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Pegasus, Bucephalus, Champion,

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Trigger, Seabiscuit, Red Rum.

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00:00:17,520 --> 00:00:19,960
I'm talking about the stuff

4
00:00:19,960 --> 00:00:21,960
of myth and legend.

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00:00:31,640 --> 00:00:34,160
Just look at her.

6
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She's absolutely

7
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gorgeous, aren't you?

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Equus ferus caballus - the horse, to
you and I.

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00:00:46,320 --> 00:00:48,800
A statuesque pinnacle

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00:00:48,800 --> 00:00:50,680
of natural art.

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This is a creature

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supremely shaped to move.

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Thanks to 700 mighty muscles...

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..and a heart the size of a
football...

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..the horse is one of the fastest

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and most powerful animals on the
planet.

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They don't call it horsepower for
nothing.

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So how did the horse

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become one of nature's

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greatest athletes?

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00:01:59,000 --> 00:02:00,960
To answer that...

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..we must travel back in time...

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..to meet the key

24
00:02:12,120 --> 00:02:13,600
movers and shakers...

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..before hooves thundered...

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..or hearts raced.

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Back to a time

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when almost nothing at all

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moved.

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The story of the horse

31
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and, in fact, the story of movement

32
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can be traced, incredibly,

33
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right to our own doorstep.

34
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This is a quintessential

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English landscape, a rural idyll of

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rolling hills and ancient woodlands.

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But I've got to tell you

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that I was standing here just over
half a billion years ago,

39
00:03:28,640 --> 00:03:30,960
the view would have been very
different. In fact, I wouldn't

40
00:03:30,960 --> 00:03:34,520
have been standing, I'd have been
submerged deep beneath the waves

41
00:03:34,520 --> 00:03:38,120
on the ocean floor. And over millions
of years,

42
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these rocks have been pushed up and
laid bare.

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And they tell us of the history of
that time,

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00:03:44,440 --> 00:03:47,320
a history written in sand and silt.

45
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A history with some fascinating clues.

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Hiding in plain sight

47
00:03:57,000 --> 00:03:59,560
are some of the most precious

48
00:03:59,560 --> 00:04:01,360
fossils on the planet.

49
00:04:03,320 --> 00:04:07,320
But millions of years of weathering
have warped these rocks,

50
00:04:07,320 --> 00:04:10,360
making them very hard to spot.

51
00:04:12,200 --> 00:04:14,920
Now, I did tell you they were tricky
to see,

52
00:04:14,920 --> 00:04:18,280
but there is one right in front of me
here.

53
00:04:18,280 --> 00:04:21,160
Just follow my fingers.

54
00:04:21,160 --> 00:04:23,120
It starts up here,

55
00:04:23,120 --> 00:04:25,200
then it arches down.

56
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You can see the ridges in the rock,

57
00:04:27,360 --> 00:04:29,720
particularly visible here.

58
00:04:29,720 --> 00:04:31,400
And then it comes up towards

59
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my shoulder, and this bit follows

60
00:04:33,960 --> 00:04:35,480
right up past my ear.

61
00:04:35,480 --> 00:04:37,760
These would have been made by fronds

62
00:04:37,760 --> 00:04:39,280
and they would have been attached

63
00:04:39,280 --> 00:04:40,680
around a centre point, which

64
00:04:40,680 --> 00:04:42,880
could have been somewhere here.

65
00:04:42,880 --> 00:04:45,200
This is a fossil of Bradgatia.

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00:04:45,200 --> 00:04:48,400
And I know it doesn't look like much,
it might look like

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00:04:48,400 --> 00:04:50,920
an old cabbage that's been pressed in
the rock to you,

68
00:04:50,920 --> 00:04:52,680
but it wasn't an old cabbage.

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It wasn't a plant at all.

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00:04:54,560 --> 00:04:57,240
And this is a very, very important
fossil

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00:04:57,240 --> 00:05:01,360
because it's a fossil of one of the
earliest animals

72
00:05:01,360 --> 00:05:03,400
that ever lived on Earth.

73
00:05:08,040 --> 00:05:10,920
Over half a billion years ago,

74
00:05:10,920 --> 00:05:12,720
this slab of rock...

75
00:05:17,080 --> 00:05:20,880
..was home to some of the very first
animals.

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00:05:26,240 --> 00:05:28,680
Theirs is a peaceful life.

77
00:05:36,560 --> 00:05:39,280
But this strange community

78
00:05:39,280 --> 00:05:41,560
does have a problem.

79
00:05:43,800 --> 00:05:46,280
When animals with large, complex

80
00:05:46,280 --> 00:05:48,760
bodies first evolved,

81
00:05:48,760 --> 00:05:50,480
they couldn't move.

82
00:05:52,040 --> 00:05:54,360
We call them sessile.

83
00:05:57,680 --> 00:05:59,800
Rooted to the ground,

84
00:05:59,800 --> 00:06:02,160
they must rely on the ocean

85
00:06:02,160 --> 00:06:03,920
to bring them what they need...

86
00:06:06,200 --> 00:06:07,840
..and they're powerless

87
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if it doesn't.

88
00:06:12,160 --> 00:06:14,040
Animal life could have remained

89
00:06:14,040 --> 00:06:16,920
stuck in this way forever,

90
00:06:16,920 --> 00:06:21,360
if it wasn't for an evolutionary
maverick.

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00:06:24,480 --> 00:06:30,160
This is a cast of a fossil that's
about 565 million years old,

92
00:06:30,160 --> 00:06:34,160
which means it formed around the same
time as Bradgatia. Now,

93
00:06:34,160 --> 00:06:36,920
when the scientists first looked at
it, they were initially confused.

94
00:06:36,920 --> 00:06:38,400
It's quite difficult to see.

95
00:06:38,400 --> 00:06:41,840
Look, it starts up here and it runs
down here.

96
00:06:41,840 --> 00:06:45,120
It's almost as if someone has been
running their fingertip

97
00:06:45,120 --> 00:06:47,360
over some soft mud,

98
00:06:47,360 --> 00:06:49,720
and then it terminates down here.

99
00:06:49,720 --> 00:06:51,240
But if you look here,

100
00:06:51,240 --> 00:06:52,880
you can see there are a few little

101
00:06:52,880 --> 00:06:56,200
half-moon shapes. Now, the reason

102
00:06:56,200 --> 00:06:58,840
those scientists were initially
confused is they were probably

103
00:06:58,840 --> 00:07:02,800
looking for a fossil of an animal, but
this is not that.

104
00:07:02,800 --> 00:07:05,720
What it is is a fossil of something

105
00:07:05,720 --> 00:07:07,880
an animal left behind.

106
00:07:10,280 --> 00:07:14,480
Now, we think the story goes something
like this.

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00:07:15,880 --> 00:07:20,640
In amongst the creatures stuck to the
seabed is a tiny animal,

108
00:07:20,640 --> 00:07:23,440
little more than a gelatinous blob.

109
00:07:25,280 --> 00:07:27,320
Like other animals here,

110
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it eats specks of food

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00:07:29,080 --> 00:07:31,200
that drift on the ocean currents.

112
00:07:33,200 --> 00:07:36,080
But today, the current has shifted...

113
00:07:37,720 --> 00:07:42,400
..and is now carrying the meagre
morsels just out of reach.

114
00:07:45,840 --> 00:07:48,600
Deprived of food, the only option

115
00:07:48,600 --> 00:07:50,800
for this stationary population

116
00:07:50,800 --> 00:07:52,920
is to sit and wait for their luck

117
00:07:52,920 --> 00:07:56,080
and the currents to change.

118
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But this animal is a pioneer.

119
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You see, this little blob

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can do something

121
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that the other animals can't.

122
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Abandon the safety of its home...

123
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..and move.

124
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With every heave...

125
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..it leaves a mark.

126
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Some of the earliest animal tracks on
the planet.

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One small step for this tiny blob,

128
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one giant leap for animalkind.

129
00:09:18,560 --> 00:09:22,720
Now, we'll never know exactly when the
first step was taken.

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We can presume that there were some
missteps -

131
00:09:25,960 --> 00:09:29,280
evolutionary stumbles, if you like -

132
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but that leap between being sessile
and motile was a profound one.

133
00:09:36,720 --> 00:09:38,480
Today...

134
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..whether they are finding food...

135
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..or mates...

136
00:09:48,320 --> 00:09:50,080
..or shelter...

137
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..our planet is an extravaganza

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of motion.

139
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An estimated 97% of animals

140
00:10:01,920 --> 00:10:05,200
moving in weird and wonderful ways.

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00:10:06,880 --> 00:10:09,080
And none of this would be possible

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00:10:09,080 --> 00:10:12,440
without one key ingredient.

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Muscle.

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HORSES WHINNY

145
00:10:25,760 --> 00:10:30,240
To understand just how powerful muscle
can be,

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we need a demonstration from an
expert.

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I give you...the leech.

