Molecular phylogenies of bacteria are mostly built on the analysis of conserved molecules such as 16S ribosomal RNA. But there is evidence for horizontal gene transfer of photosynthesis genes, so any debate about the origin of photosynthesis must look directly at the evolution of that gene group, independent of its bacterial host. This is what Xiong
Thousands of people around the world gathered to show support for science today. Here’s a sampling of sights and signs from the Marches for Science in Berlin, Chicago, and Washington, DC.