DarkSyd at UTI has a great series on hominid evolution.
This got me to thinking (again) about how taxonomists overly split the hominid lineage. If we were talking about any other mammal, everything within the genus Homo would be one species (possibly broken into subspecies), and all apes would be classified as a single genus (or maybe just Homo, Pan and Gorilla). Of course, mammalian taxa are overly split relative to other vertebrate taxa, vertebrate taxa are overly split relative to other animal taxa, and (I'm assuming) animal taxa are overly split relative to plants, fungi, and prokaryotes.
Taxonomy is a combination of observation and classification (a fairly objective process) and hierarchical naming (more subjective). Some of the oversplitting of certain taxa could be due to the amount of knowledge we have regarding those taxa. For example, we know much more about primates because we are interested in our origins so paleontologists search for those fossils. This contrasts with, say, what we know about insects -- there has been much less study on these critters relative to the amount of species diversity within this group. This is the subjectivity involved in observation and classification.
The other reason for oversplitting of hominids, mammals, animals, etc is that we tend to oversplit things that are similar to us. We put chimpanzees in a separate genus (we even put other hominids in separate genera!) despite the fact that we diverged from them within the last 10 million years. Contrast this with another well characterized group: Drosophila. According to the most recent molecular dating, the last common ancestor of all Drosophila species existed approximately 60 million year ago, yet they are considered a single genus. Granted, this genus is split into subgenera, groups, subgroups, species complexes, species, and (sometimes) subspecies, but they are all still considered to be in the same genus.
I think I'm done beating this drum to a dead horse -- to mix my metaphors.