Dinosaurs are a subject that has been close to my heart ever since I saw the first Jurassic Park movie. Amazingly, it has been 27 years since that movie came out, and probably 15 years since I first witnessed the trilogy of awe-inspiring reptiles brought to life. That is why I know that since it took me until a University course to understand the timeline of evolution properly that there are a lot of people out there with the same misconceptions that I had. This subject could be an entire book, which it probably already is, so I will try to keep it concise.
First and foremost, mammals and birds lived at the same time as the dinosaurs, not after the dinosaurs. It is misleading when we are shown iconic pictures of evolutionary trees showing birds coming from Archaeopteryx (currently disputed) and the other bipedal carnivores in a straight line. The trees are there to show the steps and order, which are generally accurate until new discoveries are made. The thing the evolutionary trees (cladograms usually) can’t easily show you are the time periods they lived in. Dinosaurs first walked the earth in the Triassic period (251 – 201 Million years ago), then continued through the Jurassic, and ended at the Late Cretaceous when a meteor struck the Gulf of Mexico and caused the fifth mass extinction 66 million years ago. Mammals evolved from reptiles, specifically Therapsids which were mammal-like reptiles, in the Late Triassic period (210 million years ago). This means mammals had existed for about 144 million years before the meteor ever struck the earth. Birds are a similar story since the first birds, and I mean the ones that could really fly and not the first step evolving from dinosaurs, were in the air in the Cretaceous period 145-66 million years ago. The origin of the bird is still disputed, and they still had teeth at this time, but there were undoubtedly birds flying around for millions of years alongside Pterosaurs and over the heads of dinosaurs.
The second misconception is one that scientists, specifically taxonomists, have been battling for years: just because the animal lived before 66 million years ago does not make it a dinosaur. Dinosaurs are a type of reptile that had an upright posture, which means their legs and feet were under their body and not out to the side like a lizard. There are other features as well but that is the easiest one to think about to address this misunderstanding. Crocodilians, turtles, lizards, and even snakes existed alongside the dinosaurs but weren’t dinosaurs. Flying reptiles like Pterosaurs were closely related to dinosaurs but only had a semi-upright posture, and marine reptiles like Plesiosaurs roamed the oceans in the Late Triassic period but had ancestors in the water before dinosaurs ever walked the earth. That being said, birds are still descendants of dinosaurs, just not in the strict timeline some people may assume.
The last idea I want to address is that prehistoric evolution is set in stone (pun intended). The fact is that evolution on a whole is a giant puzzle that is missing a lot of pieces. In the current world, we are able to at least use advanced genetic techniques to help bring detail to the picture, but you can’t use genetic analysis on a rock. Every day there are scientists working to uncover new fossils, categorize them, and even re-categorize the ones already found to make a better picture. New fossils are found and techniques for analyzing fossils are consistently being developed which may lead to changes in our understanding of how things are related. For example, classic dinosaur categorization has Sauropods and Therapods (the long-necked dinosaurs and two-legged carnivores) closely related and then all other dinosaurs on a different branch based on hip structure. There is a hypothesis from 2017 that suggests Therapods should be grouped with all other dinosaurs and Sauropods are the ones that aren’t like the others, meaning that, just like our idea of how many planets are in the solar system, we may have to rethink dinosaur relationships as well.
Science, especially science involving analyzing the past, is an ever-evolving process. I wrote this to present information that people may not have known and to allow them to change their understanding if they wanted to. Change isn’t a bad thing and is at the core of science. Science is about the pursuit of knowledge and the understanding of how things work. Once upon a time, there was the idea that everything consisted of the four elements and now we know there are 118 elements and that radiation can help heal but working closely with radioactive isotopes for a long time isn’t good for your health. While it means that the learning is never done, I for one look forward to the new discoveries, realizations, and advancements to come from scientists digging deeper.
Alternate dinosaur lineage https://www.nature.com/articles/nature21700