1
00:00:06,006 --> 00:00:08,008
[ominous music playing]

2
00:00:09,300 --> 00:00:12,804
[Morgan Freeman] Millions of years
before the age of dinosaurs…

3
00:00:15,140 --> 00:00:19,728
our planet was ruled
by equally magnificent beasts.

4
00:00:24,899 --> 00:00:26,484
[low grunting]

5
00:00:28,028 --> 00:00:31,114
Two great dynasties had emerged

6
00:00:31,823 --> 00:00:34,492
and were vying for domination.

7
00:00:35,285 --> 00:00:37,328
[wailing]

8
00:00:37,412 --> 00:00:42,751
This is the story
of the battle to conquer land…

9
00:00:42,834 --> 00:00:44,419
[growling]

10
00:00:45,211 --> 00:00:50,633
…and how it changed everything
for life on our planet.

11
00:00:51,134 --> 00:00:53,386
[roaring]

12
00:00:55,055 --> 00:00:57,057
[rousing music playing]

13
00:01:19,537 --> 00:01:21,956
[snarling]

14
00:01:22,040 --> 00:01:24,125
[trilling]

15
00:01:25,960 --> 00:01:27,212
[screeching]

16
00:01:27,295 --> 00:01:29,297
[rousing music continues]

17
00:01:38,389 --> 00:01:40,308
[growling]

18
00:01:40,391 --> 00:01:42,310
[wind howling]

19
00:01:44,395 --> 00:01:46,356
[rumbling]

20
00:01:48,191 --> 00:01:50,193
[rousing music intensifies]

21
00:01:52,695 --> 00:01:54,906
[music fades]

22
00:01:57,659 --> 00:01:59,661
[somber music playing]

23
00:02:13,591 --> 00:02:15,760
For most of our planet's history,

24
00:02:16,636 --> 00:02:18,972
land has been inhospitable to life.

25
00:02:23,143 --> 00:02:25,562
A bleak and desolate realm…

26
00:02:33,903 --> 00:02:36,364
more like the surface of the moon…

27
00:02:39,075 --> 00:02:40,618
than like Earth today.

28
00:02:47,041 --> 00:02:49,460
It's hard to imagine

29
00:02:49,544 --> 00:02:54,632
how anything could ever make
this hostile place its home.

30
00:03:02,682 --> 00:03:04,809
But from beneath the waves,

31
00:03:04,893 --> 00:03:08,563
where life had thrived
for more than a billion years,

32
00:03:10,231 --> 00:03:15,361
one curious life-form was among the first
to rise to the challenge.

33
00:03:18,656 --> 00:03:20,992
Lichen may not look remarkable,

34
00:03:21,910 --> 00:03:25,330
but they are in fact completely unique.

35
00:03:26,539 --> 00:03:28,750
A pioneering partnership.

36
00:03:28,833 --> 00:03:30,418
[intriguing music playing]

37
00:03:34,130 --> 00:03:36,633
Neither plant nor animal,

38
00:03:37,425 --> 00:03:42,764
lichen are a strange combination
of fungi and algae…

39
00:03:45,808 --> 00:03:48,895
that only together had what it took

40
00:03:48,978 --> 00:03:52,982
to overcome the extreme hostility
of barren Earth.

41
00:03:54,275 --> 00:03:56,277
[ethereal music playing]

42
00:04:07,121 --> 00:04:10,500
But they were more than just pioneering.

43
00:04:11,793 --> 00:04:13,628
They were groundbreaking.

44
00:04:21,135 --> 00:04:22,387
As they spread…

45
00:04:22,470 --> 00:04:24,764
[stirring music playing]

46
00:04:24,847 --> 00:04:28,268
…their tiny filaments
helped to break down rock

47
00:04:29,269 --> 00:04:32,272
and produce the first ever soil…

48
00:04:35,984 --> 00:04:39,195
paving the way for plants to take over.

49
00:04:42,490 --> 00:04:46,953
Micro plants, like moss,
were first to appear.

50
00:04:50,039 --> 00:04:52,542
With leaves only one cell thick,

51
00:04:53,126 --> 00:04:55,378
they couldn't grow upwards,

52
00:04:55,461 --> 00:04:57,505
but could spread out.

53
00:05:01,509 --> 00:05:04,137
Reproducing faster than lichen,

54
00:05:04,220 --> 00:05:06,514
they soon carpeted the land,

55
00:05:06,597 --> 00:05:12,520
which they ruled undisturbed
for the next 40 million years.

56
00:05:12,603 --> 00:05:14,605
[music intensifies]

57
00:05:25,033 --> 00:05:26,909
[music fades]

58
00:05:26,993 --> 00:05:29,203
But a green revolution was coming…

59
00:05:32,665 --> 00:05:35,835
that would change the landscape forever.

60
00:05:39,297 --> 00:05:42,800
Key was the evolution of a new compound,

61
00:05:43,801 --> 00:05:44,802
lignin.

62
00:05:47,221 --> 00:05:50,892
Lignin strengthened
the plants' cell walls…

63
00:05:53,019 --> 00:05:58,566
allowing them to grow bigger and stronger
than ever before.

