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THESE SUBTITLES DO NOT PLAY CORRECTLY IN SYNCH WITH THE MOVIEREMEMBER NAMES OF ORGANISMS (SPECIES OF APES, ETC)REMEMBER DATES OF FOSSILS / OF ORIGIN OF EACH GIVEN SPECIESREMEMBER CHARACTERISTICS OF EACH SPECIES AND HOW THEY DIFFERED FROM EACH OTHERREMEMBER HYPOTHETICAL TRANSITIONS FROM ONE TO ANOTHER SPECIES AND TO HUMAN000:00:01,000 --> 00:00:04,000Downloaded From www.AllSubs.org
100:00:02,267 --> 00:00:03,967NARRATOR:Humans...
200:00:04,033 --> 00:00:08,100Without a doubt, the smartestanimal on earth,
300:00:08,167 --> 00:00:12,900yet we're unmistakably tiedto our ape origins.
400:00:12,967 --> 00:00:14,633Millions of years ago,
500:00:14,700 --> 00:00:18,200we were apesliving ape lives in Africa.
600:00:18,267 --> 00:00:20,800So how did we get from that...
700:00:20,867 --> 00:00:22,900to this?
800:00:25,500 --> 00:00:26,733What happened?
900:00:26,800 --> 00:00:30,700What set us on the pathto humanity?
1000:00:30,767 --> 00:00:32,933The questions are huge.
1100:00:33,000 --> 00:00:35,900But now, there are answers.
1200:00:35,967 --> 00:00:38,267At the threshold of humanity,
1300:00:38,333 --> 00:00:42,367one ancestor containstantalizing secrets.
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1400:00:42,533 --> 00:00:44,867It is known as Homo erectus.
1500:00:44,933 --> 00:00:47,100RICHARD WRANGHAM:Homo erectus had
a slightly smaller brain,
1600:00:47,167 --> 00:00:50,667slightly bigger jaw,but it's basically us.
1700:00:50,733 --> 00:00:57,967NARRATOR:Basically us--almost two million years ago.
1800:00:58,033 --> 00:01:02,333New finds are revealing
the truth about the ancestors
1900:01:02,400 --> 00:01:05,267at the heart of our evolution.
2000:01:05,333 --> 00:01:09,567Here were the trailblazerswho first left Africa--
2100:01:09,633 --> 00:01:13,933the first fire makers,the first hunters.
2200:01:14,000 --> 00:01:15,333JOHN SHEA:These creatures were capable
2300:01:15,400 --> 00:01:17,367of analyzing possible usesof tools
2400:01:17,633 --> 00:01:19,133and coming up witha technological solution
2500:01:19,200 --> 00:01:21,067to the problem of how you killa big, dangerous animal
2600:01:21,133 --> 00:01:23,567without getting killed yourself.
2700:01:23,633 --> 00:01:27,800NARRATOR:
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Homo erectus pioneeredwhat it means to be human,
2800:01:27,867 --> 00:01:29,900colonizing whole continents
29
00:01:29,967 --> 00:01:33,667and creating the firsthuman societies.
3000:01:33,733 --> 00:01:38,033SARAH HRDY:Our ancestors began to careabout what others thought
3100:01:38,100 --> 00:01:42,667and care about what thatindividual thought about them.
3200:01:42,733 --> 00:01:45,733NARRATOR:Now, new discoveries arebringing them alive
3300:01:45,800 --> 00:01:47,400as never before.
3400:01:47,467 --> 00:01:52,300At last, we come face to facewith the ancestors
3500:01:52,367 --> 00:01:56,300at the birth of humanity,right now on NOVA.
3600:02:11,300 --> 00:02:14,967Major funding for NOVAis provided by the following:
3700:02:15,033 --> 00:02:16,833ExxonMobil,
3800:02:16,900 --> 00:02:19,533taking on the world'stoughest energy challenges.
3900:02:19,600 --> 00:02:21,300And by:
4000:02:25,700 --> 00:02:27,533And...
4100:02:36,867 --> 00:02:39,933
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And by the Corporationfor Public Broadcasting
4200:02:40,000 --> 00:02:43,033and by contributionsto your PBS station from:
4300:03:00,833 --> 00:03:03,567NARRATOR:The Great Rift Valleyof East Africa.
4400:03:06,733 --> 00:03:10,933Two million years ago, thesespectacular plains and canyons
4500:03:11,000 --> 00:03:14,800witnessed a mysterious event,
4600:03:14,867 --> 00:03:21,167the birth of the first ancestor
we can really call human.
4700:03:21,233 --> 00:03:25,900New discoveries are revealing acreature surprisingly like us--
4800:03:25,967 --> 00:03:32,167a world traveler, a toolmaker,a hunter, tamer of fire,
4900:03:32,233 --> 00:03:35,033creator of the firsthuman societies.
5000:03:36,367 --> 00:03:39,567Amazingly, the qualitiesthat make us human
5100:03:39,633 --> 00:03:44,467began not with our own species,Homo sapiens.
5200:03:47,367 --> 00:03:52,600The true birth of humanity beganmuch further back in time,
5300:03:52,667 --> 00:03:56,633millions of years ago.
5400:03:56,700 --> 00:04:00,600Imagine the entire spanof recorded human history,
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5500:04:00,667 --> 00:04:02,933about 5,000 years,
5600:04:03,000 --> 00:04:06,200taking us backto the Egyptian pyramids.
5700:04:06,267 --> 00:04:10,333Double it-- 10,000 years,to the time when plants
5800:04:10,400 --> 00:04:14,100are domesticatedand agriculture begins.
5900:04:14,167 --> 00:04:17,833Double it again-- 20,000 years.
6000:04:17,900 --> 00:04:22,433Ice Age hunters are paintingstunning images on cave walls.
6100:04:22,500 --> 00:04:25,533And keep doubling,six more times.
6200:04:25,600 --> 00:04:30,433Only then do we encounterour ancestor Homo erectus
6300:04:30,500 --> 00:04:33,300in Africa's Great Rift Valley.
6400:04:37,367 --> 00:04:42,133For millions of years, thismassive geological fault line
6500:04:42,200 --> 00:04:44,333running the lengthof East Africa
6600:04:44,400 --> 00:04:50,633was a stage on which our humanevolution was played out.
6700:04:50,700 --> 00:04:53,933It all started with the firstapes to walk upright
6800:04:54,000 --> 00:04:57,967on two legs aboutsix million years ago.
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6900:05:00,800 --> 00:05:03,100There were many different types,
7000:05:03,167 --> 00:05:06,200all variationson the same theme,
7100:05:06,500 --> 00:05:10,600apelike creatureswith small brains.
7200:05:10,667 --> 00:05:15,167The fossil known as Lucyis the most famous example.
7300:05:15,233 --> 00:05:19,100Here she is, just three foot,eight inches tall,
7400:05:19,167 --> 00:05:21,500with a brain the sizeof a chimp's.
7500:05:24,533 --> 00:05:28,467For millions of years, creatureslike her roamed the forests
7600:05:28,533 --> 00:05:30,967and grasslands of Africa.
7700:05:31,033 --> 00:05:33,933But then something changed.
7800:05:37,167 --> 00:05:39,900About two million years ago,
7900:05:39,967 --> 00:05:42,800new creatures appeared withabilities never seen before
8000:05:42,867 --> 00:05:44,467in the animal kingdom.
8100:05:44,533 --> 00:05:50,733Meet Homo erectus,a toolmaker and hunter.
8200:05:50,800 --> 00:05:55,667One of the first members of ourgenus, the genus Homo-- humans.
8300:05:55,733 --> 00:05:57,967
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DANIEL LIEBERMAN:The transition to Homo
8400:05:58,033 --> 00:06:00,167
was probably one of the mostimportant transformations
8500:06:00,233 --> 00:06:02,800that occurredin human evolution.
8600:06:02,867 --> 00:06:07,833NARRATOR:Arms got thinner, legs gotlonger, brains got bigger.
8700:06:07,900 --> 00:06:12,200It was a huge evolutionary stepfrom ape bodies
8800:06:12,267 --> 00:06:15,167to bodies like ours.
8900:06:15,233 --> 00:06:19,067But what about the thingsthat make us distinctly human--
9000:06:19,133 --> 00:06:24,600creativity, intelligence,caring for each other?
9100:06:24,667 --> 00:06:29,667How can we knowwhen these got started?
9200:06:29,733 --> 00:06:32,867With only skulls and bonefragments to go on,
9300:06:32,933 --> 00:06:34,400how could we ever know
9400:06:34,467 --> 00:06:38,000what those first humanswere really like?
9500:06:38,067 --> 00:06:42,700It would take a momentous findto shed light on their lives.
9600:06:46,300 --> 00:06:50,467Lake Turkana, northern Kenya,
97
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00:06:50,533 --> 00:06:55,000surrounded by volcanoes and vastexpanses of baking desert.
9800:06:55,067 --> 00:07:00,967In 1984, famed anthropologistsRichard and Meave Leakey
9900:07:01,033 --> 00:07:03,700were workingat this remote inland sea.
10000:07:03,767 --> 00:07:06,233MEAVE LEAKEY:I was actually onthe east side of the lake.
10100:07:06,300 --> 00:07:08,500Then Richard flew overand said, "You've got to come.
10200:07:08,567 --> 00:07:11,467There's somethingreally exciting."
10300:07:11,533 --> 00:07:14,467NARRATOR:As the first familyof paleoanthropology,
10400:07:14,533 --> 00:07:17,600the Leakeys were usedto fossil finds.
10500:07:17,667 --> 00:07:21,400But this was very special.
