Here's a breakdown of different perspectives:
* Earliest animal-like organisms: Fossil evidence suggests that organisms with some animal-like characteristics, like sponge-like creatures, appeared around 760 million years ago. This is based on fossils found in Namibia.
* First definitive animals: The first fossils of true animals, like the Ediacaran biota, date back to about 575 million years ago. These are more complex and have a wider range of body forms.
* Diversification of animal life: The "Cambrian explosion," a period of rapid diversification of animal life, occurred around 541 million years ago. This is when we see the appearance of most major animal groups in the fossil record.
* Molecular clock estimates: By analyzing genetic differences, scientists estimate that the last common ancestor of all living animals lived around 800 million years ago. This is a theoretical ancestor that we haven't found direct fossil evidence for.
In short:
* The earliest animal-like creatures appeared around 760 million years ago.
* The first clear-cut animal fossils date back to about 575 million years ago.
* Animal life underwent a major diversification around 541 million years ago.
* Molecular evidence suggests that the ancestor of all living animals may have lived around 800 million years ago.
It's important to remember that our understanding of animal origins is constantly evolving as new discoveries are made.