Bats Killed the Dinosaurs
~ no, I am not trolling ~
TL;DR — This is a testable hypothesis. Unfortunately, the way to test it is: sample Rabies from Bat Caves around the World. Bat Viruses, again. If the Lyssavirus family shows-up as at least 73 Million years old, that is the smoking gun: Veloci-rabies.
The Asteroid
Yes, a giant impact struck us 66 Million years ago. Everything within thousands of miles was hit with a shockwave that squeezed the air with so much pressure that it heated like an oven. Trees burst into toothpicks, and then those toothpicks burst into flames. It was bad.
And, on the opposite side of the globe, the ECHO of that impact whacked a crack into the ocean floor, spewing a field of lava hundreds of miles for THOUSANDS of years. Those are the Deccan Traps, most of southern India.
Those lava-flows in particular were what made the REST of the world apocalyptic. They released sulfur, which dimmed the sun, which reduced evaporation from the oceans, which diminished rainfall, so that plants withered. And when it DID finally rain? It was sulfuric, defoliating and killing microbes and roots. Those dead-dry forest burned. In the fossil record, after we see the micro-diamonds from the Impact, there is only a layer of charcoal. Covering the entire Earth. Everything burned.
So, yeah — that is definitely a good-enough reason for dinos to go extinct!
Yet… it doesn’t do a very good job of explaining all the weird details that we see, leading-up-to and after the extinction of Dinosaurs. There are THREE Mysteries, in particular. And all three of those Mysteries can be answered using existing models in textbooks, IF we hypothesize ONE thing:
“The Ancestors of Bats were being Eaten by the Ancestors of Birds when the Bats began evolving Rabies, 73 Million Years Ago.”
THAT is what I hypothesize. Look at how we can put all the puzzle-pieces into a coherent whole:
Bats Back Then?!
We do not see a lot of bats in the fossil record, in general. Their bones are tiny, and they rarely fall into mud-puddles, which are our only way to find them. Yet! Fully 52 Million years ago, 80% of the way to Dino-days, there were ALREADY bats across ALL the major Continents. And those bats were fully-formed modern-bat shaped. They even had echo-location sockets in their skull.
So, it is not fanciful or strange to suppose that the proto-bat ancestors, some sort of flying-squirrel morsel, were being eaten by Archaeopteryx kin some 73 Million years ago. That would make sense, because the bird-dino was selecting for tasty fliers, and mammals often evolve into tree-gliders. Sadly, those proto-bats would have been tiny compared to Archaeopteryx, and most of them got gnashed in its teeth, so we may never find Bat fossils from that time-period.
However, each colony of Bat that we have observed, in all historical records, has at least THREE variants of Lyssavirus circulating amongst them. Ick! So, by collecting all the Lyssavirus variants from each region, we can use Mutation-Rates to estimate the age of that Family of Viruses! Ah-hah! No Bat-fossils, but Virus-fossil! I expect it to be at least 73 Million years old, because that solves the First Mystery:
When to Die?
You would think that, if the Impact was the cause of Dinosaur extinctions, then the number of species would be roughly steady for millions of years? And then, only after the impact, you would see a collapse in the number of species, right? Yeah, I thought that too.
But that isn’t what we see in the fossil record. For Seven MILLION years BEFORE the Asteroid, we find wave upon wave of dinosaur-species dying out. Dozens of species going extinct, region by region. Were they just excited about the Asteroid, seven million years hence, and they couldn’t wait? It’s a Mystery, because those regions saw no change in climate, no new predators or competitors. They seemed like stable ecologies.
Then, why would so many species of dino die there, long before the clod got lobbed? Answer: Rabies was BECOMING lethal.
We see this pattern in diseases: “A Disease does NOT want to kill you. It would prefer to mutate its way into obscurity, unknown, so that it has a chance to spread to everyone! Your own body is what creates the deadly reaction to a virus, so that your death SAVES all the other members of your species from a similar infection.”
Yet, some diseases seem to be intentionally vicious! Why would they seek that, when it guarantees they have little time to spread? Answer! Vermin.
