Resurrected protein suggests that crocodiles' ancestors roamed at night.
A reptile from the Triassic period may have done its stalking at night. So suggest scientists who have resurrected a 240-million-year-old eye protein that sees dim light1.
Such a molecule may have been found in the eyes of the earliest archosaurs, which were predecessors of the dinosaurs. Similar proteins, called rhodopsins, perceive low levels of light in humans and other animals.
Thomas Sakmar of Rockefeller University in New York and his colleagues used a computer program to extrapolate the DNA sequence of the ancient rhodopsin from known sequences in alligator, birds, frogs and fish.
Sakmar then built the extinct gene from DNA building blocks, and breathed life into it by placing it in a monkey cell. "It worked beautifully," says Sakmar.
Conventional wisdom holds that archosaurs were active during daylight, like their closest modern relatives, birds and crocodiles, says palaeontologist David Weishampel of Johns Hopkins University in Baltimore, Maryland. But they could also have roamed at night, he concedes.
Wieshampel points out that archosaur rhodopsin, like that of birds, might have played only a minor role in vision. The resurrected protein reacts most to a wavelength of light closest to that detected by birds' rhodopsin - redder than the light that the human version is tuned to.
Many scientists have traced back the sequence of ancestral genes - but this may be the first time that a protein from an extinct animal has been built. "It's cool," says evolutionary biologist Caro-Beth Stewart of the University of California in Berkeley at the University at Albany in New York. "There's probably nothing on the planet that has that sequence."
In theory, several dinosaur proteins could be put together - but building up an entire eye or animal is still beyond reach. "It's not the same as resurrecting a dead dinosaur," says Stewart.
Chang, B.S.W. et al.Recreating a functional ancestral archosaur visual pigment. Molecular Biology and Evolution, 19, 1483 - 1489, (2002).