ZA: The fact that hominins lived in a mosaic environment is, I think, an established fact. The information comes from fauna, sediments, isotopes and what have you, so the environments were there. The big question is, which part of that environment was essential for their survival, for their adaptation? That is what we need to nail down. The earliest hominins lived in woodlands, in forested environments, for example. But it doesn't mean that they were completely out of the relatively open environment. I think they would venture into these environments when they needed to. There are recent works by Peter Ungar [of the University of Arkansas] concerning fallback resources and how hominin species might actually live in an environment when things are good. But when things go bad they fall back on another type of food, which means another type of environment.?
KW: There have been so many ideas over the years about why hominids became bipeds. Do you have any thoughts about this?
ZA: I believe we should just put the savannah theory aside. I think they basically became biped while they were living in a wooded, covered environment. The savannah could explain two other things. Actually, we should say grassland, because savanna is a more complicated term. But the relatively open environment was out there to be tried--be it later with Homo, when it was very dominant, or be it before, with the earliest hominins. Hominins were experimenting with all sorts of environments. But at some point they had some preferences. It's very hard to do, but only when we are able to [identify] their preferences can we talk about the mechanisms behind what triggered bipedalism, what triggered megadontia, what triggered brain expansion.
KW: One last question, about the hyoid. The only other fossil hominin hyoid on record is the one from the Kebara Neanderthal. There has been lots of speculation about whether that can reveal anything about Neanderthal language. What does this bone tell you about afarensis vocalization?
ZA: Since the relationship between articulated language and the hyoid bone is not established, any inference that you make about language based on this bone is not substantiated. However, we now know [based on this hyoid] that early hominins--at least afarensis--had these laryngeal air sacs, suggesting a voice box similar to that of chimps. But what does this mean when it comes to language? One has to functionally demonstrate first that this bone is actually relevant to language or the lack thereof before any conclusion can be drawn.?