Sponges were among the earliest animals. While chemical compounds from sponges are preserved in rocks as old as 700 million years, molecular evidence points to sponges developing even earlier.
It depends on what you mean by animal. If you mean with a vertebrae…it was jawless fish about 500 million years ago. If you mean any animal, it would be the sponges about 700 million years ago. Have a nice day.
