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Hidden Ancestors Still Live in Our DNA · The Last Observer: Science and Beyond

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  Speaker 1: I want you to try and imagine your own DNA,
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  Speaker 1: and you know, not as that pristine, glowing, singular blueprint
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  Speaker 1: that you always see spinning around in sci fi.
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  Speaker 2: Movies, right, yeah, the perfect little holodey.
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  Speaker 1: Exactly the perfect hologram. Instead, picture it as this incredibly ancient,
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  Speaker 1: just heavily edited manuscript. Think of a book that hasn't
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  Speaker 1: just been carefully handed down from generation to generation, but
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  Speaker 1: one that has been absolutely battered by time.
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  Speaker 2: Oh absolutely batter It's.
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  Speaker 1: Got notes scribbled in the margins in totally different languages,
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  Speaker 1: Entire pages have been torn out, paragraphs pasted in from
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  Speaker 1: completely different texts, and there are these hidden chapters written
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  Speaker 1: in invisible ink that we are only like just right
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  Speaker 1: now learning how to read.
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  Speaker 2: Yeah, it is a profoundly messy and honestly chaotic text.
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  Speaker 2: And for the longest time, the scientific community really only
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  Speaker 2: knew how to read the surface level narrative of that manuscript.
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  Speaker 2: You know, we were just completely missing the subtext entirely, which.
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  Speaker 1: Makes sense, right, I mean, think about the story of
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  Speaker 1: human origins that pretty much most of us learn in school.
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  Speaker 1: It was presented as this incredibly simple, triumphant, linear branching tree,
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  Speaker 1: the classic march of progress, Right. The narrative was always
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  Speaker 1: that Homo sapiens emerged in Africa, we developed these superior
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  Speaker 1: cognitive abilities and complex tools, and then we just confidently
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  Speaker 1: marched out across the globe.
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  Speaker 2: Yeah, the assumption was always that as we moved across
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  Speaker 2: Europe and Asia, we simply replaced all the older hominin
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  Speaker 2: species we encountered.
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  Speaker 1: You were the pinnacle, you know, the final draft, and
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  Speaker 1: everyone else just kind of faded away into the evolutionary
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  Speaker 1: background because they couldn't compete.
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  Speaker 2: It's an incredibly comforting narrative, isn't it. I mean, it
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  Speaker 2: places us entirely alone at the summit of biological achievement.
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  Speaker 2: But well, as genetics advanced, that whole linear tree model
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  Speaker 2: just began to totally collapse.
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  Speaker 1: And the first really major crack in that story came
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  Speaker 1: with a paleogenomics revolution real, Oh, definitely, when scientists finally
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  Speaker 1: developed the technology to actually sequence the genomes of Neanderthals
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  Speaker 1: and Tenisivans from preserved bones. I mean, the results forced
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  Speaker 1: a total rewrite of our history. They absolutely did, because
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  Speaker 1: they found that modern non African populations actually carry roughly
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  Speaker 1: what one to two percent Neanderthal.
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  Speaker 2: DNA, yeah, about one to two percent.
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  Speaker 1: And then when you look at indigenous populations in Asia
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  Speaker 1: and Oceania, they carry up to four to five percent
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  Speaker 1: Denisivan genetic material.
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  Speaker 2: Which is a huge amount evolutionarily speaking.
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  Speaker 1: It's massive. So the evidence was just undeniable. We didn't
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  Speaker 1: just replace our evolutionary cousins when we expanded across the globe,
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  Speaker 1: We integrated with them.
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  Speaker 2: And that realization fundamentally shifted our entire understanding of species boundaries.
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  Speaker 2: I mean, it proved that human evolution wasn't a story
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  Speaker 2: of replacement, it was the story of biological exchange. But
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  Speaker 2: you know, there was a really massive limitation to all
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  Speaker 2: of those early discoveries. They were entirely dependent on physical.
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  Speaker 1: Evidence because you needed the actual bones exactly.
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  Speaker 2: We only knew about Neanderthals and dnis fins because we
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  Speaker 2: managed to literally dig up their bones, extract some fragmented
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  Speaker 2: DNA from like a tooth or tiny piece of skull,
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  Speaker 2: and then physically compare it to a modern human genome.
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  Speaker 1: It was entirely comparative science. You had to have the
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  Speaker 1: physical artifact in your hand to prove the genetic connection.
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  Speaker 2: Right.
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  Speaker 1: But and this is where it gets crazy. Recent breakthroughs
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  Speaker 1: from computational genetics labs, particularly out of UC Berkeley, have
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  Speaker 1: completely flipped this whole methodology on its head.
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  Speaker 2: They really have. It's brilliant work.
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  Speaker 1: They've discovered an anomaly deep within our genetic code that
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  Speaker 1: is just far stranger than Neanderthal or dimissive an ancestry.
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  Speaker 1: They're calling them ghost lineages.
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  Speaker 2: It's such a perfectly evocative term too, ghost lineages, it
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  Speaker 2: really is.
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  Speaker 1: And today we are going to explore the presence of
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  Speaker 1: two completely separate, previously unidentified ghost lineages that are hiding
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  Speaker 1: right now, deep within your very own genome.
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  Speaker 2: Yeah, and to define that for a second, these are
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  Speaker 2: ancient human species that lived, adapted, and successfully interbred with
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  Speaker 2: our direct ancestors. They left permanent, fully functioning biological code
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  Speaker 2: inside our living cells. But they left behind absolutely zero
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  Speaker 2: physical fossils, nothing at all, no bones, no recoverable ancient DNA.
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  Speaker 2: Archaeologically speaking, they are entirely one hundred percent invisible.
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  Speaker 1: Which instantly brings up this massive logical paradox. Right, we
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  Speaker 1: don't have a single bone, not a single tooth, or
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  Speaker 1: single physical fossil from these species. How in the world
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  Speaker 1: can we definitively prove their DNA is sitting inside us.
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  Speaker 2: Right now, it sounds impossible.
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  Speaker 1: It feels a bit like trying to prove someone was
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  Speaker 1: in a locked room without camera footage, without fingerprints, and
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  Speaker 1: without any witnesses. So before we get into the brilliant
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  Speaker 1: mathematics that actually solved this, let's just address the physical
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  Speaker 1: problem first. Why can't we just dig deeper and find
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  Speaker 1: their bones?
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  Speaker 2: Well, that comes down to the absolutely ruthless biochemistry of
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  Speaker 2: biological degradation. See, we actually have a highly skewed view
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  Speaker 2: of the prehistoric past purely because of where fossils happen
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  Speaker 2: to survive.
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  Speaker 1: Uh right, it's a survivorship bias.
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  Speaker 2: When we talk about finding Neanderthal or Denisovan DNA, we
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  Speaker 2: are almost exclusively talking about remains that were found in freezing, dry.
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  Speaker 1: Environments like those caves in Siberia.
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  Speaker 2: Yeah, Denisova Cave in Siberia, or high altitude mountain ranges
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  Speaker 2: in Eurasia.
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  Speaker 1: So a frozen cave is essentially just a natural time capsule.
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  Speaker 2: It acts exactly like a deep freeze. But you have
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  Speaker 2: to remember where the vast majority of early human evolution
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  Speaker 2: actually took.
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  Speaker 1: Place, right sub Saharan Africa and Southeast Asia.
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  Speaker 2: Exactly warm, deeply humid, totally tropical environments, and from a
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  Speaker 2: paleontological perspective, those environments are just highly, highly.
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  Speaker 1: Destructive because of the moisture.
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  Speaker 2: The heat and the moisture they dramatically accelerate the breakdown
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  Speaker 2: of biological material. I mean, when an organism dies in
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  Speaker 2: a humid savannah or tropical rainforest, the microbial activity is
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  Speaker 2: immediate and it is incredibly aggressive.
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  Speaker 1: The environment is just actively consuming.
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  Speaker 2: The evidence precisely, and if we look at the DNA
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  Speaker 2: molecule itself, DNA is held together by these chemical bonds
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  Speaker 2: that are highly susceptible to a process called hydrolysis.
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  Speaker 1: Hydrolysis meaning water.
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  Speaker 2: Yeah, water, water molecules effectively sneak in and sever the
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  Speaker 2: chemical links between the genetic letters. Even under perfect ideal conditions,
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  Speaker 2: DNA has a biological half life, but in a warm,
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  Speaker 2: moist environment, the rate of what we call depurination, which
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  Speaker 2: is when the DNA strands lose their purin bases and
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  Speaker 2: just shatter into these tiny, totally unreadable fragments, is incredibly.
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  Speaker 1: Fact So the water literally cuts the DNA apart exactly
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  Speaker 1: finding structurally sound bones in these climates after hundreds of
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  Speaker 1: thousands of years is exceptionally rare on its.
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  Speaker 2: Own, but finding recoverable DNA inside those bones it is
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  Speaker 2: virtually a statistical impossibility.
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  Speaker 1: Wow, Which means our map of human history has this massive,
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  Speaker 1: massive geographic and climatic blind spot. If an ancient Hominin
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  Speaker 1: lived and died near the equator, the Earth just completely
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  Speaker 1: erased their physical records, So we can't look in the
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  Speaker 1: dirt anymore. We have to look in the code. And
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  Speaker 1: this is where that incredible computational leap comes in, right,
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  Speaker 1: because scientists realized they had to stop looking for physical
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  Speaker 1: ancient DNA and instead start reverse engineering modern DNA.
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  Speaker 2: That was the breakthrough moment.
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  Speaker 1: Yeah. They developed these highly sophisticated algorithms, and one of
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  Speaker 1: the most pivotal techniques they use is called Trace.
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  Speaker 2: Trace. Yes, and Trace is just a fascinating piece of
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  Speaker 2: computational architecture. Rather than relying on physical fossils at all,
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  Speaker 2: Trace reconstructs evolutionary history using only the genetic material of
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  Speaker 2: diverse populations living on the planet.
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  Speaker 1: Today, just living people, just us.
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  Speaker 2: It functions by mapping out what we call the ancestral
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  Speaker 2: recombination graph or the ARG.
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  Speaker 1: Okay, you're going to have to walk me through the
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  Speaker 1: ancestral recombination graph, because how exactly does looking at modern
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  Speaker 1: DNA allow a computer to see a ghost from a
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  Speaker 1: million years ago.
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  Speaker 2: I know it sounds like magic, but it revolves around
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  Speaker 2: the actual mechanics of how DNA is passed down from
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  Speaker 2: generation to generation. When two parents reproduce, they don't just
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  Speaker 2: hand down their chromosomes as solid, unbroken blocks of code.
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  Speaker 2: During myosis, the chromosomes actually line up right next to
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  Speaker 2: each other and physically swap segments of genetic code. This
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  Speaker 2: process is called crossing over or recombination.
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  Speaker 1: So a child's DNA is quite literally a patchwork quilt
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  Speaker 1: of their parents' DNA.
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  Speaker 2: Exactly, It's a quilt. And here's the key. In every
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  Speaker 2: single subsequent generation, that quilt gets cut up and stitched
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  Speaker 2: back together into smaller and smaller and smaller patches. Oh
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  Speaker 2: I see, yeah, So, over tens of thousands of years,
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  Speaker 2: specific sequences of DNA get chopped into tinier fragments. What
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  Speaker 2: the ARG does is mathematically track the size and the
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  Speaker 2: distribution of those recombined fragments across modern populations.
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  Speaker 1: Those looking at the size the patches on the quilt. Yes.
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  Speaker 2: By measuring the density of mutations and the size of
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  Speaker 2: these genetic blocks, the algorithm can calculate exactly how much
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  Speaker 2: time has passed since a specific sequence was originally introduced
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  Speaker 2: into the human genome. It's essentially reading a biological clock.
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  Speaker 1: I really want to make sure the scale of this
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  Speaker 1: is clear for you listening, because the algorithm isn't just
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  Speaker 1: looking at one person's DNA. It's analyzing the genomes of
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  Speaker 1: one hundreds, sometimes thousands of modern individuals simultaneously, just comparing
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  Speaker 1: every single microscopic sequence to find these patterns exactly.
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  Speaker 2: The data set is massive.
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  Speaker 1: Let me try an analogy here to see if I
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  Speaker 1: have this right. Imagine you feed millions of modern English tweets, emails,
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  Speaker 1: and novels into this incredibly powerful linguistic algorithm. The computer's
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  Speaker 1: just scanning for structural patterns, right, but certainly it flags
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  Speaker 1: a very specific, weird grammatical qure, something totally out of place,
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  Speaker 1: like I don't know, ancient Sumerian syntax just sitting perfectly
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  Speaker 1: integrated into the middle of a modern English sentence. Okay, Yeah.
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  Speaker 1: By analyzing the surrounding text, the algorithm can mathematically prove
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  Speaker 1: that this syntax must have come from a complete, different,
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  Speaker 1: lost language that we have never actually heard spoken. It
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  Speaker 1: knows the ancient language existed solely based on the structural
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  Speaker 1: echoes that were left in the modern one.
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  Speaker 2: That analogy perfectly captures the methodology. That is exactly what
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  Speaker 2: is happening. The algorithm is scanning the genetic letters of
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  Speaker 2: our modern DNA, and occasionally it hits a sequence that
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  Speaker 2: simply does not fit the evolutionary timeline of Homo sapiens.
