00:00Have you ever truly considered
00:01the weight of your family tree?
00:05I am not talking about your great-grandparents.
00:09I am speaking of Alinea stretching back
00:11hundreds of millions of years.
00:15A story written in stone, in flesh, and in genes.
00:20Today we confront a profound question.
00:22What is the evidence for our own origins?
00:25We will explore the overwhelming proof
00:27for the theory of evolution.
00:30This is not just a story about finches and fossils.
00:33This is the story of us.
00:36Our first chapter begins with the rock layers.
00:40The grand library off our planet's past.
00:42Imagine each sedimentary stratum
00:44as a page in a history book.
00:48As we dig deeper into the earth,
00:51we travel further back in time.
00:53And what do we find in these ancient pages?
00:57We find a sequential record.
01:00Simple bacterial life appears in the oldest layers.
01:03Then the first complex cells.
01:06Then soft-bodied organisms.
01:09Then shelled creature astrilobites and nautiloids.
01:12Fish then follow in the geological record.
01:15Then amphibians crawl onto the land.
01:17Reptiles diversify and grow to immense sizes.
01:21Mammals appear and finally.
01:24The most recent layer shrivel our own genus Homo.
01:27This is the fossil sequence.
01:30It is a predictable pattern.
01:33You never find a rabbit in the Cambrian explosion.
01:35You never find a dinosaur.
01:39With the first flowering plants.
01:42The order is always consistent.
01:45This is powerful testimony.
01:48It shows life has changed drastically over time.
01:51But the fossil record provides more.
01:53It gives us transitional forms.
01:57These are the famous missing links.
02:00They are not missing anymore.
02:03Consider Tiktaalik for instance.
02:06This creature is a perfect mosaic.
02:09It had gills and lungs.
02:12It had a neck like a land animal.
02:15But its fins were becoming wrists.
02:18It was caught in the act.
02:21Of transitioning from water to land.
02:24Or look at the lineage of whales.
02:27We have a complete series.
02:30It begins with a land-dwelling wolf-like creature.
02:33Then we find Ambulocetus.
02:35A walking whale that swam with an up and down motion.
02:40Later species like Radhosidus.
02:42Had more streamlined bodies.
02:45Their nostrils migrated back towards their skull.
02:49Eventually we see Basilosaurus.
02:51A fully marine jaunt with vestigial hind legs.
02:55These are not isolated examples.
02:57We have transitions for birds.
03:00The magnificent Archaeopteryxod feathers and wings.
03:03But it also had teat and a bony tail.
03:07It was a dinosaur becoming a bird.
03:10We have transitions for horses.
03:12For elephants and for humans.
03:15The evidence is etched in stone.
03:18Now let us turn our gaze inward.
03:21To the anatomical evidence.
03:24Why do we have goosebumps?
03:27Our body is trying to fluffer.
03:30We no longer possess.
03:32Why does the laryngeal nerve.
03:36Take such a bizarre route.
03:39In a giraffe it travels all the way down the neck.
03:42And then back up again.
03:45This makes no engineering sense.
03:48Unless you understand evolution.
03:50In our fish ancestors this nerve made sense.
03:53It went from the brain to the gills directly.
03:55As the neck along the tuth nerve was stretched.
04:00It is a relic of our past.
04:03A historical constraint.
04:06Now consider homologous structures.
04:09Look at your own arm.
04:12The same bones that form your humerus.
04:15Your radius and ulna.
04:17Are found in a cat's leg.
04:21In a whale's flip earned in a bat's wing.
04:24The same fundamental blueprint.
04:27This is not intelligent design.
04:30It is descent with modification.
04:33A common ancestor beck with this pattern.
04:35Now, we dive deeper still.
04:39Into the molecular evidence.
04:42The code of life itself DNA.
04:45All living things share with same genetic language.
04:48This is a profound unity.
04:51We share 98% off our DNA with chimpanzees.
04:55We share 60% with a banana.
04:58This is not because of our half banana.
05:00It is because we share in ancient common ancestor.
05:04The molecular clock ticks within our cells.
05:07Mutations accumulate over time.
05:09By comparing these mutations we can build a tree.
05:12A family tree of life.
05:15This molecular phylogeny.
05:18Matches the tree built from fossils and anatomy.
05:21It is a consistent story.
05:24We find pseudogenesis in our own genome.
05:27Broken genes that no longer function.
05:30Like the gene for making vitamin C.
05:33Most mammals can synthesize it.
05:36But we primates cannot.
05:39We have the gene but it is broken.
05:42A mutation disabled light in our distant past.
05:45This is a shared error.
05:48We share this broken genu with other primates.
05:52It is a mark of our common ancestry.
05:54Now consider biogeography.
05:56The geographic distribution of species tells a story.
06:01Why are marsupial so dominant in Australia?
06:04While placental mammals rule elsewhere.
06:07Australia became isolated early in mammalian evolution.
06:10Marsupials evolved in isolation.
06:13They filled the ecological niches.
06:15Why do islands often have unique flightless birds?
06:19Like the dodo of Moridius.
06:21In the absence of predator's flight is less crucial.
06:25Evolution favors synergy conservation.
06:27Wings become smaller over generations.
06:30This is natural selection in action.
06:33And we can observe it directly.
06:36Think of the peppered moth in industrial England.
06:40So darken the tree bark.
06:41Light-colored moths were easily seen by birds.
06:46Dark-colored moths shot a survival advantage.
06:49Within decades the population shifted.
06:51This was evolution witnessed.
06:53We see it in bacteria becoming resistant to antibiotics.
06:57We see it in viruses evading our vaccines.
07:00Evolution is not a historical relic.
07:03It is happening right now.
07:06All this evidence converges.
07:08The fossils, the anatomite molecules, the distribution.
07:13They all tell the same story.
07:15Life has changed over vast time.
07:18All species are connected be common descent.
07:21This is not a random process.
07:24Natural selection shapes life.
07:28It is the great sculptor.
07:30Carving adaptation from random mutation.
07:33So what does this mean for us?
07:35We are not the pinnacle of creation.
07:39We are a branch on a mighty tree.
07:42A tree with roots in a primordial past.
07:45Our existence is a testament.
07:48To the power of deep time and natural forces.
07:52This understanding is humbling.
07:54It is also empowering.
07:57We are the first species in this planet.
07:59To comprehend our own origins.
08:03We can read the book of life.
08:06We can understand processes that made us.
08:09This knowledge is a great gift.
08:12It connects us to every other living thing.
08:15From the smallest bacterium to the largest whale.
08:19We are all part of one family.
08:21The evidence for evolution is overwhelming.
08:23It is etched in stone written in our bodies.
08:27And coated in our very genes.
08:30To deny it is to denny reality itself.
08:33Thank you for listening.
08:36Now go and look at the world anew.
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