A dino in the hand is worth two in the bush

Birds are dinosaurs.

My wife is probably bored of hearing me say this. Whenever I am on the topic of birds, or hear someone speaking about the extinction of dinosaurs, my inner pedant takes over and insists I remind her our feathered friends are in fact dinosaurs. Of all the misunderstandings about science, this is the one which gets me the most, and I will take every opportunity to correct the understanding. Even my jigsaw videos cannot escape my pedantry, with the charity choice for my dinosaur puzzle being the Royal Society for the Protection of Birds/Dinosaurs.

The latest opportunity for my ire came in the form of a TV documentary; Dinosaur with Stephen Fry. As I write this post I have the third episode of the series on in the background. I should say it has on the whole included some interesting insights into non-avian (i.e. not birds) dinosaurs. Overall the science (as a layman at least) seems pretty good, for example it is made clear pterosaurs are not dinosaurs but rather cousins, and flowering plants only appear in the Cretaceous, relatively late on in Earth history. Fry even mentions later in the programme that birds are living dinosaurs.

But this admission cannot forgive the unforgivable sin made early in the programme, when Fry claims the Chicxulub asteroid led to the extinction of the dinosaurs. Given I can stick my head out of the window and see/hear a variety of birds flying around my garden, and given birds are dinosaurs, it follows the asteroid hitting the Earth 66 million years ago cannot have wiped out all the dinos.

What’s in a name?

Stephen Fry (or likely his script writer) is far from the only person to make this error, and I am sure it will continue for many, many years to come (but hopefully not 66 million more). Part of the issue I suspect comes from a mis- (or likely lack of-) understanding of how the scientific classification of species works.

More formally known as Taxonomy, this is the scientific attempt to group and classify species to try and develop an understanding of relationships between species and their evolutionary history. The Linnaean system (first developed by Carl Linnaeus) is probably familiar to all you Homo sapiens, introducing two part scientific naming (binomial nomenclature), and grouping species into the likes of Kingdoms, Domains and Phyla which you may remember from school biology classes.

A more modern understanding of classification, which tries to take into account some of the complexities of life which Linnaeus could not have begun to imagine, is called Cladistics. I’m not going to go into the fine details of how cladistics works, or the problems with this system, as it is not important for this post. The basics of what you need to know goes something like this:

• All life on Earth evolved from a common ancestor (the most recent common ancestor of all life, known as LUCA, lived approx. 3.5-3.8 billion years ago).
• When speciation occurs (basically two lines of descent begin to differ so much from each other that they can be considered different species) they start a new branch on the cladogram (a fancy term for a biological family tree)
• While each new branch on the tree will get a new species name, they also keep the classifications which occurred higher up the tree.

It might be helpful to have an example which is not related to biology (at least directly) to make the last point clear. It is likely most people reading this will have the surname of their father (or at least had it at birth). But in your family history there will also be surnames of your mum, grandmas and maternal male ancestors which will have been lost because of the system of naming common in much of Europe and North America.

If we imagine surnames like cladistics, while the names which have been lost are not used day to day, they would still form part of our definition. Alice Archer would also be a Baker, Collins, Davidson and many more surnames besides, all the way back to the very invention of surnames.

There is no question scientifically that birds and dinosaurs shared an ancestor, so if we apply this naming approach to our feathered dino friends, and while we might think birds (or Aves in sciency speak) have evolved into a separate group which are their own grouping, they in fact keep the classification of dinosaur, as well as all the others picked up during their evolutionary history such as reptile, animal etc. Birds are still dinosaurs, or more accurately, Avian Dinosaurs are the only living dinosaurs, with non-Avian Dinosaurs having gone extinct approximately 66 million years ago.

Roast dinosaur dinner?

It might feel like calling birds dinosaurs is pedantry in the extreme, but I think it is an important clarification to make. Yes, birds have evolved significantly in the last 66 million years and would be unrecognisable to the animals we typically think of as Dinosaurs. But, evolutionarily they evolved from a common ancestor, biologically they share a lot of common traits, and cladistically, birds are dinosaurs. Whether this is news to you or confirmation of what you already knew, make sure to remind everyone of the fact the next time you are tucking in to a roast chicken dinner. Leg or breast anyone?!