Why do animals have such different lifespans? - Joao Pedro de Magalhaes
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0:08 - 0:11For the microscopic lab worm, C. elegans
-
0:11 - 0:15life equates to just
a few short weeks on Earth. -
0:15 - 0:20Compare that with the tortoise,
which can age to more than 100 years. -
0:20 - 0:24Mice and rats reach the end of their lives
after just four years, -
0:24 - 0:28while for the bowhead whale,
Earth's longest-lived mammal, -
0:28 - 0:32death can come after 200.
-
0:32 - 0:33Like most living things,
-
0:33 - 0:38the vast majority of animals gradually
degenerate after reaching sexual maturity -
0:38 - 0:41in the process known as aging.
-
0:41 - 0:44But what does it really mean to age?
-
0:44 - 0:48The drivers behind this process are varied
and complicated, -
0:48 - 0:53but aging is ultimately
caused by cell death and dysfunction. -
0:53 - 0:56When we're young,
we constantly regenerate cells -
0:56 - 0:59in order to replace dead and dying ones.
-
0:59 - 1:02But as we age, this process slows down.
-
1:02 - 1:07In addition, older cells don't perform
their functions as well as young ones. -
1:07 - 1:10That makes our bodies go into a decline,
-
1:10 - 1:13which eventually results
in disease and death. -
1:13 - 1:16But if that's consistently true,
-
1:16 - 1:21why the huge variance in aging patterns
and lifespan within the animal kingdom? -
1:21 - 1:24The answer lies in several factors,
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1:24 - 1:25including environment
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1:25 - 1:27and body size.
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1:27 - 1:31These can place powerful evolutionary
pressures on animals to adapt, -
1:31 - 1:36which in turn makes the aging process
different across species. -
1:36 - 1:40Consider the cold depths of the Atlantic
and Arctic Seas, -
1:40 - 1:43where Greenland sharks can live
to over 400 years, -
1:43 - 1:48and the Arctic clam known as the quahog
can live up to 500. -
1:48 - 1:51Perhaps the most impressive of these
ocean-dwelling ancients -
1:51 - 1:54is the Antarctic glass sponge,
-
1:54 - 1:58which can survive over 10,000 years
in frigid waters. -
1:58 - 2:04In cold environments like these,
heartbeats and metabolic rates slow down. -
2:04 - 2:09Researchers theorize that this also
causes a slowing of the aging process. -
2:09 - 2:13In this way, the environment
shapes longevity. -
2:13 - 2:16When it comes to size,
it's often, but not always, -
2:16 - 2:21the case that larger species have a longer
lifespan than smaller ones. -
2:21 - 2:24For instance, an elephant or whale
will live much longer -
2:24 - 2:26than a mouse, rat, or vole,
-
2:26 - 2:31which in turn have years on flies
and worms. -
2:31 - 2:34Some small animals, like worms and flies,
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2:34 - 2:38are also limited by the mechanics
of their cell division. -
2:38 - 2:42They're mostly made up of cells that can't
divide and be replaced when damaged, -
2:42 - 2:45so their bodies expire more quickly.
-
2:45 - 2:49And size is a powerful evolutionary driver
in animals. -
2:49 - 2:52Smaller creatures are more prone
to predators. -
2:52 - 2:57A mouse, for instance, can hardly expect
to survive more than a year in the wild. -
2:57 - 3:01So, it has evolved to grow and reproduce
more rapidly, -
3:01 - 3:06like an evolutionary defense mechanism
against its shorter lifespan. -
3:06 - 3:10Larger animals, by contrast, are better
at fending off predators, -
3:10 - 3:13and so they have the luxury of time
to grow to large sizes -
3:13 - 3:16and reproduce multiple times
during their lives. -
3:16 - 3:23Exceptions to the size rule include bats,
birds, moles, and turtles, -
3:23 - 3:26but in each case, these animals have other
adaptations -
3:26 - 3:29that allow them to escape predators.
-
3:29 - 3:33But there are still cases where animals
with similar defining features, -
3:33 - 3:35like size and habitat,
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3:35 - 3:38age at completely different rates.
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3:38 - 3:40In these cases, genetic differences,
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3:40 - 3:43like how each organism's cells
respond to threats, -
3:43 - 3:48often account for the discrepancies
in longevity. -
3:48 - 3:50So it's the combination
of all these factors -
3:50 - 3:53playing out to differing degrees
in different animals -
3:53 - 3:58that explains the variability we see
in the animal kingdom. -
3:58 - 4:00So what about us?
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4:00 - 4:04Humans currently have
an average life expectancy of 71 years, -
4:04 - 4:09meaning that we're not even close to being
the longest living inhabitants on Earth. -
4:09 - 4:13But we are very good at increasing
our life expectancy. -
4:13 - 4:18In the early 1900s, humans only lived
an average of 50 years. -
4:18 - 4:22Since then, we've learned to adapt
by managing many of the factors -
4:22 - 4:23that cause deaths,
-
4:23 - 4:26like environmental exposure
and nutrition. -
4:26 - 4:29This, and other increases
in life expectancy -
4:29 - 4:32make us possibly the only species
on Earth -
4:32 - 4:35to take control over our natural fate.
- Title:
- Why do animals have such different lifespans? - Joao Pedro de Magalhaes
- Speaker:
- Joao Pedro de Magalhaes
- Description:
-
View full lesson: http://ed.ted.com/lessons/why-do-animals-have-such-different-lifespans-joao-pedro-de-magalhaes
For the microscopic lab worm C. elegans, life equates to just a few short weeks on Earth. The bowhead whale, on the other hand, can live over two hundred years. Why are these lifespans so different? And what does it really mean to ‘age' anyway? Joao Pedro de Magalhaes explains why the pace of aging varies greatly across animals.
Lesson by Joao Pedro de Magalhaes, animation by Sharon Colman.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:57
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