嘿 进化之神 我们为何没有巨型宠物？
Hey, evolution, why aren’t giant pets a thing yet, huh?
If dinosaurs grew enough to fill a whole room, why can’t I have a big red dog the size
of a house?
Hey everyone, Lissate here for DNews.
Part of what captures our imagination about dinosaurs is just how huge some of them were.
The American Museum of Natural History has a cast of a titanosaur that’s so big it
doesn’t completely fit in the dinosaur wing.
The 37 meter (122 foot) long behemoth’s head has to poke out towards the elevators.
It’s got individual bones bigger than people.
The very name of the group of dinosaurs it belongs to has the word TITAN in it.
But when you start to consider the size of some of these extinct species, it can make
you a philoso-raptor.
“Why isn’t any land animal this huge today?” you may wonder…
Well you’re not the only one. Lucky for us
Paleontologists have been debating the same question, and they’ve come up with a number
of different factors that could explain why some giant reptiles of yesteryear dwarf modern
It’s important to keep in mind that dinosaurs lived a long time ago.
No doubt, right?
But what you may not realize is, before the dinosaurs were wiped out they were living
on a completely different kind of earth than we live in today.
Dinosaurs actually started coming onto the scene about 230 million years before present.
During their existence, CO2 levels were all over the place.
Estimates vary but (for some stretches) there could have been 3 to 5 times as much carbon
dioxide in the atmosphere as there is today.
This means the world as a whole was a lot hotter even if at higher latitudes
而且 在中生代初期 大陆还是一整块的
And, because at the beginning of the Mesozoic Era, all land was clumped together in Pangea,
the ocean didn’t have as much of a cooling effect on the supercontinent.
This would make the planet a more hospitable place for, I don’t know, giant cold-blooded
reptiles that wouldn’t have to waste energy maintaining body heat.
See… another reason to worry about global warming.
别坐车啦 改骑单车吧 除非你想在后视镜里看到霸王龙
Get out of that SUV and onto a bike unless you want to see T-rexes in your sideview mirror.
It may comfort you to know that paleontologists aren’t all in agreement on the exact amount
the atmosphere’s impacted dinosaur size.
It could have had no effect at all, and whether or not dinosaurs were all cold-blooded
is even up for debate.
Their size could have also been driven by an abundance of food.
All that CO2 meant there was likely more vegetation.
If there’s plentiful vegetation, then large herbivores can thrive.
They’d actually benefit from being bigger because longer intestines would be better
at breaking down plant matter and extracting its nutrients.
然后 他们可以花更少的时间咀嚼 花更多的时间大快朵颐
Then they could spend less time chewing, and more time stuffing green down their giant gullets
Also if the herbivores grew larger, then they were harder for predators to take down.
Until the predators got bigger.
Then the herbivores would get bigger.
Then the predators would get bigger again.
You see where this is going and it’s not good
But there is an upper limit to size, because of physical constraints — like gravity.
Part of the reason whales can get so huge is because the ocean supports their weight.
On land, a similar sized animal would crush itself
without some clever life hacks.
Huge dinosaurs like sauropods had lightweight bones compared to mammals
because theirs were hollow.
Dinosaurs also had another advantage over mammals, when it comes to living large
They laid eggs.
If they had to give birth to live young, it would be much harder for them to have large
比如 大象妊娠期长达22个月 由于
For instance, elephants have 22 month gestation periods… they can’t breed very quickly because
live-birth is so resource intensive — and it requires a large birth canal.
Interestingly, these traits of hollow bones and egg-laying have come in handy in a very
different way today: they make it possible for the descendants of dinosaurs to fly.
That’s right, I’m talking about birds.
Why they were so big is still a matter of debate, and hopefully we’ll find more research out there
But at the moment they’re trying to put together a hundred-million-year-old
puzzle with a lot of missing pieces.
Want to learn more on huge salt water creatures that are alive today
Don’t miss new episodes of River Monsters every Thursday at 9/8c on Animal Planet!
Seriously, though, dinosaurs equal birds.
Here’s a video all about their gradual shift from ferocious predators to feathered peckers.
Separate research also published in Science last month theorizes that
all dinosaurs had feathers.
Some were more primitive like hairs or bristles,
while others were soft and downy like modern Birds
So are you glad giant reptiles no longer run amok,
or would you want a pet raptor?
Share your thoughts in the comments and remember to subscribe to DNews,
so you never miss an episode.
Thanks for watching, guys.
嘿 进化之神 我们为何没有巨型宠物？