The earliest life on Earth might have been just as purple as it is green today, a scientist claims. Ancient microbes might have used a molecule other than chlorophyll to harness the Sun’s rays, one that gave the organisms a violet hue. Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum. ‘Why would chlorophyll have this dip in the area that has the most energy?’ said Shil DasSarma, a microbial geneticist at the University of Maryland. After all, evolution has tweaked the human eye to be most sensitive to green light (which is why images from night-vision goggles are tinted green). So why is photosynthesis not fine-tuned the same way? Possible answer DasSarma thinks it is because chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth. Retinal, today found in the plum-colored membrane of a photosynthetic microbe called halobacteria, absorbs green light and reflects […]