10600:07:21,467 --> 00:07:24,067One of Leakey's team had founda skull fragment
10700:07:24,133 --> 00:07:26,600of one of those early humans.
10800:07:26,667 --> 00:07:31,267He could tell from its sizeand shape itwas Homo erectus,
10900:07:31,333 --> 00:07:34,500and there was morethan just a fragment.
11000:07:34,567 --> 00:07:36,033So we starting looking
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at the site
11100:07:36,100 --> 00:07:38,267on a more extensive basis,and of course once we did,
112
00:07:38,333 --> 00:07:40,267we found the rest of the skull.
11300:07:40,333 --> 00:07:42,600NARRATOR:A complete skullwas rare enough,
11400:07:42,667 --> 00:07:45,233but it was just the beginning.
11500:07:45,300 --> 00:07:48,033Soon, parts ofthe Homo erectus skeleton
11600:07:48,100 --> 00:07:52,100which had never been foundbefore started to emerge.
11700:07:52,167 --> 00:07:55,333MEAVE LEAKEY:We couldn't believe it, but westarted getting pieces of ribs.
11800:07:55,400 --> 00:07:57,067These were partsof Homo erectus
11900:07:57,133 --> 00:07:59,833that nobody actually knew about,nobody had ever seen before.
12000:07:59,900 --> 00:08:01,967So every bone thatcame out of the ground
12100:08:02,033 --> 00:08:03,500was something brand newto science
12200:08:03,567 --> 00:08:05,467and we are lookingat these things
12300:08:05,533 --> 00:08:08,400and it was really amazing.
124
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00:08:08,467 --> 00:08:13,300NARRATOR:And here they are, the actualbones of a human ancestor
12500:08:13,367 --> 00:08:16,633
who lived over 1.5 million
years ago.
12600:08:16,700 --> 00:08:20,900It's the earliest human skeletonever discovered.
12700:08:20,967 --> 00:08:26,167The Leakeys called himTurkana Boy.
12800:08:26,233 --> 00:08:29,200His bones have revolutionizedour understanding
12900:08:29,267 --> 00:08:31,800of the transitionfrom ape to human.
13000:08:31,867 --> 00:08:34,767SUSAN ANTN:The really important thingabout Turkana Boy
13100:08:34,833 --> 00:08:36,267is how complete he is.
13200:08:36,367 --> 00:08:40,100We've got arms and legs andbits of his spine and his ribs.
13300:08:40,167 --> 00:08:44,133And usually when we find thesethings we get very excited
13400:08:44,200 --> 00:08:46,200about one little bit of bone,
13500:08:46,267 --> 00:08:49,167but that little bit can't tellus very much
13600:08:49,233 --> 00:08:50,667about an individual,
13700:08:50,733 --> 00:08:53,400so having a nearlycomplete skeleton,
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13800:08:53,467 --> 00:08:55,500we can start to askbig questions.
13900:08:57,567 --> 00:09:01,967
NARRATOR:The first big question was,what did he look like?
14000:09:02,033 --> 00:09:05,167His skeleton tells us he wasfive feet, three inches tall,
14100:09:05,233 --> 00:09:08,733with a build closer to a man'sthan an ape's.
14200:09:10,200 --> 00:09:11,767But how close?
14300:09:15,000 --> 00:09:17,633Paleoartist Viktor Deakspecializes
14400:09:17,700 --> 00:09:20,933in painting and sculptingour human ancestors
14500:09:21,000 --> 00:09:23,400with precise anatomicalaccuracy.
14600:09:30,533 --> 00:09:32,867Viktor is going to addTurkana Boy
14700:09:32,933 --> 00:09:36,133to his familyof ancient faces.
14800:09:36,200 --> 00:09:38,667DEAK:At this stage of the game,
14900:09:38,967 --> 00:09:41,500I know that Turkana Boyis not an ape.
15000:09:41,567 --> 00:09:44,333He is a very early true human,
15100:09:44,400 --> 00:09:46,967
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and so here we havea modern human skull.
15200:09:47,200 --> 00:09:50,667The faces are very similarto one another,
15300:09:50,733 --> 00:09:53,833but Turkana Boy's skullis a bit more primitive
15400:09:53,900 --> 00:09:59,500and has a lower forehead anda much smaller brain capacity.
15500:09:59,567 --> 00:10:05,000NARRATOR:Viktor will build Turkana Boy'sface muscle by muscle,
15600:10:05,067 --> 00:10:10,667based on his studies of cadaversand modern anatomy.
15700:10:13,733 --> 00:10:16,600While his head may be primitive,
15800:10:16,667 --> 00:10:20,433Turkana Boy's skeleton issurprisingly human.
15900:10:20,500 --> 00:10:23,967His hips are a little wider,his arms a little longer,
16000:10:24,033 --> 00:10:28,633but his overall body shapeis just like ours.
16100:10:28,700 --> 00:10:30,967DEAK:Turkana Boy and erectus--
16200:10:31,033 --> 00:10:32,700that's something thatif you were to see
16300:10:32,767 --> 00:10:35,267from a hundred feet away,you'd think,
16400:10:35,333 --> 00:10:38,600well, there's a large naked manthere, or woman or, you know.
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16500:10:38,667 --> 00:10:40,033But it's a human.
16600:10:45,033 --> 00:10:51,700NARRATOR:
It will take Viktor a weekto flesh out Turkana Boy's face.
16700:10:51,767 --> 00:10:55,967Meanwhile, a team of animatorsis at work creating scenes
16800:10:56,033 --> 00:11:00,500that will bring Turkana Boyand his people to life.
16900:11:00,567 --> 00:11:03,467To make sure they do itaccurately, they have enlisted
17000:11:03,533 --> 00:11:07,767the help of Harvardanthropologist Dan Lieberman.
17100:11:07,833 --> 00:11:09,233They had a moreforward position
17200:11:09,300 --> 00:11:10,933of the palms when they ran,
just slightly.
17300:11:11,000 --> 00:11:12,867There you go.
17400:11:12,933 --> 00:11:17,100NARRATOR:The blue-suited actors are thereto create movement references
17500:11:17,133 --> 00:11:19,267for the artists.
17600:11:19,333 --> 00:11:22,100In the final animations,they will be replaced
17700:11:22,167 --> 00:11:23,633by Homo erectus bodies...
17800:11:23,700 --> 00:11:25,967DIRECTOR:
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And... action!
17900:11:26,033 --> 00:11:29,467NARRATOR:...their heads and faces basedclosely on Viktor's model.
18000:11:32,267 --> 00:11:35,633As Turkana Boy's forensicallyreconstructed head
18100:11:35,700 --> 00:11:41,267nears completion, a face emergesthat looks a lot like us.
18200:11:43,567 --> 00:11:47,100Now for the first time ina million and a half years,
18300:11:47,167 --> 00:11:50,167here he is, our ancestor,
18400:11:50,233 --> 00:11:54,367the Homo erectuscalled Turkana Boy.
18500:11:54,433 --> 00:11:59,467But what he looked like is onlythe beginning of his story.
18600:11:59,533 --> 00:12:04,300To reconstruct his life, we needto find out how old he was.
18700:12:04,367 --> 00:12:07,867And if we lookat his skeleton, we can see
18800:12:07,933 --> 00:12:10,100that the growthplates on his limbs
18900:12:10,167 --> 00:12:14,700that would fuse when he'sfully adult are all unfused,
19000:12:14,767 --> 00:12:18,300so even though he's very tall,we know that he's still growing.
19100:12:19,967 --> 00:12:23,067NARRATOR:The fact that Turkana Boywas not fully grown
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19200:12:23,133 --> 00:12:26,067has turned out to bea boon to researchers.
19300:12:26,133 --> 00:12:28,067
MEAVE LEAKEY:You can answer questions like,
19400:12:28,133 --> 00:12:31,333did the boy grow up likea modern human?
19500:12:31,400 --> 00:12:34,333Or did he grow upmore like an ape?
19600:12:34,400 --> 00:12:38,433NARRATOR:Turkana Boy was alreadyfive feet, three inches tall.
19700:12:38,500 --> 00:12:42,167When scientists comparedhis bones and teeth to ours,
19800:12:42,233 --> 00:12:45,767he seemed to beabout 14 years old.
19900:12:45,833 --> 00:12:48,133But when dentalspecialist Chris Dean
20000:12:48,200 --> 00:12:51,700began to study his teeth,he was in for a shock.
20100:12:53,900 --> 00:12:57,400It turns out that all teeth--fossil or not--
20200:12:57,467 --> 00:13:01,800preserve a remarkably preciserecord of childhood.
20300:13:01,867 --> 00:13:04,267DEAN:This is a fossil tooth
20400:13:04,500 --> 00:13:06,500and we can see the enamel cap
205
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00:13:06,567 --> 00:13:10,100which covers the core of thetooth, which is made of dentine.
20600:13:10,167 --> 00:13:12,867Dentine is just another wordfor ivory.
20700:13:12,933 --> 00:13:16,767And within the enamel you cansee the rods, which are running
20800:13:16,833 --> 00:13:18,467from the enamel-dentine
junction here
20900:13:18,533 --> 00:13:21,300out to the surfaceof the tooth.
21000:13:21,367 --> 00:13:23,967NARRATOR:Enamel has a regulargrowth pattern,
21100:13:24,033 --> 00:13:26,900like the rings of a tree.
21200:13:26,967 --> 00:13:28,900Under an electron microscope,
21300:13:29,000 --> 00:13:32,133it looks like rodsmade of tiny beads.