64
00:06:08,409 --> 00:06:11,621
No longer confined to carpeting the land,

65
00:06:12,538 --> 00:06:16,125
plants began to battle
for the real estate above,

66
00:06:16,876 --> 00:06:20,380
fighting for access to light.

67
00:06:20,463 --> 00:06:22,465
[dramatic music playing]

68
00:06:26,344 --> 00:06:27,845
[music fades]

69
00:06:27,929 --> 00:06:32,183
Eventually, some plants grew so tall,

70
00:06:32,266 --> 00:06:35,311
they towered above the world around them.

71
00:06:38,356 --> 00:06:40,441
[majestic music playing]

72
00:06:45,029 --> 00:06:49,033
Today's redwoods are nature's skyscrapers.

73
00:06:54,622 --> 00:06:57,375
Reaching heights
of more than a hundred meters,

74
00:06:58,668 --> 00:07:03,423
they are the tallest living things
to have ever existed.

75
00:07:11,139 --> 00:07:17,812
But redwoods are just one
of more than 400,000 species of plant,

76
00:07:19,522 --> 00:07:23,276
the most visible signs of life
on our planet.

77
00:07:26,112 --> 00:07:28,114
[music fades]

78
00:07:30,950 --> 00:07:34,745
Back in Earth's distant past,
the arrival of plants

79
00:07:35,329 --> 00:07:39,834
created new habitats
for the next invaders from the sea.

80
00:07:39,917 --> 00:07:41,961
[unsettling music playing]

81
00:07:46,799 --> 00:07:52,722
The first animals to ever set foot on land
were the arthropods.

82
00:07:56,767 --> 00:07:58,478
Relatives of the trilobites,

83
00:08:00,104 --> 00:08:04,942
their hard exoskeletons
had served as useful armor underwater.

84
00:08:11,991 --> 00:08:14,994
On land, that armor supported them

85
00:08:15,995 --> 00:08:18,080
and prevented them from drying out.

86
00:08:23,753 --> 00:08:27,590
They could also breathe
through this tough exterior.

87
00:08:32,386 --> 00:08:36,599
And with oxygen levels 60% higher
than they are today,

88
00:08:38,100 --> 00:08:40,520
some grew to be giants.

89
00:08:53,658 --> 00:08:59,705
Arthropleura, the largest millipede
to ever walk the Earth.

90
00:09:05,461 --> 00:09:10,216
At over two and a half meters long
and a half meter wide,

91
00:09:11,133 --> 00:09:13,344
he has no natural enemies…

92
00:09:13,970 --> 00:09:15,972
[peaceful music playing]

93
00:09:17,515 --> 00:09:22,728
…so can focus all his energy
on finding a mate.

94
00:09:26,399 --> 00:09:31,612
But for Arthropleura,
the pursuit of the perfect partner is

95
00:09:32,488 --> 00:09:34,073
not straightforward.

96
00:09:34,574 --> 00:09:36,576
-[soft thud]
-[music stops]

97
00:09:37,368 --> 00:09:40,496
For he's virtually blind…

98
00:09:40,580 --> 00:09:42,373
[music resumes]

99
00:09:42,456 --> 00:09:47,878
…and his world extends
only as far as he can sense.

100
00:10:08,524 --> 00:10:11,110
The fern forest is vast,

101
00:10:12,153 --> 00:10:15,489
and a female could be anywhere.

102
00:10:23,080 --> 00:10:26,375
But his search isn't as hopeless
as it might seem.

103
00:10:30,087 --> 00:10:35,343
Females ready to mate
leave scent trails for males to follow.

104
00:10:37,887 --> 00:10:40,890
A lifeline in the darkness.

105
00:10:42,600 --> 00:10:44,602
[whooshing]

106
00:10:46,771 --> 00:10:48,773
[pensive music playing]

107
00:10:54,862 --> 00:11:00,618
And yet, sensing where she once was
is not the same

108
00:11:01,494 --> 00:11:04,038
as sensing where she is.

109
00:11:10,461 --> 00:11:12,463
[whimsical music playing]

110
00:11:45,121 --> 00:11:47,123
[peaceful music playing]

111
00:11:51,419 --> 00:11:56,006
Finally, his chance to charm can begin.

112
00:11:56,757 --> 00:11:58,759
[chirping]

113
00:12:00,469 --> 00:12:06,225
By rubbing together parts of his shell,
he creates his own unique love song.

114
00:12:06,308 --> 00:12:08,310
-[music stops]
-[chirping continues]

115
00:12:15,401 --> 00:12:17,403
[peaceful music continues]

116
00:12:21,198 --> 00:12:22,700
[soft chirping]

117
00:12:22,783 --> 00:12:24,827
[music swells]

118
00:12:34,086 --> 00:12:37,381
Mating on land can be an awkward affair.

119
00:12:38,799 --> 00:12:42,136
Success requires the perfect alignment.

120
00:12:44,889 --> 00:12:49,059
So it's important at this critical stage

121
00:12:49,769 --> 00:12:52,897
not to put a foot wrong.

122
00:12:52,980 --> 00:12:54,982
[music intensifies]

123
00:13:04,575 --> 00:13:05,785
[music ends]

124
00:13:05,868 --> 00:13:07,870
[birds tweeting]

125
00:13:09,580 --> 00:13:12,833
345 million years later,

126
00:13:12,917 --> 00:13:15,503
and in today's forests,

127
00:13:15,586 --> 00:13:20,674
the arthropod art of seduction
has come a long way.