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  Speaker 1: But wait, I have to push back here a little bit. Sure,
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  Speaker 1: because our DNA mutates all the time, right, that's literally
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  Speaker 1: the core mechanism of evolution. How does the algorithm definitively
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  Speaker 1: know that a weird sequence is from a ghost species
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  Speaker 1: and not just a normal random mutation that happened in
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  Speaker 1: some group of modern humans like fifty thousand years ago.
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  Speaker 2: It's a great question, and it all comes down to
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  Speaker 2: the sheer mathematical density of the variation. See when the
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  Speaker 2: algorithm maps the branches of our ancestral tree, most of
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  Speaker 2: our DNA converges back to a common Homo sapiens ancestor
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  Speaker 2: within a relatively expected normal timeframe.
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  Speaker 1: The clockmap exactly.
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  Speaker 2: The mutation rate aligns with what we know about our
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  Speaker 2: species history. But when the algorithm finds a ghost segment,
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  Speaker 2: it detects a chromosomal branch that just doesn't converge with
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  Speaker 2: the rest of our genome.
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  Speaker 1: It goes way too far.
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  Speaker 2: Back, way too far back. The mutation density within that
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  Speaker 2: specific segment is so incredibly high that its evolutionary branch
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  Speaker 2: stretches back hundreds of thousands or even millions of years
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  Speaker 2: before it finally rejoins the main trunk of our lineage.
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  Speaker 1: So it's a mathematical red flag. The mucations are just
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  Speaker 1: too concentrated to have happened recently exactly.
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  Speaker 2: The math simply does not work any other way. A
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  Speaker 2: segment of DNA with that specific dense pattern of variation
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  Speaker 2: had to be evolving in a completely separate, isolated species
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  Speaker 2: for hundreds of thousands.
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  Speaker 1: Of years, just incubating.
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  Speaker 2: Yes, incubating in a totally different hominin, accumulating its own
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  Speaker 2: unique mutations in isolation, before it was suddenly injected back
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  Speaker 2: into our genetic code through an interbreeding event.
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  Speaker 1: So the algorithm serves as this incredible molecular magnified glass.
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  Speaker 1: And when geneticists pointed this magnifying glass that the modern
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  Speaker 1: human genome, the first massive anomaly they uncovered was right
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  Speaker 1: near the root of our human family tree, right the
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  Speaker 1: first ghost lineage. And man, this completely changes our understanding
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  Speaker 1: of our earliest days.
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  Speaker 2: It really does. And the timeline of this first discovery
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  Speaker 2: is totally pivotal. The computational data reveals that this first
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  Speaker 2: identified ghost lineage split from the line leading to modern
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  Speaker 2: humans roughly eight hundred thousand years ago.
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  Speaker 1: Eight hundred thousand years I just want to put that
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  Speaker 1: into perspective. That is the middle Pleistocene epoch. That is
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  Speaker 1: around the exact same time that the ancestors of Neanderthals
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  Speaker 1: and Denysivans diverged from our common lineage too, So we're
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  Speaker 1: looking at this massive multidirectional fork in the road of
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  Speaker 1: human evolution having all at basically at the same time.
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  Speaker 2: Yeah, it was incredibly busy time for hominin divergence. And
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  Speaker 2: you know, we know that the ancestors of Neanderthals and
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  Speaker 2: Denisivans eventually migrated out of Africa, settling in Europe and Asia.
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  Speaker 2: But the genetic signature of this particular ghost lineage tells
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  Speaker 2: a very different story. This group stayed. They evolved entirely
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  Speaker 2: in parallel with our direct ancestors, and the interbreeding event
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  Speaker 2: actually happened inside Africa.
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  Speaker 1: Inside Africa, and prior to fifty thousand years ago. Yes,
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  Speaker 1: which is crucial because it means this genetic exchange took
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  Speaker 1: place before the major out of Africa migration, you know,
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  Speaker 1: before early Homo sapiens pushed into Europe and Asia to
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  Speaker 1: populate the rest of the globe. Precisely so, because this
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  Speaker 1: mixing happened at the route before we expanded, this ghost
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  Speaker 1: lineage isn't regional, it is universal.
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  Speaker 2: And the implications of that universality are just staggering. I mean,
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  Speaker 2: when we discuss Neanderthal introgression, we are primarily talking about
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  Speaker 2: non African populations, and DENISOV and DNA is highly concentrated
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  Speaker 2: in Oceania and parts of Asia. But this eight hundred
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  Speaker 2: thousand year old African ghost lineage is a shared inheritance. Wow,
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  Speaker 2: every single modern human walking the Earth today, regardless of
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  Speaker 2: whether their ancestors state in Africa or migrated to the
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  Speaker 2: absolute furthest corners the globe, carries roughly point five to
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  Speaker 2: one point one percent of this extinct ancestors DNA.
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  Speaker 1: It's just incredible to think about a piece of a
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  Speaker 1: phantom species is universally binding us all together today. But
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  Speaker 1: you know, it's not just the fact that this DNA
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  Speaker 1: is sitting in our genome that is fascinating. It's the
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  Speaker 1: specific real estate that it occupies.
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  Speaker 2: Yeah, this was perhaps the most unexpected finding of the
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  Speaker 2: entire analysis, because geneticists mapped the exact chromosomal locations of
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  Speaker 2: these ghost segments, and they found traces of this archaic
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  Speaker 2: DNA intruding directly into what we call genomic deserts.
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  Speaker 1: Genomic deserts. That sounds incredibly deslate. What exactly does a
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  Speaker 1: desert look like in a genetic landscape?
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  Speaker 2: Well, in genetics, a desert is a region of our
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  Speaker 2: DNA that is incredibly resistant to change. Evolutionarily speaking, these
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  Speaker 2: areas are under what we call strong purifying selection.
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  Speaker 1: Purifying selection meaning natural selections, is just actively scrubbing out
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  Speaker 1: any variations.
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  Speaker 2: Exactly. These regions code for such fundamental, critically important biological
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  Speaker 2: functions that almost any random mutation that occurs there is
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  Speaker 2: highly detrimental.
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  Speaker 1: Oh, I get it. So if a mistake happens there,
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  Speaker 1: things break right.
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  Speaker 2: If a mutation happens in a genomic desert, it usually
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  Speaker 2: compromises the organism's ability to survive or reproduce, so natural
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  Speaker 2: selection just eliminates that genetic line immediately. Because they are
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  Speaker 2: so heavily conserved, these deserts were long thought to be
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  Speaker 2: the untouched core blueprint of what makes a modern Homo
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  Speaker 2: sapiens uniquely human.
