They Ruled The Earth Before Us

The Age of Reptiles ended because it had gone on long enough and it was all a mistake in the first place.

- Will Cuppy, How To Become Extinct (1941)

I haven't read the book nor did I hear about it until a week ago when I was surfing away on the World Wide Web and chanced upon this quote from the book (I have to admit - the title is quite eye-catching and I might be found reading it in the near future). I also do not know the context in which this sentence is used within the book but I do disagree with Mr. Cuppy's view here. For those less proficient in the Geologic Time Scale, the Age of Reptiles was the Mesozoic era which started around 251 million years ago and ended nearly 65 million years ago. It is so called because of the ridiculous dominance that the reptiles enjoyed over Earth, especially the most popular among their family, the dinosaurs for the whole duration of this era. These 'terrible lizards' (the literal meaning of dinosaur in Greek) were the undisputed rulers of this planet for nearly 186 million years. In comparison, we, Homo sapiens, have been around for just about 2,50,000 years out of which nearly half that time was spent solely in the continent of Africa. I don't think we have earned the right. So, what unique characteristics did the dinosaurs possess that helped them lord over the lands for that amount of time? How were they different from their contemporaries?

The Age of Reptiles, a 34 m mural depicting the period when reptiles were the dominant creatures on the earth, painted by Rudolph Franz Zallinger.(for full image: http://donglutsdinosaurs.com/wp-content/uploads/2012/02/Age-of-Reptiles-1000x302.jpg

Numerous theories have been put forth to explain this long reign of the dinosaurs. Ranging from post-apocalyptic survivors to sheer luck, these theories cover almost all the ways that they could have adopted to pull through some hard times. I wish I had the time to discuss all of them.

The first dinosaurs appear in the fossil record some time after the largest mass extinction in the Earth’s history at the end of the Permian period. Known as the ‘Great Dying’, the Permian extinction event decimated most of the existing reptile and amphibian groups. A large part of the ecosystems and various kinds of ecological niches were up for grabs after being vacated in such dramatic fashion. According to studies, the dinosaurs formed a part of the group that led the recovery of these ecosystems in the Triassic period that followed. However, in the early years of their evolution, dinosaurs were one of subordinate groups and largely remained under the radar as other reptile groups diversified. This would remain unchanged throughout the Triassic and, as luck would have it, another major mass extinction event occurred, this time at the boundary of the Triassic and Jurassic period. This event is attributed to have accelerated the rise of the dinosaurs (who survived) to the top by getting rid of the competition.

It was not just mass extinction events that helped the dinosaurs on their way. Evolution played its role too. A variety of unique features are shared by all dinosaurs that set them apart from any other vertebrates and more importantly, the other reptile groups. Anatomically, there were two changes that are of particular importance, providing an important evolutionary advantage to early predatory dinosaurs. Unlike their contemporaries and predecessors, the dinosaurs had an upright stance. This was aided by strong knee and ankle joints which were firmly attached to the shin bones with a hinge joint at both ends. This vastly improved their speed and agility and gave them that extra edge over other slower organisms.

Dinosaurs were odd physiologically as well. You see, most reptiles today are ectotherms i.e. they are cold blooded and need external sources to maintain their body temperature. However, our illustrious giant lizards were allegedly endotherms (warm blooded) and there’s proof. Their growth rate was phenomenal when compared to their reptilian brethren and it is comparable to living warm blooded animals. Their bone textures (irregular as in mammals as compared to the neat parallel rows of typical reptiles) and oxygen isotope ratios of extremities (¹⁶O and ¹⁸O ratios depend on temperature) also point to the same conclusion – dinosaurs maintained their own body temperature.

I really want to talk more on this topic but the other reasons are way above my level and I wouldn't be able to do justice to those theories (also, I can't risk losing my readers, can I?). I would be glad if someone has something to contribute to this though. So, I will bring this post to an end with a cheesy and dramatic paragraph.

It is truly remarkable that this group of animals, nearly non-existent at the start of the Triassic, could go on to leave such an everlasting impact on the planet’s history so much so that young human beings would be fascinated when a movie featuring them would be made nearly 65 million years after their demise. We may never learn the reason behind this dominance but one thing is for sure – it was not a mistake.