128
00:13:23,302 --> 00:13:27,473
Especially for some of the less armored
members of the group.

129
00:13:29,016 --> 00:13:31,018
[brooding music playing]

130
00:13:36,023 --> 00:13:38,609
Unlike the ancient Arthropleura,

131
00:13:40,152 --> 00:13:43,906
male jumping spiders have superb vision

132
00:13:45,658 --> 00:13:48,953
and are no larger than a grain of rice.

133
00:13:49,036 --> 00:13:50,996
[music becomes playful]

134
00:13:53,499 --> 00:13:55,084
But what they lack in stature…

135
00:13:59,755 --> 00:14:02,424
they make up for in style.

136
00:14:06,804 --> 00:14:10,891
Each species has
its own signature dance move

137
00:14:11,559 --> 00:14:13,394
to attract female attention.

138
00:14:18,983 --> 00:14:20,025
The peacock.

139
00:14:22,361 --> 00:14:23,612
The side shuffle.

140
00:14:25,906 --> 00:14:27,116
The disco dancer.

141
00:14:30,035 --> 00:14:32,663
And the feather shake.

142
00:14:37,626 --> 00:14:40,754
While the males evolved colorful costumes

143
00:14:41,338 --> 00:14:43,090
and intricate dance moves…

144
00:14:45,968 --> 00:14:50,264
females developed impeccable taste.

145
00:14:53,684 --> 00:14:56,186
His side shuffle has caught her attention.

146
00:15:01,483 --> 00:15:04,111
But has he got the moves
she's looking for?

147
00:15:07,364 --> 00:15:09,575
Only the very best will do.

148
00:15:10,200 --> 00:15:12,202
[lively jazz music playing]

149
00:15:22,630 --> 00:15:28,344
Waving her abdomen
signals she's not impressed.

150
00:15:28,427 --> 00:15:30,054
[dramatic music playing]

151
00:15:31,931 --> 00:15:33,515
[music fades]

152
00:15:34,016 --> 00:15:35,559
He needs to be careful,

153
00:15:35,643 --> 00:15:41,440
for fussy females
sometimes eat their suitors.

154
00:15:41,523 --> 00:15:43,817
[tense music playing]

155
00:15:56,997 --> 00:15:57,957
Still…

156
00:15:58,040 --> 00:16:00,042
[lively jazz music resumes]

157
00:16:01,627 --> 00:16:04,380
…it's worth one more try.

158
00:16:14,056 --> 00:16:15,808
[music slows, fades]

159
00:16:15,891 --> 00:16:18,143
Clearly, he's not getting the message.

160
00:16:20,771 --> 00:16:22,481
[tense music playing]

161
00:16:32,616 --> 00:16:34,451
He may be unlucky in love,

162
00:16:35,285 --> 00:16:39,999
but his arthropod dynasty
has had better luck.

163
00:16:42,418 --> 00:16:46,839
They now make up over 80%
of all animal species.

164
00:16:50,050 --> 00:16:53,053
The secret to arthropod success

165
00:16:54,138 --> 00:16:57,182
lies in their simple segmented body plan…

166
00:16:57,683 --> 00:16:59,685
[sinister music playing]

167
00:17:02,521 --> 00:17:05,899
…which has evolved
in countless different directions.

168
00:17:09,570 --> 00:17:11,572
[music intensifies]

169
00:17:14,158 --> 00:17:16,201
Some have ears in their legs.

170
00:17:18,912 --> 00:17:21,832
Others, eyes on stalks.

171
00:17:24,918 --> 00:17:28,255
And armor plating for battle.

172
00:17:31,675 --> 00:17:34,595
Variation after variation,

173
00:17:36,138 --> 00:17:41,560
arthropods are evolution run wild.

174
00:17:44,146 --> 00:17:48,692
Including the greatest runner of them all,

175
00:17:49,485 --> 00:17:51,070
the tiger beetle.

176
00:17:53,781 --> 00:17:58,077
Its design has been fine-tuned
over millions of years.

177
00:18:00,245 --> 00:18:04,041
The latest model is built for speed.

178
00:18:13,926 --> 00:18:18,847
For its size, it is
one of the fastest sprinters on Earth.

179
00:18:22,392 --> 00:18:24,603
If scaled up to human proportions,

180
00:18:26,480 --> 00:18:27,815
it would run

181
00:18:28,774 --> 00:18:32,277
at over 1,000 kilometers per hour.

182
00:18:34,738 --> 00:18:37,950
But there is one drawback
to life in the fast lane.

183
00:18:41,161 --> 00:18:43,789
His brain can't keep up.

184
00:18:45,749 --> 00:18:49,878
He must frequently stop
to get his bearings

185
00:18:51,255 --> 00:18:55,092
while hunting down his next victim.

186
00:18:56,218 --> 00:18:58,220
[tense music playing]

187
00:19:06,436 --> 00:19:11,358
But his frantic search for food
can lead him into dangerous territory…

188
00:19:14,820 --> 00:19:17,239
because sometimes the hunter

189
00:19:18,407 --> 00:19:19,783
can also be

190
00:19:21,243 --> 00:19:22,202
the hunted.