21400:13:32,200 --> 00:13:35,100DEAN:Each of the little beadsalong these prisms
21500:13:35,167 --> 00:13:36,933represent one day's growth,
21600:13:37,000 --> 00:13:39,500because the cellswhich produce enamel
21700:13:39,567 --> 00:13:43,500are actually under the influenceof a circadian, or daily, clock.
21800:13:43,567 --> 00:13:46,767And those secretionsduring the day
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21900:13:46,833 --> 00:13:49,233speed up and then slow down,
22000:13:49,300 --> 00:13:53,000and there's a permanent record
of that in every tooth.
22100:13:53,067 --> 00:13:57,800So you can see rods running allthe way through this tissue,
22200:13:57,867 --> 00:14:01,367and every day along the rodthere is a wobble
22300:14:01,433 --> 00:14:03,533where the tissue slows down
22400:14:03,600 --> 00:14:05,767and then speeds up.
22500:14:05,833 --> 00:14:08,467NARRATOR:So if you count the beadsin these strings,
22600:14:08,533 --> 00:14:11,367you can figure outexactly how many days
22700:14:11,433 --> 00:14:14,133that tooth has been growing.
22800:14:14,200 --> 00:14:16,367When Chris lookedat the fossilized teeth
22900:14:16,433 --> 00:14:20,000of Turkana Boy,he got a huge surprise.
23000:14:20,067 --> 00:14:22,633
Turkana Boywasn't 14 years old.
23100:14:22,700 --> 00:14:24,467He was eight.
23200:14:24,533 --> 00:14:29,333DEAN:What that implies is thatthe growth of the Turkana Boy
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23300:14:29,600 --> 00:14:32,167resembled more closelythat of chimpanzees today.
23400:14:32,233 --> 00:14:35,933
NARRATOR:To be five-foot threeat age eight,
23500:14:36,000 --> 00:14:39,000Turkana Boy must havegrown up very fast,
23600:14:39,067 --> 00:14:43,300at a rate closer to chimpsthan us.
23700:14:43,367 --> 00:14:45,333A chimpanzee's childhoodis short.
23800:14:45,400 --> 00:14:49,767It is sexually matureat about seven.
23900:14:49,833 --> 00:14:55,267Human childhood is longer;we reach puberty at about 12.
24000:14:55,333 --> 00:15:01,133So as humans evolved from apes,childhood was extended.
24100:15:01,200 --> 00:15:03,667But what advantagecould be gained
24200:15:03,733 --> 00:15:07,633by having helpless childrenaround to feed and care for
24300:15:07,700 --> 00:15:10,500who take so long to grow up?
24400:15:10,567 --> 00:15:14,433The mystery of prolongedchildhood is at the heart
24500:15:14,500 --> 00:15:16,700of human evolution.
24600:15:16,767 --> 00:15:19,833
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It may be related to brain size.
24700:15:23,167 --> 00:15:26,767We humans have the biggestbrains in the animal kingdom
248
00:15:26,833 --> 00:15:29,767in relation to our body size.
24900:15:29,833 --> 00:15:33,133They're so big that most ofour brain growth has to happen
25000:15:33,200 --> 00:15:34,667outside the womb
25100:15:34,733 --> 00:15:38,433or our heads would neverget through the birth canal.
25200:15:38,500 --> 00:15:42,100A long, slow childhoodgives our brains time
25300:15:42,167 --> 00:15:44,533to grow after birth
25400:15:44,600 --> 00:15:48,100and time to learn everythingwe need to function
25500:15:48,167 --> 00:15:51,433in our complex human societies.
25600:15:51,500 --> 00:15:54,767That's the advantageof prolonged childhood
25700:15:54,833 --> 00:15:57,000for us, at least.
25800:15:57,067 --> 00:16:00,367But what about Turkana Boy?
25900:16:00,433 --> 00:16:03,567His brain was900 cubic centimeters,
26000:16:03,633 --> 00:16:09,233smaller than ours but more thantwice as large as a chimp's.
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26100:16:09,267 --> 00:16:15,000So was he on the way to thinkingand talking like us?
26200:16:15,067 --> 00:16:18,133Ralph Holloway believes he was.
26300:16:18,200 --> 00:16:21,933He's been collecting the brainendocasts of human ancestors
26400:16:22,000 --> 00:16:23,700for over 30 years.
26500:16:23,767 --> 00:16:29,433An endocast is a mold takenfrom the inside of the skull
26600:16:29,500 --> 00:16:32,200which reveals the shapeof the brain.
26700:16:32,267 --> 00:16:34,133Ralph is particularly interested
26800:16:34,200 --> 00:16:37,533in something calledthe Broca's area.
26900:16:37,600 --> 00:16:39,100HOLLOWAY:Broca's area is involved
27000:16:39,167 --> 00:16:40,533with memory functions,
27100:16:40,600 --> 00:16:44,933executive functions, but it doeshave a very important role
27200:16:45,000 --> 00:16:47,600to play in the motor aspectsof speech.
27300:16:47,667 --> 00:16:52,433NARRATOR:In the brain of Turkana Boy,Ralph believes he sees evidence
27400:16:52,500 --> 00:16:54,333for something remarkable--
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00:16:54,400 --> 00:16:59,400a change in the Broca's areatied to communication.
27600:16:59,467 --> 00:17:01,300HOLLOWAY:Broca's caps regions
27700:17:01,367 --> 00:17:03,100on the Turkana Boy
27800:17:03,167 --> 00:17:06,167are fully modern in termsof their appearance.
27900:17:06,233 --> 00:17:10,567It is good, solid evidencefor having the ability
280
00:17:10,633 --> 00:17:13,867of symbolic communication--in other words, language.
28100:17:13,933 --> 00:17:16,567NARRATOR:It's a controversial idea
28200:17:16,633 --> 00:17:21,767and we'll never know for sureif Turkana Boy could speak.
28300:17:21,833 --> 00:17:24,633But there are other cluesto his intelligence--
28400:17:24,700 --> 00:17:29,133the stone toolshe left behind.
28500:17:29,200 --> 00:17:32,200Homo erectus made toolslike this hand ax here.
28600:17:32,267 --> 00:17:34,033It's been chipped extensivelyon both sides.
28700:17:34,100 --> 00:17:36,133The point enables one to dopiercing tasks,
28800:17:36,200 --> 00:17:38,267the heavy bit here can be usedfor cracking bone
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28900:17:38,333 --> 00:17:39,667or chopping wood.
29000:17:39,733 --> 00:17:43,033It's a very, very versatile tool
and a sharp one.
29100:17:43,100 --> 00:17:47,033NARRATOR:It may not look like much,but the stone hand ax
29200:17:47,100 --> 00:17:50,867marks the birth of technology.
29300:17:50,933 --> 00:17:56,433Homo erectus has left us manysigns of his inventiveness.
29400:17:56,500 --> 00:18:00,133Here in central Kenya,Rick Potts has been studying
29500:18:00,200 --> 00:18:05,533a treasure troveof Homo erectus stone tools.
29600:18:05,600 --> 00:18:08,667POTTS:Stone tools representeda momentous change,
29700:18:08,733 --> 00:18:10,933because once you had toolsin your hands,
29800:18:11,000 --> 00:18:14,200all the foods in the worldcould open up to you.
29900:18:14,267 --> 00:18:17,700That represented a tremendoussurvival advantage.
30000:18:19,733 --> 00:18:23,900NARRATOR:Here is a cacheof over 500 stone hand axes
30100:18:23,967 --> 00:18:26,533made by Homo erectus.
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00:18:26,600 --> 00:18:28,633Just a mile away,Rick visits the quarry
30300:18:28,700 --> 00:18:32,467where for thousandsof years these ancestors came
30400:18:32,533 --> 00:18:38,300to shape stone into tools,leaving behind unused fragments.
30500:18:38,367 --> 00:18:40,700In the crevicesat my feet,
30600:18:40,767 --> 00:18:43,233there were thousandsof fragments of stone
30700:18:43,300 --> 00:18:44,467from tool making.
30800:18:44,533 --> 00:18:47,767And there are several scarswhere Homo erectus
30900:18:47,833 --> 00:18:49,767struck huge flakes.
31000:18:49,833 --> 00:18:53,000We also see evidence that theycould recognize flaws.
31100:18:53,067 --> 00:18:56,433They could see which ones wouldbreak if they took them away,
31200:18:56,500 --> 00:18:58,800so they simplydiscarded them here.
31300:18:58,867 --> 00:19:01,567What's amazing about that isyou could imagine
31400:19:01,633 --> 00:19:06,100an early Homo erectus sittingright here, making decisions.
31500:19:06,167 --> 00:19:08,400NARRATOR:The kind of decision-makingit takes
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31600:19:08,467 --> 00:19:12,167to create a stone tool has beenresearched extensively
31700:19:12,233 --> 00:19:13,833
by John Shea.
31800:19:13,900 --> 00:19:16,533SHEA:I'm just going to tap ita little bit.
31900:19:16,600 --> 00:19:19,633I'm just checking it out to seeif there's any internal flaws
32000:19:19,700 --> 00:19:20,833before I do it.
32100:19:20,900 --> 00:19:22,133There may be one here.
32200:19:22,200 --> 00:19:24,000It feels like there might besomething in there,
32300:19:24,067 --> 00:19:26,367but I like a challengeso I'll knap it anyway.
32400:19:26,433 --> 00:19:31,133NARRATOR:Even for an expert, makinga hand ax is not easy.
32500:19:31,200 --> 00:19:33,433SHEA:Yeah, there's the flaw,but we can get around it.
32600:19:33,500 --> 00:19:35,400NARRATOR:A good toolmakerhas to understand
32700:19:35,467 --> 00:19:36,933the properties of stone.
