Island rodents take on nightmarish proportions

Rodents of unusual size are 17 times more likely on islands than elsewhere

Date:June 22, 2015

Source:Duke University

Summary:Researchers have analyzed size data for rodents worldwide to distinguish the truly massive mice and giant gerbils from the regular-sized rodents. They found that the furry animals with chisel-like teeth are 17 times more likely to evolve to nightmarish proportions on islands than elsewhere. 

The results are in keeping with an idea called the 'island rule,' which previous studies claimed didn't apply to rodents. 

The study appears online in the journal Proceedings of the Royal Society B.

Duke University biologists Paul Durst and Louise Roth analyzed data from more than 1,000 rodent populations representing more than 60 species across the globe. The dataset included mice, rats, squirrels, hamsters and porcupines, ranging in size from the tiny 0.2-ounce harvest mouse to the nearly 50-pound North American beaver.

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Americans' Heads Getting Bigger

Modern life may be going to your head.

It's not clear why—medicine? cars? supermarkets?—but the skulls of white Americans, and perhaps of other races and nationalities, have become slightly taller and roomier, according to new forensic research.

New measurements of hundreds of skulls of white Americans born between 1825 and 1985 suggest that their typical noggin height has grown by about a third of an inch (eight millimeters).

It may not sound like much, but the growth translates to roughly a tennis ball's worth of new brain room.

"I can't guess the implications of this jump in cranial size, but other research shows a bigger cranium doesn't necessarily mean more intellect," said University of Tennessee biological anthropologist Richard Jantz, who presented the findings with colleagues at an American Association for Physical Anthropology meeting in April.

Ups and Downs of Evolution

Beginning with the dawn of the first Homo species, human skulls evolved to be increasingly bigger until about 30,000 years ago, when head size plateaued.

Continued:  http://news.nationalgeographic.com/news/2012/06/120606-americans-heads-getting-bigger-science-health-skulls-evolution/