Ego sum Daniel

Understanding our evolutionary past through the language of our genes

As vertebrates, we are united by a common ancestry that stretches back to the Cambrian period, some 500 million years ago. Since then, vertebrates have occupied an astonishingly diverse set of ecological niches. Vertebrates live on almost every place on earth; from deep ocean trenches to arid deserts. The early evolution of vertebrates was a period of great innovation. It set the foundation for the great variety of complex and specialised functions that have allowed us to diversify and spread. Our mineralised bone structures and complex nervous systems stem back to this period, for example.

There is now convincing evidence that a group of our early ancestors doubled their genetic material twice during this period. This happened through a process called whole-genome duplication. It is the most drastic mutation possible: The doubling of the total genetic content, including genes, regulatory sequences, and non-functional DNA. We know that this had a great impact on vertebrate evolution because we can still find many of those twice duplicated genes in now-living vertebrates. A third whole-genome duplication occurred in the early evolution of teleost fishes. Similarly, we can find additional gene copies in teleosts resulting from this event.

Duplication, be it of individual genes, segments of chromosomes, or of whole genomes, is one of evolution's driving forces. It is how families of related genes arise in evolution. Duplication generates new genetic material that mutation and selection can act upon to generate new functions while still keeping the original function in one of the copies. In this way, evolution can add new genetic building blocks on top of a previously laid foundation. In On the Origin of Species, Darwin hinted at this: "it is quite probable that natural selection, during a long-continued course of modification, should have seized on a certain number of the primordially similar elements, many times repeated, and have adapted them to the most diverse purposes." Of course Darwin did not know about genes, but the fundamental principle is the same.

Since the publication of the first draft of the human genome in 2001, we have seen an unprecedented advance in DNA sequencing technologies and bioinformatics tools. There is now openly available genome data from an ever growing number of organisms, including many vertebrates. This allows us to study the consequences of ancient whole-genome duplications, as well as other genomic events, with greater accuracy and resolution than ever before. Because we share a common ancestry, we can explore the evolution of vertebrates by comparing DNA sequences across different vertebrate groups. Like archaeologists looking for clues to the past in the soil, or naturalists exploring new and unknown environments, we can wade through the vast stretches of DNA and explore the contents of different genomes; trying to identify genes and figuring out how they are related to each other and how they have evolved.

This has been the backdrop for my research in the past ten years, which has explored the evolution of neurobiological and endocrine gene families in vertebrates. That is, families of genes involved in the nervous system and the hormonal control of bodily functions. By combining genomic analyses with molecular phylogenetics, my research has shown that the ancient whole-genome duplications in vertebrates likely contributed greatly to the evolution of processes such as vision, neural communication, body growth, the control of water balance, and social behaviours. Currently, I am also working on understanding the evolution of the ampullae of Lorenzini. These are small electro-sensory organs on the heads of cartilaginous fishes which allow them to detect weak electromagnetic fields generated by the muscular activity of their prey.

Understanding our evolution through the language of our genes is not only an interesting evolutionary puzzle. It also benefits applied biological and biomedical research. Functional studies can profit greatly from the combination of genomic and evolutionary approaches. Not least through the discovery of novel genes and functions, and through the increased understanding of model organisms used in laboratories to understand human diseases. But at its core, knowing more about our evolutionary past, where we come from and how we got here, is a fundamental human pursuit. It gives us context and binds us to other beings. As we move towards increasing climate change and a possible sixth mass extinction, including of many vertebrate species, this is more important than ever.