3 Answers

Matter of opinion.

If you're religious, God put the first person here.

If your religious but are open to other possibilities, then it was aliens coming to a new home.

If you're an evolutionist, then it was the big bang.

The most accepted explation is the theory of evolution and the origin of species can be dated  to at least the 6th century BCE ith the Greek philosopher Anaxmander. Others who considered evolutionary ideas, included the Greek philosopher Empedocles the Roman philosopher.

Charles Darwin Formulated his idea of natural selection in 1838, and was still developing his theory in 1858 when Alfred Rusell  Wallace snt him a similar theory, and they both were presented to the Linneas Society of London in separate papers. At the end in 1859, Darwins publication of the origin of species explained natural selections in detail and presented evidence leading to increasingly wide acceptence of the accurrance of evolution.

aliens