Big History
When the Goldilocks condition is met (that is, when everything is just right), the universe creates things of growing complexity. The more thresholds one crosses, the more complex the results and the more specific the following threshold. The important thresholds that we need to know are:
|
|
TIMELINE OF DINOSAURS
Dinosaurs lived during the Mesozoic Era (248-65 mya): (left to right)
TRIASSIC PERIOD (248-208 mya)
|
JURASSIC PERIOD (208-146 mya)
|
CRETACEOUS PERIOD (146-65 mya)
|
KT = Cretaceous-Tertiary boundary extinction
The theory of extinction
Why the dinosaurs left us bereft is debated exhaustively. Scientists discovered large amounts of iridium in rock specimens dating to the time of KT extinction and have several theories:
ASTEROID
Iridium is rare on Earth, but is often found on extraterrestrial objects like an asteroid. Theory: an asteroid hit the Earth 65 mya and vaporized, leaving iridium to settle into the ground. Proof:
|
VOLCANIC ACTIVITY
Iridium is rare near Earth's surface, but there are rich stores of it in Earth's core. Theory: a lot of volcanic activity occurred at the time. The volcanic activity would have spread Earth's core's iridium, as well as sunlight-blocking debris, soot and greenhouse gases. Proof:
|
BOTH ASTEROID AND VOLCANIC ACTIVITY TOGETHER
or TWO ASTEROID IMPACTS Proof:
|
It is important to note however, that the extinction of dinosaurs was not an immediate thing. The asteroid/meteorite did not just hit the Earth and all dinosaurs were immediately vaporized. The process of extinction may have took around 200 000 years, which is still a very short amount of time in the geological time scale. This brings up the question on how we can label the dinosaurs' disappearance as having all gone extinct at one time when some dinosaur species must have died out before others did (refer to the timeline of dinosaurs above). We call it an extinction because after the last group of dinosaurs died out, there was not another group of dinosaurs that replaced them, unlike before with the minor extinctions.
The process of extinction would've been gradual. For example, if we were to commit to the theory of a meteor impact, the belief would be that the impact raised a huge cloud of dust that obstructed sunlight and that in turn killed off vegetation, herbivores and then the carnivores that fed on the herbivores. In all theories however, the consequences of the catastrophic event helped influence the eventual extinction of the different lifeforms on Earth at the time.
The process of extinction would've been gradual. For example, if we were to commit to the theory of a meteor impact, the belief would be that the impact raised a huge cloud of dust that obstructed sunlight and that in turn killed off vegetation, herbivores and then the carnivores that fed on the herbivores. In all theories however, the consequences of the catastrophic event helped influence the eventual extinction of the different lifeforms on Earth at the time.
Dinosaurs & human's relationship status: it's complicated
As we know, nature focuses not on perfecting the individual but its DNA. This can be connected to what we know about evolution: populations evolve, not individuals. DNA mutations underwent natural selection, eventually leading to dinosaurs.
And then, approximately 65 million years ago (mya), an asteroid* hit Earth in the Yucatan Peninsula and the resulting environmental changes wiped out the rest of the dinosaurs.
The dinosaur extinction therefore left a niche open for top predators, and our mammalian ancestors began adapting in the goal of taking over that niche- about 10 million years after the KT extinction.
Like we said, complicated.
*the theory of what happened to cause this mass dinosaur extinction is hotly debated. See above for more theories of extinction.
And then, approximately 65 million years ago (mya), an asteroid* hit Earth in the Yucatan Peninsula and the resulting environmental changes wiped out the rest of the dinosaurs.
The dinosaur extinction therefore left a niche open for top predators, and our mammalian ancestors began adapting in the goal of taking over that niche- about 10 million years after the KT extinction.
Like we said, complicated.
*the theory of what happened to cause this mass dinosaur extinction is hotly debated. See above for more theories of extinction.