idea where it is than Davison, and perhaps they know less.
He does change the world for Davison, however. In our previous timeline, Davison arrived at a world full of humans. Now Thane has advanced primates to take over the planet. Davison has another very uncomfortable adventure ahead of him; and I would wager that in the end he might just return to that blonde girl and that very sweet chimpanzee friend back in Apeland to live out the rest of his days in a better place. This, of course, might well cause an anomaly, because if he arrived while they were still young he would be in a position to use his knowledge of Thane's trip to prevent it, and so destroy his knowledge. But in all likelihood he either will never return to Apeland or will reach it at a future time when he cannot impact Thane's trip.
It would seem that although there are some places in which a disaster might happen, the limited time travel in Planet of the Apes sets up some benign if complicated interlocking N-jumps. Time will continue after this story; and while Earth may not be the place we would hope for our future and that of our children, perhaps we can take consolation that somewhere in the galaxy there is a place where humans and other intelligent creatures live together in harmony, mutual respect, and even perhaps love.