32800:19:37,000 --> 00:19:40,267To make this thing niceand thin, easier to carry,
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00:19:40,333 --> 00:19:42,500easier to transport and moreof a sharp cutting edge,
33000:19:42,567 --> 00:19:44,533I'm going to do somethingkind of counterintuitive.
33100:19:44,600 --> 00:19:48,100I'm going to dull the edge sothat the next time I strike it,
33200:19:48,167 --> 00:19:51,600it won't fail until I havea lot of pressure on it.
33300:19:51,667 --> 00:19:54,300So if I hit it really hard, thefracture will go much further
33400:19:54,367 --> 00:19:55,633than it otherwise would.
33500:19:55,700 --> 00:19:58,267So that Homo erectus did this
33600:19:58,333 --> 00:20:00,933tells us they were capableof thinking ahead
33700:20:01,000 --> 00:20:03,033and planning the consequencesof their actions.
33800:20:03,100 --> 00:20:04,400So let's have a look here.
33900:20:04,467 --> 00:20:05,833What'll happen here?
34000:20:05,900 --> 00:20:08,833NARRATOR:Many of these stoneshave hidden defects.
34100:20:08,900 --> 00:20:11,333Failing to spot themcould spell disaster.
34200:20:11,400 --> 00:20:13,133There's stilla flaw in there.
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00:20:13,200 --> 00:20:14,633I can hear it.I can tell.
34400:20:14,700 --> 00:20:15,633Yeah, see this?
34500:20:15,700 --> 00:20:17,133It's right there.
34600:20:17,200 --> 00:20:20,333Now, I've worked around it,but if I were an early human
34700:20:20,400 --> 00:20:23,300and spotted this, I would stopmaking the hand ax right now.
34800:20:23,367 --> 00:20:26,800If I'm out running around in thesavannas, chasing a rhinoceros
34900:20:26,867 --> 00:20:28,033and, you know,or butchering a rhinoceros
35000:20:28,100 --> 00:20:30,200as the lions are circlingand my hand ax breaks,
35100:20:30,267 --> 00:20:31,633I'm in trouble.
35200:20:31,700 --> 00:20:34,300So, you know, I go home tonight,I'm still going to get fed,
35300:20:34,367 --> 00:20:36,367even though I didn't makea perfect hand ax.
35400:20:36,433 --> 00:20:39,100As Homo erectus, I might end upbeing the meal instead.
35500:20:41,433 --> 00:20:42,933NARRATOR:A skilled craftsman,
35600:20:43,000 --> 00:20:48,567Homo erectus had evolveda new type o f intelligence.
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00:20:48,633 --> 00:20:53,000But his bigger braincame with hidden costs.
35800:20:53,067 --> 00:20:57,733Modern brains consume25% of our body's energy.
35900:20:57,800 --> 00:21:00,667DONALD JOHANSON:Our brain happens to bethe hungriest organ in the body.
36000:21:00,733 --> 00:21:02,800And in order to supporta brain our size,
36100:21:02,867 --> 00:21:04,000we need lots of calories.
36200:21:04,067 --> 00:21:06,767NARRATOR:With his big brain and body,
36300:21:06,833 --> 00:21:12,000a Homo erectus like Turkana Boyneeded more nutrition
36400:21:12,067 --> 00:21:14,300from his savanna environment.
36500:21:14,367 --> 00:21:16,433SHEA:Turkana Boy, had he grownto adulthood,
36600:21:16,500 --> 00:21:18,467would probably have stoodabout six feet tall.
36700:21:18,533 --> 00:21:20,167This is a big, strong creature
36800:21:20,233 --> 00:21:21,800that would have hada huge energy budget.
36900:21:21,867 --> 00:21:25,833One can satisfy an energy budgetlike that by eating plants,
37000:21:25,900 --> 00:21:29,233but you have to eat a lot,a lot of plants.
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37100:21:29,300 --> 00:21:32,767NARRATOR:But there's one food that cansupply the nutrients
372
00:21:32,833 --> 00:21:35,267a growing brain and body need...
37300:21:35,333 --> 00:21:37,700and Africa was filled with it.
37400:21:37,767 --> 00:21:41,300LIEBERMAN:The one high-quality resourcethat's probably most important
37500:21:41,367 --> 00:21:43,167for the evolutionof the genus Homo is meat
37600:21:43,233 --> 00:21:46,833and meat byproducts suchas brain and marrow and fat.
37700:21:46,900 --> 00:21:50,000They're high in protein,they're high in calories,
37800:21:50,067 --> 00:21:51,433and they're easy to digest.
37900:21:51,500 --> 00:21:55,033But the one problem with gettingmeat is that it's hard to get.
38000:21:55,100 --> 00:21:58,767NARRATOR:Most predators relyon strength or speed
38100:21:58,833 --> 00:22:00,800to kill their prey.
38200:22:00,867 --> 00:22:04,233Our ancestors had neither.
38300:22:04,333 --> 00:22:08,533Today we are on top of the foodchain, so it's hard to imagine
38400:22:08,600 --> 00:22:12,267the predicament
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of those early humans.
38500:22:12,333 --> 00:22:17,200Here was a slow-moving creaturewith no claws or fangs,
386
00:22:17,267 --> 00:22:20,933easy prey for the hungrypredators around him.
38700:22:23,100 --> 00:22:26,200POTTS:This is a fossil foreheadand brow ridge
38800:22:26,267 --> 00:22:27,600of a Homo erectus,
38900:22:27,667 --> 00:22:31,700and on the brow ridgeyou can see the bite mark
39000:22:31,767 --> 00:22:33,500of a carnivore.
39100:22:33,567 --> 00:22:37,367Well, this reminds us thatthese Homo erectus individuals
39200:22:37,433 --> 00:22:40,133weren't at the topof the food chain.
39300:22:40,233 --> 00:22:42,133NARRATOR:So how did Turkana Boy,
39400:22:42,200 --> 00:22:45,933a weakling with a big brainwhich needed calories,
39500:22:46,000 --> 00:22:48,300get his meat?
39600:22:48,367 --> 00:22:50,133SHEA:Homo erectus faced a problem:
39700:22:50,200 --> 00:22:51,633How do you kill a big,dangerous animal
39800:22:51,700 --> 00:22:53,267
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that has lots of meatand fat in it
39900:22:53,333 --> 00:22:54,933
without that animalalso killing you?
40000:22:55,000 --> 00:22:59,433I think the answer to that was avery clever set of innovations,
40100:22:59,500 --> 00:23:01,433and that is endurance running
40200:23:01,500 --> 00:23:05,000and high activityin the middle of the day.
40300:23:05,067 --> 00:23:10,967
NARRATOR:The ancestors of Homo erectus,small, hairy apes like Lucy,
40400:23:11,033 --> 00:23:16,000
were bipedal but probablydidn't do much running.
40500:23:16,067 --> 00:23:20,867But Turkana Boy's kind werebuilt to run like us.
40600:23:20,933 --> 00:23:22,867This isan accelerometer.
40700:23:22,933 --> 00:23:25,800NARRATOR:Dan Lieberman believes theycould run long distances
40800:23:26,033 --> 00:23:30,667because, like us, they had losttheir thick coat of body hair
40900:23:30,733 --> 00:23:33,533and could keep cool by sweating.
41000:23:33,600 --> 00:23:37,700This was the keyto their success.
41100:23:37,767 --> 00:23:40,500But how do we knowif these crucial changes
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41200:23:40,567 --> 00:23:43,767go back all the wayto Turkana Boy's time,
41300:23:43,833 --> 00:23:47,333
over a million years ago?
41400:23:47,400 --> 00:23:51,067Skin and hair are rarelypreserved in the fossil record,
41500:23:51,133 --> 00:23:53,600so to find out, we have to lookto a creature
41600:23:53,667 --> 00:23:57,933that's been intimately connectedwith hair for a long time:
41700:23:58,000 --> 00:23:59,367the louse.
41800:23:59,433 --> 00:24:00,633MARK STONEKING:All animals seem
41900:24:00,700 --> 00:24:03,600to have some type of liceto parasitize them.
42000:24:03,667 --> 00:24:05,867Mammals have them,birds have them,
42100:24:05,933 --> 00:24:07,833even fish have types of lice.
42200:24:07,900 --> 00:24:10,467But most other creatures haveonly one type of lice
42300:24:10,533 --> 00:24:12,667
that parasitize them.
42400:24:12,733 --> 00:24:15,867NARRATOR:Humans have one kind of louseon their heads
42500:24:15,933 --> 00:24:17,900and another in the pubic area.
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42600:24:17,967 --> 00:24:22,100Geneticist Mark Stonekingasked himself why.
42700:24:22,167 --> 00:24:23,600
STONEKING:The answer that seems obvious
42800:24:23,667 --> 00:24:26,233is that when we had body hairall over our bodies,
42900:24:26,300 --> 00:24:28,033
we had one type of lice.
43000:24:28,100 --> 00:24:29,533But then we became hairless
43100:24:29,600 --> 00:24:32,767until we only had hair on ourheads and in our pubic region,
43200:24:32,833 --> 00:24:34,367and so thereforeyou would have
43300:24:34,433 --> 00:24:38,767this hairless geographic barrierto contact between the two.
43400:24:38,833 --> 00:24:40,800NARRATOR:Mark was surprised to find out
43500:24:40,867 --> 00:24:43,367that the human pubic louseis very different
43600:24:43,433 --> 00:24:45,533from the human head louse.
43700:24:45,600 --> 00:24:50,667
Somehow in the past, it seemsto have come from gorillas.
