Oliver Pergams used a tiny caliper to measure the mice, tracking changes in size over the years. (Photo by Gabriel Spitzer)
Evolution takes place over long stretches of time: millennia and epochs. But some new research shows that animals might be changing much
faster than nearly anyone thought. Gabriel Spitzer has more on those
changes, and how they seem to be linked to humans:
Transcript
Evolution takes place over long stretches of time: millennia and epochs. But some new research shows that animals might be changing much
faster than nearly anyone thought. Gabriel Spitzer has more on those
changes, and how they seem to be linked to humans:
Tall Trees Park is a little patch of green in Glenview, Illinois – a
northern suburb of Chicago. About a hundred years ago, a lot of this area
looked a lot like this. It was mostly farms and pasture and forest. And now
of course it’s a lot of strip malls and subdivisions and stuff. And the
population has grown seventyfold. The climate has changed, too. It’s
gotten a little warmer, a little wetter.
And all this has made life a lot different for the northern white-footed
mice who live here. It’s actually not just made life different for the
mice, it’s changed the mice themselves.
That gets back to a guy named Oliver Pergams. He’s an ecologist, and in
the mid-90s, he was looking at deer mice who live on the Channel Islands
off the coast of California. And he was taking these mice and comparing
them to museum samples of the same kind of mice from the same place, but
decades earlier.
“And I found something kind of strange – that the older specimens were
larger than the newer specimens, so they shrunk in size over a period of
about 30 or 40 years.”
That got him wondering if those relatively quick changes are happening in
other places. So years later, now on the faculty at the University of
Illinois at Chicago, he gathered up some of those White Footed Mice from
the Chicago suburbs. And he went to the Field Museum of Natural History…
(sound of a cabinet opening)
… where they have a hundred years of dead mouse specimens stored in
white metal cabinets.
“Here we have trays and trays of the northern white-footed mouse.”
With a tiny caliper, he’d measure their skulls, their feet, the distance
from their eyes to their noses.
“So this one here was collected by Aikley in 1903.”
And he compared mice from before and after 1950.
“Here are some skulls, this one was collected in 1989.”
Lo and behold, these mice had grown: by more than 10% on some measures.
This phenomenon goes way beyond Chicago. Pergams measured more than 1,300
rodents from four different continents – Alaskan lemmings, Mexican
gophers, Filipino rats. Some of them got bigger, some smaller. But across
the world, most of the animals have changed over time spans thought to be
mere evolutionary eyeblinks.
The next step is to figure out why.
“You can’t get in a time machine and go back and look to see what
actually happened. So the next best thing is to see if there’s
associations or correlations with big factors.”
He found the variations correlate with changes in climate and human
population density. The exact reasons aren’t clear – more people might
mean more yummy trash for the mice to eat, for example. That’s going to
take more research to figure out, and these critters might be overdue for
some extra attention.
“One of the questions is, well, why didn’t anybody notice this before?
And I think the answer is, they haven’t looked.”
Larry Heaney curates the Field Museum’s mammal collection. He says
Pergams’s research opens up new questions about how animals respond to
changes driven by humans.
“The implication is, these animals are changing very, very rapidly. So in
a sense, it’s good: they can change. But the other side of the coin is,
they’re having to change.”
Now, the question is, is this happening in other species, too? What about
birds or bugs or plants?
“There’s been this default attitude that if you go to one place and you
capture or you observe animals or plants, that essentially there’s going
to be the same animals or plants 50 years or 100 years later. I don’t
think that’s possible to assume at all. We have to include the fact of
this change in all of our decisions, from ecology to evolutionary biology
to conservation.”
Pergams’s findings show that even the most common creatures have more to
teach us – when we ask the right kinds of questions.
For The Environment Report, I’m Gabriel Spitzer.