191
00:19:22,286 --> 00:19:24,288
[ominous music playing]

192
00:19:31,712 --> 00:19:36,341
Fast and furious
is not this trapdoor spider's style.

193
00:19:39,469 --> 00:19:44,224
She prefers to wait
for prey to come to her.

194
00:19:49,730 --> 00:19:51,732
[suspenseful music playing]

195
00:20:22,095 --> 00:20:24,097
[music intensifies]

196
00:20:24,181 --> 00:20:26,183
[dramatic music playing]

197
00:20:38,403 --> 00:20:39,529
[music fades]

198
00:20:47,621 --> 00:20:49,873
In the battle of the arthropods,

199
00:20:50,415 --> 00:20:54,962
flight would often make the difference
between life and death.

200
00:20:55,045 --> 00:20:57,047
[intriguing music playing]

201
00:20:58,507 --> 00:21:00,384
[buzzing]

202
00:21:00,968 --> 00:21:03,637
More than 300 million years ago,

203
00:21:04,304 --> 00:21:06,807
one group of arthropods

204
00:21:06,890 --> 00:21:10,811
were the first creatures
to take to the skies.

205
00:21:10,894 --> 00:21:12,646
[music intensifies]

206
00:21:17,609 --> 00:21:19,528
And the evolution of wings

207
00:21:20,946 --> 00:21:24,074
would eventually launch them
to global success.

208
00:21:27,869 --> 00:21:29,454
The insects.

209
00:21:29,955 --> 00:21:31,957
[rousing music playing]

210
00:21:36,044 --> 00:21:39,506
Today, for every human on the planet,

211
00:21:39,589 --> 00:21:42,884
there are more than a billion insects.

212
00:21:46,763 --> 00:21:50,892
They are the most abundant
group of animals on Earth.

213
00:21:57,566 --> 00:21:59,568
[music fades]

214
00:22:00,402 --> 00:22:04,364
[creatures chirping, insect buzzing]

215
00:22:07,784 --> 00:22:10,203
Despite their current success,

216
00:22:10,954 --> 00:22:15,959
the ultimate flying insects first appeared
back in the ancient swamps.

217
00:22:18,670 --> 00:22:20,297
Dragonflies.

218
00:22:24,468 --> 00:22:28,305
Their flight is as close to perfect
as it gets.

219
00:22:31,641 --> 00:22:33,518
Four flexible wings,

220
00:22:34,102 --> 00:22:36,271
independently controlled,

221
00:22:36,355 --> 00:22:39,066
give them unparalleled mobility.

222
00:22:41,568 --> 00:22:45,238
They can fly in any direction,

223
00:22:47,157 --> 00:22:49,284
pull off the tightest turns…

224
00:22:49,368 --> 00:22:51,912
[intriguing music playing]

225
00:22:52,829 --> 00:22:56,375
and accelerate faster than a fighter jet.

226
00:22:59,544 --> 00:23:04,633
A winning design
that has remained almost the same

227
00:23:04,716 --> 00:23:07,094
for hundreds of millions of years.

228
00:23:08,428 --> 00:23:10,430
[music fades]

229
00:23:12,599 --> 00:23:16,853
And yet, living in the same
prehistoric swamps,

230
00:23:17,479 --> 00:23:22,567
another group of animals
were undergoing their own radical change.

231
00:23:26,822 --> 00:23:28,240
Beneath the surface,

232
00:23:29,241 --> 00:23:32,661
vertebrates had continued to evolve…

233
00:23:35,580 --> 00:23:39,584
and a new type of fish was thriving,

234
00:23:40,669 --> 00:23:42,712
the lobe-finned fish.

235
00:23:52,806 --> 00:23:57,060
Some grew to be monstrous predators.

236
00:23:58,979 --> 00:24:00,981
[tense music playing]

237
00:24:06,445 --> 00:24:09,573
In this fish-eat-fish world,

238
00:24:10,574 --> 00:24:12,742
it pays to be big.

239
00:24:16,288 --> 00:24:18,290
[music intensifies]

240
00:24:18,373 --> 00:24:20,125
[music ends]

241
00:24:21,418 --> 00:24:25,380
For the smaller ones,
there's refuge in the shallows…

242
00:24:29,468 --> 00:24:34,514
where their unique lobed fins
are a distinct advantage.

243
00:24:37,100 --> 00:24:40,687
Muscular and highly versatile,

244
00:24:41,688 --> 00:24:44,357
they are different to those of other fish.

245
00:24:48,069 --> 00:24:50,322
Not only do they help them swim…

246
00:24:53,325 --> 00:24:57,162
but they're strong enough
to support their body weight…

247
00:25:00,790 --> 00:25:06,213
and help them crawl out of the water.

248
00:25:11,009 --> 00:25:16,056
But these fish also have
another game-changing adaptation…

249
00:25:18,141 --> 00:25:19,142
the ability…

250
00:25:19,851 --> 00:25:22,312
-[wheezes]
-…to breathe air.

251
00:25:25,273 --> 00:25:29,277
Not through gills
but through primitive lungs.

252
00:25:33,073 --> 00:25:36,993
Together, these evolutionary advances

253
00:25:37,077 --> 00:25:42,249
allowed vertebrates to leave the water
and explore the land.

