The haplodiploid sex-determination system has a number of peculiarities. Most importantly, the relatedness between the sisterhood of worker bees in a hive or nest is 0.75. This means the workers are significantly more closely related than siblings in other sex determination systems. It is this point which drives the kin selection theory of how eusociality evolved. Whether haplodiploidy did in fact pave the way for the evolution of eusociality is still a matter of debate.