It may be hard to think of something rats are good for, but
a team of scientists has figured out a unique way to look into the history of
Pacific islands—using rats.
(Image: A Pacific rat, Rattus exulans, in a New Zealand government photo.)
They looked into the bones of rats from ancient
archaeological sites, and it turned out that they could extract information
from the marrow of rat bones. They were able to figure out what the rats were
eating over time, and from that, make assessments about the changing island
environment.
A new study on this work was just published in the Proceedings
of the National Academy of Sciences. The authors are Jillian Swift, Patrick
Roberts and Nicole Boivin of the Max Planck Institute for the Science of Human
History, and Patrick Kirch of the Univeristy of California-Berkeley Department
of Anthropology. The paper is entitled "Restructuring of nutrient flows in
island ecosystems following human colonization evidenced by isotopic analysis
of commensal rats."
Some definitions: Isotopes are forms of the same element
that have different numbers of neutrons in the nuclei. Isotopic analysis in this instance is studying changes
over time in the mix of isotopes of certain elements—in this case carbon and
nitrogen. And commensal means living with something, without causing it any
particular help or harm—in this case rats living among humans.
When early Polynesians arrived on Pacific islands, they
almost always brought Pacific rats with them. People argue over whether that
was intentional or not, but it almost always happened. Pacific rats, or
Polynesian rats, are Rattus exulans.
And those rats quickly went out on their own, foraging initially
in the virgin environment, and later in the environment that humans had created
through bringing new plants, slash and burn agriculture and so forth.
"Stable isotope analysis of commensal animals provides
an effective proxy for local human environments because these species are
closely associated with human activities without being under direct human
management," the authors write.
They studied rat bones from archaeological sites in three Polynesian
island areas: Mangareva, Ua Huka in the Marquesas and Tikopia far to the west.
They found that their study of rats was able to track dramatic
changes in local environments, demonstrating "human land use, intensification
and faunal community restructuring."
More specifically, "Our results highlight the
large-scale restructuring of nutrient flows in island ecosystems that resulted
from human colonization and ecosystem engineering activities on Pacific islands."
This is complicated stuff, and I won't go into details on
how the lab work was done, but you can look it up yourself here.
This is data that the authors say is hard to get from
standard analysis of early archaeological remains, and it suggests that this
kind of stable isotope analysis can help shed more light on how and how quickly
humans changed their environments after arriving on Pacific islands.
It is also true that the rats themselves did a lot of that
modification of ecosystems—eating birds and insect and seeds and seedlings. But
that's all part of the story, since it was humans who brought the rats to these
new environments.
© Jan TenBruggencate 2018
2 comments:
Very interesting and can these studies shed light on WHEN certain island groups were colonised? Who knew rats could be so interesting?
well done, jan. a good exposition of a complex and fascinating subject.
meph
Post a Comment