For one thing, it's a lot easier and more common for the transfer to go in that ...

inimino on Oct 17, 2016 | parent | context | favorite | on: Virus stole poison genes from black widow spider

For one thing, it's a lot easier and more common for the transfer to go in that direction. If you think about the life cycles and what would have to happen in each case, one is just a lot more likely than the other.