43800:24:50,733 --> 00:24:53,300STONEKING:Because the pubic lice isactually more closely related
43900:24:53,367 --> 00:24:54,667to gorilla lice.
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44000:24:54,733 --> 00:24:57,333Now, how it is our ancestors gotpubic lice from gorillas
44100:24:57,400 --> 00:24:59,967
I wouldn't care to speculate.
44200:25:00,033 --> 00:25:03,333But nonetheless,one needs gorilla lice
44300:25:03,400 --> 00:25:07,533in order to really workthis whole thing out.
44400:25:07,600 --> 00:25:12,033NARRATOR:The most likely scenario is that
when we lost our body hair,
44500:25:12,100 --> 00:25:16,033the original human lousemigrated to our heads,
44600:25:16,100 --> 00:25:21,133leaving the pubic areatemporarily unpopulated by lice.
44700:25:21,200 --> 00:25:24,500When our ancestors had contactwith gorillas,
44800:25:24,567 --> 00:25:26,833perhaps sleeping in their nests
44900:25:26,900 --> 00:25:29,800or scavenging their bodiesfor meat,
45000:25:29,867 --> 00:25:34,133the gorilla louse colonizedtheir pubic region.
45100:25:34,200 --> 00:25:39,200Eventually, it turned intothe human pubic louse of today.
45200:25:39,267 --> 00:25:41,133So if we could find out
45300:25:41,200 --> 00:25:45,467when the human pubic louse and
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the gorilla louse diverged,
45400:25:45,533 --> 00:25:50,633we would have a rough ideaof when we lost our body hair.
455
00:25:50,700 --> 00:25:54,133Fortunately, there's a wayto figure that out:
45600:25:54,200 --> 00:25:59,267the genetic dating techniqueknown as the molecular clock.
45700:25:59,333 --> 00:26:02,833It's based on the fact thatthe sequence of chemical bases
45800:26:02,900 --> 00:26:07,700which make up DNAmutate at a regular rate.
45900:26:07,767 --> 00:26:10,367STONEKING:It's just a very simple idea
46000:26:10,667 --> 00:26:12,967that the rate of changein DNA sequences
46100:26:13,033 --> 00:26:15,200is more or less constantover time.
46200:26:15,267 --> 00:26:18,533And that means that you havea way of determining
46300:26:18,600 --> 00:26:21,667when two species last shareda common ancestor.
46400:26:21,733 --> 00:26:25,033NARRATOR:By counting the numberof differences
46500:26:25,100 --> 00:26:27,200in the genetic codeof two species,
46600:26:27,267 --> 00:26:31,133scientists can determine howlong they've been evolving
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46700:26:31,200 --> 00:26:33,233away from each other.
46800:26:33,300 --> 00:26:36,633When Mark used the molecular
clock to count the differences
46900:26:36,700 --> 00:26:41,333between the DNA of gorilla liceand human pubic lice,
47000:26:41,400 --> 00:26:44,833he came up with a datefor their divergence.
47100:26:44,900 --> 00:26:47,000STONEKING:The estimated datefor the divergence
47200:26:47,067 --> 00:26:49,133is roughlythree million years ago.
47300:26:49,200 --> 00:26:53,500NARRATOR:That means longbefore Turkana Boy,
47400:26:53,567 --> 00:26:54,967maybe even around Lucy's time,
47500:26:55,033 --> 00:27:01,867our ancestors had slowly begunto lose their body hair.
47600:27:01,933 --> 00:27:06,033Turkana Boy was mostly hairless,
just like us...
47700:27:08,667 --> 00:27:13,667...and that may be what gave himan edge over other predators.
47800:27:13,733 --> 00:27:18,033Most animals are at adisadvantage in the midday sun
47900:27:18,100 --> 00:27:19,533because they overheat.
48000:27:19,600 --> 00:27:22,500
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They can only cool downby panting.
48100:27:22,567 --> 00:27:26,633And when they run fast,they can't pant.
48200:27:26,700 --> 00:27:31,700That means they can only runin short sprints.
48300:27:31,767 --> 00:27:34,367LIEBERMAN:Quadrupeds can gallopfor about 10 to 15 minutes
48400:27:34,433 --> 00:27:35,500and then they overheat,
48500:27:35,567 --> 00:27:39,033but hominids can cool downby sweating.
48600:27:39,100 --> 00:27:43,433They use their entire bodylike a dog's tongue.
48700:27:43,500 --> 00:27:48,233NARRATOR:Our hairless bodies allow airto circulate freely on our skin
48800:27:48,300 --> 00:27:51,367and cool us downas sweat evaporates.
48900:27:51,433 --> 00:27:54,433This makes us one of the bestlong-distance runners
49000:27:54,500 --> 00:27:57,433in the animal kingdom.
49100:27:57,500 --> 00:28:00,833Dan Lieberman believesthis gave our ancestors
49200:28:00,900 --> 00:28:03,667the ability to huntin a very unusual way.
49300:28:03,733 --> 00:28:06,733It's called persistence hunting.
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49400:28:08,733 --> 00:28:12,133And he believes the modernethnographic record
49500:28:12,200 --> 00:28:14,800can show us how it was done.
49600:28:17,067 --> 00:28:21,467The Bushmen of the Kalaharioffer us an insight
49700:28:21,533 --> 00:28:27,200into how Homo erectus might havehunted two million years ago.
49800:28:27,433 --> 00:28:32,467The Bushmen know that at middayanimals rest in the shade,
49900:28:32,533 --> 00:28:36,433which is why it's the perfecttime to be hunting.
50000:28:36,500 --> 00:28:41,033Once they locate their prey--in this case a kudu--
50100:28:41,100 --> 00:28:43,000the marathon begins.
50200:28:48,700 --> 00:28:54,667Their strategy is simple:run it to exhaustion.
50300:28:54,733 --> 00:28:59,100Every time the animal tries torest, the hunters track it down
50400:28:59,167 --> 00:29:00,600and get it moving again.
50500:29:00,667 --> 00:29:04,433They never give it a chanceto cool down.
50600:29:04,500 --> 00:29:09,500And the reason they can keepgoing is that they can sweat.
50700:29:12,533 --> 00:29:16,800So if the theory is right, theBushman hunt may help explain
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50800:29:16,867 --> 00:29:21,433how Turkana Boy got his meat.
50900:29:21,500 --> 00:29:25,933Homo erectus had come up
with an innovative way
51000:29:26,000 --> 00:29:27,967of feeding his hungry brain.
51100:29:32,200 --> 00:29:37,267In this modern hunt, the Bushmenran in the fierce heat
51200:29:37,333 --> 00:29:40,467for over four hours.
51300:29:40,533 --> 00:29:45,033The kudu was finally immobilizedby heat stroke.
51400:29:47,600 --> 00:29:50,167Turkana Boy wouldn't havehad steel-tipped spears
51500:29:50,233 --> 00:29:55,000like the Bushmen, but hewouldn't have needed them.
51600:29:57,033 --> 00:30:00,633SHEA:Homo erectus probably huntedwith close-quarters weapons--
51700:30:00,700 --> 00:30:03,633with spears that were thrown atanimals from a short distance,
51800:30:03,700 --> 00:30:05,833clubs, throw rocks,weapons like that.
51900:30:05,900 --> 00:30:07,567They weren't using long-distanceprojectile weapons,
52000:30:07,667 --> 00:30:09,233that we know of.
52100:30:12,833 --> 00:30:17,767NARRATOR:The Homo erectus huntwas simple but effective.
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52200:30:17,833 --> 00:30:20,600It fed not justtheir larger brains,
52300:30:20,667 --> 00:30:25,833
but the growing complexityof that early human society.
52400:30:28,733 --> 00:30:34,067There are other social animals,but none quite like us.
52500:30:37,567 --> 00:30:40,967Society is in every cornerof our lives--
52600:30:41,033 --> 00:30:43,800our relationships,communication,
52700:30:43,867 --> 00:30:46,933rules, symbolism--
52800:30:47,000 --> 00:30:50,367all the thingsthat bind us together.
52900:30:50,433 --> 00:30:51,667What's behind it?
53000:30:51,733 --> 00:30:55,000Why did we become so social?
53100:30:55,067 --> 00:30:59,967Could it have something to dowith another innovation,
53200:31:00,033 --> 00:31:05,067something unprecedentedin our evolution,
53300:31:05,133 --> 00:31:08,833
building fires and cooking?
53400:31:08,900 --> 00:31:11,867Here we go to erectus, the firstspecies that looks like us,
53500:31:11,933 --> 00:31:14,200and I think only cooking canexplain the magnitude
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53600:31:14,267 --> 00:31:15,633of this change.
53700:31:15,700 --> 00:31:19,533NARRATOR:The earliest evidencethat our ancestors
53800:31:19,600 --> 00:31:22,167deliberately used firefor cooking
53900:31:22,233 --> 00:31:26,033dates to longafter Turkana Boy's time.
54000:31:26,100 --> 00:31:30,967But Richard Wrangham is sureHomo erectus was building fires
54100:31:31,033 --> 00:31:33,600much earlier.
54200:31:33,667 --> 00:31:36,600WRANGHAM:Now for the first time we hada species that was committed
54300:31:36,667 --> 00:31:38,000to living on the ground,
54400:31:38,067 --> 00:31:40,333because they losetheir climbing adaptations.
54500:31:40,400 --> 00:31:43,033Well, how were they sleeping?
54600:31:43,100 --> 00:31:47,633They had to be able to protectthemselves from wild animals.
547
00:31:47,700 --> 00:31:52,267NARRATOR:On the African savanna, fullof predators who hunt by night,
54800:31:52,333 --> 00:31:54,833Richard believes Turkana Boyand his people
54900:31:54,900 --> 00:31:58,800
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couldn't have survivedwithout fire.
