To begin at the beginning of POTA is to read the novel. Here's an introduction (from wikipedia):
La Planète des Singes, known in English as Planet of the Apes and Monkey Planet, is a 1963 science fiction novel by French author Pierre Boulle. It was adapted into the 1968 film Planet of the Apes, launching a media franchise.
In a frame story, a frivolous couple sailing alone in space, Jinn and Phyllis, rescue and translate a manuscript from a floating bottle. The manuscript was written by journalist Ulysse Mérou, who in the year 2500 was invited by wealthy Professor Antelle to accompany him and his disciple, physician Arthur Levain, to Betelgeuse.
Because they travel close to the speed of light, time dilation causes centuries to pass on Earth during their two years in transit. They reach orbit around a temperate, lushly forested planet they name Soror (Latin for sister). They launch a shuttle to land on the surface. They can breathe the air, drink the water, and eat the fruit. Attracted by a lovely golden naked woman they call Nova, they swim below a scenic waterfall. She is frightened by their pet chimpanzee, Hector, and she strangles it. Her tribe, who comport themselves as dumb animals, wreck the newcomers' clothing and shuttle.
Fully dressed gorilla hunters attack the tribe with firearms. Many are killed, including Arthur. Ulysse is captured with the survivors.
I was seized by a deadly terror when I saw their troop advancing. After witnessing their cruelty, I thought they were going to engage in wholesale massacre.
The hunters, all of them gorillas, led the advance. I noticed that they had abandoned their weapons, which gave me a little hope. Behind them came the loaders and beaters, among whom there was a more or less equal number of gorillas and chimpanzees. The hunters seemed to be the masters and their manner was that of aristocrats. They did not appear to be ill-disposed, and chatted among themselves as cheerfully as one could wish....
In fact, I am now so accustomed to the paradoxes of this planet that I wrote the preceding sentence without thinking of the absurdity it represents. And yet it's the truth! The gorillas had the manner of aristocrats. They chatted together happily in an articulate language, and each moment their faces expressed human sentiments, not a trace of which I had found in Nova. Alas! What had become of Nova? I shuddered as I recalled the bloodstained alley. I now understood her emotion at the sight of our chimpanzee. There existed a fierce hatred between the two races. To realize this one only had to see the attitude of the captive men at the apes' approach. They struggled frenziedly, thrashing out with hands and feet, ground their teeth, foamed at the mouth, and gnawed furiously at the strings of the net.
Without paying attention to this hubbub, the hunter gorillas—I caught myself calling them the nobility—gave some orders to their servants. Some big carts, rather low-lying and completely caged in, were lined up on a track on the other side of the net. Into these we were bundled, ten or so to a vehicle: a fairly lengthy operation, for the prisoners struggled desperately. Two servant gorillas, their hands encased in leather gloves to protect them from bites, took hold of the prisoners one by one, freed them from the trap, and flung them into the cages, the doors of which were then shut fast, while the nobles directed the operation leaning negligently on their walking sticks.
When it came to my turn, I tried to draw attention to myself by talking. But no sooner had I opened my mouth than one of the apes, no doubt mistaking my action for a menace, brutally stuffed his enormous glove into my face. I was forcibly silenced and thrown like a bundle into a cage together with a dozen men and women who were still too agitated to pay any attention to me.
When we were all loaded inside, one of the servants checked the lock on each cage and went to report to his master. The latter gave a signal, and a roar of engines echoed through the forest. The carts started to move forward, each one towed by a sort of tractor driven by an ape. I could distinctly see the driver of the vehicle behind mine. He was a chimpanzee. From time to time he made sarcastic remarks at us, and when the engines slowed down I could hear him humming a rather melancholy little tune not altogether lacking in harmony.
This first stage was so short that I scarcely had time to recover my senses. After driving for a quarter of an hour along a rough track, the convoy came to a halt on a stretch of open ground in front of a house built of stone. It was the edge of the forest; beyond it I could see a plain covered with crops that looked like cereals.
The house, with its red tiled roof, green shutters, and an inscription on a panel at the entrance, looked like an inn. I realized at once it was a meeting place for the hunt. The she-apes had come here to wait for their lords and masters, who presently arrived in private cars along the same track we had taken. The lady gorillas sat around in armchairs chatting together in the shade of some big trees that looked like palms. One of them was sipping a drink through a straw.
As soon as the vehicles were parked, the females drew nearer, curious to see the results of the hunt and especially the game that had been shot, which some gorillas, protected by aprons, were extracting from two big vans to display in the shade of the trees.
It was a classical hunting scene. Here again the apes worked methodically. They placed the bleeding bodies on their backs, side by side, in a long row as though along a chalk line. Then, while the she-apes uttered little cries of admiration, they applied themselves to making the game attractive. They stretched the arms down along the sides of the bodies and opened the hands with the palms facing upward. They straightened the legs, arranging the joints so as to give each body a less corpselike appearance, corrected a clumsily twisted limb, and reduced the contraction of a neck. Then they carefully smoothed down the hair, particularly the women's, as some hunters smooth down the coat or feathers of an animal they have just shot.