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  Speaker 1: Well, wait, I have to challenge this premise.
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  Speaker 2: Go ahead.
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  Speaker 1: If a genomic desert is an area where any biological
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  Speaker 1: change usually results in an evolutionary failure, how did a
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  Speaker 1: massive chunk of foreign ghost DNA manage to wedge itself
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  Speaker 1: into these regions without causing a catastrophic breakdown? Doesn't that
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  Speaker 1: totally contradict the whole idea of natural selection.
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  Speaker 2: That is the exact question that makes this discovery so profound,
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  Speaker 2: because the only way foreign DNA survives in a genomic
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  Speaker 2: desert is if it wasn't a random broken mutation see
• 15:58
  Speaker 2: random errors destroy or the system. But the ghost DNA
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  Speaker 2: wasn't an error. It was a highly refined, heavily tested
• 16:04
  Speaker 2: block of genetic code. It had been evolving, improving its
• 16:07
  Speaker 2: biological utility and another human species for eight hundred thousand years,
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  Speaker 2: so when it entered our genome, it didn't disrupt the desert.
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  Speaker 2: It integrated seamlessly, and it perhaps even upgraded the local machinery.
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  Speaker 1: It was essentially a pre vetted, highly compatible software.
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  Speaker 2: Update, exactly a biological software update.
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  Speaker 1: And here's where it gets really interesting. One of the
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  Speaker 1: specific genomic deserts where this ghost DNA was found surrounding
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  Speaker 1: is a gene called FOXP two.
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  Speaker 2: Yeah, FOXP two.
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  Speaker 1: We really need to dive into this because FOXP two
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  Speaker 1: is not just any random string of code. It is
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  Speaker 1: intimately tied to one of the most defining characteristics of
• 16:44
  Speaker 1: our entire species, the ability to speak.
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  Speaker 2: FOXP two is fundamentally crucial to the neurological and fine
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  Speaker 2: motor control that is required for complex language. I mean,
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  Speaker 2: to produce speech. Your brain has to coordinate incredibly rapid,
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  Speaker 2: highly precise movements of the jaw, the tongue, the lips,
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  Speaker 2: and the larynx.
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  Speaker 1: It's wild when you actually think about the mechanics of it.
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  Speaker 2: It is a stunning mechanical feet and when the FOXP
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  Speaker 2: two gene is damaged or mutated in modern humans, it
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  Speaker 2: leads to severe speech and language disorders like verbal dyspraxia.
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  Speaker 1: Meaning they can't speak well.
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  Speaker 2: The individual has the cognitive desire to speak, they know
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  Speaker 2: what they want to say, but the brain simply cannot
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  Speaker 2: coordinate the physical mechanics required to articulate the words.
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  Speaker 1: So it's the actual bridge between the thought and the
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  Speaker 1: physical vocalization exactly. And we've long viewed our capacity for
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  Speaker 1: nuanced complex language as our crowning achievement, right it is
• 17:39
  Speaker 1: the thing that separates us from the animal kingdom. But
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  Speaker 1: if genetic trace is from an eight hundred thousand year
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  Speaker 1: old extinct cousin a species that evolved on a completely
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  Speaker 1: separate trajectory for nearly a million years, are lingering in
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  Speaker 1: the regulatory regions surrounding the gene responsible for speech? I
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  Speaker 1: mean that completely flips the narrative.
• 17:58
  Speaker 2: It really does.
• 17:58
  Speaker 1: Did we actually invent on our own or did we
• 18:01
  Speaker 1: borrow a critical piece of the hardware from a ghost?
• 18:04
  Speaker 2: It certainly challenges the very core of human exceptionalism. We
• 18:08
  Speaker 2: tend to view cognitive evolution as a solitary climb to
• 18:11
  Speaker 2: the top, but the intrusion of ghost DNA and near
• 18:13
  Speaker 2: FOXP two strongly suggests that the genetic architecture supporting speech
• 18:17
  Speaker 2: was not built in a vacuum.
• 18:19
  Speaker 1: It was a team effort.
• 18:20
  Speaker 2: It was a collaborative mosaic. Yeah, we may have absorbed
• 18:23
  Speaker 2: beneficial genetic variations from this ghost lineage that enhanced or
• 18:28
  Speaker 2: stabilized or maybe fine tuned our own capacity for complex.
• 18:33
  Speaker 1: Vocalization, which is just wild.
• 18:36
  Speaker 2: It is, and it strongly implies that these extinct dominants
• 18:39
  Speaker 2: were not the primitive grunting caricatures we always imagine. I mean,
• 18:43
  Speaker 2: they possessed genetic traits so biologically valuable that our own
• 18:47
  Speaker 2: species preserve them in the most critical sensitive regions of
• 18:50
  Speaker 2: our genome.
• 18:51
  Speaker 1: So who were they? I mean, we have this incredibly
• 18:54
  Speaker 1: specific biological profile. We know they split from our lineage
• 18:57
  Speaker 1: eight hundred thousand years ago, We know they stayed in Africa,
• 19:00
  Speaker 1: and we know they were anatomically similar enough to interbreed
• 19:03
  Speaker 1: with our direct ancestors. Who were the prime pilliontological suspects
• 19:07
  Speaker 1: for this universal African cousin.
• 19:09
  Speaker 2: Given the timeline and the geography, paleontologists looked toward the
• 19:12
  Speaker 2: middle Pleistocene Homo species that ranged widely across the African
• 19:16
  Speaker 2: continent during that exact era.
• 19:18
  Speaker 1: Okay, so who are the candidates.
• 19:20
  Speaker 2: The strongest candidates are late surviving forms of homohydel bergensis
• 19:23
  Speaker 2: or Homo rhodathiensis.
• 19:24
  Speaker 1: What do we know about them? What did they actually
• 19:27
  Speaker 1: look like?
• 19:27
  Speaker 2: Well, these were incredibly robust, large brained hominins. They were
• 19:32
  Speaker 2: formidable like big, big, strong, and highly sophisticated tool makers.
• 19:38
  Speaker 2: They were creating complex stone blades and hand axes. They
• 19:42
  Speaker 2: were coordinated group hunters that took down large game, and
• 19:45
  Speaker 2: they were remarkably adaptable to the changing African climate.
• 19:49
  Speaker 1: Wow.
• 19:49
  Speaker 2: They shared the landscape with our early Homo sapiens ancestors
• 19:53
  Speaker 2: for a long time, and clearly they interacted.
• 19:57
  Speaker 1: It just paints such a vivid cinematic picture. I mean,
• 20:00
  Speaker 1: imagine our direct ancestors walking the African savannah or navigating
• 20:04
  Speaker 1: a dense woodland and they encounter a completely different species
• 20:08
  Speaker 1: of human and they don't just fight or ignore each other.
• 20:10
  Speaker 1: They interact, They learn, and they literally have children together.
• 20:13
  Speaker 2: They merged.
• 20:15
  Speaker 1: That species eventually faded into extinction, physically swallowed by the environment,
• 20:19
  Speaker 1: like you said, but they effectively immortalize themselves in our
• 20:22
  Speaker 1: genetic code.
• 20:23
  Speaker 2: Beautifully put.
• 20:24
  Speaker 1: But as incredible as that African exchange is, the computational
• 20:27
  Speaker 1: algorithms found a second lineage that is even more mind
• 20:30
  Speaker 1: bending because this second ghost didn't enter our genome directly.
• 20:34
  Speaker 2: Right, the first ghost lineage was a direct, localized exchange
• 20:38
  Speaker 2: in Africa, but the second discovery is exponentially older, and
• 20:42
  Speaker 2: the mechanism by which we inherited it is incredibly complex.
• 20:46
  Speaker 2: In the field, this one is referred to as the
• 20:48
  Speaker 2: super archaic lineage.
• 20:50
  Speaker 1: Super archaic, I mean the name alone conveys a completely
• 20:54
  Speaker 1: different magnitude of time. The data shows this hominin group
• 20:57
  Speaker 1: separated from the human evolutionary tree a staggering one point
• 21:01
  Speaker 1: eight million years ago.
• 21:03
  Speaker 2: Yeah, one point eight million.
• 21:04
  Speaker 1: One point eight million, We are talking about a timeframe
• 21:07
  Speaker 1: that is almost impossible to even conceptualize on a human scale.
• 21:10
  Speaker 2: To frame that depth of time, one point eight million
• 21:13
  Speaker 2: years ago is the dawn of the genus Homo itself.
• 21:16
  Speaker 2: Oh wow, it aligns perfectly with the very first major
• 21:19
  Speaker 2: hominin expansions out of the African continent. This super archaic
• 21:23
  Speaker 2: lineage split off from our ancestors near the very beginning
• 21:26
  Speaker 2: of our evolutionary story. They evolved on an entirely isolated
• 21:29
  Speaker 2: trajectory across drastically different environments for nearly two million years.
• 21:33
  Speaker 1: And here's the paradox that makes this second discovery so fascinating.
• 21:37
  Speaker 1: This super archaic group did not interbreed with modern humans.
• 21:41
  Speaker 2: No they didn't.
• 21:42
  Speaker 1: We never met them, We never crossed paths with them
• 21:44
  Speaker 1: on a savannah, we never shared a cave with them,
• 21:46
  Speaker 1: We never existed in the same geographic space at the
• 21:49
  Speaker 1: same time. So how did a sequence of DNA from
• 21:53
  Speaker 1: a one point eight million year old phantom end up
• 21:56
  Speaker 1: inside you and me today?
• 21:58
  Speaker 2: Through a biological phenomenon known and as secondary.
• 22:00
  Speaker 1: Introgression secondary intrograt It.
• 22:02
  Speaker 2: Is essentially an evolutionary handoff. While this super archaic group
• 22:06
  Speaker 2: never encountered Homo sapiens, their populations did overlap with the
• 22:10
  Speaker 2: Nissivans in Eurasia roughly two hundred thousand, three hundred thousand
• 22:14
  Speaker 2: years ago.
• 22:14
  Speaker 1: Let me try to visualize this. It's kind of like
• 22:16
  Speaker 1: a game of genetic telephone, or maybe like a set
• 22:19
  Speaker 1: of Russian nesting dolls.
• 22:20
  Speaker 2: Oh, the Russian nesting doll is a brilliant way to
• 22:23
  Speaker 2: conceptualize the structural inheritance.
• 22:25
  Speaker 1: Let's use that, okay, So imagine the outermost doll is
• 22:28
  Speaker 1: us modern Homo sapiens. The next doll tucked inside that
• 22:32
  Speaker 1: one is the Denisovan, and tucked away deep inside the
• 22:34
  Speaker 1: Denisovan doll is the super archaic ghost. So hundreds of
• 22:38
  Speaker 1: thousands of years ago, the super archaic species interbred with
• 22:42
  Speaker 1: the dinisivants. They passed their one point eight million year
• 22:45
  Speaker 1: old genetic fragments into the Denisovan genome. The Dinsivans then
• 22:49
  Speaker 1: carried that foreign DNA in their own cells generation after
• 22:52
  Speaker 1: generation for tens of thousands.
• 22:54
  Speaker 2: Of years, safely incubating it.
• 22:56
  Speaker 1: Right and much later, when early Homo sapiens might go
• 23:00
  Speaker 1: out of Africa and pushed into Eurasia, we encountered the
• 23:03
  Speaker 1: densivants and we interbred with them. The Dinicivans basically acted
• 23:06
  Speaker 1: as a biological courier, like a genetic vessel.
• 23:09
  Speaker 2: They unwittingly smuggled the DNA of a species we never
• 23:12
  Speaker 2: actually met, right into our own genome.
• 23:14
  Speaker 1: That is just yeah, the statistical improbability of that sequence
• 23:19
  Speaker 1: of events is staggering.
• 23:20
  Speaker 2: Consider what that DNA actually had to survive. The genetic
• 23:23
  Speaker 2: material of a one point eight million year old lineage
• 23:27
  Speaker 2: survived not just the physical extinction of its original host species,
• 23:30
  Speaker 2: but it successfully hitch a ride in a secondary host
• 23:33
  Speaker 2: species right the Dinis events. It survived their eventual extinction,
• 23:36
  Speaker 2: navigated the brutal gauntlet of natural selection twice, and continues
• 23:40
  Speaker 2: to actively replicate in ourselves today.
• 23:42
  Speaker 1: It is the ultimate story of biological persistence. And because
• 23:46
  Speaker 1: this DNA was delivered to us specifically through the Dinisivans,
• 23:49
  Speaker 1: we can actually trace its geographic footprint today. Right where
• 23:54
  Speaker 1: is this ancient echo the loudest in modern populations?
• 23:57
  Speaker 2: Well, it tracks directly with what we know about Denisivan
• 24:00
  Speaker 2: migration patterns. Denis of an ancestry is highest in indigenous Australian,
• 24:04
  Speaker 2: Papuin and Melanesian populations. Okay, therefore, these exact groups retain
• 24:09
  Speaker 2: the clearest, most concentrated genetic footprints of this one point
• 24:13
  Speaker 2: eight million year old, super archaic ghost ancestor.
