“When you get extraordinary results, you need to look for
extraordinary ideas to explain them.” — NICHOLAS HUMPHRE Y
Case for cold-blooded dinos dims

By Meghan Rosen

Life stories written in mammal bones are being used to debunk a key argument for cold-bloodedness in dinosaurs.

Annual growth lines etched in the leg bones of 115 wild warm-blooded mammals such as giraffes, reindeer and gazelles are similar to those previously seen in the remains of dinosaurs and other reptiles, researchers report online June 27 in Nature.

“People always said that mammals do
not show these lines,” says study lead au-
thor Meike Köhler, a paleontologist at the
University of Barcelona. This assumption
is “like a myth that’s going around; you
read it everywhere,” she says. “But people
haven’t really studied mammals.”
In reptiles, including dinosaurs, yearly
cycles of growth are stamped in the bones
like the rings of a tree. In fat months,
animals pack on blood vessel–rich bone
tissue. In lean months they lay down
only thin sheets. Under a microscope,
the slender sheets of bone look like dark
lines. Because these “lines of arrested
growth” or “rest lines” stripe bones, some
scientists assumed that dinosaurs, like
surviving reptiles, were cold-blooded. But
the new work shows that warm-blooded
mammals have banded bones, too.

Köhler’s team analyzed bone slices from 41 species of ruminants — mammals with multichambered stomachs — native to 23 different climate zones, from the polar tundra of Norway to the humid subtropics of South Africa. Every mammal the researchers examined showed cyclical growth: fast and furious when food was plentiful, slow and sluggish when resources were scant. What’s more, the rest lines from the specimens looked just like those seen in dinosaur fossils.

“It’s probably not going to close the debate whether dinosaurs were warm-blooded or not,” says paleontologist Martin Sander of the University of Bonn in Germany, “but the argument that [rest lines] mean cold-blooded is certainly not valid any longer.” s

floats an alternative explanation for
Ayumu’s performance: Ayumu might
have synesthesia, a brain condition that
makes him see numbers in colors. If
Humphrey is right, Ayumu’s feat isn’t
such a monumental accomplishment.
“When you get extraordinary results,
you need to look for extraordinary ideas
to explain them,” says Humphrey.

Because synesthesia usually applies to strings of symbols like letters or numbers, there would be no reason to think that animals other than humans would experience it. No reason, that is, until Ayumu and his chimp colleagues learned numbers, Humphrey says.

Chimp recall feat
may be mirage
Psychologist suggests ape
sees numbers as colors

By Laura Sanders

In what seems like a blow for humankind, a very smart chimpanzee in Japan crushes any human challenger at a number memory game.

After the numbers 1 through 9 make a split-second appearance on a computer screen, the chimp, Ayumu, gets to work. His bulky index finger flies gracefully across the screen, tapping white squares where the numbers had flashed, in order. So far, no human has topped him.

Ayumu’s talent has grown legendary since Tetsuro Matsuzawa of the Primate Research Institute at Kyoto University and colleagues first reported it in 2007.

But psychologist Nicholas Humphrey
of Cambridge University in England says
the hype may be overblown. In the July
Trends in Cognitive Sciences, Humphrey
If Ayumu does perceive the num-
bers on the screen in colors, then when
the digits disappear each white square
that replaces them would, in his mind,
have a distinct aftereffect color. Ayumu
could simply be ordering these colors in
a learned sequence without having to
remember the original numbers.