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I know, not everyone's favourite
animal,

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00:10:42,680 --> 00:10:45,200
but it won't surprise you to know

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00:10:45,200 --> 00:10:48,800
that I'm rather a fan of the leech.

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00:10:48,800 --> 00:10:50,040
What are they?

152
00:10:50,040 --> 00:10:51,800
Well, they're a type of worm,

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and there are about 700 species

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in the world.

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Many, like this one, are parasitic.

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This is a medicinal leech,

157
00:11:00,040 --> 00:11:01,520
and it's been used by

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00:11:01,520 --> 00:11:02,960
medical practitioners

159
00:11:02,960 --> 00:11:07,600
to suck the blood from humans for
3,500 years.

160
00:11:07,600 --> 00:11:09,200
But I digress.

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00:11:09,200 --> 00:11:10,600
What about its movement?

162
00:11:12,320 --> 00:11:14,960
Well, let's take a look at their body.

163
00:11:14,960 --> 00:11:17,160
First thing you'll notice - no legs.

164
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Its body is made up almost

165
00:11:18,920 --> 00:11:20,960
entirely of muscles.

166
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Muscles are built from tiny cells
called myocytes.

167
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We sometimes call them muscle fibres.

168
00:11:38,400 --> 00:11:40,040
Within the leech,

169
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there are thousands,

170
00:11:42,280 --> 00:11:44,320
while an animal like the horse

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contains millions

172
00:11:46,440 --> 00:11:49,080
and millions of them.

173
00:11:49,080 --> 00:11:53,400
They work thanks to their superpower -

174
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their ability to contract.

175
00:11:59,120 --> 00:12:01,240
Now, this leech's muscle cells

176
00:12:01,240 --> 00:12:03,440
are arranged in opposing sets.

177
00:12:03,440 --> 00:12:05,040
There are circular muscles

178
00:12:05,040 --> 00:12:06,480
that run around its body

179
00:12:06,480 --> 00:12:08,160
and longitudinal muscles,

180
00:12:08,160 --> 00:12:10,520
which run from one end to the other.

181
00:12:10,520 --> 00:12:13,360
So how exactly does it move? Well,

182
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I'll try and demonstrate that here.

183
00:12:14,960 --> 00:12:16,400
Come on.

184
00:12:21,440 --> 00:12:23,480
It stretches forward

185
00:12:23,480 --> 00:12:26,240
using those circular muscles,

186
00:12:26,240 --> 00:12:30,080
and then contracts its longitudinal
muscles

187
00:12:30,080 --> 00:12:32,000
and pulls itself forward...

188
00:12:33,600 --> 00:12:36,680
..so that it can slowly inch across

189
00:12:36,680 --> 00:12:38,240
the palm of my hand

190
00:12:38,240 --> 00:12:39,880
and down my fingers.

191
00:12:41,280 --> 00:12:43,680
Something that I find

192
00:12:43,680 --> 00:12:45,200
quite therapeutic.

193
00:12:47,040 --> 00:12:48,760
You may consider it perverse,

194
00:12:48,760 --> 00:12:50,840
but I'm rather enjoying this.

195
00:12:58,920 --> 00:13:01,840
Today, it's easy to take muscles for
granted...

196
00:13:03,720 --> 00:13:06,520
..but half a billion years ago,

197
00:13:06,520 --> 00:13:09,040
it was primitive muscle cells

198
00:13:09,040 --> 00:13:11,640
that turned contraction

199
00:13:11,640 --> 00:13:13,240
into action...

200
00:13:14,800 --> 00:13:17,240
..allowing pioneering animals

201
00:13:17,240 --> 00:13:20,240
to take a leap into the unknown.

202
00:13:25,400 --> 00:13:27,440
And the importance of this

203
00:13:27,440 --> 00:13:30,760
simply can't be underestimated,

204
00:13:30,760 --> 00:13:34,640
because from this point on, movement
would become

205
00:13:34,640 --> 00:13:39,840
one of the most powerful driving
forces in animal evolution.

206
00:13:41,560 --> 00:13:44,880
To reach the next step in the story of
the horse,

207
00:13:44,880 --> 00:13:46,640
we must hit fast-forward.

208
00:13:49,840 --> 00:13:52,880
For the next 40 million years,

209
00:13:52,880 --> 00:13:55,240
evolution gallops on.

210
00:14:02,440 --> 00:14:04,760
THUNDERCLAP

211
00:14:04,760 --> 00:14:06,640
Muscles stretch

212
00:14:06,640 --> 00:14:09,160
and shape animal life,

213
00:14:09,160 --> 00:14:11,760
and more and more time is spent...

214
00:14:15,880 --> 00:14:17,680
..on the go.

215
00:14:34,640 --> 00:14:39,920
As they say, necessity is the mother
of invention,

216
00:14:39,920 --> 00:14:43,040
and that was certainly the case for
animals experimenting

217
00:14:43,040 --> 00:14:45,200
with early locomotion.

218
00:14:48,560 --> 00:14:51,240
Down here, every trip across

219
00:14:51,240 --> 00:14:54,760
the seafloor demands energy,

220
00:14:54,760 --> 00:14:56,320
and lots of it.

221
00:15:01,080 --> 00:15:03,240
And to get from A to B,

222
00:15:03,240 --> 00:15:08,360
it's thought that ancestors of the
horse had evolved to use muscle

223
00:15:08,360 --> 00:15:11,800
in a totally new way. Incredibly,

224
00:15:11,800 --> 00:15:13,880
evidence of this

225
00:15:13,880 --> 00:15:16,800
can still be seen today.

226
00:15:16,800 --> 00:15:21,000
Inside this little plastic tub here,

227
00:15:21,000 --> 00:15:25,120
I have a beautiful animal.

228
00:15:26,280 --> 00:15:29,520
It's called a sea squirt, or a
tunicate,

229
00:15:29,520 --> 00:15:32,920
and it's a chordate, which means we're
actually related to this.

230
00:15:32,920 --> 00:15:35,280
I know it's difficult to believe, but
it's true.

231
00:15:35,280 --> 00:15:39,160
And the benefit of looking at this
particular species

232
00:15:39,160 --> 00:15:41,240
is that it's transparent.

233
00:15:41,240 --> 00:15:42,840
I can see inside it.

234
00:15:42,840 --> 00:15:46,160
And I can see a tube running around
its body,

235
00:15:46,160 --> 00:15:48,600
and that tube is filled full of

236
00:15:48,600 --> 00:15:51,680
oxygen, minerals and sugar.

237
00:15:53,440 --> 00:15:56,080
It's its blood.

238
00:15:56,080 --> 00:15:59,440
And that tube is contracting.

239
00:16:00,720 --> 00:16:04,800
Waves of muscle contraction are
pushing that blood around the body.

240
00:16:06,920 --> 00:16:08,960
Fundamentally,

241
00:16:08,960 --> 00:16:12,520
this is a simple heart.

242
00:16:12,520 --> 00:16:15,480
It's thought that systems like this

243
00:16:15,480 --> 00:16:18,240
allowed this ancestor of the horse

244
00:16:18,240 --> 00:16:20,920
to enjoy an active lifestyle.

245
00:16:30,920 --> 00:16:33,200
Just like the rest of its kind,

246
00:16:33,200 --> 00:16:34,960
nutrient-rich blood

247
00:16:34,960 --> 00:16:36,840
is being pumped through its body,

248
00:16:36,840 --> 00:16:40,320
making its muscles fizz with energy.

249
00:16:45,280 --> 00:16:47,600
Now, most of these creatures

250
00:16:47,600 --> 00:16:49,560
wouldn't win any races,

251
00:16:49,560 --> 00:16:51,040
spending their energy just

252
00:16:51,040 --> 00:16:53,640
wriggling along the seabed.

253
00:16:53,640 --> 00:16:56,960
But the ancestor of the horse

254
00:16:56,960 --> 00:17:00,480
seems to have had an extra boost,

255
00:17:00,480 --> 00:17:02,240
meaning...

256
00:17:07,160 --> 00:17:10,880
..it can swim harder, better,

257
00:17:10,880 --> 00:17:13,080
faster, stronger.

258
00:17:39,560 --> 00:17:42,360
Its remarkable athletic ability

259
00:17:42,360 --> 00:17:46,120
is thanks to an innovative use of
muscle

260
00:17:46,120 --> 00:17:49,800
that unlocked the full potential of
the heart.

261
00:17:58,840 --> 00:18:03,280
At this point, evolution all starts to
go a bit Frankenstein.

262
00:18:03,280 --> 00:18:05,440
You see, for any muscle to contract,

263
00:18:05,440 --> 00:18:07,480
it requires a stimulus, an order,

264
00:18:07,480 --> 00:18:12,120
and that typically comes in the form
of a tiny electric zap.

265
00:18:13,520 --> 00:18:15,120
And it's thought that some

266
00:18:15,120 --> 00:18:16,680
muscle cells inside some of

267
00:18:16,680 --> 00:18:19,480
the earliest hearts took charge,

268
00:18:19,480 --> 00:18:22,520
specialised and started to send out

269
00:18:22,520 --> 00:18:25,520
a series of rhythmic zaps.

