KW: How do you know that LB1 isn't simply an aberrant individual?
PB: There are small-bodied normal modern humans just as there are small-bodied abnormal modern humans. Small-bodied normal modern humans, normally called pygmies, have small stature, but they have brain sizes and skull proportions which are similar to those of the large-bodied populations around them. So it's easy to rule out the pygmy analogy. It's more difficult to rule out, I suppose, the analogy with abnormal modern humans, like pituitary dwarfs or microcephalic dwarfs, because there you can have small-bodied people who have small brain sizes as well. Very few of these people actually reach adulthood and they have a range of distinctive features, depending upon which particular syndrome they have, throughout the cranial vault and rest of the skeleton. None of these features are found in Liang Bua. It has a suite of clearly archaic traits which are replicated in a variety of early hominids and these archaic traits are not found in any abnormal humans which have ever been recorded. We now have the remains of 5 or 6 other individuals from the site, so it's not just one. There's a population of these things now and they all share the same features.
KW: The overall trend in human evolution is one characterized by increases in body size and brain size. How do you explain this apparent reversal?
PB: There's no actual evidence for dwarfing [in Homo] on the island. We don't have any putative large-bodied ancestors on Flores for [the Liang Bua people] to have dwarfed from as yet. There's evidence of stone tools on Flores at 840,000 years ago, which was reported a couple of years ago. But from the cave itself we only have these small people. So there are a couple of possibilities. Either they dwarfed on another island and then proceeded to get to Flores one way or another; or they may have dwarfed on Flores; or maybe this lineage has greater antiquity--for which there is no evidence at present--and they represent an earlier migration, before Javan Homo erectus entered that part of Asia. In other words, an earlier migration out of Africa via Europe or wherever.
Looking at the distribution of small-bodied animals around the world today, they tend to occur in rainforests. [Editor's note: being small bodied enables animals to better regulate their body temperatures and to subsist on fewer calories, which rainforests have in limited supply.] And certainly that's where small-bodied humans tend to be found. We don't know much about the paleoenvironment on Flores yet, but everything's consistent with it being heavily rainforested back in the Pleistocene and probably heavily rainforested until agricultural humans arrived and started clearing the rainforest. The fauna is consistent with that sort of environment as well. Maybe there just wasn't a lot to eat. The island is only about 14,000 square kilometers, there's not a lot of it there. So I think the most likely scenario is that as part of their adaptation to [having fewer] calories living in a rainforest--and maybe thermoregulation as well--there was this long-term selection for smaller body size. There may be other possibilities, but this seems most likely to me at the present.
KW: What other sorts of animals lived on Flores when LB1 was alive?
PB: The faunal analysis is still ongoing, but one of the most common items in the deposit is this pygmy stegodon [an extinct elephant relative]. They tend to be baby stegodons and baby stegodons probably didn't normally live in caves, so we assume they are the result of hunting. Stegodon underwent several periods of introduction and dwarfing on Flores. They came in as the normal size stegodons (sort of an Indian elephant size), they dwarfed, became extinct for whatever reason--maybe tectonic activity, volcanoes, we don't really know--and then subsequently large stegodons came in again and dwarfed. We have these dwarfing episodes reflected not only in Liang Bua but other deposits on Flores. So there are lots of baby stegodons in the deposit and very few adult stegodons--maybe [the baby stegodons] were tastier. There's also a Komodo dragon, another large [monitor lizard], very large rodents, bats, birds and a range of other things, some of which occur naturally in caves. The main evidence of human activity, I suppose, is the Stegodon remains.