We're sure you've heard the whole 'dinosaurs were wiped out by a meteor' theory that is often presented as fact. Very dramatic! But did you know that dinosaurs didn't actually go extinct? At least not all of them. In fact, there are around 10,000 species of dinosaur still present on earth today.
Birds.
The dinosaur species that survived continued to breed and evolve over the epochs, leading to the beautifully colourful and diverse group of animals we now fondly know as the birds. So, yep, birds are dinosaurs! It's not that hard to believe when you compare their skeletons to those of theropod dinosaurs (carnivorous dinosaurs that usually walked on two legs, like velociraptors). The bird-like dinosaur Archaeopteryx has long been considered a stepping stone between non-avian dinosaurs and birds, but scientists now know that dinosaurs developed bird-like characteristics long before Archaeopteryx was around.
So the dinosaurs didn't go extinct completely - there's a fun fact to annoy your friends with!
Of course, many species of dinosaurs were wiped out in the mass extinction event, but the reality is that no one actually knows for sure what happened to them.
Scientists have three main theories.
THEORY #1: CATASTROPHIC EXTRATERRESTRIAL (AKA, the meteor)
Perhaps the most well-known of all the theories, this was proposed by Alvarez in 1990. This theory suggests that the extinction event was incredibly quick and was cause by a meteor striking the planet's surface.
THEORY #2: CATASTROPHIC VOLCANOLOGICAL (AKA, volcanic eruptions)
This theory, proposed by Courtillot in 1990, blamed volcanic eruptions for the extinction of the dinosaurs. This would have also been a quick event, though not quite as instantaneous as the meteor. The Deccan Traps in India were thought to have been the source of this volcanic activity.
THEORY #3: GRADUALIST ECOLOGICAL SUCCESSION (AKA, climate change)
The last theory was proposed by Sloan et al. in 1986, and should sound familiar to us in the modern age - the theory was climate change. The subtropical, lush environment that the dinosaurs were adapted to became highly seasonal, temperate and coniferous. This event would have taken much longer than the previous two theories - about half a million years, in fact!
None of these theories have been definitively proven yet, so we don't have a solid answer for you at the moment. But what do we know?
Well, here are some fun facts about the extinction event that may help you form your own opinion about these three theories:
The extinction had no clear pattern - it wasn’t size-, habitat- or region-specific
Lots of species had already been in decline, or died out (could this lend credence to theory #3?)
The sample sizes are too small for us to give a real answer (there are too few fossils. Maybe when we find more, things will become clearer!)
We know that the Deccan Traps were erupting around this time. These eruptions could have caused a variety of atmospheric disturbance with potentially global consequences, but we cannot prove that they were responsible (or solely responsible) for the extinction event.
A layer of Iridium was found to cover the earth 65 million years ago. This could only have been caused by extraterrestrial material (e.g. a vaporised meteor) or from the earth’s core (e.g. a volcanic eruption).
The Chicxulub crater in Mexico is said to be the sight of the meteor. The famous one. The maybe-dinosaur-killing one.
So... no solid conclusions. It's a head scratcher! What do you think? Could it have been a combination of all the above that wiped out the dinosaurs?
Thanks for reading and remember to always keep learning!
-- Charlie and Tiana
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