270
00:18:25,520 --> 00:18:29,280
And all of the surrounding muscle
cells complied by contracting,

271
00:18:29,280 --> 00:18:33,280
generating a single powerful pulse.

272
00:18:35,680 --> 00:18:38,360
Now, these mutant zapping cells

273
00:18:38,360 --> 00:18:41,840
are called pacemakers, and almost all
animals have them.

274
00:18:41,840 --> 00:18:46,840
We have a single primary pacemaker
called the sinoatrial node.

275
00:18:46,840 --> 00:18:51,720
And as soon as those ancient
pacemakers began to pulse,

276
00:18:51,720 --> 00:18:54,840
they instigated a revolution.

277
00:18:58,400 --> 00:19:01,280
In the ancestor of the horse,

278
00:19:01,280 --> 00:19:04,320
those specialised pacemaker cells

279
00:19:04,320 --> 00:19:06,160
have now clustered together

280
00:19:06,160 --> 00:19:07,960
in a localised region...

281
00:19:07,960 --> 00:19:09,680
HEARTBEAT

282
00:19:11,560 --> 00:19:13,120
..giving its heart

283
00:19:13,120 --> 00:19:15,080
a more powerful beat.

284
00:19:20,240 --> 00:19:22,920
And over many generations...

285
00:19:24,440 --> 00:19:26,920
..the beat gets stronger.

286
00:19:30,960 --> 00:19:34,000
The muscle walls around the pacemaker
thicken...

287
00:19:36,840 --> 00:19:38,320
..chambers form...

288
00:19:40,400 --> 00:19:41,760
..and valves...

289
00:19:42,920 --> 00:19:44,840
..directing blood flow

290
00:19:44,840 --> 00:19:46,640
around the body...

291
00:19:51,440 --> 00:19:53,920
..becoming an iconic,

292
00:19:53,920 --> 00:19:56,040
life-sustaining organ.

293
00:19:58,440 --> 00:20:01,640
It's an ingenious use of muscle,

294
00:20:01,640 --> 00:20:05,560
one that transformed animal
locomotion.

295
00:20:07,520 --> 00:20:11,160
When hearts went from being a simple
pump to a more complex

296
00:20:11,160 --> 00:20:12,840
muscular mechanism,

297
00:20:12,840 --> 00:20:17,320
it led to a step change in the
evolution of movement.

298
00:20:17,320 --> 00:20:21,080
It allowed animals to become bigger,
stronger, faster.

299
00:20:21,080 --> 00:20:25,440
It allowed them to get off of that
seabed into the world above.

300
00:20:25,440 --> 00:20:27,360
And from that point on,

301
00:20:27,360 --> 00:20:30,200
life would become a slithering,

302
00:20:30,200 --> 00:20:32,520
crawling, walking, running,

303
00:20:32,520 --> 00:20:35,600
jumping and climbing adventure.

304
00:20:35,600 --> 00:20:37,400
Today...

305
00:20:38,960 --> 00:20:41,520
..across the globe,

306
00:20:41,520 --> 00:20:43,520
beating hearts are pumping oxygen

307
00:20:43,520 --> 00:20:45,360
through all sorts of bodies.

308
00:20:48,320 --> 00:20:51,520
Around 2.5 billion heartbeats

309
00:20:51,520 --> 00:20:53,840
will supply your muscles with

310
00:20:53,840 --> 00:20:55,360
the energy they need...

311
00:20:56,920 --> 00:20:59,720
..from your first breath

312
00:20:59,720 --> 00:21:02,960
till your last.

313
00:21:04,840 --> 00:21:08,680
It's a rhythm that connects us all

314
00:21:08,680 --> 00:21:11,400
to the first beats,

315
00:21:11,400 --> 00:21:14,400
over half a billion years ago.

316
00:21:18,520 --> 00:21:21,280
Time to take a leap forward...

317
00:21:23,160 --> 00:21:25,360
..as the descendants of those

318
00:21:25,360 --> 00:21:27,320
early swimmers get bigger,

319
00:21:27,320 --> 00:21:29,640
stronger and faster.

320
00:21:31,040 --> 00:21:33,360
They shapeshift through countless

321
00:21:33,360 --> 00:21:35,200
iterations until

322
00:21:35,200 --> 00:21:39,000
140 million years later...

323
00:21:41,920 --> 00:21:43,280
..they have become...

324
00:21:44,680 --> 00:21:46,080
..fish.

325
00:21:51,240 --> 00:21:55,200
This is an ocean full of powerful
bodies.

326
00:21:57,240 --> 00:22:00,320
But here, it's not how many muscles

327
00:22:00,320 --> 00:22:02,800
you've got that counts,

328
00:22:02,800 --> 00:22:04,760
it's how you use them.

329
00:22:08,400 --> 00:22:10,480
Now, there are many forces

330
00:22:10,480 --> 00:22:12,320
shaping evolution.

331
00:22:14,080 --> 00:22:16,920
The need to find food, the need to
find mates.

332
00:22:19,080 --> 00:22:22,320
But there are even greater forces at
play,

333
00:22:22,320 --> 00:22:25,000
those forces which shape the entire
universe.

334
00:22:25,000 --> 00:22:28,920
I'm talking about the laws of physics.

335
00:22:28,920 --> 00:22:31,040
And when it comes to locomotion,

336
00:22:31,040 --> 00:22:33,760
harnessing these would be key.

337
00:22:33,760 --> 00:22:38,000
And fish have achieved that with a
remarkable innovation,

338
00:22:38,000 --> 00:22:40,800
something that's startling in its
simplicity,

339
00:22:40,800 --> 00:22:43,400
but significant in its importance.

340
00:22:48,080 --> 00:22:49,960
Something that, today,

341
00:22:49,960 --> 00:22:54,640
has helped make fish the success story
of our oceans.

342
00:22:57,880 --> 00:23:00,600
Attached to their streamlined bodies,

343
00:23:00,600 --> 00:23:02,960
structures of flesh, cartilage

344
00:23:02,960 --> 00:23:04,840
and bone have evolved.

345
00:23:06,800 --> 00:23:09,160
Tools which their muscles

346
00:23:09,160 --> 00:23:13,200
can control, expanding the mechanics

347
00:23:13,200 --> 00:23:15,360
of movement available to them.

348
00:23:18,360 --> 00:23:21,000
They can be gliders,

349
00:23:21,000 --> 00:23:22,560
thrusters,

350
00:23:22,560 --> 00:23:25,040
rudders.

351
00:23:25,040 --> 00:23:28,520
I'm talking about fins.

352
00:23:34,600 --> 00:23:38,280
And 380 million years ago,

353
00:23:38,280 --> 00:23:40,400
the ancestor of the horse

354
00:23:40,400 --> 00:23:43,840
was a fish, with fins like this.

355
00:23:46,480 --> 00:23:49,320
You can see the fin here.

356
00:23:49,320 --> 00:23:51,040
But look at the base.

357
00:23:51,040 --> 00:23:52,960
It's made up of a series of

358
00:23:52,960 --> 00:23:56,120
robust, strong bones which anchor it
to the body,

359
00:23:56,120 --> 00:23:59,640
and they would have been covered with
powerful muscles.

360
00:23:59,640 --> 00:24:02,080
And it's this stalk, or lobe,

361
00:24:02,080 --> 00:24:04,760
which gives this group of fishes their
name.

362
00:24:04,760 --> 00:24:08,240
We call them the lobe-finned fishes.

363
00:24:08,240 --> 00:24:11,440
Now, I've got to be honest with you,
in the open ocean,

364
00:24:11,440 --> 00:24:14,440
this set-up probably didn't confer
them with much of

365
00:24:14,440 --> 00:24:15,680
a competitive advantage,

366
00:24:15,680 --> 00:24:18,080
but under certain circumstances,

367
00:24:18,080 --> 00:24:20,960
it proved to be a real bonus.

368
00:24:30,320 --> 00:24:32,640
This is Onychodus...

369
00:24:34,360 --> 00:24:36,040
..an ancient predator

370
00:24:36,040 --> 00:24:37,840
as big as a crocodile...

371
00:24:39,960 --> 00:24:42,880
..with muscular lobed fins.

372
00:24:47,080 --> 00:24:49,080
Now, its size and weight

373
00:24:49,080 --> 00:24:51,240
should be an advantage,

374
00:24:51,240 --> 00:24:54,240
making Onychodus a formidable foe.

375
00:24:56,240 --> 00:24:57,840
But when it swims...

376
00:25:00,280 --> 00:25:03,240
..the water around it is churned up,

377
00:25:03,240 --> 00:25:05,120
giving the game away.

378
00:25:11,080 --> 00:25:14,440
So how does this ocean giant catch its
dinner?

