The assumption about the lone Australian Moggridgea spider had been that it was a relict species of a bygone era, separated from its African relatives by continental drift. Its a perfectly reasonable explanation, but not one that had been directly tested. To confirm that the continental split up was behind this familial fragmentation, the timing of the separation of the African and Australian spider populations would need to line up with the timing of the African and Australian landmasses. Luckily, modern genetic techniques can allow scientists to estimate just how long ago different species diverged from one another, and this is exactly what a team of Australian scientists did with these tree trapdoor spiders. The research team took DNA samples from several species of African Moggridgea spiders, the Australian oddball spider Moggridgea rainbowi, and some other close, Australian trapdoor spider relatives Bertmainius. In analyzing the DNA, the researchers found specific differences between several genes in the spiders, and compared them to ascertain the evolutionary relationships between species. This verified that the Australian Moggridgea species was indeed most closely related to the African spiders. Then, to figure out when all these species separated from each other, the scientists used a molecular clock, which relies on the fact that DNA mutations accrue at a predictable rate. The results showed that the Australian Moggridgea species is fairly young, separating from its African relatives only about two million years ago. This is way too recently to support the idea that Moggridgea rainbowi is an Aussie because of the supercontinent shake upAfrica and Australia broke apart from each other 1. At the same time, the divergence is also much older than any occupation of Kangaroo Island by 1. European settlers, which theoretically could have introduced the spider from Africa via ships. Two million years ago, the most logical way for a trapdoor spider to get from Africa to Australia was by going right across the Indian Ocean. Unlike some other spiders, which can use their silk to balloon and even direct their aerial path over huge ocean distances, trapdoor spiders are firmly grounded. This means that their most likely method of transport was passively floating there, sailing the high seas on a mat of plant debris. This phenomenoncalled raftingis a wild card way for living things to spread across the globe. Madagascar appears to have received many of its mammals this way, as does South America in regards to burrowing worm lizards. Weve even seen it occur in real time, when hurricane debris allowed iguanas to colonize a Caribbean island. Somewhat ironically, the trapdoor spiders stationary lifestyle is probably what made its epic journey possible. Cozy in their burrows, they would be oblivious as a storm or landslide sent their wooden domiciles into the sea. Basically, these spiders are less Bilbo fleeing Bag End for a grand adventure, and more guy accidentally becoming a stowaway by passing out in a ships cargo hold. While this rafting scenario is still a hypothesis, it is the only explanation so far that fits with the timeline of divergence of the African and Australian species. The proposal would be solidified if future genetics research on the other island spiders also shows an evolutionary timeline that doesnt match up with geologic events, or if trapdoor spiders are discovered in a vegetation raft at sea. This studys revelations highlight the burgeoning role of modern genetics in uncovering the epic and unexpected origins of what we thought were familiar organisms. Just this year, genetics research also upended how we think of modern elephant relationships, and helped reveal a species of praying mantis with sexes that look nothing alike. As newer genetic methods develop, our understanding of the Tree of Life will continue to radically change. Jake Buehler is a Seattle area science writer with an adoration for the Tree of Lifes weird, wild, and unsungfollow him on Twitter or at his blog.