Fossils

Fossilized imprints of raindrops that were sealed into stone 2.7 billion years ago indicate that Earth's early atmosphere could have been packed with greenhouse gases, according to new research that addresses a long-standing paradox of the planet's early history. About 2 billion years ago, the young sun was far less bright, emitting less than 85% of the light and heat it puts out today. With such weak sunlight, Earth should have remained frozen. But ancient water-damaged rocks and algae-like fossils show clear evidence that there was indeed liquid water in the distant past.

Lucy, that starlet among ancient human relatives, may have shared the stage with a hominin very different from herself, a newly discovered fossil suggests. Out of the Ethiopian desert, researchers have unearthed a rare, 3.4-million-year-old partial foot that resembles those belonging to Ardipithecus ramidus , a species thought to have roamed East Africa a million years before Lucy and other members of her species, Australopithecus afarensis . The findings, published in Thursday's edition of the journal Nature, provide the first good evidence that another bipedal human relative was still climbing trees at the same time that Lucy and her kind had their feet planted on the ground.

California has a state bird, a state flower and even a state fossil — the saber-toothed cat. Joining the bunch could be an official state marine reptile. A bill introduced last week by Assemblyman Paul Fong (D-Cupertino) would name the endangered Pacific leatherback sea turtle to a growing list of symbols that includes the California quail, the gray whale, the California poppy and the garibaldi — the state marine fish. The leatherback, the world's largest sea turtle, would claim an entry in the law books right below — and not to be confused with — its relative the desert tortoise, a landlubber that has held the title of state reptile since 1972.

Construction cranes rise like storks 40 stories above the Mojave Desert. In their midst, the "power tower" emerges, wrapped in scaffolding and looking like a multistage rocket. Clustered nearby are hangar-sized assembly buildings, looming berms of sand and a chain mail of fencing that will enclose more than 3,500 acres of public land. Moorings for 173,500 mirrors -- each the size of a garage door -- are spiked into the desert floor. Before the end of the year, they will become six square miles of gleaming reflectors, sweeping from Interstate 15 to the Clark Mountains along California's eastern border.

Renewable energy is surpassing fossil fuels for the first time in new power-plant investments, shaking off setbacks from the financial crisis and an impasse at the United Nations global warming talks. Electricity from the wind, sun, waves and biomass drew $187 billion last year compared with $157 billion for natural gas, oil and coal, according to calculations by Bloomberg New Energy Finance using the latest data. Accelerating installations of solar- and wind-power plants led to lower equipment prices, making clean energy more competitive with coal.

California is on track to meet an ambitious goal of putting solar panels on up to 3 million Golden State homes by 2016, according to a new report by an environmental group. The $3.3-billion initiative, which provides subsidies to homeowners, has spurred the installation of 800 megawatts of rooftop panels over the last five years. That's the energy equivalent of two gas-burning power plants. With the prices of photovoltaic panels plummeting, California's installations are expected to triple over the next five years, helping the state reach its goal of 3,000 megawatts of rooftop solar by 2016.

After examining the fossils of two hominids that lived nearly 2 million years ago, anthropologists said that the anatomical features of the adult female and young male strongly suggest they could be members of a species that was a direct ancestor of modern humans. In a series of reports published in Friday's edition of the journal Science, the researchers describe the Australopithecus sediba specimens as having a curious mix of primitive and modern features that could prompt experts to redraw the human family tree.

Searching across the Tibetan plateau, paleontologists have discovered a species of woolly rhinoceros that may be an ancestor of the great ice age beasts that roamed the plains of North America, Europe and Asia. The Coelodonta thibetana fossil dates to about 3.7 million years ago, about a million years before other known woolly rhinos. The findings, published in Friday's edition of the journal Science , lead researchers to believe that before the ice age began, the chilly Tibetan highlands may have served as an evolutionary cradle for cold-hardy mammals whose descendants thrived in the glacial times that followed.

Plesiosaurs — giant marine reptiles that ruled the oceans 75 million years ago — gave birth to single large babies and may even have nurtured their young, according to a new study. F. Robin O'Keefe, a paleontologist at Marshall University in Huntington, W.Va., and Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum in Los Angeles, teamed up to study the only known fossil of a plesiosaur mother and her unborn baby. The ancient relic is considered the first evidence that these aquatic behemoths gave birth in the water instead of laying eggs on land, the researchers reported online Thursday in the journal Science.

The famous winged and feathered fossil Archaeopteryx has been knocked off its perch as the oldest known bird, according to new research. Instead, it was most likely a dinosaur. Archaeopteryx, discovered in Germany in 1861, lived during the late Jurassic period — about 150 million years ago. On the basis of its part-bird, part-reptile features, paleontologists placed it in the avialan family, which includes the earliest ancestors of birds. Avialans are related to deinonychosaurs, bird-like dinosaurs such as Anchiornis and Microraptor that lived during the late Jurassic and subsequent Cretaceous.