379
00:25:20,880 --> 00:25:24,080
The answer lies in those lobed fins.

380
00:25:24,080 --> 00:25:27,240
Inside there is a tool that's just
begging to be used,

381
00:25:27,240 --> 00:25:30,200
a tool with enormous potential.

382
00:25:30,200 --> 00:25:32,840
I'm talking about a lever.

383
00:25:38,240 --> 00:25:41,920
You see, the relatively small distance
travelled by my hand

384
00:25:41,920 --> 00:25:47,400
and arm here is magnified out there at
the tip of the oar,

385
00:25:47,400 --> 00:25:50,000
which is moving far further.

386
00:25:56,880 --> 00:25:59,600
When it comes to generating movement,

387
00:25:59,600 --> 00:26:01,920
muscles are fantastic,

388
00:26:01,920 --> 00:26:03,960
but they do have their limitations.

389
00:26:06,480 --> 00:26:11,360
The lever is life's great multiplier.

390
00:26:16,520 --> 00:26:19,480
Look, a small amount of force

391
00:26:19,480 --> 00:26:22,360
applied by my arms in the boat

392
00:26:22,360 --> 00:26:24,800
is transferred to the tip of those
oars,

393
00:26:24,800 --> 00:26:29,280
and it allows me to propel the boat
forward.

394
00:26:29,280 --> 00:26:33,080
Not exactly with Olympic prowess, I
have to confess,

395
00:26:33,080 --> 00:26:35,200
but with a degree of efficiency.

396
00:26:41,280 --> 00:26:44,200
And it's thought this same principle

397
00:26:44,200 --> 00:26:46,280
helped this hulking fish

398
00:26:46,280 --> 00:26:49,080
to move with incredible delicacy...

399
00:26:50,800 --> 00:26:52,480
..by doing something

400
00:26:52,480 --> 00:26:54,480
very unfish-like.

401
00:26:59,680 --> 00:27:02,360
Using four of its lobed fins,

402
00:27:02,360 --> 00:27:05,440
along with the physics of levers,

403
00:27:05,440 --> 00:27:08,280
Onychodus turns minimum effort

404
00:27:08,280 --> 00:27:10,920
into maximum movement

405
00:27:10,920 --> 00:27:13,160
and propels itself

406
00:27:13,160 --> 00:27:16,240
stealthily across the seafloor.

407
00:27:30,240 --> 00:27:33,080
Swapping swimming for walking,

408
00:27:33,080 --> 00:27:38,520
it saves its energy for one final,

409
00:27:38,520 --> 00:27:41,000
powerful thrust.

410
00:27:47,600 --> 00:27:51,760
Thanks to its four lobed fins,

411
00:27:51,760 --> 00:27:54,960
Onychodus is a master of the ambush.

412
00:28:01,120 --> 00:28:03,200
So, with skills like these,

413
00:28:03,200 --> 00:28:07,920
you'd expect there to be plenty of
lobe-finned fish in the sea,

414
00:28:07,920 --> 00:28:13,240
but today, they have almost entirely
vanished from our waters.

415
00:28:19,800 --> 00:28:21,360
My goodness!

416
00:28:22,960 --> 00:28:25,360
That was a bit of a workout.

417
00:28:25,360 --> 00:28:29,040
Now, look, levers are very useful in
water,

418
00:28:29,040 --> 00:28:33,040
but they could become even more useful
somewhere else.

419
00:28:36,600 --> 00:28:39,000
When fish like Onychodus begin

420
00:28:39,000 --> 00:28:41,360
to use their lobed fins to walk,

421
00:28:41,360 --> 00:28:43,720
rather than swim,

422
00:28:43,720 --> 00:28:46,800
they set off a chain reaction.

423
00:28:53,120 --> 00:28:55,640
Over millions of years...

424
00:28:57,120 --> 00:28:58,840
..the thick bridge of bones

425
00:28:58,840 --> 00:29:01,600
inside those four fins lengthen...

426
00:29:04,640 --> 00:29:06,640
..and the muscles surrounding them

427
00:29:06,640 --> 00:29:08,400
shift and alter...

428
00:29:10,400 --> 00:29:14,200
..creating strong, tough appendages.

429
00:29:15,800 --> 00:29:18,360
No longer fins at all...

430
00:29:20,520 --> 00:29:24,080
..but four levered limbs.

431
00:29:25,440 --> 00:29:29,400
This was the birth of the tetrapods.

432
00:29:31,240 --> 00:29:33,960
And today, there are more than

433
00:29:33,960 --> 00:29:36,600
30,000 species,

434
00:29:36,600 --> 00:29:38,080
inhabiting every continent.

435
00:29:45,960 --> 00:29:48,200
A diverse supergroup,

436
00:29:48,200 --> 00:29:50,800
all descendants of those fish

437
00:29:50,800 --> 00:29:52,400
with four lobed fins,

438
00:29:52,400 --> 00:29:55,520
are now putting them to use

439
00:29:55,520 --> 00:29:57,480
in very different ways.

440
00:29:59,040 --> 00:30:01,480
Including the horse.

441
00:30:07,720 --> 00:30:09,960
For many tetrapods today,

442
00:30:09,960 --> 00:30:13,400
moving on land is second nature,

443
00:30:13,400 --> 00:30:17,480
but for their ancestors crawling out
of the sea,

444
00:30:17,480 --> 00:30:19,640
it was a very different story.

445
00:30:22,760 --> 00:30:25,320
Moving from one ecosystem

446
00:30:25,320 --> 00:30:28,000
to another which is completely
different,

447
00:30:28,000 --> 00:30:33,280
requires a painfully slow process of
adaptation.

448
00:30:33,280 --> 00:30:35,920
But the creatures that were making
that transition

449
00:30:35,920 --> 00:30:39,040
looked a little bit like this.

450
00:30:43,160 --> 00:30:45,080
Oh, yes.

451
00:30:46,960 --> 00:30:49,240
Look at that.

452
00:30:49,240 --> 00:30:51,040
That's special.

453
00:30:51,040 --> 00:30:53,720
One of nature's jewels.

454
00:30:53,720 --> 00:30:55,440
Absolutely beautiful.

455
00:30:55,440 --> 00:30:59,120
This is a marbled newt.

456
00:30:59,120 --> 00:31:02,720
You see how it got its name, with that
marbling running down

457
00:31:02,720 --> 00:31:04,280
its back there.

458
00:31:05,960 --> 00:31:07,880
It's an amphibian.

459
00:31:07,880 --> 00:31:11,240
It spends its spring in ponds going
through its breeding cycle

460
00:31:11,240 --> 00:31:13,960
and then at the end of summer, it
emerges onto land,

461
00:31:13,960 --> 00:31:16,080
where it spends the rest of the year.

462
00:31:16,080 --> 00:31:20,560
But, of course, it's gone through
millions of years of evolution,

463
00:31:20,560 --> 00:31:23,920
which allow it to exploit the best of
both worlds -

464
00:31:23,920 --> 00:31:26,200
the wet and the dry.

465
00:31:26,200 --> 00:31:28,320
But what about its movement?

466
00:31:28,320 --> 00:31:32,120
Well, in the ponds, it's a fairly good
swimmer, to be fair.

467
00:31:32,120 --> 00:31:33,920
What about on land?

468
00:31:33,920 --> 00:31:35,360
Let's give it a go.

469
00:31:44,560 --> 00:31:47,360
They're tentative, they're slow,

470
00:31:47,360 --> 00:31:49,480
they're laborious, they're calculated.

471
00:31:49,480 --> 00:31:52,200
Their little bodies bending from side
to side,

472
00:31:52,200 --> 00:31:54,600
as they rather lethargically

473
00:31:54,600 --> 00:31:56,320
move through the environment.

474
00:31:57,840 --> 00:32:00,760
I've never seen a newt galloping or
frolicking.

475
00:32:00,760 --> 00:32:03,160
I'm never going to. But this does

476
00:32:03,160 --> 00:32:05,640
tell us something very important.

477
00:32:07,800 --> 00:32:10,720
Movement on land is hard.

478
00:32:10,720 --> 00:32:12,160
Very hard.

479
00:32:18,960 --> 00:32:22,240
This newt can get away with having

480
00:32:22,240 --> 00:32:26,160
four left feet because in a pinch,

481
00:32:26,160 --> 00:32:28,560
it can retreat to a habitat

482
00:32:28,560 --> 00:32:31,040
it finds easier to negotiate.

483
00:32:37,840 --> 00:32:41,520
But 350 million years ago,

484
00:32:41,520 --> 00:32:43,440
if the ancestors of the horse

485
00:32:43,440 --> 00:32:45,040
were to pursue a life

486
00:32:45,040 --> 00:32:47,240
solely on solid ground,

487
00:32:47,240 --> 00:32:51,480
they would need to be far more
coordinated.

488
00:32:51,480 --> 00:32:56,400
And the answer to their coordination
conundrum came, once again,

489
00:32:56,400 --> 00:32:59,000
with an evolutionary innovation

490
00:32:59,000 --> 00:33:02,440
from the ever-adaptable muscle.

