"And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth."
More simply, if you're creating a moral system that values human life to prevent a number of bad things, it's useful to put humans apart from other beings, so that you can justify commandments like "don't kill yourselves please" at the same time as the people being commanded see all other animals killing each other, and themselves need to kill other animals for survival. Put more bluntly, how do you get masses of uneducated people to not behave like animals? You tell them they are special, and definitely not like animals, and you hold them to a higher standard.
Most of everything in the bible at least is used as an illustrative reason to guide you towards some specific behavior. If man isn't made in the image of god and isn't special there's a bunch of things in there that get harder to demand or explain.
In post modern philosophical thinking, there's a reinvention of nature where animals are more "all the same" and should have similar rights to humans, should not be killed etc, which is part of the wider movement to treat the whole earth as our home and to see humans as a part of a wider system rather than special.