When did animal life first emerge on Earth? Ancient chemical traces, known as biomakers, have revealed that the Geodia phlegraei species of sponge existed at least 635 million years ago, making them the oldest known form of animal life. Those sponges, also known as demosponges, are still around today. They might be the oldest form of animal life (multi-celled), but single-celled life on Earth has been around for much longer – the oldest record of life on land, a fossilized mat of microbes, dates to 3.2 billion years ago.
https://www.livescience.com/63916-oldest-animal-life.html
https://www.newsweek.com/oldest-animal-life-discovered-635-million-year-old-fossil-1171769
Engineers used biomarkers to find the preserved chemicals from the animal’s bodies in ancient rocks.
https://www.youtube.com/watch?v=WhmbYqb3BNI
