Desert hopes

still your go-to example of a missing link? Well, it turns out that palaeontology has made great strides since you were at school and there are now numerous beautiful examples of transitional forms, from fossilised creatures linking land and marine mammals to half-ant-half-wasps preserved in amber and many others. What is more, these transitional forms are always dated to the right point in history. Similarly, you know that the appendix is a vestige of our more herbivorous ancestors, but there are numerous more eloquent examples of evolutionary history preserved in living organisms. These include the laryngeal nerve which runs from the neck down the chest and loops around the aorta before returning to almost where it came from in the larynx. No designer could come up with such a tortuous route, but its provenance is easily understood once the evolution of the larynx from what was a gill arch in our aquatic ancestors is understood. Just as informative are the pseudogenes or 'dead genes' that litter genomes throughout the living world and turn up almost wherever DNA sequencing allows us to look, revealing past capacities now lost through lack of use and lack of selection: silent genes for detecting airborne odours in dolphins, and nearly everything we primates need for making vitamin C apart from one tiny piece of the chain which we have lost (as have a few other mammals who can generally rely on getting vitamin C in their diet). Coyne marshals the biogeographic evidence with no less effect — where do we expect to find fossil kangaroos? Where are they found? Australia. Islands have far fewer species — does God dislike islands or is it because they're hard to colonise if you can't swim or fly? If it is just that He dislikes them, how come the plants and animals missing from islands are the ones that have trouble crossing water, and why are the organisms on islands invariably most similar to those on the neighbouring continents? The distribution of life also teaches us about the capricious nature of evolution — the same problem has many solutions, some of them more elegant than others. The forms we see depend on the vagaries of chance events that brought different animals and plants to different areas, and of the chance mutations that allowed them to adapt to the new opportunities on offer. Having provided us with eloquent testimony for …