254
00:25:46,294 --> 00:25:50,298
The race was on
to colonize this new world.

255
00:25:58,473 --> 00:26:01,142
But it was already too late

256
00:26:02,644 --> 00:26:04,896
for these lobe-finned fish.

257
00:26:08,775 --> 00:26:11,736
Others had made this transition
before them.

258
00:26:14,406 --> 00:26:15,448
[grunting]

259
00:26:18,243 --> 00:26:20,245
[dramatic music playing]

260
00:26:27,919 --> 00:26:30,922
Like the three-meter-long Anthracosaurus…

261
00:26:31,965 --> 00:26:33,967
[low growling]

262
00:26:34,634 --> 00:26:37,304
…that had already found its feet.

263
00:26:37,387 --> 00:26:38,555
[grunts]

264
00:26:47,981 --> 00:26:52,485
The evolution from fin to limb
took millions of years.

265
00:26:52,569 --> 00:26:54,571
[stirring music playing]

266
00:26:57,949 --> 00:27:01,244
But once completed, life on land

267
00:27:02,370 --> 00:27:04,623
would never be the same again.

268
00:27:18,136 --> 00:27:20,138
The age of amphibians

269
00:27:21,514 --> 00:27:22,641
had begun.

270
00:27:31,358 --> 00:27:34,110
[ethereal music playing]

271
00:27:40,909 --> 00:27:47,248
Today, there are more
than 8,000 species of amphibian.

272
00:27:50,543 --> 00:27:53,963
A peculiar but diverse group…

273
00:27:54,047 --> 00:27:56,091
[long croak]

274
00:27:57,676 --> 00:27:58,927
…of newts,

275
00:27:59,678 --> 00:28:00,845
frogs,

276
00:28:01,513 --> 00:28:02,847
salamanders,

277
00:28:03,765 --> 00:28:04,849
and toads.

278
00:28:05,850 --> 00:28:07,060
[music intensifies]

279
00:28:07,143 --> 00:28:10,105
Not quite the giants they once were,

280
00:28:11,022 --> 00:28:13,525
but still successful hunters…

281
00:28:13,608 --> 00:28:15,610
[music fades]

282
00:28:16,528 --> 00:28:19,864
…with their own killer style.

283
00:28:19,948 --> 00:28:21,950
[birds tweeting]

284
00:28:28,915 --> 00:28:32,335
Hundreds of millions of years
after Anthracosaurus,

285
00:28:33,461 --> 00:28:37,966
swamplands remain a stronghold
for amphibians.

286
00:28:38,049 --> 00:28:40,051
[tranquil music playing]

287
00:28:42,137 --> 00:28:45,390
Here in Europe's Danube delta,

288
00:28:45,473 --> 00:28:48,893
marsh frogs live in their thousands

289
00:28:49,686 --> 00:28:53,106
and have become expert insect hunters…

290
00:28:55,692 --> 00:28:57,819
with a particular taste

291
00:28:59,279 --> 00:29:00,905
for dragonflies.

292
00:29:04,659 --> 00:29:06,745
[tense music playing]

293
00:29:07,829 --> 00:29:09,956
Thanks to their wraparound vision,

294
00:29:12,459 --> 00:29:15,044
catching one isn't easy.

295
00:29:16,421 --> 00:29:22,552
But marsh frogs have evolved
some quirky adaptations of their own.

296
00:29:32,687 --> 00:29:35,732
Webbed feet help them get airborne.

297
00:29:44,115 --> 00:29:49,037
And a projectile tongue
gives them extraordinary reach.

298
00:29:57,045 --> 00:30:01,049
Even so, dragonflies in flight

299
00:30:01,132 --> 00:30:05,094
can be just too hard to catch.

300
00:30:10,099 --> 00:30:14,562
Waiting for the aerial acrobats to land
might make things easier.

301
00:30:53,560 --> 00:30:55,562
Time to take a different approach.

302
00:31:00,942 --> 00:31:05,154
A female laying eggs in the water.

303
00:31:10,785 --> 00:31:12,495
Half-submerged,

304
00:31:13,538 --> 00:31:16,165
she should be an easier target.

305
00:31:25,008 --> 00:31:26,759
[dramatic music playing]

306
00:31:44,986 --> 00:31:49,532
The dragonflies are just too fast.

307
00:31:53,411 --> 00:31:55,413
[suspenseful music playing]

308
00:32:02,045 --> 00:32:05,214
And they can barrel-roll.

309
00:32:26,611 --> 00:32:27,862
Missed again.

310
00:32:30,573 --> 00:32:35,203
But frogs are nothing if not persistent.

311
00:32:35,286 --> 00:32:37,288
[suspenseful music playing]

312
00:32:42,752 --> 00:32:44,337
[music ends]

313
00:32:50,009 --> 00:32:52,303
Despite the low hit rate,

314
00:32:52,387 --> 00:32:58,518
amphibians have survived
for over 350 million years.

315
00:33:03,022 --> 00:33:08,277
And yet, they never conquered
every environment the planet had to offer…

316
00:33:10,613 --> 00:33:15,827
because there's something
all amphibians need to raise their young.

317
00:33:19,122 --> 00:33:20,123
Water.

318
00:33:23,543 --> 00:33:27,213
This is the strawberry dart frog
of Costa Rica.

