Photosynthesis is crucial for life on Earth, and scientists studied the evolution of photosynthesis in ancient bacteria. They compared the relationships between different types of photosynthetic bacteria using key proteins and enzymes. The findings show that bacteriochlorophyll biosynthesis evolved earlier in green bacteria than in purple bacteria. Different lineages of purple bacteria evolved independently, with the Rhodobacterales being the youngest group. The study highlights the complex evolutionary history of photosynthesis in bacteria.