Dinosaur Luck

We humans tend to look with fascination upon the dinosaurs; being those formidable, scary beasts who once roamed ancient Earth’s surface (as well as modern film thrillers), but then suddenly became extinct, some 65 million years ago. They had their time, but just couldn’t last, we think. In fact, they had the bad luck of being susceptible to a meteorite that crashed into the Yucatan Peninsula.

In the aftermath of the impact, the dinosaurs disappeared, and little mammals—previously hovering on the fringes, cowering from the lizard monsters—prospered. Some of those mammals were our ancestors. Had the meteorite missed Earth, evolution would have played out a different story. If so, today’s most dominant species could be an intelligent Tyrannosaurus rex (with opposable thumbs, of course), rather than Homo sapiens. Bad luck, dinosaurs; good luck, quadrupedal and bipedal mammals.

But there’s more to the story than that. If we look even further back in time—some 200 million years and more—there were two great families of critters who competed to dominate the Earth: dinosaurs and crocodile ancestors. Both were big bruisers, both were prospering, both were diverse (fostering myriad species), both lived in similar places and filled similar ecological niches, and both were evolving at the same rate (fast). The future looked great for them. Something happened, however, that allowed the dinosaurs to shove aside the ancient crocs and go on to dominate the terrestrial ecosystem for over 100 million years, evolving into a fantastic variety of critters, while the crocs muddled along as smaller creatures, mostly hiding underwater.

What allowed the dinos to triumph, even when the croc ancestors initially had them outnumbered? Why didn’t the crocs have the dinos on the ropes? Until recently, scientists have assumed—given evolution’s survival-of-the-fittest depiction—that dinosaurs possessed some characteristic that helped them out-compete their crocodile competitors. It is not clear what that advantage may have been. The issue is under ongoing investigation.

One recently published scientific paper, however, suggests that the dinos did not possess any superior quality that the crocs lacked… it may have simply been pure luck. They dodged a bullet that the crocs caught. That’s fascinating!

Then a crashing meteorite some 65 million years ago brought the dinosaurs bad luck. They were kicked off the evolutionary mountain and we mammals replaced them. Prior to that—some 200 million years ago—another random incident may have smiled upon the dinos, displacing their competitors. A meteorite? A croc-specific disease? If so, it was the dinos’ good luck back then. Were it not for chance at that ancient time, we mammalian humans again might never have come about. Smart crocs (with opposable thumbs, of course) could have been the long time winners.

So, before we get too big a head about our dominance over today’s Earth, two facts should bring us humans a little humility: (1) we wouldn’t be here if it wasn’t for a string of favorable coincidences (our good luck) and (2) the extinct crocs and dinos flourished for a period a thousand times longer than we have been around. We can’t claim true bragging rights for at least another few million years.