Lungfish still retain the basic appearance of our shared common ancestor, so it may surprise you to learn that they have subsequently evolved enormous genomes. In fact one species, the marbled lungfish, currently holds the record for the largest genome of any animal: 133 billion letters, compared to our measly 3 billion. This highlights the rather subtle link between a creature’s DNA and its outward appearance, an important topic to which we shall return when we meet the only other living lobe-fins, the deep-sea coelacanths.
