It's impossible to definitively say which species was the absolute first on Earth. There is no fossil record of the very earliest life forms, which were likely single-celled organisms.

However, scientists believe that the first life forms arose from abiotic (non-living) matter through a process called abiogenesis. This likely happened in a series of steps over millions of years, and there are various scientific theories about how it occurred.

Here's what we do know:

* Early life was probably single-celled: The earliest life forms were likely simple, single-celled organisms, similar to bacteria.

* Life arose in extreme environments: The first life forms probably emerged in environments that were hostile to life today, like deep-sea vents or hot springs.

* The fossil record is limited: Fossils from the very early Earth are extremely rare and often poorly preserved, making it difficult to pinpoint the first species.

While we may never know for sure which specific species was the first, the study of early life continues to shed light on the origins of life on Earth and the amazing diversity of life that exists today.