491
00:33:02,440 --> 00:33:06,600
Inside almost every muscle in my body,

492
00:33:06,600 --> 00:33:09,800
I have something called a stretch
sensor.

493
00:33:09,800 --> 00:33:13,480
And stretch sensors are highly
specialised muscle fibres

494
00:33:13,480 --> 00:33:17,520
that are constantly monitoring how and
when

495
00:33:17,520 --> 00:33:20,000
those muscles are moving.

496
00:33:20,000 --> 00:33:25,040
The key thing is that they are all
linked together in a complex web,

497
00:33:25,040 --> 00:33:27,360
so each individual muscle knows

498
00:33:27,360 --> 00:33:30,920
exactly when every...other muscle

499
00:33:30,920 --> 00:33:35,080
is moving. Now, despite the fact that
this is an incredibly

500
00:33:35,080 --> 00:33:39,240
complicated system, I bet that you've
never even thought about it,

501
00:33:39,240 --> 00:33:41,920
and that's because you don't have to,

502
00:33:41,920 --> 00:33:43,880
despite the fact that it's crucial

503
00:33:43,880 --> 00:33:46,200
for every single move that we make.

504
00:33:55,800 --> 00:33:59,960
Tiny stretch sensors allow the muscles
to communicate

505
00:33:59,960 --> 00:34:02,360
with the central nervous system,

506
00:34:02,360 --> 00:34:05,240
giving us and most living tetrapods

507
00:34:05,240 --> 00:34:07,560
the ability to co-ordinate movement

508
00:34:07,560 --> 00:34:10,120
with astonishing precision.

509
00:34:10,120 --> 00:34:13,360
Often, faster than you can think.

510
00:34:20,360 --> 00:34:22,000
Look at that.

511
00:34:28,200 --> 00:34:30,160
Just look at the legs there.

512
00:34:30,160 --> 00:34:33,960
Every part of them is moving
independently,

513
00:34:33,960 --> 00:34:36,000
in isolation, at the same time.

514
00:34:36,000 --> 00:34:38,600
And then the weight -

515
00:34:38,600 --> 00:34:42,640
that's got to be balanced between all
four feet.

516
00:34:42,640 --> 00:34:44,760
And running down those legs -

517
00:34:44,760 --> 00:34:47,520
just going to speed it up, look at
that -

518
00:34:47,520 --> 00:34:50,560
are ripples of muscles.

519
00:34:50,560 --> 00:34:52,880
That's the glutes, that's the quads,

520
00:34:52,880 --> 00:34:57,040
that's the hamstrings, all working in
unison.

521
00:35:00,040 --> 00:35:02,200
Without these little gizmos,

522
00:35:02,200 --> 00:35:04,560
these stretch sensors hiding in
muscles

523
00:35:04,560 --> 00:35:07,400
and the complex network that joins
them all together,

524
00:35:07,400 --> 00:35:11,840
animals with bodies like this simply
would not have been able to evolve.

525
00:35:15,880 --> 00:35:18,320
It was down to this innovation

526
00:35:18,320 --> 00:35:19,960
that animal bodies could become

527
00:35:19,960 --> 00:35:22,360
radically more coordinated,

528
00:35:22,360 --> 00:35:25,800
and those tiny little bones, once
hidden in those fish's fins,

529
00:35:25,800 --> 00:35:27,680
could really come into their own.

530
00:35:29,680 --> 00:35:33,280
Those fully terrestrial animals

531
00:35:33,280 --> 00:35:38,320
could put one foot in front of the
other with extreme precision...

532
00:35:40,320 --> 00:35:42,680
..and this was a game-changer.

533
00:35:48,040 --> 00:35:50,440
Time for us to motor on.

534
00:35:53,560 --> 00:35:56,760
Over the next 300 million years,

535
00:35:56,760 --> 00:35:59,320
the tetrapods scattered across the
Earth.

536
00:36:05,240 --> 00:36:08,400
Whilst life faced some cosmic
curveballs...

537
00:36:10,200 --> 00:36:12,320
..it was never fully derailed.

538
00:36:14,640 --> 00:36:16,440
And evolution carried on...

539
00:36:19,600 --> 00:36:21,280
..tumbling us...

540
00:36:25,080 --> 00:36:26,720
..into a new world...

541
00:36:30,920 --> 00:36:32,560
..where the way you move...

542
00:36:34,080 --> 00:36:37,720
..can be a matter of life

543
00:36:37,720 --> 00:36:39,360
and death.

544
00:36:44,400 --> 00:36:46,640
This is Phenacodus.

545
00:36:54,280 --> 00:36:57,560
Life looks pretty serene,

546
00:36:57,560 --> 00:37:00,600
but Phenacodus must constantly

547
00:37:00,600 --> 00:37:04,200
be on guard, because this world

548
00:37:04,200 --> 00:37:06,880
is full of expert movers...

549
00:37:06,880 --> 00:37:08,400
BRANCH SNAPS

550
00:37:08,400 --> 00:37:10,120
..whose bodies...

551
00:37:12,080 --> 00:37:14,640
..have evolved for the chase.

552
00:37:18,280 --> 00:37:20,640
GROWLING
When the hunt is on...

553
00:37:20,640 --> 00:37:23,920
..surging adrenaline, thumping hearts

554
00:37:23,920 --> 00:37:26,800
and straining muscles will only take
you so far.

555
00:37:31,280 --> 00:37:33,360
Faced with a situation it can't

556
00:37:33,360 --> 00:37:35,040
muscle its way out of...

557
00:37:36,920 --> 00:37:39,080
..the secret to Phenacodus's

558
00:37:39,080 --> 00:37:43,320
survival lies in its feet.

559
00:37:48,000 --> 00:37:50,200
Come on, Siddy! Nance, come on!

560
00:37:50,200 --> 00:37:51,760
DOG BARKS

561
00:37:56,880 --> 00:38:00,960
Do you know, sometimes, people say,
"Why poodles?

562
00:38:00,960 --> 00:38:03,680
"Why poodles?" they say. And I
facetiously reply,

563
00:38:03,680 --> 00:38:05,200
"Are there other breeds of dog?"

564
00:38:05,200 --> 00:38:06,400
I mean, look at them.

565
00:38:06,400 --> 00:38:09,800
Boundless energy, incredibly loyal,

566
00:38:09,800 --> 00:38:11,400
and they can also help us

567
00:38:11,400 --> 00:38:14,200
with an important part of our story.

568
00:38:14,200 --> 00:38:16,000
You see, hidden beneath

569
00:38:16,000 --> 00:38:18,960
this curly fur here is a crucial

570
00:38:18,960 --> 00:38:21,880
step change in evolution.

571
00:38:21,880 --> 00:38:24,720
Now, I don't need to tell you about my
foot and leg,

572
00:38:24,720 --> 00:38:27,000
you've got your own. Starts off at the
toe,

573
00:38:27,000 --> 00:38:28,560
goes across the foot to the ankle,

574
00:38:28,560 --> 00:38:32,400
then you've got the shin, the knee,
the thigh.

575
00:38:32,400 --> 00:38:34,400
We put our feet down

576
00:38:34,400 --> 00:38:36,040
onto the ground, we plant them

577
00:38:36,040 --> 00:38:38,200
flat on the ground like that.

578
00:38:38,200 --> 00:38:39,560
We're what we call

579
00:38:39,560 --> 00:38:43,520
plantigrade animals. It's quite an
efficient way of walking.

580
00:38:43,520 --> 00:38:46,720
Nancy, on the other hand, is
altogether different.

581
00:38:46,720 --> 00:38:48,920
Let's take a look at her back leg
here.

582
00:38:48,920 --> 00:38:51,280
You see, her toes stretch

583
00:38:51,280 --> 00:38:52,760
from here to here.

584
00:38:52,760 --> 00:38:54,640
The rest of her foot bones

585
00:38:54,640 --> 00:38:56,280
all the way up to here, which looks

586
00:38:56,280 --> 00:38:57,840
like a backward-pointing knee,

587
00:38:57,840 --> 00:39:01,120
but this is, in fact, her ankle.

588
00:39:01,120 --> 00:39:02,840
Her knee is all the way

589
00:39:02,840 --> 00:39:04,520
up here. So Nancy

590
00:39:04,520 --> 00:39:07,120
is effectively standing up

591
00:39:07,120 --> 00:39:10,040
on her toe bones.

592
00:39:10,040 --> 00:39:13,280
She's a digitigrade animal,

593
00:39:13,280 --> 00:39:15,320
and that's altogether different.

594
00:39:15,320 --> 00:39:18,240
It means that you move in a very
different way, doesn't it?

595
00:39:18,240 --> 00:39:19,920
Shall we show them?

596
00:39:19,920 --> 00:39:22,400
Come on, let's go. Come on.

597
00:39:30,880 --> 00:39:33,760
Right, Sid, Nancy.

598
00:39:33,760 --> 00:39:35,520
Let's see them in action.

599
00:39:35,520 --> 00:39:37,040
BARKING

600
00:39:42,000 --> 00:39:44,840
Woo-hoo-hoo!
BARKING

601
00:39:44,840 --> 00:39:46,560
Look at them go! You see,

602
00:39:46,560 --> 00:39:50,360
this change in anatomy allows the leg
to become longer,

603
00:39:50,360 --> 00:39:52,400
the stride to become longer,

604
00:39:52,400 --> 00:39:56,080
and more efficient use of all of that
elastic energy

605
00:39:56,080 --> 00:39:58,800
stored in the muscles and tendons

606
00:39:58,800 --> 00:40:00,720
above their ankle.

607
00:40:00,720 --> 00:40:01,880
Look at that!

608
00:40:01,880 --> 00:40:03,200
Bouncing about.

609
00:40:03,200 --> 00:40:05,160
BARKING

610
00:40:05,160 --> 00:40:08,320
Alacrity, agility.

611
00:40:08,320 --> 00:40:10,320
Critically, speed.

612
00:40:10,320 --> 00:40:13,240
That is a happy poodle.

613
00:40:14,480 --> 00:40:17,680
And, you know, this adaptation has
occurred a number of times

614
00:40:17,680 --> 00:40:21,280
in terrestrial animals. But having
said that,

615
00:40:21,280 --> 00:40:25,120
if you really want to be a creature
living life in the fast lane,

616
00:40:25,120 --> 00:40:29,640
evolution can offer you one more gear.

617
00:40:29,640 --> 00:40:32,080
Siddy, Nance, come on! Come on!

618
00:40:34,280 --> 00:40:38,360
When it comes to speed and efficiency,
plantigrade -

619
00:40:38,360 --> 00:40:41,760
that's us - will get you from A to B.

620
00:40:41,760 --> 00:40:44,920
Digitigrade - like my dogs -

621
00:40:44,920 --> 00:40:47,040
ups the revs.

622
00:40:48,760 --> 00:40:51,520
But 56 million years ago,

623
00:40:51,520 --> 00:40:55,440
Phenacodus was on the verge of
something new.

624
00:40:56,480 --> 00:41:00,800
Not just bouncing on the balls of its
feet,

625
00:41:00,800 --> 00:41:05,440
but pushing off from the very tips of
its toes...

626
00:41:08,920 --> 00:41:11,680
..lengthening its stride even further.

627
00:41:13,040 --> 00:41:16,200
So future generations take the
concept...

628
00:41:17,320 --> 00:41:18,920
..and run with it.

629
00:41:23,920 --> 00:41:25,960
As bones elongate

630
00:41:25,960 --> 00:41:27,560
and muscles bulk up...

631
00:41:28,800 --> 00:41:30,320
..they spend more

632
00:41:30,320 --> 00:41:32,600
and more time on tiptoe...

633
00:41:35,920 --> 00:41:37,320
..and in the process...

634
00:41:38,840 --> 00:41:40,600
..find the most efficiency

635
00:41:40,600 --> 00:41:42,480
in trading many toes

636
00:41:42,480 --> 00:41:45,600
for one large,

637
00:41:45,600 --> 00:41:47,600
powerful shock absorber.

638
00:41:52,720 --> 00:41:54,520
Look at this.

639
00:41:54,520 --> 00:41:57,520
This is clearly a cast

640
00:41:57,520 --> 00:41:59,880
of a fossil of a hoof.

641
00:41:59,880 --> 00:42:04,120
A hoof at the end of a very long leg.

642
00:42:04,120 --> 00:42:08,080
A leg that's clearly all about
movement.

643
00:42:08,080 --> 00:42:11,800
A leg, though, that is surprisingly
different than ours.

644
00:42:11,800 --> 00:42:13,840
You see, essentially, it's foot

645
00:42:13,840 --> 00:42:15,680
all the way from here to here.

646
00:42:15,680 --> 00:42:18,480
This is the equivalent of our ankle.

647
00:42:18,480 --> 00:42:21,120
The bone here would be like those in
the sole of our foot.

648
00:42:21,120 --> 00:42:22,480
And down here,

649
00:42:22,480 --> 00:42:26,480
it's balancing on a single tiptoe.

650
00:42:26,480 --> 00:42:29,520
The hoof itself would have been made
of keratin,

651
00:42:29,520 --> 00:42:31,560
just like our fingernail.

652
00:42:31,560 --> 00:42:33,640
And also, what's interesting is at the
other end,

653
00:42:33,640 --> 00:42:36,640
the front legs weren't attached to the
skeleton.

654
00:42:36,640 --> 00:42:38,080
They were embedded

655
00:42:38,080 --> 00:42:40,880
in a heavy mass of powerful muscle,

656
00:42:40,880 --> 00:42:45,360
and this gave it the capacity for a
greater stride.

657
00:42:45,360 --> 00:42:47,480
You see this groove here?

658
00:42:47,480 --> 00:42:50,040
Running down here would have been a
tendon,

659
00:42:50,040 --> 00:42:51,920
perhaps half a metre long,

660
00:42:51,920 --> 00:42:54,920
a giant elastic band.

661
00:42:54,920 --> 00:42:57,360
But it is a leg with compromises.

662
00:42:57,360 --> 00:43:00,480
I mean, you can't pick anything up
with a hoof,

663
00:43:00,480 --> 00:43:02,040
you can't manipulate anything.

664
00:43:02,040 --> 00:43:04,440
It's lost all dexterity,

665
00:43:04,440 --> 00:43:06,720
at the expense of speed.

666
00:43:09,000 --> 00:43:13,160
This three-million-year-old hoof

667
00:43:13,160 --> 00:43:15,720
tells us of the arrival

668
00:43:15,720 --> 00:43:19,080
of a new group of animals.

669
00:43:19,080 --> 00:43:22,360
Animals we call Equus.

670
00:43:34,560 --> 00:43:37,040
These single-hoofed mammals

671
00:43:37,040 --> 00:43:40,040
first evolved on the plains of North
America...

672
00:43:42,160 --> 00:43:44,440
..before spreading across the globe.

673
00:43:47,160 --> 00:43:49,600
Among them

674
00:43:49,600 --> 00:43:52,560
was one remarkable species.

675
00:43:54,720 --> 00:43:57,200
Equus ferus.

676
00:44:00,360 --> 00:44:04,560
Known to you and I as the horse.

677
00:44:10,720 --> 00:44:12,400
Its body shaped

678
00:44:12,400 --> 00:44:14,680
generation after generation...

679
00:44:19,520 --> 00:44:22,200
..by the evolutionary drive to move.

680
00:44:25,560 --> 00:44:29,080
700 muscles, passed down

681
00:44:29,080 --> 00:44:31,240
over half a billion years,

682
00:44:31,240 --> 00:44:34,040
from a pioneer who changed the world.

683
00:44:34,040 --> 00:44:37,440
A huge heart, with an ancient beat,

684
00:44:37,440 --> 00:44:41,000
that began deep beneath the waves.

685
00:44:41,000 --> 00:44:43,240
Long levered limbs

686
00:44:43,240 --> 00:44:46,800
that once helped a fish to walk...

687
00:44:48,360 --> 00:44:51,120
..and four large hooves,

688
00:44:51,120 --> 00:44:53,160
the legacy of ancestors

689
00:44:53,160 --> 00:44:56,280
who had to run for their lives.

690
00:44:57,600 --> 00:45:01,000
But there's one final twist

691
00:45:01,000 --> 00:45:03,360
in the story of the horse,

692
00:45:03,360 --> 00:45:05,240
because Equus ferus

693
00:45:05,240 --> 00:45:07,560
was about to encounter

694
00:45:07,560 --> 00:45:09,960
a new force of evolution.

695
00:45:17,400 --> 00:45:19,200
Another species

696
00:45:19,200 --> 00:45:22,760
on an evolutionary journey of its own.

697
00:45:22,760 --> 00:45:25,000
A bipedal tetrapod,

698
00:45:25,000 --> 00:45:27,240
with opposable thumbs,

699
00:45:27,240 --> 00:45:31,360
and an overinflated sense of
self-worth.

700
00:45:48,720 --> 00:45:51,960
4,000 years ago, Homo sapiens -

701
00:45:51,960 --> 00:45:53,840
that's us - inhabited

702
00:45:53,840 --> 00:45:55,320
much of the planet.

703
00:45:55,320 --> 00:45:56,840
HORSE WHINNIES

704
00:45:56,840 --> 00:45:59,880
We had city states and agriculture.

705
00:45:59,880 --> 00:46:02,640
Empires were beginning to grow.

706
00:46:04,840 --> 00:46:07,720
And at this time, in Europe and Asia,

707
00:46:07,720 --> 00:46:09,520
we begin to see evidence

708
00:46:09,520 --> 00:46:12,040
of a growing relationship

709
00:46:12,040 --> 00:46:14,160
between horses

710
00:46:14,160 --> 00:46:15,960
and humans.

