The principles of evolution indicate that species adapt in optimal ways to enhance their probability of survival. Scientists are largely stumped on why the photosynthesis process makes use of blue and red wavelengths. Shil DasSarma, from the University of Maryland, proposes that Earth’s early life used the more potent green wavelengths. Rather than chlorophyll, light was synthesized using a compound called retinal. Fossil evidence indicates early organisms and bacteria were rife with retinal and plants may have evolved to use the reflected blue and red wavelengths for their own photosynthesis. As a side effect, a fledgling Earth would have had a dominant purple cast in lieu of today’s green.