WASHINGTON - The unusually large brains of mammals apparently didn't evolve so that we could ponder philosophy - but so we could sniff our way to success.
A new analysis of some of the earliest mammals and mammallike creatures shows their complex brains evolved in stages, starting with the regions that handle the sense of smell.
The tiny creatures that evolved into today's mammals "exploited a world of information dominated to an unprecedented degree by odors and scents," report researchers led by Timothy B. Rowe, a paleontologist at the University of Texas.
"If I had to tell a freshman class what it means to become a mammal, it means to become a superb smeller," Rowe said by telephone.
Enlargement of the brain's smell-sensing region was followed by upgrades in the brain areas that deal with touch sensitivity from body hair, and then parts providing improved movement, Rowe and colleagues report in today's edition of the journal Science.
People are also reading…
Among mammals, today's humans have traded away some of that ability to smell for improved vision and hearing, Rowe observed, but we still have close companions called dogs that exploit the sense of smell heavily.
As the mammal brain evolved, the area involved in sensory response "underwent particularly spectacular development," said R. Glenn Northcutt of the Scripps Institution of Oceanography, who was not part of Rowe's team. The studies "provide the first solid evidence of the stages of mammalian brain evolution," Northcutt said.
The report is "very significant because it outlines, for the first time, the evolutionary history of major brain regions in the closest relatives of mammals, and early mammals," said Hans-Dieter Sues, curator of vertebrate paleontology at the Smithsonian's National Museum of Natural History.
Scientists think these tiny creatures were active at dusk or during the night, said Sues, who was not part of the research team. "Thus, smell and tactile senses, but also improved hearing, would have been really important to these animals."
Mammals are warm-blooded animals with backbones, and with females that have milk-secreting organs to feed their young. They include humans, apes, many four-legged animals, whales, dolphins and bats.
What researchers are learning could one day lead to construction of machines or robots with the ability to smell, which could be valuable in security situations, for product inspections and other uses, Rowe said. Every person, he pointed out, has an individual odor.
On StarNet: Find more science, technology and health stories at azstarnet.com/science
