Next time you see a mole digging in tree-root-filled soil in search of supper, take a moment to ponder the mammal's humerus bones. When seen in the lab, they are nothing like the long upper arm bones of any other mammal, says Samantha Hopkins, a paleontologist at the University of Oregon.
Hopkins, a professor of geology in the UO's Robert D. Clark Honors College, studies the evolutionary history of burrowers, in search of why and how they adapted a physique for digging in response to environmental influences or other forced changes in habitats.
In a talk at the annual meeting of the Geological Society of America, Hopkins presented preliminary findings of one line of her research. Moles and mole rats, she said, are examples of mammals that have adapted to moving soil in rocky, root-packed soils, in opposition to most other burrowing mammals that prefer softer, dryer sandy soils.
"It requires a lot of morphological adaptation, a lot of tradeoffs, to be good at digging," she said. "That's intuitive to us as humans who have handled a shovel in the backyard. We know that it's really hard work to shift soil. Burrowing mammals acquire a complex of features that lets them handle whole days moving soil. They make for a great case for understanding convergent evolution because in spite of how difficult it is to do this -- in spite of all the costs of doing this -- it seems to be worthwhile enough that many mammals have done it through time."
Convergent evolution is the development of similar characteristics, necessary for survival, among unrelated organisms in the same environmental conditions. Hopkins studies living burrowers as well as the fossil records of such mammals, living and extinct worldwide, to understand why some choose to live -- and dig for their food and to avoid predators -- in harsher regions. Conventional thinking, she said, is that mammals evolved into burrowers after being driven into grassland habitats, where goi
|Contact: Jim Barlow|
University of Oregon