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The most noticeable difference between the modern human face and that of the hunter-gatherers, who lived on Earth over 200,000 years ago, is the forehead. While we now have flat, smooth foreheads with visible eyebrows, our ancestors sported a pronounced brow ridge. Experts have always believed that the thick rim, and the evolution to the beautiful tufts of facial hair, served a physiological function. Now, a team of scientists from UK's University of York and Portugal's Algarve University suggest that the facial features help with our social relationships.

The team has come up with a new argument for the need of the unique facial feature. They suggest it serves a social purpose rather than a mechanical one. The scientists assert that similar to the antlers on a stag, the jutting brow ridge signaled dominance and aggression in our early ancestors. However, as we switched from being hunter-gathers to farmers, our lifestyle changed dramatically, and the need to create more extensive social networks increased.

Thanks to the dietary variety and the lower physical effort required by the agricultural lifestyle, our faces gradually became smaller, causing the jutting brow ridge to transform into a flatter forehead. The need for social communication rather than intimidation started to show in the form of more expressive eyebrows that could facilitate critical social signals in modern humans, like expressions of surprise or anger.

Spanish paleontologist Markus Bastir, who was not part of the study, says that while the theory does open up "exciting prospects for future research," it should be taken with a grain of salt. That's because Kabwe 1, the specimen used to create the 3-D model, is missing the mandible or lower jaw. Professor O'Higgins and his team, therefore, had to substitute it with a jawbone from a Neanderthal, which is a different species. Bastir believes that the substitution may have altered the results of the model and bite stresses. Regardless of the real reason for the brow ridge's evolution, we all have at some point experienced the power of the raised eyebrow!

For decades, solar energy has been touted as an alternative power source. Increasingly, however, solar energy is standing toe-to-toe with traditional power sources as a viable, cost-effective option for electricity.

When solar energy burst onto the scene in the 1980s, nobody was making an economic case for including it in America's utility electric fleet. The argument in favour of solar energy was primarily environmental. Photovoltaic (PV) panels generate energy without carbon emissions or the constant need for fuel. Since 1998, however, the cost of panels has fallen by about 8% every year. Now, it is reaching what is known as "grid parity", which means that the electricity produced by PV is costcompetitive on a per-kilowatt basis with electricity from natural gas or coal plants. At the point of grid parity, advocates of the technology can use both pure cost analysis and environmental benefits to make their case. Recently, the EPA released its Clean Power Plan, which is likely to define the environmental legacy of the Obama administration. The plan calls for a nationwide 30% reduction in carbon emissions by 2030. While environmental benefits were certainly part of the motivation behind the plan, its feasibility largely hinges on the affordability of renewable energy technology.

Traditionally, electric utilities in the United States are vertically integrated monopolies. Vertical integration means one company produces and delivers a product to consumers. Solar energy, however, is already breaking up those vertically integrated monopolies. While it doesn't make sense for everyone to have their own coal plant, photovoltaic electricity gives every American the opportunity to produce their own power. This has come to be known as "energy democratization". Today, people have an unprecedented level of choice. Many homeowners are crunching the numbers and realising that an investment in their own electricity production can save them thousands over the life of the system.

It's not only individuals taking advantage of declining prices on their own rooftops. The utility companies themselves have seen the writing on the wall and have begun to invest in large-scale solar systems. There are now several solar power farms located throughout the United States. They are strategically constructed in areas with high solar resources, such as the Mojave Desert. The largest of these farms have a production capacity of upwards of 500 megawatts.

Americans are increasingly aware of the need for a clean energy future and the economic advantages of producing electricity at home. Solar energy is coming into its own as the economic and environmental choice of the future.