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Tuesday, December 13, 2011

Humans and snakes, beyond the Garden

There's a paper in press in PNAS describing human-snake relations among Agta hunter-gatherers in the Philippines. The paper is pretty neat, as it describes a pretty complex relationship between, in this case, reticulated pythons and humans (and generally between other snakes and primates). Humans have been attacked (and presumably eaten) by large pythons. Conversely, Agta have killed and eaten pythons. There is also a good deal of overlap in prey species eaten by humans and pythons. So at once, the relationship between humans (at least the Agta) and pythons could be described as predator-prey, prey-predator and competitors; given this dynamic, maybe Genesis readers should be more surprised that Eve and the serpent didn't try to eat one another.

The paper also has some great pictures of a huge python that was killed and flayed by an Agta group in the early 1970s (check it out free with more coverage at ScienceMag). At right is another sweet pic from the paper, an X-ray of a snake that has swallowed whole TWO juvenile monkeys!

On the far right you can clearly see the head and spine of one, and on the left half by the 'bend' in the snake you can see the head, spine and upper limb of the other, its legs visible in the bottom left corner. Nuts!

The authors write that because of the swallow-whole style that pythons ingest their prey, it may be impossible to determine whether fossil hominids fell prey to such a swallowing serpent. But I think this is itself a potentially testable hypothesis. If the snake X-rayed above was alive, researchers could have waited for the snake to expel its stomach contents, to see if death-by-python leaves any special signatures on the skeleton. Stomach acids the used by the snake to digest prey may leave a special mark on bone; because constricting snakes usually squeeze the ** out of their prey to subdue them, this could result in a characteristic pattern of bone breakage [Briana Pobiner and colleagues (2007) did a similar study based on the skeletal aftermaths of chimpanzee hunts]. So f we know what a snake's primate meal looks like when vacated, we could potentially see if there are any such serpentine signatures in the fossil record. Assuming that swallowed-by-snake could be detected, even if no fossil hominids (or apes and monkeys, for that matter) bear such signatures, that doesn't mean it didn't happen, but simply that we can't say for sure whether it did.

ResearchBlogging.orgReferences
Headland, T., & Greene, H. (2011). PNAS Plus: Hunter-gatherers and other primates as prey, predators, and competitors of snakes Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1115116108

Pobiner, B., DeSilva, J., Sanders, W., & Mitani, J. (2007). Taphonomic analysis of skeletal remains from chimpanzee hunts at Ngogo, Kibale National Park, Uganda Journal of Human Evolution, 52 (6), 614-636 DOI: 10.1016/j.jhevol.2006.11.007

2 comments:

Lars said...

Death by constrictor doesn't leave anything much - their digestive juices are ferocious and almost all osseous material is dissolved. The faeces of a snake which has been feeding upon mammals typically consist mostly of keratinous material. I don't think that you'll recover any hominid remains in python coprolites, except possibly teeth. Now that would be worth looking at - the effect of snake ingestion upon primate teeth. You'd go through a lot of monkeys, though.

Zachary Cofran said...

NIH would LOVE that: http://news.sciencemag.org/scienceinsider/2011/12/nih-curtails-chimpanzee-research.html?ref=hp