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When Does It Make Sense To Kill Your Sibling? - Video học tiếng Anh
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When Does It Make Sense To Kill Your Sibling?
When Does It Make Sense To Kill Your Sibling?
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When a baby sand tiger shark hatches
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from its egg, it finds itself trapped
0:04
inside its mom's uterus, [music] forced
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to eat its siblings or to be eaten. It's
0:09
super weird, but pitting your kids
0:11
against each other [music] can actually
0:13
sometimes be a winning parental
0:15
strategy. Hi, I'm Cameron and this is
0:18
Minute Earth.
0:20
Minute Earth. Is that copyrighted? It's
0:23
common for siblings to fight for food,
0:25
for attention, or to establish
0:27
dominance. And in many cases, parents
0:30
step in to make sure the rivalry doesn't
0:32
go too far. Not just out of, you know,
0:34
love and whatnot, but because the more
0:36
babies you have, the more genes you get
0:38
to pass on. In some species, though,
0:40
parents actually promote a fight to the
0:43
death. Take black [music] eagles for
0:45
example. A black eagle pair will always
0:47
lay two eggs per nest, despite the
0:49
[music] fact that there's never enough
0:51
food around to actually feed two hungry
0:53
eagle chicks. This scenario forces the
0:55
chicks to fight for survival. It is
0:58
brutal, but [music] let's think about it
0:59
for a second. If the parents had just
1:01
laid one egg, they'd still need to spend
1:04
the same amount of time and energy
1:05
building the nest, defending it from
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intruders and predators, and incubating
1:09
the egg. But sometimes that one egg
1:12
might not hatch, or the resulting chick
1:14
might get sick and die. In those cases,
1:16
all that work is for nothing. So, as
1:18
long as the parents have to go to all of
1:20
that trouble, it makes sense to lay two
1:22
eggs so that one can serve as a backup.
1:24
If both eggs are healthy, the parents
1:26
only have to take care of the stronger,
1:28
healthier one that emerges victorious
1:30
[music]
1:30
from the thundome. And black eagles
1:33
aren't alone in this. Some other birds
1:35
and insect species also bear extra
1:37
offspring as an insurance policy, only
1:39
to pit the survivors against each other.
1:41
But the sand tiger shark takes sibling
1:44
rivalry to an extreme. A mama [music]
1:46
shark can incubate as many as 20 eggs at
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a time in her uterus. So theoretically,
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she could birth 20 babies at once. But
1:53
all of those babies would be way too
1:55
small to thrive. They couldn't hunt or
1:57
escape predators. So instead, female
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sand tiger sharks have evolved
2:00
reproductive systems that trap their
2:02
babies inside after hatching, forcing
2:04
them to snack on their own siblings in
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order to survive. And after several
2:08
months, the sole survivor is born. It's
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now a meter long with a full mouth of
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razor teeth and ready to take on the
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open ocean. In contrast to such brutal
2:17
beginnings, isn't it nice that our human
2:20
parents mostly just want us to get
2:22
along?
2:26
This video is brought to you by [music]
2:28
you. That's because you guys have been
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buying our awesome new animal taxonomy
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posters by the buttload, [music]
2:34
which I found out recently is actually a
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technical term. Old English beer casks
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were called butts. So, a buttload means
2:41
something like 500 L, which equals
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roughly a thousand poster tubes. [music]
2:46
Our most popular poster isn't about
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head over to dftba.com/minuteearth.
3:04
That's dftba.com/mminar.
3:07
Thanks a buttload.