• 24:17
  Speaker 1: That perfectly aligns with the ancient migration routes. As our
• 24:21
  Speaker 1: ancestors pushed through Southeast Asia navigating the archipela goes down
• 24:24
  Speaker 1: into Oceania, they were moving straight through the heartland of
• 24:27
  Speaker 1: dinisiv In.
• 24:28
  Speaker 2: Territory, Yes, right through it.
• 24:29
  Speaker 1: They absorbed this deeply ancient genetic material along the way.
• 24:33
  Speaker 1: So if we know they split one point eight million
• 24:35
  Speaker 1: years ago and seeded Eurasia with their DNA. Who is
• 24:38
  Speaker 1: the prime suspect for the super archaic ghost.
• 24:41
  Speaker 2: Well, when you look for a hommin and lineage diverging
• 24:43
  Speaker 2: exactly one point eight million years ago that subsequently conquered
• 24:47
  Speaker 2: the Eurasian landscape, all the evidence points to one of
• 24:50
  Speaker 2: the most successful species in history, Homo erectus.
• 24:55
  Speaker 1: Homo erectus the upright walker. I mean, they're a legendary
• 24:58
  Speaker 1: in the fossil record.
• 24:59
  Speaker 2: Oh, they were the old pioneers. Homoerectus was the first
• 25:02
  Speaker 2: hominin to have body proportions remarkably similar to our own,
• 25:06
  Speaker 2: longer legs, shorter arms, perfectly built for a terrestrial life
• 25:10
  Speaker 2: buil for walking and running. They were the first to
• 25:13
  Speaker 2: truly master endurance running, which fundamentally changed how they hunted
• 25:17
  Speaker 2: and interacted with the landscape. They possessed the cognitive ability
• 25:21
  Speaker 2: to create a Shulian hand axes, and they survived across
• 25:25
  Speaker 2: drastically different climates, from the freezing Caucasus Mountains in Georgia
• 25:29
  Speaker 2: to the tropical jungles of Indonesia for well over a
• 25:32
  Speaker 2: million years.
• 25:33
  Speaker 1: They were just the ultimate survivalists. They essentially seeded the
• 25:36
  Speaker 1: ancient world with their biological legacy. That Denisovans harvested some
• 25:41
  Speaker 1: of that legacy, carried it from millennia, and then passed
• 25:44
  Speaker 1: it on to us. But this brings up a massive
• 25:46
  Speaker 1: biological question because it's one thing to inherit a random
• 25:50
  Speaker 1: string of DNA through a chance encounter. It is another
• 25:53
  Speaker 1: thing entirely for that specific string of code to survive
• 25:56
  Speaker 1: an r genome for hundreds of thousands of years. Absolutely
• 26:00
  Speaker 1: is not sentimental. Natural selection is incredibly ruthless. If a
• 26:05
  Speaker 1: gene is useless, it degrades. If it's harmful, the organism
• 26:08
  Speaker 1: dies and the gene is scrub from the population. So
• 26:11
  Speaker 1: why didn't our bodies reject this ghost DNA? Why do
• 26:15
  Speaker 1: we keep it?
• 26:16
  Speaker 2: That is the pivotal question of introgression dynamics. As you said,
• 26:19
  Speaker 2: the genome is highly efficient introgressed DNA, which is genetic
• 26:23
  Speaker 2: material transferred laterally between distinct species, It rarely survives over
• 26:28
  Speaker 2: evolutionary time scales by sheer accident.
• 26:30
  Speaker 1: It needs a purpose.
• 26:31
  Speaker 2: Right If a foreign sequence of DNA is still present
• 26:33
  Speaker 2: in the modern human genome today, and particularly if it
• 26:36
  Speaker 2: is maintained at a high frequency across an entire population,
• 26:40
  Speaker 2: it almost certainly conferred a major immediate adaptive benefit to
• 26:44
  Speaker 2: our ancestors.
• 26:45
  Speaker 1: We didn't keep this DNA as a biological souvenir. We
• 26:47
  Speaker 1: kept it because it gave us a distinct advantage. We
• 26:50
  Speaker 1: needed it to survive.
• 26:51
  Speaker 2: Precisely, the ghost DNA provided immediate solutions to new environmental pressures.
• 26:57
  Speaker 2: And when geneticists analyze exactly where the surviving ghost segments
• 27:01
  Speaker 2: are concentrated in modern genomes, a very clear functional pattern emerges.
• 27:05
  Speaker 2: They are clustered around regions responsible for three major areas
• 27:09
  Speaker 2: of human survival.
• 27:11
  Speaker 1: Okay, what's the first one.
• 27:12
  Speaker 2: The first and perhaps most critical is immune system function.
• 27:16
  Speaker 1: You know this makes absolute logical sense. Picture an early
• 27:20
  Speaker 1: population of Homo sabians finally leaving their original homeland in Africa.
• 27:25
  Speaker 1: They're pushing into completely uncharted ecological zones.
• 27:28
  Speaker 2: Right, totally new environments.
• 27:29
  Speaker 1: They are encountering different climates, different flora, different water sources,
• 27:34
  Speaker 1: and most dangerously totally unfamiliar pathogens, parasites, and viruses.
• 27:39
  Speaker 2: Exactly when a virgin population enters a novel environment, they
• 27:42
  Speaker 2: are exquisitely vulnerable to local diseases. A single highly contagious
• 27:47
  Speaker 2: local virus can wipe out an entire migrating group. If
• 27:50
  Speaker 2: they had to rely solely on their own natural mutation rates,
• 27:53
  Speaker 2: it could take thousands of generations for their immune systems
• 27:56
  Speaker 2: to adapt to these new threats.
• 27:58
  Speaker 1: But the ghost populations and the denisivans carrying the super
• 28:01
  Speaker 1: archaic DNA, they had already been living in these specific
• 28:05
  Speaker 1: regions for hundreds of thousands of years.
• 28:07
  Speaker 2: Yes, their immune systems had spent millennia locked in a
• 28:11
  Speaker 2: biological arms race with the local pathogens. Let's look at
• 28:15
  Speaker 2: a specific mechanism like toll like receptors or TLR.
• 28:19
  Speaker 1: Genes tler genes.
• 28:21
  Speaker 2: Yeah, these are essentially the security guards of your immune system.
• 28:24
  Speaker 2: They sit right on the surface of your cells in
• 28:26
  Speaker 2: our programmed to recognize the specific molecular patterns of invading
• 28:30
  Speaker 2: viruses and bacteria.
• 28:31
  Speaker 1: So to use an analogy, if a local virus is
• 28:34
  Speaker 1: a burglar trying to break into the cell, the toll
• 28:37
  Speaker 1: like receptor is the security guard checking IDs at the door.
