The Not Quite Adventures of a Professional Archaeologist and Aspiring Curmudgeon

Friday, September 3, 2010

Hyena Vomit and Human Evolution

The 1950s through 1980s were a time of very active change in archaeology. New technologies coupled with changes in the way that humans are viewed by archaeologists (less mythic "man the conqueror", more practical "humans as a specieis adapted to life on Earth") spurred a number of advances in the way that archaeologists study our evolutionary past.

One of the first steps along the path to re-evaluating our evolutionary past was determining whether or not many of the archaeological sites that had been used to argue for the particular model of the human past were, in fact, archaeological sites at all. High on this list were caches of animal bones that litter the African landscape. Often found in caves or rock shelters, these caches of bone indicate selection - only certain pieces of bone are found, not entire skeletons, and the types of bones are fairly consistent across sites - and show signs of modification - marks on the bones and bone breakage. The selection of bone and the signs of modification had long been taken as evidence of homonid (the family of animals to which humans belong, and of which humans are the only surviving member) activity, and specifically of hunting and butchering.

This changed as archaeologists began to look at the behavior of other animals that are present in the parts of Africa where our ancestors wandered. Researchers discovered that the feeding habits of certain large cats likely created some of the bone caches that had been found, with the marks on the bone coming from teeth or post-depositional environmental factors.

One particularly important book, The Hunters or the Hunted?, by a fellow with the delightful name of C.K. Brain, discussed bone caches found in African caves with an eye towards evaluating what materials came from homonid activities, and what was due to animals, both large and small, that also selectively leave bones behind.

However, the study that really grabbed my attention as an undergraduate involved the examination of hyena vomit. Yes, the study was done in the 1970s, and everyone was on drugs then, but there actually was a valid reason to study hyena vomit.

You see, hyenas have been around for approximately 26 million years, meaning that they were wandering the African savannah along with our early ancestors. Hyenas also are scavengers, meaning that they get access to carcasses after other animals have already had a chance to take what they want from them. Hyenas are well-adapted to scavenging because one of the many things that they can do is swallow bone and vomit it back up on demand. "How does this help them" you ask? Simple - the swallow the bone and their stomach begins to digest the grease and meat left on and in the bone, allowing them to gain nourishment from remains for which other animals would have little use. Once their system has extracted what it can from the bone, they vomit it back up, leaving behind select pieces of bone in piles that might look like a homonid had gone about picking up choice cuts of meat and leaving the bone behind to be discovered by it's descendants a couple of million years later.

With the results of this study, people studying homonids were better able to eliminate hyena puke sites from their lists o' potential archaeological sites. A useful thing to be sure, and a tool that allowed the view of humanity's evolutionary past to be refined.

Perhaps the most interesting thing about the study of homonids during this period is that it reflected how a change in how we think about ourselves can allow data to be more fully examined. Prior to this period, it had been common to think about "man the hunter" and "man the conqueror" - whether this was glorified or villified, we were seen as beings that could and did take the world by force and make it as we wished, and this was reflected in many of the models of our evolutionary past. With Post-WWII social change, not to mentiont echnological change, we began to look at ourselves and our ancestors in a different light, and began to consider that the data might be saying something different than what we had initially assumed. The image that began to emerge as the data was evaluated with better techniques was that our homonid ancestors did eventually become hunters, but that they likely spent quite a bit of time scavenging, and we were shaped by our environment at least as much as we would eventually shape it (probably more so).

No comments: