Global Positioning System (GPS): that’s a function. Maintaining a suite of satellites is one method for achieving the function. But there are other ways to figure out where in the world you are, and two very different animals show the way – naturally – using Earth’s global magnetic field.
Pigeon GPS: A team of researchers from Baylor College inserted electrodes into pigeons’ brains, then exposed them to artificial magnetic fields in the absence of visual cues. According to New Scientist, they found that 53 particular neurons associated with the pigeon’s inner ear became particularly active when the magnetic field was altered. They surmise these neurons are part of the bird’s auditory map, “acting as a biological GPS.” The neurons even responded to the polarity of the field. This would allow a pigeon released below the equator to orient itself correctly to fly home.
The BBC News focused on how this new finding contradicts earlier studies that located the birds’ magnetic sense in the beak or eye. “Be puzzled, because I am,” remarked David Dickman, one of the authors of the study. Other mysteries to be resolved include how the birds detect the Earth’s magnetic field in the first place, and how they don’t become disoriented when they tilt their heads. “One possibility is that they use a combination of the magnetic GPS and the pull of gravity to triangulate their position,” the article surmised. See also 4/24/2007 about pigeon navigation.
Butterfly GPS: Another article by the BBC News from September 2009 talked about biological GPS – in this case, among Monarch butterflies. That study indicated that the insects’ GPS is located in the antennae. For previous entries about Monarch navigation, see 7/29/2002, 5/23/2003 and 5/09/2005. The documentary Metamorphosis from Illustra Media brings the wonder of Monarch migration to life on the screen.
Given that many animals migrate, including fish, reptiles and mammals, in addition to birds and insects, there may be many and varied biological methods for achieving the function of GPS. For previous stories about biological GPS, see 6/29/2006 about ants, and 7/15/2009 about dragonfly long-distance migration. Even the human body possesses GPS-like devices (see 12/27/2008).
No mention of evolution in these articles. A natural wonder? No evolution? No wonder.