• 28:40
  Speaker 2: Perfect analogy, yes, but imagine the local burglars have evolved
• 28:43
  Speaker 2: specific disguises that the new migrating security guards have never
• 28:47
  Speaker 2: seen before.
• 28:48
  Speaker 1: They just walk right in right.
• 28:50
  Speaker 2: The local hominins, however, had spent hundreds of thousands of
• 28:53
  Speaker 2: years evolving new guards that could easily spot those specific
• 28:56
  Speaker 2: local disguises. So when our ancestors ariya An interbred with
• 29:01
  Speaker 2: the local populations, they didn't have to wait to slowly
• 29:03
  Speaker 2: evolve their own defenses. They simply acquired the genetic blueprints
• 29:07
  Speaker 2: for the local security guards.
• 29:08
  Speaker 1: Wow, we effectively downloaded a vital security update for our
• 29:13
  Speaker 1: immune system directly from the local inhabitants. We copied their
• 29:16
  Speaker 1: lock designs.
• 29:17
  Speaker 2: That is an incredible evolutionary shortcut.
• 29:20
  Speaker 1: So immunity kept us from being wiped out by invisible viruses.
• 29:24
  Speaker 1: But I mean, surviving a local pathogen doesn't help much
• 29:27
  Speaker 1: if you freeze to death or starve in a completely
• 29:29
  Speaker 1: new climate. Did this ghost DNA do anything for us physically?
• 29:34
  Speaker 1: What is the second major benefit?
• 29:36
  Speaker 2: The second major cluster of introgress DNA is tied to
• 29:39
  Speaker 2: metabolism and energy storage. As modern humans expanded globally, they
• 29:43
  Speaker 2: encountered dramatically different environmental stressors that their African adapted bodies
• 29:48
  Speaker 2: had just never experienced. Like what well they faced the
• 29:51
  Speaker 2: freezing climates of northern latitudes, entirely novel sources of fat
• 29:55
  Speaker 2: and propane, and extended brutal periods of sinimal starvation.
• 29:59
  Speaker 1: They needed to change how their bodies process fuel.
• 30:02
  Speaker 2: Exactly, ghost DNA helped modify vital metabolic pathways. It influenced
• 30:07
  Speaker 2: how our ancestors digested new lipid rich diets, how they
• 30:11
  Speaker 2: synthesized complex proteins, how their bodies efficiently stored energy during
• 30:16
  Speaker 2: times of famine, and how they regulated heat production in
• 30:19
  Speaker 2: extreme cold.
• 30:20
  Speaker 1: Well, that makes so much sense.
• 30:21
  Speaker 2: A famous parallel example of this is the EPAS one
• 30:25
  Speaker 2: gene found in modern Tibetans. That gene was inherited from Denucovians,
• 30:29
  Speaker 2: and it allows for survival in extreme oxygen deprived high altitudes.
• 30:34
  Speaker 1: Right because their bodies don't overproduce red blood cells at
• 30:36
  Speaker 1: high altitudes, which prevents their blood from thickening and causing strokes.
• 30:40
  Speaker 2: Precisely, the ghost DNA provided similar deeply embedded metabolic tweets.
• 30:45
  Speaker 2: Rather than painfully evolving these metabolic traits from scratch through
• 30:48
  Speaker 2: trial and air over thousands of years, our species co
• 30:52
  Speaker 2: opted the biological solutions that had already been beta tested
• 30:55
  Speaker 2: by other hominins over immense spans of time.
• 30:57
  Speaker 1: It's basically biological plagiarism, and it saved our lives, it
• 31:00
  Speaker 1: really did. And the third major benefit brings us back
• 31:03
  Speaker 1: to something we touched on earlier, which might be the
• 31:05
  Speaker 1: most philosophically profound neurological architecture.
• 31:09
  Speaker 2: The survival of ghost DNA in regions tied to cognitive processing,
• 31:13
  Speaker 2: sensory adaptation, and brain development is highly, highly significant. We
• 31:18
  Speaker 2: already discussed the intrusion near FOXP two and the mechanics
• 31:22
  Speaker 2: of speech, but it goes much deeper than vocalization. Our
• 31:26
  Speaker 2: mental toolkit, the way our brains process complex sensory information,
• 31:30
  Speaker 2: the way we adapt our circadian rhythms to environments with
• 31:33
  Speaker 2: vastly different daylight hours, and the way we interpret social cues.
• 31:37
  Speaker 2: All of these show signs of archaic introgression.
• 31:41
  Speaker 1: Meaning our cognitive evolution, the very way we perceive reality
• 31:45
  Speaker 1: and interact with the world, wasn't an isolated, solitary event.
• 31:49
  Speaker 2: It proves that the human brain is a mosaic structure.
• 31:52
  Speaker 2: The cognitive flexibility that allowed us to conjure every environment
• 31:55
  Speaker 2: on Earth was partially fueled by genetic variations we absorbed
• 31:59
  Speaker 2: from species that are now entirely extinct.
• 32:02
  Speaker 1: Okay, let's unpack this because when we step back and
• 32:04
  Speaker 1: look at the big picture here when we look at
• 32:06
  Speaker 1: the borrowed immune receptors fighting off local viruses, the metabolic
• 32:11
  Speaker 1: tweaks allowing us to survive the freezing cold, the neurological
• 32:15
  Speaker 1: architecture influencing our speech. We didn't conquer the globe just
• 32:19
  Speaker 1: because we were inherently genetically superior out of the gate.
• 32:22
  Speaker 2: Now we really weren't.
• 32:24
  Speaker 1: We conquered it by biologically crowdsourcing our survival traits. We
• 32:28
  Speaker 1: took the absolute best adaptations from the local hominins who
• 32:32
  Speaker 1: had already lived there, who had already suffered, adapted, and
• 32:35
  Speaker 1: survived for hundreds of thousands of years, and we just
• 32:39
  Speaker 1: integrated their biological brilliance right into our own blueprint.
• 32:43
  Speaker 2: Crowdsourcing survival is a beautifully accurate way to phrase the
• 32:47
  Speaker 2: mechanics of human expansion and all of these highly specific
• 32:51
  Speaker 2: biological details, these algorithmic discoveries pulling ghosts out of the math.
• 32:55
  Speaker 2: They forced us to do something very uncomfortable.
• 32:58
  Speaker 1: Okay, they forced us to.
• 32:59
  Speaker 2: Compose, deletely rethink the fundamental philosophy of what a human
• 33:03
  Speaker 2: being actually.
