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One day, 250 years ago
a young teacher named Abraham Trembley
was walking through a field, and he came to a pond ...
... looked in, and there in the water he saw
this thing
it was very little with wavy tentacles on top and a tube-like body
And just to see what would happen
he cut it in half!
Much to his surprise instead of dying on the spot ...
... the animal grew back into two full-sized adults.
So he did it again.
The same thing happened.
And again.
This animal just wouldn't die!
The hydra (that's what its called) has extraordinary powers of regeneration
almost as if its built not to die ever
which is ridiculous because everything dies, we assume.
In science, however, you don't assume - you check!
In the 1990's
a curious young scientist - Daniel Martinez
having heard that hydras go on and on and on
decided to do an experiment.
He gathered a bunch of hydra from a pond in Long Island, NY
put them in some tanks where he could keep an eye on them
and he thought,"Alright, I'm going to wait until I see them die naturally."
and hydra do die - you take 'em out of water
they'll shrivel up
but in a natural environment? Nobody knows.
Daniel waited.
First his hydras had babies.
Then a week passed.
Then months passed.
Meanwhile, Daniel's school year ended.
He got a job out west in California.
Rather than miss the death of his hydras he put them in a cooler
travelled cross country with his brother
and everyday wherever he was
he fed them, washed them, and he waited.
A year passed.
Then two years.
Three years - still no deaths.
Four years out Daniel published a science paper that said hydras apparently never die.
Well, what he really said was:
"Mortality patterns suggest lack of senescence in hydra."
Now you'd think four years is kind of a short term for a claim like this...
I mean, a lot of us are past our fourth birthdays and we still expect to die. But here's the thing:
There's a well known pattern in nature.
The sooner you have babies,
the sooner you die.
If you're a tiny fly you have your babies quickly
after a couple of weeks
and you die ... here, after a couple of months
If you're a huge elephant you wait thirteen years to have your babies, you live for another 40 or 50 years
and then you die right around here.
And this is true across the animal kingdom
except when it comes to hydra.
Remember, hydra have their babies after a couple of days
so they should die after say a month.
But Dan's hydra had lived for four years when he published his paper
and they are still going strong today. They've now lived for more than 8 years.
T hat is 100 times their expected life span.
That's like an elephant living for 5,000 years.
It's like everybody else got the memo that in the end you die
but not the hydra.
So what's going on?
Daniel says - "Here's my theory:"
Most animals -- humans and hydras both --
begin with a cell, a single cell, and they multiply.
In humans, our cells multiply a lot then specialize, age, break down and eventually they wear out
and so we die.
In a hydra, the cells a) don't specialize much
(most hydra cells are embryonic cells,
and embryonic cells, like embryos - they're simple and great at staying young)
So you can watch them here, moving up the tentacles
moving down to the foot
and before they have a chance to get much older
they flake off
to be replaced as you see here by newer cells.
Over four years the hydra replaces all its cells -- its entire body -- over 60 times.
Every cell in the body is completely new every 20 days.
It even looks like a fountain of youth.
For all intents and purposes, Daniel says, these animals are,
and I want to use his word,
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The Animal That Wouldn't Die (w/Robert Krulwich) | SKUNK BEAR

147 Folder Collection
Anbe2623 published on December 30, 2019
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