Add another branch to the family tree. Scientists have just discovered a new species of human ancestors deep in a South African cave. More than 1,500 bones from at least 15 individuals — ages have yet to be determined — have been unearthed. One researcher suggests that these members of the previously unknown homo naledi species may have been trapped there by other humans, which could mean primitive man displayed complex behaviors. The team is getting to know these long-lost relatives and hopes their investigations improve our understanding of human origins.