• 33:03
  Speaker 1: Is, because it completely shatters that middle school textbook tree
• 33:07
  Speaker 1: we talked about at the very beginning of the show
• 33:09
  Speaker 1: the simple straight line of progress.
• 33:12
  Speaker 2: It formally and undeniably deconstructs the entire metaphor. Evolution was
• 33:17
  Speaker 2: not a clean linear tree. The idea of isolated branches
• 33:21
  Speaker 2: growing straight up or suddenly snapping off into total extinction
• 33:25
  Speaker 2: without affecting the rest of the tree is a relic
• 33:27
  Speaker 2: of an older, much simpler way of thinking. The computational
• 33:31
  Speaker 2: data tells a far more dynamic story.
• 33:33
  Speaker 1: So if the tree metaphor is dead, what is the
• 33:36
  Speaker 1: new metaphor? How should we visualize our history?
• 33:38
  Speaker 2: The new, widely accepted paradigm in paleogenomics is the braided stream.
• 33:43
  Speaker 1: A braided stream, so imagine a massive, sprawling river system
• 33:47
  Speaker 1: flowing slowly across a vast geological plane.
• 33:50
  Speaker 2: Yes, visualize human evolution not as a single solid trunk
• 33:54
  Speaker 2: of wood, but as a complex fluid web of water.
• 33:57
  Speaker 2: Over millions of years, populations of hominins separated from each other,
• 34:01
  Speaker 2: flowing into different channels.
• 34:02
  Speaker 1: Okay, I see it.
• 34:03
  Speaker 2: They became geographically isolated, They adapted to their local environments,
• 34:07
  Speaker 2: their DNA mutated, and they developed highly unique biological traits
• 34:10
  Speaker 2: over hundreds of thousands of years.
• 34:12
  Speaker 1: But they didn't stay separated in their own channels forever.
• 34:15
  Speaker 2: No, they didn't. The channels inevitably merged back together. The
• 34:18
  Speaker 2: streams crossed, as climates shifted and populations migrated, These distinct
• 34:23
  Speaker 2: groups reunited, they interbred. The genetic waters mixed, creating entirely
• 34:28
  Speaker 2: new combinations of traits before perhaps separating again into new channels.
• 34:32
  Speaker 1: Wow.
• 34:33
  Speaker 2: This process of divergence and convergence happened repeatedly over immense
• 34:37
  Speaker 2: scales of time. It was a dynamic, fluid exchange of biological.
• 34:41
  Speaker 1: Information that reframes our entire identity as a species. We
• 34:45
  Speaker 1: are not a pure genetic line that evolved in a vacuum,
• 34:49
  Speaker 1: completely isolated from the rest of the natural world. Every
• 34:52
  Speaker 1: single person listening to this right now is an evolutionary mosaic.
• 34:56
  Speaker 1: You are a living, breathing repository carrying active biological code
• 35:00
  Speaker 1: written by extinct cousins.
• 35:02
  Speaker 2: We are, by definition hybrids. The concept of biological purity
• 35:05
  Speaker 2: and human evolution is an absolute myth. We are the
• 35:08
  Speaker 2: sum total of countless interactions, an amalgamation of the evolutionary
• 35:12
  Speaker 2: successes of multiple different human species.
• 35:14
  Speaker 1: We have covered a massive amount of ground today. We
• 35:17
  Speaker 1: started with that old comforting family tree and watched it
• 35:20
  Speaker 1: get completely dismantled by the palaeogenomics revolution. We learned that
• 35:25
  Speaker 1: because heat and humidity destroy physical fossils, scientists couldn't rely
• 35:29
  Speaker 1: on digging in the dirt of Africa or Asia, right.
• 35:32
  Speaker 2: They had to look at the code.
• 35:33
  Speaker 1: So they turned to the trace algorithm, analyzing the ancestral
• 35:37
  Speaker 1: recombination graph to find ghosts hiding in the mathematical mutation
• 35:41
  Speaker 1: rates of modern genomes. We uncovered a universal eight hundred
• 35:44
  Speaker 1: thousand year old African cousin that left traces in every
• 35:47
  Speaker 1: single human alive today, even embedding your code near the
• 35:51
  Speaker 1: genes that control our physical ability to speak.
• 35:53
  Speaker 2: And we trace the impossibly complex journey of the one
• 35:56
  Speaker 2: point eight million year old super archaic ancestors, a lineage
• 36:00
  Speaker 2: likely tracing back to homoerectus, whose ancient DNA was smuggled
• 36:04
  Speaker 2: into our genome like our Russian nesting doll by Denisovans,
• 36:07
  Speaker 2: leaving an indelible mark on indigenous populations.
• 36:10
  Speaker 1: Today, we discovered that we didn't just passively keep this
• 36:13
  Speaker 1: ancient DNA, we weaponized it. It provided the evolutionary arsenal
• 36:17
  Speaker 1: we needed to survive the pre trained immune systems. The
• 36:20
  Speaker 1: crucial metabolic tweaks and the neurological architecture necessary to thrive
• 36:25
  Speaker 1: in a hostile, ever changing world. We are the ultimate
• 36:28
  Speaker 1: product of that braided stream. But before we wrap up
• 36:31
  Speaker 1: today's deep dive into our collective past, I want to
• 36:33
  Speaker 1: leave you with one final lingering thought. Tam all over.
• 36:37
  Speaker 2: If we accept the reality of this genetic data, if
• 36:40
  Speaker 2: we accept that the very things we consider to be
• 36:42
  Speaker 2: the defining hallmarks of modern humanity, like our complex, robust
• 36:45
  Speaker 2: immune systems, are highly adaptable metabolisms, and even the intricate
• 36:50
  Speaker 2: genetic architecture surrounding our ability to articulate speech and process language,
• 36:54
  Speaker 2: If we accept that these traits were heavily shaped, enhanced,
• 36:57
  Speaker 2: and stabilized by the DNA of completely different, totally extending
• 37:00
  Speaker 2: common in species, then human consciousness itself is not a
• 37:03
  Speaker 2: solo achievement.
• 37:05
  Speaker 1: It's not a solitary victory.
• 37:06
  Speaker 2: It is a profoundly collaborative, hybrid effort spanning millions of years.
• 37:12
  Speaker 2: The ghosts of the past aren't just buried in the dirt,
• 37:15
  Speaker 2: and they aren't just abstract mathematical anomalies on a computer screen.
• 37:18
  Speaker 2: They are alive. They are actively shaping the way you think,
• 37:22
  Speaker 2: the way your body fights off disease, the way you speak,
• 37:24
  Speaker 2: and the way you live your life today
• 37:26
  Speaker 1: The ancient manuscript of your DNA is filled with their handwriting,
• 37:30
  Speaker 1: and we are only just beginning to read it,