Little rodents don’t have a lot of ways to defend themselves. So they keep resorting to germ warfare! In Mongolia, the Marmot is a Terrier-sized Gerbil, and it is the native reservoir for Bubonic Plague. Each Marmot may have a 1% of suffering the Plague in a given year. That’s negligible. Yet, an Eagle or Wolf who hopes to eat Marmot each day will inevitably catch the Plague! These little fur-monsters kill their predators with sick.
Same story, different desert: in the Atlas Mountains of Morocco, a tiny rodent is the native reservoir of transmissible Leprosy. Too cute!
Bats did the exact same thing, making Rabies so insanely horrible that it is 100% LETHAL. They had to work their way up-to that lethality, however. If Archaeopteryx was the one encouraging them to do that, then I call Bingo. Look at that process:
Food Fight
Proto-Bats, 74 Million BCE, are sick from proto-rabies. It doesn’t kill you. But Archaeopteryx gets sick from it, too. And so, the sicker that proto-rabies gets you, the more Archaeopteryx suffers. Bats start selecting, accidentally, for “who can survive the nastier variant of rabies, guys?”
While Bats ratchet-up the fatality-rate of rabies, those Archaeopteryx are desperately trying to catch-up! Pre-bird is evolving RABIES RESISTANCE. That is the Second Mystery:
“Even though Birds can be infected by rabies, and it can circulate in their blood for months… they are generally resistant to it. It is almost never lethal. The ONLY other creatures who are BOTH compatible for rabies AND resistant to it are Bats and Rodents.”
Dogs have had many more encounters with rabid bats than PIGEONS. Wtf don’t dogs have rabies-resistance? Why would all birds have residual rabies resistance, unless Archaeopteryx was eating Bats WHEN they were evolving Rabies Lethality? Archaeopteryx must have been eating them while that Lethality rose; if a predator tried to eat bats AFTER Lethality was 100%, then they never get a chance to evolve resistance. They died every time! (see: Dogs)
Second Mystery down.
The Third Mystery
We want a ‘decision-tree’ were we ask a series of questions, and the answers sort every critter into a ‘bucket’ of Survivors or Extinctions. Let's work through the examples:
Semi-aquatic and aquatic creatures did NOT go extinct. Their populations suffered somewhat, due to the sulfur changing the ocean’s pH a bit. It wasn’t really that bad. So, we still have turtles, crocodiles, sharks, fish, amphibians. They were basically fine. “Did you spend at least part of your life in the water? If ‘Yes,’ then you did NOT go extinct!” It’s kinda like a game-show quiz, Survivor Planet.
Meanwhile, the BIG land-beasts, all of them dino-kind… yeah. Big animals are always the most fragile niches. As soon as the environment is disrupted — even just a little! — then they plop on the ground and a tiny violin starts to play. “Are you a LARGE land animal? If ‘Yes,’ we’re sorry — you are EXTINCT!” The crowd swoons ‘awwww…’ in sympathetic pain as you trundle off the stage.
But here comes that Mystery Question: “What question would I need to ask, to explain WHY the Birds, Bats, and Rodents survived… while NONE of the SMALL dinos made it?” Totally Meta-question. It’s kinda tricky:
There were actually thousands of species of tiny-dino. Triceratops that only grew to the size of a baby hippo! After the forest all burned, where was Archaeopteryx living, that they were able to survive? While EVERY ground-dino died? And if it was tough ‘being on the ground’ then how come the Rodents made it? There isn’t a clear question we can ask, to divide these groups into Survivor/Extinction…
…except for Rabies.
“Are you resistant to Rabies? If ‘No,’ then you are Extinct!”
That was it. That was the question that decided who made it and who didn’t. Sure, the Asteroid was Apocalypse #1, which made things bad. But, if you ALSO had to grapple with Apocalypse #2, Veloci-rabies? That was a combo-attack that NONE of those Thousands of toy-dinos could handle. Otherwise, some random island or rainy mountain would have kept their reserve of mini-dinos, who would then re-populate, re-inflate. We would have had big dinos again, in only a few Million years!
Bats are to blame.
And, let that lesson resonate: “The greatest weapon in the History of Life… was a Wrath of Weakness. The spread of Weakness defeats the greatest Strength.”
