Patterns in Palaeontology – Deducing the tree of life

Some areas of life and human endeavour have the luxury of certainty. Along these paths of discovery, there are things we can know to be true or false. In others, it is impossible to assess the concept of truth: it can’t be established, or just isn’t a consideration. And between these extremes is a whole mess of important stuff. Palaeontology almost always lies somewhere on this gradation. Researchers studying past life are often juggling multiple layers of uncertainty. We try to balance the need to say something useful — something with meaning, that moves a field and its consensus closer to the truth — with the risk of over-interpreting our data. If the data is too incomplete, we could be moving closer or further away from the truth, and wouldn’t be able to tell. As such, palaeontologists have to draw a line somewhere, and where might differ between people. In other words, palaeontology is very much a human endeavour. It is subject to paradigm shifts in our understanding brought about by new discoveries and methods, but is also influenced by the human nature of those who practise it as fashions and traditions change — normally in search of a better way of doing things. Often, these shifts are driven by arguments that explode onto the scene in which proponents of different ideas — held with passion and fervour — disagree about something harder to pin down and less concrete than a new fossil. This is a position in which palaeontologists who enjoy trying to work out the shape of the tree of life currently find ourselves. Two competing approaches to working out the relationships between different species — their phylogeny — are battling it out in the scientific literature. It’s exciting, engaging and undeniably driven by a desire to improve understanding of the natural world in all its complexity. But it’s also one of those situations in which working out what is closest to the truth can be challenging. Before I write about it any further, we need some context. This article provides both the history of, and current debates surrounding, how we deduce the shape of the tree of life.