319
00:33:27,296 --> 00:33:29,007
[croaking]

320
00:33:33,094 --> 00:33:35,972
Her tadpoles are in mortal danger.

321
00:33:38,558 --> 00:33:41,853
Their tiny puddle, almost dry.

322
00:33:54,449 --> 00:33:56,034
[croaking]

323
00:33:57,452 --> 00:33:59,454
Their only means of escape

324
00:34:00,955 --> 00:34:03,041
is on their mother's back.

325
00:34:06,377 --> 00:34:09,630
The hard part is finding water.

326
00:34:14,177 --> 00:34:15,011
Luckily…

327
00:34:15,094 --> 00:34:17,096
[croaking]

328
00:34:18,931 --> 00:34:21,642
…she knows exactly where to go.

329
00:34:23,269 --> 00:34:25,855
[croaking]

330
00:34:28,316 --> 00:34:29,859
Twenty meters above her,

331
00:34:31,402 --> 00:34:33,863
a bromeliad collects rainwater.

332
00:34:37,283 --> 00:34:40,703
The perfect pool for her precious tadpole.

333
00:34:43,247 --> 00:34:46,292
But first, she must get there…

334
00:34:48,753 --> 00:34:51,881
one hop at a time.

335
00:34:55,259 --> 00:34:57,261
[invigorating music playing]

336
00:35:02,016 --> 00:35:05,103
Barely the size of a human thumbnail,

337
00:35:05,770 --> 00:35:09,107
this is her own personal Everest.

338
00:35:11,400 --> 00:35:13,277
[ethereal vocalizing]

339
00:35:28,376 --> 00:35:30,378
[croaking]

340
00:35:33,131 --> 00:35:35,133
[music fades]

341
00:35:36,092 --> 00:35:38,010
Safe at last.

342
00:35:39,303 --> 00:35:41,556
[croaking]

343
00:35:48,020 --> 00:35:52,316
No matter what great heights amphibians
reached in their conquest of land…

344
00:35:55,444 --> 00:35:58,364
they never escaped their tie to water…

345
00:36:00,408 --> 00:36:05,288
a tie that would be their undoing
when conditions on Earth…

346
00:36:07,331 --> 00:36:09,000
radically changed.

347
00:36:12,545 --> 00:36:14,797
[ominous music playing]

348
00:36:21,721 --> 00:36:24,599
During the period known
as the Carboniferous,

349
00:36:25,391 --> 00:36:28,686
Earth's great land masses merged,

350
00:36:28,769 --> 00:36:32,648
and the supercontinent of Pangaea
was born.

351
00:36:35,443 --> 00:36:37,111
As the land dried,

352
00:36:37,945 --> 00:36:40,531
the vast swamps began to disappear.

353
00:36:43,034 --> 00:36:47,288
Lacking water, most amphibians struggled.

354
00:36:48,956 --> 00:36:50,958
[music fades]

355
00:36:52,376 --> 00:36:53,669
But not all.

356
00:36:55,254 --> 00:37:00,676
One evolved a revolutionary adaptation
that enabled it to thrive.

357
00:37:06,474 --> 00:37:10,144
Its egg developed a protective shell

358
00:37:10,228 --> 00:37:15,149
that held the embryo
in its own private pool of fluid.

359
00:37:18,945 --> 00:37:24,700
Inside, the young could develop safely
without drying out.

360
00:37:25,701 --> 00:37:27,703
[serene music playing]

361
00:37:38,172 --> 00:37:43,010
The tie to water was finally broken
by the evolution

362
00:37:44,303 --> 00:37:46,555
of this amniotic egg.

363
00:37:52,812 --> 00:37:55,147
Known as the amniotes,

364
00:37:55,231 --> 00:37:58,651
these creatures
could colonize the drier land

365
00:37:58,734 --> 00:38:01,279
in a way that amphibians could not.

366
00:38:02,446 --> 00:38:04,448
[music intensifies]

367
00:38:06,659 --> 00:38:10,663
And from this one common ancestor,

368
00:38:10,746 --> 00:38:14,500
all mammals, reptiles, birds,

369
00:38:14,583 --> 00:38:18,087
and dinosaurs would descend.

370
00:38:18,170 --> 00:38:20,047
[sinister music playing]

371
00:38:52,204 --> 00:38:54,206
[music fades]

372
00:38:57,293 --> 00:39:01,547
Sixty million years after the evolution
of the amniotic egg,

373
00:39:03,132 --> 00:39:06,135
amniotes have spread across Pangaea…

374
00:39:06,844 --> 00:39:09,347
[majestic music playing]

375
00:39:10,890 --> 00:39:16,812
…producing two new dynasties
and the start of an endless rivalry.

376
00:39:22,818 --> 00:39:28,491
These sleeping armored beasts
are a primitive type of reptile.

377
00:39:35,122 --> 00:39:40,252
Scutosaurus,
among the largest animals on land.

378
00:39:46,967 --> 00:39:48,260
[distant bellowing]

379
00:39:52,306 --> 00:39:53,724
[grunting]

380
00:39:59,605 --> 00:40:01,232
Weighing over a ton,

381
00:40:02,983 --> 00:40:06,362
they are the first giant plant-eaters
to roam the planet.