55000:31:58,867 --> 00:32:01,967And he thinks only cooking,
551
00:32:02,033 --> 00:32:04,100which makes food more softand digestible,
55200:32:04,167 --> 00:32:08,233can explain why Homo erectusevolved smaller teeth
55300:32:08,300 --> 00:32:10,533and a much smaller gut.
55400:32:10,600 --> 00:32:12,200WRANGHAM:These things are compatible
55500:32:12,267 --> 00:32:14,133with the reduced costof digestion
55600:32:14,200 --> 00:32:15,233produced by cooking food.
55700:32:15,300 --> 00:32:16,633Nothing else is.
55800:32:16,700 --> 00:32:21,100NARRATOR:As our ancestors reapedthe benefits of cooking,
55900:32:21,167 --> 00:32:25,667something else happened too,at least according to Wrangham--
56000:32:25,733 --> 00:32:28,767we became more social.
561
00:32:28,833 --> 00:32:31,233WRANGHAM:Humans have this wonderfullycalm temperament
56200:32:31,300 --> 00:32:33,200compared to chimpanzees, say.
56300:32:33,500 --> 00:32:35,200Where did it come from?
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56400:32:35,267 --> 00:32:39,100We were drawn to a common place,the fireplace.
56500:32:39,167 --> 00:32:43,600
NARRATOR:Wrangham believes we learnedto share and communicate
56600:32:43,667 --> 00:32:50,100sitting around fires,waiting for food to cook.
56700:32:50,167 --> 00:32:53,933It's speculative,but one thing is for sure:
56800:32:54,000 --> 00:32:56,067In the Homo erectus world,
56900:32:56,133 --> 00:33:00,333new social relationshipshad to be evolving.
57000:33:00,400 --> 00:33:03,400The bonds between mothersand children must have been
57100:33:03,500 --> 00:33:05,767very different from the apes.
57200:33:07,700 --> 00:33:12,933SARAH HRDY:For example, a mother orangutanwill not allow
57300:33:13,000 --> 00:33:15,667any other individualto take her infant,
57400:33:15,733 --> 00:33:18,700will be in constantskin-to-skin contact
57500:33:18,933 --> 00:33:22,433with that baby for at leastthe first six months of life.
57600:33:22,500 --> 00:33:25,100Not a moment out of contact.
57700:33:25,167 --> 00:33:28,600
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NARRATOR:Secure in this unbreakablemother-infant bond,
57800:33:28,667 --> 00:33:32,767ape babies need less capacityto read the intentions of others
57900:33:32,833 --> 00:33:36,467than human babies, whose bondwith their mothers
58000:33:36,533 --> 00:33:40,367is surprisingly less secure.
58100:33:40,433 --> 00:33:44,467The shocking fact is that humanmothers abandon their infants
58200:33:44,533 --> 00:33:46,933much more oftenthan ape mothers.
58300:33:47,000 --> 00:33:51,700Infanticide by a motheris more common among humans
58400:33:51,767 --> 00:33:54,300than any other higher ape.
58500:33:54,367 --> 00:33:55,533HRDY:Maternal commitment
58600:33:55,600 --> 00:33:57,567is a lot more contingentin humans
58700:33:57,700 --> 00:34:00,200than it seems to bein other apes.
58800:34:00,267 --> 00:34:02,467NARRATOR:Unlike most primates,
58900:34:02,533 --> 00:34:07,100human mothers share parentingwith others.
59000:34:07,167 --> 00:34:11,467A child's survival can dependon making itself appealing
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59100:34:11,533 --> 00:34:13,933to a number of caregivers.
59200:34:14,000 --> 00:34:17,500Perhaps that's why human infantshave evolved
59300:34:17,567 --> 00:34:20,367a uniquely acute sensitivity.
59400:34:20,433 --> 00:34:25,200HRDY:Human infants are bornconnoisseurs of mothers,
59500:34:25,267 --> 00:34:31,067reading her facial expression,looking for signs of commitment.
59600:34:32,567 --> 00:34:35,300NARRATOR:We are born hard-wiredwith an awareness
59700:34:35,367 --> 00:34:39,267of the intentions and emotionsof others,
59800:34:39,333 --> 00:34:42,733which is uniquein the animal world.
59900:34:42,800 --> 00:34:46,533HRDY:When did humans developthis gift
60000:34:46,600 --> 00:34:50,433for attributing mental statesand feelings to others
60100:34:50,500 --> 00:34:54,200and for caring about what othersthought about them?
60200:34:55,667 --> 00:34:58,100NARRATOR:Could these social instinctshave developed
60300:34:58,167 --> 00:35:00,200with Homo erectus,
604
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00:35:00,267 --> 00:35:03,733along with cooperative hunting,bigger brains,
60500:35:03,800 --> 00:35:09,333longer childhoodsand the use of fire?
60600:35:09,400 --> 00:35:13,133Perhaps Turkana Boyand his people already had
60700:35:13,167 --> 00:35:16,867social skills that would befamiliar to us.
60800:35:16,933 --> 00:35:19,267Here were intelligentsocial beings
60900:35:19,333 --> 00:35:23,667with an increasing capacityfor cooperation.
61000:35:27,133 --> 00:35:29,667It may bethis that made possible
61100:35:29,733 --> 00:35:32,867another great achievement--the exodus from Africa.
61200:35:35,400 --> 00:35:37,000For millions of years,
61300:35:37,067 --> 00:35:41,333our earliest ancestors stayedon the African savannas.
61400:35:41,400 --> 00:35:44,667But at some point,they started to leave.
61500:35:46,100 --> 00:35:49,467Ancient fossil skullsand tools have been found
61600:35:49,533 --> 00:35:53,433as far awayas China and Indonesia.
61700:35:53,500 --> 00:35:58,700The question is, when didthey leave Africa, and why?
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61800:36:00,333 --> 00:36:02,367When Turkana Boy was found,
61900:36:02,433 --> 00:36:05,267scientists thought
they had the answer.
62000:36:05,333 --> 00:36:08,600Here was a strong,large-brained ancestor
62100:36:08,667 --> 00:36:11,833capable of an arduous migration.
62200:36:11,900 --> 00:36:15,300He had the lookof a world conqueror.
62300:36:15,367 --> 00:36:17,100ANTN:I the mid-1980s,
62400:36:17,167 --> 00:36:20,600we were thinking that a hominidlike this one had left Africa
62500:36:20,667 --> 00:36:24,967but had done it maybeabout a million years ago.
62600:36:25,033 --> 00:36:27,767NARRATOR:For decades, scientists believed
62700:36:27,833 --> 00:36:30,467big, strapping humanslike Turkana Boy
62800:36:30,533 --> 00:36:33,600left Africa a million years ago.
62900:36:33,667 --> 00:36:37,733
But new discoveries are showingthe migration may have started
63000:36:37,800 --> 00:36:40,133a lot earlier than that.
63100:36:41,700 --> 00:36:44,833Dmanisi, Georgia.
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63200:36:44,900 --> 00:36:46,800The mountains and plainsof the Caucasus,
63300:36:46,867 --> 00:36:50,467thousands of miles
from the Great Rift Valley,
63400:36:50,533 --> 00:36:56,467had never produced any fossilsof early human ancestors.
63500:36:56,533 --> 00:37:01,267But then an astonishingdiscovery was made.
63600:37:01,333 --> 00:37:04,367(man speaking Georgian)
63700:37:04,433 --> 00:37:09,500(translated):It was a lower jaw,with teeth downward...
63800:37:09,567 --> 00:37:12,467this way in the ground.
63900:37:12,533 --> 00:37:16,500So when I started to clean,those front teeth came to light.
64000:37:16,567 --> 00:37:21,500It became obvious to me that wehad found some kind of hominid.
64100:37:21,567 --> 00:37:23,500But what kind?
64200:37:25,167 --> 00:37:29,467NARRATOR:The jaw seemed to be a primitiveform of Homo erectus,
64300:37:29,533 --> 00:37:34,800but at first hardly anyonebelieved it.
64400:37:34,867 --> 00:37:37,500In '91, when we found this jaw,
64500:37:37,567 --> 00:37:41,933this was... a lot of scientistswere quite skeptical about it,
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64600:37:42,000 --> 00:37:45,467because it was very hardto imagine Georgia, Caucasus,
64700:37:45,533 --> 00:37:48,167
to be on the mapof the human evolution.
64800:37:49,933 --> 00:37:54,133NARRATOR:Since then, Dmanisi has been puton the map of human evolution
64900:37:54,200 --> 00:37:55,533in a big way.
65000:37:55,600 --> 00:37:58,600The site has turned upa treasure trove
65100:37:58,667 --> 00:38:01,533of Homo erectus fossils.
65200:38:01,600 --> 00:38:03,933They've transformedour understanding
65300:38:04,000 --> 00:38:07,500of who left Africa and when.
65400:38:07,567 --> 00:38:10,567They showed that the firsthumans to leave Africa
65500:38:10,633 --> 00:38:13,867
were much more primitivethan TurkanaBoy.
65600:38:13,933 --> 00:38:17,167JORDI AGUST:People thought thatthe hominids that left Africa
65700:38:17,233 --> 00:38:18,333were very tall
65800:38:18,400 --> 00:38:21,600like Turkana Boy,with big brains,
65900:38:21,667 --> 00:38:23,000advanced technology,
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66000:38:23,067 --> 00:38:25,000and Dmanisi proved the opposite.
