Back when I was a kid, paleontology was simple. Life had evolved from one-celled creatures to fish to lizards to dinosaurs to mammals and finally to Tory-voting, club-going Englishmen – all in a giant and wonderful ‘advance’, a relentless march of ‘progress’ during which each new form automatically doomed the last to extinction.
Today we’ve learned that things weren’t so cut and dried. Take the death of the dinosaurs, for instance. Back in the nineteenth century, the best explanation as to why there (supposedly) weren’t any around today was that they’d been too slow and stupid. Mammals had out-competed them in a kind of evolutionary market contest. The very term ‘dinosaur’ became a perjorative – a synonym for somebody who couldn’t adapt to change.
That idea persisted for a remarkably long time. Even after evidence emerged in the late twentieth century of a massive metoric or cometary impact on the Yucatan peninsula, precisely at the time when the dinosaurs allegedly disappeared, it took nearly a generation for the notion of a global cataclysm to be fully accepted.
Even then, there were debates. Why did it just kill dinosaurs? And what about the Deccan Traps, a vast field of volcanic outpouring dated to the same period, which almost certainly invoked climate change of its own?
In many ways these questions were themselves incomplete – products of the patchy information of the time. The picture today is of a more complex pattern of change at the end of the Cretaceous. Earth’s biota was already under stress before the Yucatan ‘dino-killer’ blow, also known as the ‘K-T event’. And when that hit, the cataclysm killed off a lot of Earth’s biodiversity, plant and animal alike. Forests were burned and poisoned to nothing, leaving the emerging Paleocene-era world with many more grasslands than before. Dinosaurs were not especially singled out, but they happened to be the largest group, with some of the biggest creatures among them, so they also took the biggest hit.
The thing is that by current classifications, dinosaurs actually survived. These days birds (aves) are defined as a family of flying dinosaurs that lived alongside the others at the time. That’s right – by current thinking, birds didn’t evolve from dinosaurs. They are dinosaurs. And after the K-T event, they swiftly diversified on four of the five main continental areas into which Earth was divided at the time. New types such as Gastornis flourished – peaking in the Diatryma, which which was basically the T-rex of its day: bipedal, armless (wingless) and with a monster jaw, rimmed with a bony beak. This was the apex predator of the Paleocene period that followed the Cretaceous. Birds, of course, continued to spread and flourish to the point where, by current biological classification, there are more dinosaur species alive today than we know of in the Cretaceous.
Mammals weren’t automatically assured of a future as the Paleocene unfolded, either. After the K-T event, many species remained small and largely nocturnal – especially on continents where the predatory birds flourished. Elsewhere, there were virtually no mammals at all. New Zealand, for instance – then a huge low land mass on the edge of Gondwanaland – retained its residual Cretaceous biota of birds and plants. The only native mammal was a species of bat. New Zealand basically kept its dinosaur biology, unmolested by mammalian diversity, right up until humans arrived in the mid-late thirteenth century (yup, my country really was the ‘lost world’). Australia, meanwhile became a land of marsupials and home to the platypus, the last monotremes.
Only in Paleocene-era Asia – where predatory aves (dinosaurs!) weren’t flourishing – was there any diversity of placental mammals – meaning, the type that dominates the world today, including us. Even then, the mammal ‘revolution’ didn’t really happen until five or more million years after the end of the Cretaceous, in the Eocene period proper. There is evidence of another climate-changing hammer blow from space helping the process, along with climate change that warmed the world and opened up access from Asia to the rest of the world when ice barriers melted.
All this is still being disentangled by palaeontologists, but it’s a fascinating view of the way things were. A lot of it is mediated by the way we classify things. By identifying birds (‘aves’) as a specialised dinosaur – which is logical, when you look at their origins – the whole idea of ‘dinosaurs becoming extinct’ goes out the window, just by changing the categories into which life is divided.
What’s more, the old notion of dinosaurs being doomed to extinction because they were ill-adapted is revealed for the silliness it always was. Sure, they did things differently from mammals, but they dominated mammals – utterly – for over 150 million years. And probably would still be doing so, if it hadn’t been for that meteor.
For me the coolest part of the new science is that dinosaurs don’t need Hollywood SFX to realise – there are a lot of them still about today. I like mine pressure-cooked and served with eleven secret herbs and spices. Do you?
Copyright © Matthew Wright 2017