So how did humans actually evolve according to the Vedas?
Most Hindu scriptures including the Vedas consider the universe around us to be a Creation (सृष्टि; sṛṣṭi) as opposed to something that can evolve on its own (without needing a Creator).
Here's what the Bṛhadāraṇyaka Upaniṣad says on how humans and other lifeforms came about:
Chapter I > Section IV - The Creation and Its Cause
In the beginning, this (universe) was but the self (Virāj) of a human form. He reflected and found nothing else but himself. He first uttered, ‘I am he.’ Therefore he was called Aham (I). Hence, to this day, when a person is addressed, he first says, ‘It is I,’ and then says the other name that he may have. Because he was first and before this whole (band of aspirants) burnt all evils, therefore he is called Puruṣa. He who knows thus indeed burns one who wants to be (Virāj) before him. (1.4.1)
He was afraid. Therefore people (still) are afraid to be alone. He thought, ‘If there is nothing else but me, what am I afraid of?’ From that alone his fear was gone, for what was there to fear? It is from a second entity that fear comes. (1.4.2)
He was not at all happy. Therefore people (still) are not happy when alone. He desired a mate. He became as big as man and wife embracing each other. He parted this very body into two. From that came husband and wife. Therefore, said Yājñavalkya, this (body) is one-half of oneself, like one of the two halves of a split pea. Therefore this space is indeed filled by the wife. He was united with her. From that men were born. (1.4.3)
(Commentary: He, the Virāj called Manu, was united with her, his daughter called Śatarūpā, whom he conceived of as his wife. From that union men were born.)
She thought, ‘How can he be united with me after producing me from himself? Well, let me hide myself.’ She became a cow, the other became a bull and was united with her; from that cows were born. The one became a mare, the other a stallion; the one became a she-ass, the other became a he-ass and was united with her; from that one-hoofed animals were born. The one became a she-goat, the other a he-goat; the one became a ewe, the other became a ram and was united with her; from that goats and sheep were born. Thus did he project every-thing that exists in pairs, down to the ants. (1.4.4)
He knew, ‘I indeed am the creation, for I projected all this.’ Therefore he was called Creation. He who knows this as such becomes (a creator) in this creation of Virāj. (1.4.5)
Then he rubbed back and forth thus, and produced fire from its source, the mouth and the hands...This is the super-creation of Virāj that he projected the gods, who are even superior to him. Because he, although mortal himself, projected the immortals, therefore this is a super-creation. He who knows this as such becomes (a creator) in this super-creation of Virāj.