<human>:  How many species of humans are there?
<bot>: There are many different species of humans, but the most common classification is Homo sapiens. We have several subspecies of humans, such as Homo sapiens sapiens, Homo sapiens neanderthalensis, and Homo sapiens denisova. There are also a number of extinct species of humans, such as Homo erectus, Homo habilis, and Homo heidelbergensis.