Change of body means we are carried by the subtle body to another gross body. This is the process, nature's way. You cannot say that "I will not change body." No, you will be forced. Just like a young man can say, "I will not become old man." No, nature will force you to become an old man, or change your body. This is the law of nature. You cannot surpass the laws of nature. Similarly, change of body, that is forced by the nature. Prakṛteḥ kriyamāṇāni guṇaiḥ karmāṇi sarvaśaḥ (BG 3.27). Prakṛteḥ, by the nature's law, we have to do. We are completely under nature's law, and we are declaring independence. This is our foolishness. This is our foolishness.
So in the Fifth Chapter, at the end of the Fifth Chapter, Śukadeva Gosvāmī has described the different sufferings, body, in the hellish condition. We are, according to change of body, we are not only going through the evolutionary process of different types of body, as we have got experience here—the aquatics, the trees, the plants, the insect, the birds, the beast, then a human being.