66100:38:25,067 --> 00:38:28,533NARRATOR:
At 4 1/2 feet tall,
66200:38:28,600 --> 00:38:31,400they were smallerthan Turkana Boy,
66300:38:31,467 --> 00:38:36,067with more apelike shouldersand a simple stone technology.
66400:38:36,133 --> 00:38:38,200LORDKIPANIDZE:They are much more primitive.
66500:38:38,267 --> 00:38:39,767They have small brains
66600:38:39,833 --> 00:38:42,233and the same time,they were using
66700:38:42,300 --> 00:38:44,033very primitive stone tools.
668
00:38:45,667 --> 00:38:50,033NARRATOR:The next surprise camewhen they dated the site.
66900:38:50,100 --> 00:38:54,467The ancient Dmanisi landscapehas been built up layer by layer
67000:38:54,533 --> 00:38:57,967over millions of years.
67100:38:58,033 --> 00:39:03,600
1.81 million years ago, massivevolcanic eruptions deposited
67200:39:03,667 --> 00:39:06,467a layer of ash.
67300:39:06,533 --> 00:39:09,500The fossils sat on topof this ash,
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67400:39:09,567 --> 00:39:11,933so must have beenslightly younger--
67500:39:12,033 --> 00:39:16,467around 1.8 million years old.
67600:39:16,533 --> 00:39:19,233To the vast majorityof scientists who believe
67700:39:19,300 --> 00:39:22,133that all our ancestors evolvedin Africa,
67800:39:22,200 --> 00:39:24,500this was a stunning surprise.
67900:39:24,567 --> 00:39:29,633How had a small, primitiveHomo erectus migrated
68000:39:29,700 --> 00:39:33,000to the Caucasusalmost two million years ago,
68100:39:33,067 --> 00:39:36,300long before Turkana Boy?
682
00:39:36,367 --> 00:39:40,667Scientists now accept that assoon as Homo erectus appeared
68300:39:40,733 --> 00:39:44,300on the savannas of Africa,they started to leave.
68400:39:46,033 --> 00:39:48,833Suddenly with the originof Homo erectus we get
68500:39:48,900 --> 00:39:51,267
this shift in body shapeand then boom,
68600:39:51,333 --> 00:39:52,800they're out of Africaright away.
68700:39:54,200 --> 00:39:55,567NARRATOR:The Georgia fossils proved
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68800:39:55,633 --> 00:39:59,033that Homo erectus left Africamuch earlier
68900:39:59,100 --> 00:40:01,167
than previously thought.
69000:40:01,233 --> 00:40:03,033An even more provocative find
69100:40:03,100 --> 00:40:08,767shows the migration may havestarted even earlier.
69200:40:08,833 --> 00:40:13,3335,000 miles from Africa...
69300:40:13,400 --> 00:40:19,333the island of Flores, Indonesia.
69400:40:19,400 --> 00:40:23,100In 2003, researchers madea discovery so strange,
69500:40:23,167 --> 00:40:26,567nobody knew what to make of it.
69600:40:26,633 --> 00:40:30,267They found the bones
of a tiny human ancestor,
69700:40:30,333 --> 00:40:32,600
just over three feet tall--
69800:40:32,667 --> 00:40:35,667even smallerthan the Dmanisi fossils.
69900:40:35,733 --> 00:40:41,533They called this baffling newancestor Homo floresiensis
70000:40:41,600 --> 00:40:46,100and, because of its tiny size,nicknamed it "The Hobbit."
70100:40:48,200 --> 00:40:51,133HOLLOWAY:This has created a tremendousamount of grief
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70200:40:51,200 --> 00:40:56,033because we're not really surewhat we're seeing here.
70300:40:56,100 --> 00:41:00,200The size of the Hobbit brain
endocast is roughly 400 cc.
70400:41:01,800 --> 00:41:05,600NARRATOR:That's barely biggerthan the brain of Lucy,
70500:41:05,667 --> 00:41:08,467the famous bipedal apefrom three million years ago.
70600:41:11,500 --> 00:41:14,500RICHMOND:
It's not just a small brainand a primitive-looking face,
70700:41:14,567 --> 00:41:15,833but the foot's primitive,the hand's primitive,
70800:41:15,900 --> 00:41:17,367the leg is primitive.
70900:41:17,600 --> 00:41:20,767SUSAN LARSON:The lower limb is very much like
the Lucy skeleton.
71000:41:20,833 --> 00:41:23,133That was a big surprise.
71100:41:24,233 --> 00:41:25,367NARRATOR:And in the cave
71200:41:25,433 --> 00:41:27,133where this primitive creaturewas found,
71300:41:27,367 --> 00:41:32,500they also uncovered stone tools,something Lucy never had.
71400:41:33,833 --> 00:41:35,433SHEA:People for a long time said,
715
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00:41:35,500 --> 00:41:37,800"You need a big brain to makestone tools."
71600:41:37,867 --> 00:41:39,967Well, okay, if Homo floresiensisis making stone tools,
71700:41:40,033 --> 00:41:42,100this creature has a brainthe size of an orange;
71800:41:42,167 --> 00:41:43,467clearly that equation's gone.
71900:41:45,900 --> 00:41:49,967NARRATOR:Everything about thesecreatures is an enigma.
72000:41:50,033 --> 00:41:53,467Where did they come fromand what were they?
72100:41:53,533 --> 00:41:55,033RICHMOND:Some researchers have argued
72200:41:55,100 --> 00:41:57,967that floresiensis is justa dwarfed population
72300:41:58,033 --> 00:42:01,467of modern people thatsuffered some kind of disease
72400:42:01,533 --> 00:42:03,167that caused them to both dwarf
72500:42:03,233 --> 00:42:05,133and have relativelysmall brains.
72600:42:05,200 --> 00:42:09,133NARRATOR:But when scientists tooka closer look,
72700:42:09,267 --> 00:42:12,133most saw no evidenceof disease.
72800:42:12,200 --> 00:42:16,333The stone tools and the shape
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of the face moved the focus
72900:42:16,400 --> 00:42:19,167to our old friend, Homo erectus.
73000:42:19,233 --> 00:42:20,700
RICHMOND:Some researchers think
73100:42:20,933 --> 00:42:25,667that Homo floresiensis evolvedfrom Homo erectus.
73200:42:25,733 --> 00:42:29,033NARRATOR:But how did they get so small?
73300:42:29,100 --> 00:42:33,933Something called island dwarfism
may be the answer.
73400:42:34,000 --> 00:42:36,800Isolated on islands
with limited food,
73500:42:36,867 --> 00:42:40,500large mammals sometimes shrinkover time.
73600:42:40,567 --> 00:42:47,000On Flores, there were once pygmyelephants the size of cows.
73700:42:47,067 --> 00:42:50,133Could the sameevolutionary pressure
73800:42:50,200 --> 00:42:54,200have acted on Homo erectusto produce the Hobbit?
73900:42:54,267 --> 00:42:57,167Or was this mysteriouscreature descended
74000:42:57,233 --> 00:43:02,100from an even moreprimitive ancestor?
74100:43:02,167 --> 00:43:04,067So perhaps we're samplinga period
742
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00:43:04,133 --> 00:43:06,633which is at the very beginningof the Homo lineage.
74300:43:06,700 --> 00:43:12,200NARRATOR:So whatever the Hobbit was,
perhaps its ancestors were
74400:43:12,267 --> 00:43:16,500the very first waveof migration out of Africa,
74500:43:16,567 --> 00:43:20,967some unknown creature:part bipedal ape like Lucy
74600:43:21,033 --> 00:43:23,900and part Homo erectus.
74700:43:28,300 --> 00:43:29,633LIEBERMAN:So if that's the case,
74800:43:29,700 --> 00:43:32,333then what we see in Indonesiamakes sense.
74900:43:32,400 --> 00:43:33,867It's a kind of a body
75000:43:33,933 --> 00:43:37,967that existed before human bodiesbecame more modern.
75100:43:41,833 --> 00:43:47,033NARRATOR:What would push such primitivecreatures out of Africa?
75200:43:51,333 --> 00:43:54,300A key driving forcebehind the migration
75300:43:54,367 --> 00:43:58,000was probably a climate shift
75400:43:58,067 --> 00:44:02,033which spread grasslandsfrom Africa into Asia.
75500:44:05,867 --> 00:44:09,967And with the grasseswent the game animals.
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75600:44:10,033 --> 00:44:12,267LIEBERMAN:Animals are going to be movingout of Africa,
757
00:44:12,333 --> 00:44:14,833and the hominids will just bekeeping pace with those animals.
75800:44:14,900 --> 00:44:16,200After all,that's their livelihood.
75900:44:16,500 --> 00:44:20,133NARRATOR:Of course, our ancestorsdidn't know
76000:44:20,200 --> 00:44:21,900they were leaving Africa.
76100:44:21,967 --> 00:44:24,733They just followed the animalsthey depended on,
76200:44:24,800 --> 00:44:29,000through the Sinai, up intothe Middle East and beyond.
76300:44:31,067 --> 00:44:33,567It's often been calledan exodus,
76400:44:33,633 --> 00:44:36,000but it really wasn't like that.
76500:44:36,067 --> 00:44:37,700SHEA:When people think of an exodus
76600:44:37,767 --> 00:44:39,767they think of the Bibleor they think of migration,
76700:44:39,833 --> 00:44:42,200they think of Europeans comingover here to the New World.
76800:44:42,267 --> 00:44:46,100It probably wasn't likeany historical migration,
769
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00:44:46,167 --> 00:44:47,967this dispersal of humansout of Africa.
77000:44:49,533 --> 00:44:53,500NARRATOR:The process was probably
very, very slow,
77100:44:53,567 --> 00:44:57,300much like the spreadof any other animal species
77200:44:57,367 --> 00:44:59,467into new territories.
