For a century after Charles Darwin published The Origin of Species in 1859, scientists could compare only physical features to describe evolutionary lineages. The picture that resulted was often illustrated as a Tree of Life.
In 1953 James Watson and Francis Crick discovered the structure of DNA – the molecular basis of genes – and showed how they encode the instructions that determine the form of every organism. Now, decades later, powerful new technologies permit comparisons of DNA and RNA, yielding detailed, objective information on the evolutionary connections between organisms. This has led to development of a new, genetically based Tree of Life, which allows deeper insight into the evolution of species than their physical features alone.
But tracing the evolution of the billions of organisms and species that have existed on Earth over billions of years will be a never-ending process in which the Tree of Life itself will evolve continuously and, along the way, provide important clues to life’s origin.