382
00:40:12,326 --> 00:40:16,664
Amniotic eggs allowed them to flourish
in the drier conditions

383
00:40:17,206 --> 00:40:20,000
and go where others could not.

384
00:40:20,709 --> 00:40:22,711
[low growling]

385
00:40:24,588 --> 00:40:27,466
But Pangaea didn't just belong to them.

386
00:40:33,139 --> 00:40:35,891
Another new bloodline had emerged.

387
00:40:36,892 --> 00:40:39,812
The ancestors of the mammals.

388
00:40:42,606 --> 00:40:44,066
[mewls]

389
00:40:47,862 --> 00:40:51,157
While a Lystrosaurus
is no match for a Scutosaur…

390
00:40:51,240 --> 00:40:53,576
-[growling]
-[mewls]

391
00:40:53,659 --> 00:40:56,537
…he has cousins here who are.

392
00:40:57,872 --> 00:41:00,040
[ominous music playing]

393
00:41:16,307 --> 00:41:18,309
[snarling]

394
00:41:20,769 --> 00:41:22,229
A gorgonopsid.

395
00:41:25,900 --> 00:41:29,320
A more impressive forerunner
to the mammals.

396
00:41:33,032 --> 00:41:37,661
At over three meters long and 300 kilos,

397
00:41:38,829 --> 00:41:42,082
she rivals any big cat alive today.

398
00:41:42,708 --> 00:41:44,710
[grunting]

399
00:41:48,589 --> 00:41:50,799
With her powerful sense of smell,

400
00:41:51,884 --> 00:41:54,011
tracking her prey is easy.

401
00:41:56,847 --> 00:41:58,891
Getting past their heavy armor

402
00:42:00,142 --> 00:42:02,144
will be her greatest challenge.

403
00:42:02,228 --> 00:42:05,064
[grunting, wailing]

404
00:42:08,442 --> 00:42:10,277
But she has a secret weapon.

405
00:42:10,361 --> 00:42:12,071
[snarling]

406
00:42:13,447 --> 00:42:15,074
Saber-like teeth.

407
00:42:22,581 --> 00:42:24,041
Even so,

408
00:42:24,875 --> 00:42:27,294
she'll need stealth to get close.

409
00:42:27,378 --> 00:42:28,504
[grunting]

410
00:42:39,181 --> 00:42:41,934
-[grunting]
-[wind whistling]

411
00:42:48,649 --> 00:42:50,651
[grunting]

412
00:43:01,078 --> 00:43:03,581
[tense music playing]

413
00:43:06,834 --> 00:43:08,752
She must choose her moment…

414
00:43:13,215 --> 00:43:14,550
and her target

415
00:43:16,385 --> 00:43:17,344
carefully.

416
00:43:17,428 --> 00:43:18,971
[grunting]

417
00:43:25,769 --> 00:43:26,812
Slowly

418
00:43:28,397 --> 00:43:29,815
and silently…

419
00:43:33,193 --> 00:43:34,320
does it.

420
00:43:34,403 --> 00:43:36,238
[tense music continues]

421
00:43:54,798 --> 00:43:56,133
[growling]

422
00:43:56,216 --> 00:43:58,385
-[grunting]
-[growls]

423
00:44:01,764 --> 00:44:04,099
-[growls]
-[wailing]

424
00:44:06,101 --> 00:44:07,102
[roars]

425
00:44:13,859 --> 00:44:16,111
[roars, snarling]

426
00:44:21,784 --> 00:44:23,118
[roars]

427
00:44:26,246 --> 00:44:28,082
-[roaring]
-[grunting]

428
00:44:31,877 --> 00:44:33,879
[dramatic music playing]

429
00:44:35,130 --> 00:44:37,132
-[music fades]
-[wailing]

430
00:44:50,437 --> 00:44:53,232
The rivalry between mammals and reptiles

431
00:44:54,149 --> 00:44:58,862
has been a feature of life on Earth
for hundreds of millions of years.

432
00:45:02,199 --> 00:45:05,452
But their early rise was not to last,

433
00:45:06,286 --> 00:45:09,915
because in the far north of Pangaea,

434
00:45:10,666 --> 00:45:13,460
something catastrophic was happening.

435
00:45:14,712 --> 00:45:16,714
[rumbling]

436
00:45:18,173 --> 00:45:20,592
Lying dormant for years on end,

437
00:45:21,218 --> 00:45:25,222
the colossal forces at work
beneath Earth's surface

438
00:45:26,140 --> 00:45:28,016
are easily forgotten.

439
00:45:33,397 --> 00:45:35,607
But the molten underworld

440
00:45:36,900 --> 00:45:39,194
is always stirring,

441
00:45:40,571 --> 00:45:42,906
always probing for weakness.

442
00:45:44,700 --> 00:45:46,702
[ominous ambient music playing]

443
00:45:48,495 --> 00:45:50,497
[wind whistling]

444
00:45:52,833 --> 00:45:54,835
Beneath Pangaea's crust,

445
00:45:56,128 --> 00:45:58,505
a plume of superheated magma

446
00:45:59,089 --> 00:46:01,467
was working its way to the surface.

447
00:46:08,682 --> 00:46:11,602
Once these Permian eruptions started…

448
00:46:14,521 --> 00:46:16,565
there was no stopping them.