77300:44:59,533 --> 00:45:02,533ANTN:You could imaginea group of Homo erectus
77400:45:02,600 --> 00:45:04,667moving their range
77500:45:04,733 --> 00:45:07,667a kilometer a yearin one direction.
77600:45:07,733 --> 00:45:12,100And doing that continually overa long enough period of time,
77700:45:12,167 --> 00:45:15,967you can get a distance fromAfrica to Indonesia covered
77800:45:16,033 --> 00:45:18,833in, say, 15,000 years.
77900:45:20,867 --> 00:45:24,933NARRATOR:By a million years ago, ourancestors had populated Asia
78000:45:25,000 --> 00:45:30,467from the Caucasus to Indonesia.
78100:45:30,533 --> 00:45:32,267And they were in Europe too,
78200:45:32,333 --> 00:45:35,500as a recent discoveryin Spain has shown.
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78300:45:35,567 --> 00:45:41,300Homo erectus had conqueredthe Old World.
78400:45:45,933 --> 00:45:49,700The fact that they made it
so far with limited technology
78500:45:49,767 --> 00:45:51,800and relatively small brains
78600:45:51,867 --> 00:45:57,767makes them seemeven more remarkable.
78700:45:57,833 --> 00:45:59,933And their longevitywas astonishing.
78800:46:00,000 --> 00:46:02,200A few pockets of Homo erectus
78900:46:02,267 --> 00:46:05,467may have been stillclinging on in Asia
79000:46:05,533 --> 00:46:08,133
just 50,000 years ago.
79100:46:08,200 --> 00:46:12,200That's a spanof two million years.
79200:46:13,667 --> 00:46:20,133Our own species has onlybeen around for 200,000.
79300:46:20,200 --> 00:46:26,100What was the secretof Homo erectus's success?
79400:46:26,167 --> 00:46:32,167The amazing finds at Dmanisihave given us one last clue.
79500:46:32,233 --> 00:46:34,900One of the skullsbelonged to an old man.
79600:46:34,967 --> 00:46:38,133His jaw bone revealedhe had lost all his teeth
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79700:46:38,200 --> 00:46:40,533well before he died.
79800:46:40,600 --> 00:46:42,067AGUST:That was a real surprise.
79900:46:42,133 --> 00:46:44,167It means that this individual
80000:46:44,233 --> 00:46:47,000survived two yearswithout teeth.
80100:46:47,300 --> 00:46:51,933NARRATOR:For an elder to have survivedthat long without teeth
80200:46:52,000 --> 00:46:56,200must mean that others inthe group were feeding him,
80300:46:56,267 --> 00:46:59,500perhaps even chewinghis food for him.
80400:46:59,567 --> 00:47:01,167HRDY:I love this story.
80500:47:01,233 --> 00:47:05,500This was a remarkable testimonyfrom the past
80600:47:05,567 --> 00:47:07,967about the qualityof emotional life
80700:47:08,033 --> 00:47:10,700that may have characterizedHomo erectus.
80800:47:12,500 --> 00:47:15,467NARRATOR:Here is a tantalizing clueto what may be
80900:47:15,533 --> 00:47:19,433this ancestor'smost important legacy:
81000:47:19,533 --> 00:47:22,533
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the instinctto look after each other.
81100:47:25,400 --> 00:47:29,333And it helps us imagine TurkanaBoy's final day on earth.
81200:47:35,933 --> 00:47:43,000In the animators' scenario,he starts the day out on a hunt.
81300:47:43,067 --> 00:47:46,767But he has trouble keeping upwith the hunting party.
81400:47:46,833 --> 00:47:49,467Why?
81500:47:49,533 --> 00:47:53,800The evidence from his skeletonis that he was sick and in pain
81600:47:53,867 --> 00:47:55,933at the time he died.
81700:47:56,000 --> 00:47:58,333If we look at his lower jaw,
81800:47:58,400 --> 00:48:01,100we can see right here,under the teeth,
81900:48:01,167 --> 00:48:04,133that we've got a bit ofan abscess and an infection.
82000:48:04,200 --> 00:48:06,767That kind of an infectioncould have entered
82100:48:06,833 --> 00:48:09,300the rest of his body,could have killed him.
82200:48:09,367 --> 00:48:12,500NARRATOR:An abscess that ateaway that much of his jawbone
82300:48:12,567 --> 00:48:16,467would have been agonizing.
82400:48:16,533 --> 00:48:19,167
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Turkana Boy is in so much pain,
82500:48:19,233 --> 00:48:22,600he's unable to continuethe hunt.
826
00:48:24,733 --> 00:48:26,533Knowing he would belooked after,
82700:48:26,767 --> 00:48:30,500perhaps he returned to hiscampsite to find comfort
82800:48:30,567 --> 00:48:34,367among the females.
82900:48:34,433 --> 00:48:36,600I think he was probablya miserable fellow,
83000:48:36,667 --> 00:48:38,867in a lot of painand very dependent
83100:48:38,933 --> 00:48:40,467on support and handouts.
83200:48:40,533 --> 00:48:44,367So it was a speciesthat already felt
83300:48:44,667 --> 00:48:47,300that here's one of our weaklingsthat, you know, we love
83400:48:47,367 --> 00:48:50,733and must protect and carefor to have got him that far.
83500:48:52,833 --> 00:48:56,100NARRATOR:But however much they may havewanted to help him,
83600:48:56,167 --> 00:48:59,300there was nothing they could doabout the infection
83700:48:59,333 --> 00:49:02,600that was probably spreadingthrough his body.
838
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00:49:05,500 --> 00:49:07,467DEAK:From what the evidence suggests,
83900:49:07,533 --> 00:49:12,233I just always imagined him notknowing what was wrong with him,
84000:49:12,300 --> 00:49:14,867and there's a sadness to it,
84100:49:14,933 --> 00:49:19,633but ultimately from that comesthis immortal being.
84200:49:22,100 --> 00:49:27,767NARRATOR:His skeleton was so complete,it is likely he died in water,
84300:49:27,833 --> 00:49:31,433which would have protected him.
84400:49:33,533 --> 00:49:36,133MEAVE LEAKEY:It's very unusualto get a skeleton,
84500:49:36,200 --> 00:49:38,767because normally these thingsare eaten by carnivores,
84600:49:38,833 --> 00:49:40,267and in this case, it seems
84700:49:40,333 --> 00:49:42,767that the boy's bodywas washed into a swamp,
84800:49:42,833 --> 00:49:45,533and so the carnivores never sawit and never destroyed it.
84900:49:45,600 --> 00:49:49,567And it gradually decomposedand as the rivers flooded,
85000:49:49,633 --> 00:49:52,600brought in more sediment,buried it,
85100:49:52,667 --> 00:49:54,433and you could see footprintsof hippos
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85200:49:54,500 --> 00:49:56,433that had walkedall over the bones,
85300:49:56,500 --> 00:49:59,467
and some of the ribs and thingswere standing vertically
85400:49:59,533 --> 00:50:01,467instead of lying flaton the ground.
85500:50:01,533 --> 00:50:03,467You could sort of reconstructthe situation
85600:50:03,533 --> 00:50:06,400and how the boy... what hadhappened after he died
85700:50:06,467 --> 00:50:08,600and why he was complete.
85800:50:08,667 --> 00:50:11,800It was just... it really was anamazing experience to see it.
85900:50:15,333 --> 00:50:17,933NARRATOR:For almost two million years,
86000:50:18,000 --> 00:50:21,100his bones were preservedby the earth.
86100:50:21,167 --> 00:50:26,767Their discovery opened a windowfor us on an unknown world,
86200:50:26,833 --> 00:50:32,333the world of the most successfulhuman ancestor of all time,
86300:50:32,400 --> 00:50:36,167Homo erectus.
86400:50:36,233 --> 00:50:39,433They've revealed to usthat mysterious moment
86500:50:39,500 --> 00:50:42,667when almost everything human
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was born:
86600:50:42,733 --> 00:50:47,800our bodies, our minds,our emotions.
867
00:50:50,333 --> 00:50:53,800Think of all we've become.
86800:50:58,400 --> 00:51:00,633Trace the threads of our origins
86900:51:00,700 --> 00:51:04,133back through the ancestorswho went before.
87000:51:04,200 --> 00:51:08,367They all lead backto Turkana Boy and his kind,
87100:51:08,433 --> 00:51:10,567the first humans.
87200:51:20,767 --> 00:51:23,600NOVA's got a brand-newevolution Web site,
87300:51:23,667 --> 00:51:25,533with lots to exploreabout our ancestors.
87400:51:25,600 --> 00:51:27,467We want to knowwhat you think.
87500:51:27,533 --> 00:51:30,667Bookmark it today,and give us your feedback.
87600:51:30,733 --> 00:51:33,633Find it at pbs.org.
87700:51:35,467 --> 00:51:39,367
Major funding for NOVAis provided by the following:
87800:51:39,433 --> 00:51:41,233ExxonMobil,
87900:51:41,300 --> 00:51:44,033taking on the world'stoughest energy challenges.
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88000:51:44,100 --> 00:51:45,800And by:
88100:51:50,200 --> 00:51:52,100And...
88200:52:01,367 --> 00:52:04,433And by the Corporationfor Public Broadcasting
88300:52:04,500 --> 00:52:07,533and by contributionsto your PBS station from:
88400:52:12,167 --> 00:52:14,767Captioned byMedia Access Group at WGBH
88500:52:15,767 --> 00:52:25,767Downloaded From www.AllSubs.org