711
00:46:18,640 --> 00:46:23,160
Now, no-one is exactly sure how the
first horse was tamed.

712
00:46:23,160 --> 00:46:25,560
Maybe someone caught one of those wild
horses,

713
00:46:25,560 --> 00:46:28,520
took it into captivity, gave it
shelter, food,

714
00:46:28,520 --> 00:46:32,240
cared for it, loved it and trained it.

715
00:46:32,240 --> 00:46:35,400
But what we do know is that in pretty
short time,

716
00:46:35,400 --> 00:46:40,080
we took these strong, efficient,
powerful animals

717
00:46:40,080 --> 00:46:43,920
and turned them into our perfect
companions.

718
00:46:43,920 --> 00:46:46,520
And, you know, we didn't just tame
them.

719
00:46:46,520 --> 00:46:49,840
Over generation after generation, we
bred them,

720
00:46:49,840 --> 00:46:52,560
choosing those characteristics which
favoured the way

721
00:46:52,560 --> 00:46:55,600
we wanted horses to be.

722
00:46:55,600 --> 00:46:58,520
So in the end, we took the wild horse

723
00:46:58,520 --> 00:47:01,800
and we turned it into the workhorse.

724
00:47:14,640 --> 00:47:16,760
We chose the strongest.

725
00:47:18,320 --> 00:47:20,000
We chose the most powerful.

726
00:47:21,560 --> 00:47:24,640
But we also chose the friendliest,

727
00:47:24,640 --> 00:47:26,880
the most amenable.

728
00:47:29,840 --> 00:47:32,480
And for better or for worse,

729
00:47:32,480 --> 00:47:34,560
over the generations,

730
00:47:34,560 --> 00:47:36,960
the horse was altered.

731
00:47:40,560 --> 00:47:42,520
The ancestors of the modern horse

732
00:47:42,520 --> 00:47:44,160
were a pretty wild bunch.

733
00:47:45,280 --> 00:47:47,800
Diverse not only in terms of their
physical appearance,

734
00:47:47,800 --> 00:47:50,760
but also, their genetic make-up.

735
00:47:50,760 --> 00:47:52,880
And about 4,000 years ago,

736
00:47:52,880 --> 00:47:55,800
we see two gene variants appear.

737
00:47:55,800 --> 00:47:57,160
HORSE WHINNIES

738
00:47:57,160 --> 00:47:59,960
Now, one of those appears to make them
less aggressive,

739
00:47:59,960 --> 00:48:01,520
more manageable.

740
00:48:03,680 --> 00:48:07,080
And the other, which appears to give
them a stronger back,

741
00:48:07,080 --> 00:48:09,760
making them easier to ride.

742
00:48:09,760 --> 00:48:11,520
Now, what's interesting is that

743
00:48:11,520 --> 00:48:14,000
within the space of just a few hundred
years,

744
00:48:14,000 --> 00:48:16,040
we'd spread those gene variants

745
00:48:16,040 --> 00:48:18,400
throughout the population.

746
00:48:20,200 --> 00:48:22,960
The wild horse was effectively gone.

747
00:48:22,960 --> 00:48:25,840
We had one global species,

748
00:48:25,840 --> 00:48:28,600
selected by humans.

749
00:48:28,600 --> 00:48:30,080
You.

750
00:48:30,080 --> 00:48:33,320
Yes. I know.

751
00:48:33,320 --> 00:48:35,320
It wasn't my fault.

752
00:48:35,320 --> 00:48:37,040
I wasn't around then.

753
00:48:49,160 --> 00:48:52,480
Today, the horse goes by a new name.

754
00:48:54,160 --> 00:48:58,160
Equus ferus caballus.

755
00:48:58,160 --> 00:49:00,080
The domestic horse.

756
00:49:01,560 --> 00:49:04,120
Our relationship is a special one.

757
00:49:05,960 --> 00:49:07,560
Together, we've travelled to

758
00:49:07,560 --> 00:49:09,480
every corner of the globe.

759
00:49:11,400 --> 00:49:12,960
Step by step...

760
00:49:14,320 --> 00:49:15,960
..and side by side.

761
00:49:21,520 --> 00:49:23,400
We often think of evolution

762
00:49:23,400 --> 00:49:25,360
as a battle between species,

763
00:49:25,360 --> 00:49:27,520
a game of winners and losers,

764
00:49:27,520 --> 00:49:29,880
a game of survival of the fittest.

765
00:49:29,880 --> 00:49:33,000
But very occasionally, species come
together

766
00:49:33,000 --> 00:49:36,880
and the result is greater than the sum
of their parts.

767
00:49:36,880 --> 00:49:40,440
Now, there's no doubt we played a
hugely instrumental role

768
00:49:40,440 --> 00:49:42,200
in the evolution of the horse,

769
00:49:42,200 --> 00:49:45,800
but then the horse has had an impact
on us too,

770
00:49:45,800 --> 00:49:50,880
because without this remarkable animal
as our greatest partner,

771
00:49:50,880 --> 00:49:55,040
we simply wouldn't be the species we
are today.

772
00:49:59,000 --> 00:50:01,800
The horse's evolutionary journey

773
00:50:01,800 --> 00:50:03,680
is just one thread

774
00:50:03,680 --> 00:50:06,360
in an extraordinary tapestry...

775
00:50:07,880 --> 00:50:11,800
..that weaves together every animal,

776
00:50:11,800 --> 00:50:14,520
in fact, every living thing

777
00:50:14,520 --> 00:50:16,240
on our planet.

778
00:50:17,920 --> 00:50:21,080
It's taken four billion years

779
00:50:21,080 --> 00:50:23,560
to get here, but, boy,

780
00:50:23,560 --> 00:50:27,000
has life come a very, very long way!

781
00:50:30,080 --> 00:50:33,000
From the cell that began it all...

782
00:50:35,160 --> 00:50:36,640
..to sex...

783
00:50:37,760 --> 00:50:39,560
..to competition...

784
00:50:40,840 --> 00:50:43,120
..to predation and protection.

785
00:50:49,560 --> 00:50:52,920
From the oceans to the land

786
00:50:52,920 --> 00:50:56,320
and, for some, back again.

787
00:50:59,680 --> 00:51:03,320
For others, onwards to the skies.

788
00:51:05,520 --> 00:51:08,560
There was a bum that changed the
world.

789
00:51:09,800 --> 00:51:11,880
There were jaws, limbs,

790
00:51:11,880 --> 00:51:14,600
hearts and minds.

791
00:51:14,600 --> 00:51:17,720
Minds which have evolved to sense,

792
00:51:17,720 --> 00:51:20,400
to move, to love,

793
00:51:20,400 --> 00:51:22,080
to contemplate...

794
00:51:25,160 --> 00:51:27,560
..and, in our case,

795
00:51:27,560 --> 00:51:29,000
to begin to understand

796
00:51:29,000 --> 00:51:31,320
our own origins.

797
00:51:37,040 --> 00:51:39,840
A journey of knowledge

798
00:51:39,840 --> 00:51:41,880
that we're still on today.

799
00:51:44,520 --> 00:51:47,000
There's an outdated view,

800
00:51:47,000 --> 00:51:48,960
a mistaken idea,

801
00:51:48,960 --> 00:51:53,960
that we humans are the be-all and
end-all of evolution.

802
00:51:53,960 --> 00:51:56,480
That everything we've explored,
everything we've shown you

803
00:51:56,480 --> 00:52:02,280
in this series was just about making
us the perfect organism,

804
00:52:02,280 --> 00:52:05,000
the paragon of life on Earth.

805
00:52:05,000 --> 00:52:07,760
But it's simply not true.

806
00:52:07,760 --> 00:52:10,680
We're not perfect and we weren't made.

807
00:52:10,680 --> 00:52:13,760
We've been shaped by exactly the same
forces

808
00:52:13,760 --> 00:52:19,440
that have shaped every organism that's
ever lived on this planet.

809
00:52:19,440 --> 00:52:22,040
And through a startling twist of fate,

810
00:52:22,040 --> 00:52:24,480
we are now having a profound effect

811
00:52:24,480 --> 00:52:26,920
on evolution ourselves.

812
00:52:26,920 --> 00:52:30,160
A dramatic, rapid and scary one

813
00:52:30,160 --> 00:52:33,120
because of what we're doing to our
environment

814
00:52:33,120 --> 00:52:38,800
and because we're driving a massive
extinction event.

815
00:52:38,800 --> 00:52:43,760
Now, evolution does feast on
extinction.

816
00:52:43,760 --> 00:52:47,320
It loves the opportunities, the
vacancies.

817
00:52:47,320 --> 00:52:51,160
So whatever we do now, life will go
on.

818
00:52:51,160 --> 00:52:54,280
Life will be bright, life will be
beautiful,

819
00:52:54,280 --> 00:52:57,720
life will be wonderful.

