There have been at least four comments regarding Jesus and the virgin birth removed from this thread. One-line references to that are not adequate answers to the OP's question. Please stop.

Not the answer to your question exactly (since I assume you mean sapient beings), but it was once believed that certain animals and plants would just "spawn" in favourable conditions; flies and maggots came from the dead, mice were born out of food items that weren't stored properly, and so on. This idea became known as spontaneous generation. This theory is sometimes mentioned in journal articles about the early beliefs of where the first humans originated (one that is popularly cited: Atomism, Atheism, and the Spontaneous Generation of Human Beings: The Debate over a Natural Origin of the First Humans in Seventeenth-Century Britain by Goodrum MR).

Though this is a one line response, I'd like to say I saw a thread regarding this in r/askanthropology. Maybe try there? http://www.reddit.com/r/AskAnthropology/comments/1dufh5/is_there_any_documentation_of_a_society_whose/