I am afraid I am unable to convey the grotesque and diabolical quality this scene had for me. Have I adequately stressed the absolutely and totally simian appearance of these monkeys, apart from the expression in their eyes? Have I described how these she-gorillas, also dressed in sports clothes but with great elegance, jostled one another to view the best specimens and point them out while congratulating their lords and masters? Have I said that one of them, taking a little pair of scissors out of her bag, leaned over a body, cut off a lock of brown hair, curled it around her finger, and then, with the others soon following her example, pinned it onto her hat?
The exhibition of the game was soon completed: three rows of bodies carefully laid out, men and women alternately, the latter displaying a line of golden breasts to the monstrous sphere blazing in the sky. Looking away in horror, I noticed a new figure, carrying an oblong box fastened to a tripod. It was a chimpanzee. I quickly recognized in him the photographer making a pictorial record of these trophies for simian posterity. The session lasted more than a quarter of an hour, the gorillas having themselves photographed first individually, in good poses, some of them placing one foot on one of their victims with a triumphant air; then as a compact group, each of them putting an arm around his neighbor's shoulder. The she-gorillas in turn were then photographed and assumed graceful postures in front of the slaughter, with their decorated hats well to the fore.
This scene was imbued with a horror incomprehensible to the normal mind. My blood boiled, but I succeeded for some time in restraining myself. However, when I noticed the body on which one of these females had sat down to take a more sensational picture, when I recognized on the face of the corpse stretched out among the others the boyish, almost childish features of my luckless companion, Arthur Levain, it was no longer possible to contain myself. My emotion exploded in an outlandish manner, in keeping with the grotesque aspect of this macabre scene. I gave way to a fit of wild hilarity, bursting out in hysterical laughter.
I had not thought of my companions in the cage. I was utterly incapable of thinking! The tumult unleashed by my laughter reminded me of their proximity, which was no doubt as dangerous for me as that of the apes. Menacing hands were stretched in my direction. I realized the peril and stifled my laughter by burying my head in my arms. I am not sure, however, that I should have avoided being strangled and tom to bits if some of the apes, alarmed by the din, had not re-established order with a few thrusts of their pikes. Moreover, another incident soon diverted the general attention. The gorillas made their way in small groups toward the house, chatting merrily together, while the photographer gathered up his equipment after taking a few shots of our cages.
We men, however, had not been forgotten. I had no idea of the fate the monkeys had in store for us, but it was clearly their policy to look after us. Before disappearing into the inn, one of the nobles gave some instructions to a gorilla who appeared to be a team leader. The latter came over to us, assembled his subordinates, and presently the servants brought us something to eat in basins and some buckets of water to drink. The food consisted of a sort of porridge. I was not hungry but was determined to eat in order to keep up my strength. I approached one of the receptacles around which several prisoners were squatting.
I did as they did and stretched out a timid hand. They gave me a surly look but, the food being ample, did not try to stop me. It was a thick mash with a cereal base that did not taste bad. I swallowed several handfuls without displeasure.
Our menu was, moreover, enriched by the good will of our guards. Now that the hunt was over, these beaters, who had so frightened me, proved to be less unpleasant so long as we behaved ourselves. They walked up and down in front of the cages and threw us some fruit from time to time, deriving great amusement from the stampede these offerings never failed to provoke. I even witnessed a scene that gave me food for thought. A little girl had caught a piece of fruit in the air, when her neighbor rushed at her to snatch it away. One of the gorillas then brandished his pike, poked it through the bars, and pushed the man back as hard as he could; then he put another bit of fruit in the same child's hand. I thus realized that these creatures were capable of pity.
When the meal was over, the team leader and his assistants set about rearranging the convoy by transferring some of the captives from one cage to another. They seemed to be making some ,sort of selection, but on what basis I could not tell. Finding myself placed in a group of extremely handsome men and women, I tried to persuade myself that this was because we were the most remarkable subjects, deriving a bitter consolation from the thought that the apes, at first glance, had judged me worthy of being included in an elite.
I was surprised and overjoyed to see Nova among my new companions. She had escaped the massacre and I gave thanks to the heaven of Betelgeuse. It was with her, above all, in mind that I had scrutinized the victims at great length, fearful of seeing at any moment her lovely body among the pile of corpses. I felt as though I had recovered a being that was dear to me and, losing my head once more, I rushed over to her, opening my arms wide. It was utter madness; my gesture terrified her. Had she forgotten, then, our intimacy of the night before? Was such a marvelous physique not animated by any sort of mind? I felt downcast to see her shrink away at my approach, her hands extended like claws as though to throttle me, which she probably would have done had I persisted.
Yet when I checked myself she calmed down fairly quickly. She lay down in a comer of the cage and I followed her example with a sigh. All the other captives had done likewise. They now looked listless, prostrate, and resigned to their fate.
Outside, the apes were getting ready for the convoy to move off. A tarpaulin was stretched over our cage and fastened halfway down the sides, letting in some light. Orders were issued; the engines started. I found myself traveling at high speed toward an unknown destination, terrified by the thought of the fresh horrors that awaited me on the planet Soror.