820
00:52:57,720 --> 00:53:01,880
But in evolutionary terms, what about
us?

821
00:53:01,880 --> 00:53:04,360
Could we become shorter,

822
00:53:04,360 --> 00:53:06,640
slower, more short-sighted?

823
00:53:06,640 --> 00:53:10,720
Might we become smarter, more stupid?

824
00:53:12,160 --> 00:53:16,360
I don't think it really matters about
our anatomy at this point.

825
00:53:17,680 --> 00:53:20,760
I think what matters is how we think,

826
00:53:20,760 --> 00:53:25,520
imagine and create our way out of our
situation.

827
00:53:27,000 --> 00:53:31,880
I think that what needs to be driving
human evolution right now...

828
00:53:33,400 --> 00:53:34,720
..is hope.

829
00:53:57,200 --> 00:53:58,920
But before we go...

830
00:54:01,560 --> 00:54:03,280
..how did we bring the story

831
00:54:03,280 --> 00:54:05,240
of evolution to life?

832
00:54:08,600 --> 00:54:10,400
The way that one animal,

833
00:54:10,400 --> 00:54:11,720
over millions of years,

834
00:54:11,720 --> 00:54:14,680
can transform into something radically
different

835
00:54:14,680 --> 00:54:17,520
was once a mystery lost to time.

836
00:54:19,240 --> 00:54:21,680
- If we think about a book, we have
lots of different pages

837
00:54:21,680 --> 00:54:23,600
that tell us the story from start to
finish.

838
00:54:25,040 --> 00:54:28,080
However, with evolution and fossils,
some of those pages are missing.

839
00:54:30,080 --> 00:54:32,080
- But occasionally, evidence

840
00:54:32,080 --> 00:54:34,040
is unearthed of the process

841
00:54:34,040 --> 00:54:38,640
in action. In 2004, palaeontologists

842
00:54:38,640 --> 00:54:40,400
in the Canadian Arctic

843
00:54:40,400 --> 00:54:43,240
discovered a ground-breaking fossil.

844
00:54:43,240 --> 00:54:45,440
- So this is a cast of Tiktaalik.

845
00:54:45,440 --> 00:54:49,640
Now, Tiktaalik lived about 375 million
years ago,

846
00:54:49,640 --> 00:54:51,720
and it's got the scales very much

847
00:54:51,720 --> 00:54:53,960
like modern-day fish have today.

848
00:54:53,960 --> 00:54:56,920
And what's quite unusual is that it
actually has a neck.

849
00:54:56,920 --> 00:54:58,480
And these bones that are around there,

850
00:54:58,480 --> 00:54:59,800
these are the sort of collar bone

851
00:54:59,800 --> 00:55:01,480
or shoulder girdle. It looks like

852
00:55:01,480 --> 00:55:04,000
a cross between a fish and an
amphibian,

853
00:55:04,000 --> 00:55:07,000
and that's because that's exactly what
it is.

854
00:55:07,000 --> 00:55:08,400
- Tiktaalik was really this kind of

855
00:55:08,400 --> 00:55:10,480
unique snapshot in evolutionary time

856
00:55:10,480 --> 00:55:12,480
at this key moment

857
00:55:12,480 --> 00:55:14,240
for the water-to-land transition.

858
00:55:15,680 --> 00:55:17,160
- So it's a perfect example of

859
00:55:17,160 --> 00:55:18,400
a transitional fossil.

860
00:55:18,400 --> 00:55:20,440
- Transitional fossils are incredibly
rare.

861
00:55:21,640 --> 00:55:24,080
They play the really important role of
filling those gaps

862
00:55:24,080 --> 00:55:26,880
between morphologies that we kind of
know are there,

863
00:55:26,880 --> 00:55:28,720
but we don't really know exactly

864
00:55:28,720 --> 00:55:30,840
what they might have looked like.

865
00:55:30,840 --> 00:55:33,400
- Transitional fossils represent

866
00:55:33,400 --> 00:55:35,200
just one out of millions,

867
00:55:35,200 --> 00:55:37,760
possibly billions, of individuals

868
00:55:37,760 --> 00:55:39,240
that, over generations,

869
00:55:39,240 --> 00:55:42,040
contribute to evolutionary change.

870
00:55:42,040 --> 00:55:45,040
Coming up with a way to illustrate
this

871
00:55:45,040 --> 00:55:47,040
posed a huge challenge

872
00:55:47,040 --> 00:55:49,760
to the visual effects team behind the
series.

873
00:55:49,760 --> 00:55:52,160
- Evolution does not move in a
straight line,

874
00:55:52,160 --> 00:55:54,440
because it is purely opportunistic

875
00:55:54,440 --> 00:55:55,880
and slightly haphazard.

876
00:55:55,880 --> 00:55:58,960
- It's tinkering. It's messing with
what's already there,

877
00:55:58,960 --> 00:56:00,440
rather than kind of always

878
00:56:00,440 --> 00:56:03,200
necessarily inventing something from
scratch.

879
00:56:03,200 --> 00:56:05,800
- It's all about a great grand
experiment

880
00:56:05,800 --> 00:56:07,280
and just seeing what happens.

881
00:56:08,600 --> 00:56:11,240
- The team spent thousands of hours

882
00:56:11,240 --> 00:56:12,960
crafting and animating

883
00:56:12,960 --> 00:56:14,760
computer-generated models

884
00:56:14,760 --> 00:56:16,200
to bring ancient animals

885
00:56:16,200 --> 00:56:17,520
back to life.

886
00:56:17,520 --> 00:56:19,800
But to illustrate the randomness

887
00:56:19,800 --> 00:56:23,160
and variation seen as life evolves,

888
00:56:23,160 --> 00:56:25,680
they needed to experiment.

889
00:56:25,680 --> 00:56:28,720
After consulting scientists to
accurately model

890
00:56:28,720 --> 00:56:30,960
the key evolutionary changes,

891
00:56:30,960 --> 00:56:33,120
they used generative AI software

892
00:56:33,120 --> 00:56:36,480
to create hundreds of variations,

893
00:56:36,480 --> 00:56:39,280
representing countless generations.

894
00:56:39,280 --> 00:56:42,440
And by hand-selecting and merging

895
00:56:42,440 --> 00:56:44,520
the best results with their original

896
00:56:44,520 --> 00:56:46,440
animations, they were able

897
00:56:46,440 --> 00:56:48,200
to condense millions of years

898
00:56:48,200 --> 00:56:50,120
of evolution...

899
00:56:50,120 --> 00:56:51,600
- Look at that!
- There's bones inside!

900
00:56:51,600 --> 00:56:52,800
- No way!

901
00:56:52,800 --> 00:56:55,600
- ..into a matter of seconds.

902
00:56:55,600 --> 00:56:57,160
- In reality, this would take

903
00:56:57,160 --> 00:56:58,520
millions of years.

904
00:57:00,440 --> 00:57:01,920
- This is a fantastic way

905
00:57:01,920 --> 00:57:04,440
to illustrate the evolution of form.

906
00:57:04,440 --> 00:57:06,640
This is basically how I imagine it
playing out in my head.

907
00:57:17,440 --> 00:57:18,960
- This series has been over

908
00:57:18,960 --> 00:57:21,200
four billion years in the making...

909
00:57:22,680 --> 00:57:25,080
..and as a certain Charles Darwin

910
00:57:25,080 --> 00:57:26,840
once wrote,

911
00:57:26,840 --> 00:57:29,280
"From so simple a beginning

912
00:57:29,280 --> 00:57:32,120
"endless forms most beautiful

913
00:57:32,120 --> 00:57:34,480
"and most wonderful have been,

914
00:57:34,480 --> 00:57:37,320
"and are being evolved."

915
00:57:37,320 --> 00:57:40,120
- One of the big key life lessons that

916
00:57:40,120 --> 00:57:42,000
I've learned from studying evolution

917
00:57:42,000 --> 00:57:44,360
is that change is constant

918
00:57:44,360 --> 00:57:46,640
and change is the norm. So things

919
00:57:46,640 --> 00:57:48,240
have always changed and will always

920
00:57:48,240 --> 00:57:49,800
continue to change, and life

921
00:57:49,800 --> 00:57:51,160
will always continue to adapt.

922
00:57:54,160 --> 00:57:55,880
- That's how it's always been,

923
00:57:55,880 --> 00:57:57,120
and there's no reason to believe

924
00:57:57,120 --> 00:57:58,960
that's not how it's going to continue
to be.

925
00:58:11,520 --> 00:58:15,040
- Do you want to know how an elephant
is related to a clownfish?

926
00:58:15,040 --> 00:58:18,760
Discover more in a poster from the
Open University on

927
00:58:18,760 --> 00:58:20,760
the tree of life. To get your free
copy,

928
00:58:20,760 --> 00:58:23,360
scan the QR code on-screen or ring...

929
00:58:27,040 --> 00:58:28,520
..or visit...