449
00:46:18,233 --> 00:46:20,486
[dramatic music playing]

450
00:46:44,051 --> 00:46:48,430
What made them unique
was their monumental scale.

451
00:46:51,600 --> 00:46:53,602
[dramatic music continues]

452
00:46:58,649 --> 00:47:00,818
They were among the largest,

453
00:47:01,860 --> 00:47:07,032
most violent eruptions
that life has ever witnessed.

454
00:47:17,960 --> 00:47:22,047
And they raged for 100,000 years.

455
00:47:24,091 --> 00:47:27,469
The devastation was unprecedented.

456
00:47:30,305 --> 00:47:33,308
An area half the size
of the United States

457
00:47:34,059 --> 00:47:36,103
lost to lava.

458
00:47:37,062 --> 00:47:39,064
[poignant music playing]

459
00:47:59,001 --> 00:48:01,169
Millions of square kilometers,

460
00:48:01,920 --> 00:48:03,922
once so full of life,

461
00:48:04,506 --> 00:48:07,926
obliterated by the Earth itself.

462
00:48:13,432 --> 00:48:15,434
[music fades]

463
00:48:17,853 --> 00:48:21,481
And that was just the beginning.

464
00:48:25,277 --> 00:48:30,657
The eruptions released something
far more dangerous than lava.

465
00:48:33,911 --> 00:48:38,874
A toxic concoction of noxious gases.

466
00:48:38,957 --> 00:48:40,959
[hissing]

467
00:48:41,043 --> 00:48:43,045
[dramatic music playing]

468
00:48:50,177 --> 00:48:52,888
When these gases combined with water…

469
00:49:00,145 --> 00:49:03,941
a potent cocktail of acid rain
poured down.

470
00:49:13,867 --> 00:49:16,453
Water, the giver of life,

471
00:49:17,412 --> 00:49:20,165
was now its destroyer.

472
00:49:26,880 --> 00:49:29,967
The toxic rain poisoned the ground…

473
00:49:32,094 --> 00:49:33,720
killing off the plants.

474
00:49:41,812 --> 00:49:44,982
Without their roots
to bind the soil together…

475
00:49:49,152 --> 00:49:52,990
entire ecosystems were washed away.

476
00:49:57,452 --> 00:49:59,454
[dramatic music playing]

477
00:49:59,538 --> 00:50:01,540
[rumbling]

478
00:50:01,623 --> 00:50:04,042
[music fades]

479
00:50:12,968 --> 00:50:19,016
And yet, there was something
even more destructive in the air.

480
00:50:22,227 --> 00:50:23,645
A silent killer.

481
00:50:26,815 --> 00:50:29,359
Carbon dioxide.

482
00:50:32,696 --> 00:50:37,242
The volcanoes released six times more CO2

483
00:50:37,868 --> 00:50:40,412
than is in our atmosphere today…

484
00:50:43,457 --> 00:50:46,918
triggering ten degrees of global warming…

485
00:50:47,544 --> 00:50:49,254
[rumbling]

486
00:50:50,797 --> 00:50:53,383
…and all the climate devastation

487
00:50:54,885 --> 00:50:56,386
that comes with it.

488
00:51:01,516 --> 00:51:03,518
[ominous music playing]

489
00:51:03,602 --> 00:51:05,812
[thunder rumbles]

490
00:51:09,691 --> 00:51:15,363
Hothouse Earth raged
as the forces of nature ran wild.

491
00:51:19,076 --> 00:51:21,411
[music intensifies]

492
00:51:40,806 --> 00:51:43,975
There was nowhere to hide from the chaos.

493
00:51:45,727 --> 00:51:49,523
And the oceans were worst affected.

494
00:51:51,983 --> 00:51:54,236
As they warmed and acidified,

495
00:51:55,112 --> 00:51:57,114
oxygen levels plummeted…

496
00:51:59,699 --> 00:52:03,787
turning the seas,
where life first took hold,

497
00:52:06,039 --> 00:52:08,208
into a desolate graveyard.

498
00:52:11,378 --> 00:52:14,005
This was the planet's third,

499
00:52:14,673 --> 00:52:18,218
and most devastating, mass extinction.

500
00:52:18,301 --> 00:52:20,178
[melancholy music playing]

501
00:52:20,262 --> 00:52:23,557
Ninety percent of all species

502
00:52:24,474 --> 00:52:26,852
lost forever.

503
00:52:33,024 --> 00:52:37,737
Entire branches torn off
the evolutionary tree.

504
00:52:46,288 --> 00:52:47,747
But in the loss of many,

505
00:52:48,748 --> 00:52:50,417
endured the few.

506
00:52:51,334 --> 00:52:52,794
[rustling]

507
00:52:56,506 --> 00:52:58,884
[breathing heavily]

508
00:52:58,967 --> 00:53:02,179
All that remained of a bygone age.

509
00:53:07,392 --> 00:53:13,064
Never had their survival
been so important.

510
00:53:17,527 --> 00:53:20,488
The future of all life

511
00:53:21,573 --> 00:53:24,534
now hung by a thread.

512
00:53:24,618 --> 00:53:26,995
[ethereal music playing]

513
00:53:32,584 --> 00:53:34,544
[music continues]