Riddles abound in science and, not surprisingly, the older they are, the more difficult they are to solve. One of the toughest problems has been to understand the molecular basis of phenotypic variation — the raw material for adaptive evolution. Rodney Mauricio reviews how this field has advanced in plants, in which the combination of powerful statistics, genomics and sophisticated molecular genetics is making it possible to identify both quantitative trait loci and the underlying molecular variation that contribute to adaptive traits.

Ken Wolfe tackles another historical riddle — the extent to which genome duplication has influenced the evolution of the vertebrate genome. The genomes of model organisms provide us with valuable clues, but the truth might never be known.

A more direct way to study the mysteries of the past relies on ancient relics, and the uses of ancient DNA in particular are reviewed by Svante Pääbo and colleagues. However, they also warn of the technical pitfalls that surround the study of ancient DNA and call for more stringent experimental approaches.

The past is one thing, but predicting the future usually lies outside the realm of science — a riddle too far perhaps. Nevertheless, Robin Bush describes in her Perspective how to use phylogenetic trees of virus sequences, for example, to detect nucleotides that are undergoing rapid diversification. In viral sequences, such nucleotides might define antigenic regions and are therefore likely sites of future evolution.

Finally, there are several new faces to introduce. We welcome four new members to our Highlights advisory panel. And we are also delighted to announce that Magdalena Skipper, our new associate editor, whose research history includes worms, chicks, mice and zebrafish, joined us last month. Welcome to the team, Magdalena.