How Blood Evolved (Many Times)

  • Published: 16 January 2019
  • Blood is one of the most revolutionary features in our evolutionary history. Over hundreds of millions of years, the way in which blood does its job has changed over and over again. As a result, we animals have our familiar red blood. But also blue blood. And purple, and green, and even white.

    Thanks to Julio Lacerda, Lucas Lima, Franz Anthony of Studio 252mya for several illustrations throughout this episode. You can find more of their work here:

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  • Science and Technology Science and Technology

Comments • 1 866

  • first last
    first last  3 hours back

    But arthropods don't have a circulatory system I thought? That's why insects can't grow too thick because they need to get oxygen from opening in their exoskeleton which can't penetrate very deep, I thought?

    • Corleone
      Corleone  6 hours back

      I didn't expect a cuckold to be commentating for PBS

      • M P
        M P  7 hours back

        We were squids, THEN we were kids.

        • Gustavo Pomar
          Gustavo Pomar  9 hours back

          After the second or third "improvement" (mutation), who might've been the lucky ones that survived and were even able to reproduce!!! One really needs lots, I mean loooooots of faith to believe this.

          • _R.N.04_ Bluefaceb
            _R.N.04_ Bluefaceb  10 hours back

            Anyone else smart that watches videos at 2x speed and still understands them, you can get thru so many videos

            • jacob reww
              jacob reww  13 hours back

              How can you dislike everything?! XD

              • Commander Rockwell
                Commander Rockwell  21 hours back

                Hank Green shows up at PBS, too?! He’s everywhere!

                • Michael Lubin
                  Michael Lubin  1 days back

                  Sequel: How vampires evolved. Many times!

                  • Dalia Capellan
                    Dalia Capellan  2 days back

                    Bloody bastards!

                    • I Scream for Ice Ring
                      I Scream for Ice Ring  2 days back

                      5:44 LOL!!! Did you know shells of living snails carbon date to 100,000 years old?

                      • I Scream for Ice Ring
                        I Scream for Ice Ring  19 hours back

                        @Jammie! Cheers to you!

                      • Jammie!
                        Jammie!  20 hours back

                        @I Scream for Ice Ring Well, this was not a response I was expecting.

                        Doubting scientific finds is the right thing to do, if we don't doubt it and ask for evidence science would stagnate, become full of half-arsed ideas and get very boring.

                        *You win this.* You felt the need to apologize and that shows to me you are not the dishonest person I thought you were.

                        You may have been wrong about the science. But I was wrong about you. My apologies.

                      • I Scream for Ice Ring
                        I Scream for Ice Ring  1 days back

                        @Jammie! no.. it's fine. You can win.. I don't know about carbon dating and I didnt take that from a paper but was repeating what sounds like s fun fact to me all by its lonesome.
                        Sorry to change the topic but it was more just s way to address the inconsistencies even in fundamental understandings. Hence my doubts with dating for proof of anything.

                      • Jammie!
                        Jammie!  1 days back

                        ​@I Scream for Ice Ring Did you actually read what I said because at no point did I say or imply what you say I did, or are you just being dishonest?

                        You seemed to think:
                        A. we use carbon dating on fossils when we don't
                        B. that just because carbon dating does not work in situations we know it wont work that it means the dating is always inaccurate.

                        In response I explained what the paper really said and that carbon dating is not used on fossils as they do not contain carbon and are too old. Rather than acknowledging this you divert the conversation to another topic.

                        I am not going to let you change the subject away from the original point to either "angular resolution" or "the horizon" as that has nothing to do with your initial scientifically ignorant comment or my rebuttal nor am I going to continue with this thread because you obviously aren't willing to stay on topic.

                        I have no doubt you will see this as a "win" on your end, but I don't care.

                        I tried.

                      • I Scream for Ice Ring
                        I Scream for Ice Ring  1 days back

                        @Jammie! Oh, so newer things get an old result and older things get a newer result? Great.
                        My friend, if you think people twiddle in the dirt and tell you the difference between 100,000 and 100,000,000 years.. you have no hope.
                        The universities dont even teach you what the horizon is for goodness sake, but tell you that's where the literal earth falls away!
                        Ask yourself just where on earth does angular resolution actually come into play? 😊

                    • Helljumper
                      Helljumper  4 days back

                      Can a human lose their consciousness?

                      • Zane Finlay
                        Zane Finlay  5 days back

                        Evolution of sap and other mechisms that plants/trees/fungi use

                        • Gender Woman
                          Gender Woman  5 days back

                          What's the difference between a tapeworm and a human embryo?
                          Tapeworm has other kind of blood than his host...

                          • Gender Woman
                            Gender Woman  5 days back

                            There's an iron.
                            So that's why fresh blood smells like warm metal...

                            • Gender Woman
                              Gender Woman  5 days back

                              -What's that colorful painting? Is it Picasso's?
                              -It's blood.

                              • JustSay That
                                JustSay That  1 weeks back

                                A Mosquito that was hacking internet just found this video!

                                • Veronica Obiglio
                                  Veronica Obiglio  1 weeks back

                                  Thank you
                                  Very interesting

                                  • Adannaya Elicia
                                    Adannaya Elicia  1 weeks back

                                    Omg thats my boy John Green

                                    • Le nearsighted Wandering trader

                                      Vampires be like: so wich flavor?

                                      • Desperado070
                                        Desperado070  2 weeks back

                                        Told ya I got blue blood...

                                        • magnum opus
                                          magnum opus  2 weeks back

                                          Looks likes Piccolo's blood has hemerythrin who knew 😀

                                          • Nime Ano
                                            Nime Ano  2 weeks back

                                            This is what youtube shall be use for 👍🏿

                                            • bulruq
                                              bulruq  3 weeks back

                                              Here's an idea worthy of investigation: Does carbon monoxide poison these different types of blood equally or are some more resistant to its' toxic effects?

                                              • K Sage
                                                K Sage  3 weeks back

                                                I love this channel so much!

                                                • Luis Vigoreaux
                                                  Luis Vigoreaux  4 weeks back

                                                  Lol my brain hurts that's amazing tho man

                                                  • David
                                                    David  4 weeks back

                                                    I’d love for him to do a video on how butterflies evolved.

                                                    • Alex Tiller
                                                      Alex Tiller  4 weeks back

                                                      *Happy kindred noises*

                                                      • Jason Scully
                                                        Jason Scully  1 months back

                                                        What if humans used copper instead of iron? Electric powers? Lol idk

                                                        • Pencil Shavings
                                                          Pencil Shavings  1 months back

                                                          Suu Whoop

                                                          • Gunnar Gude
                                                            Gunnar Gude  1 months back

                                                            When the blood evolved, was the veins and heart waiting for it to evolve, or was the blood laying around waiting for evolution? Noone sees any problem here?

                                                            • Gordon Freeman
                                                              Gordon Freeman  5 days back

                                                              What I see, is the problem and flaw in your simplistic reasoning.
                                                              The population of an organism evolves as a whole, slowly. Things just don't pop into existence fully developed.
                                                              Wings started as mere stubs not fully formed wings capable of flight, the same applies to what would become heart and veins.

                                                          • I Dream In HSV
                                                            I Dream In HSV  1 months back

                                                            I’d love a rundown on the different eras. You mention their names but it hard to keep track of the timeline

                                                            • Silver theDragon
                                                              Silver theDragon  1 months back

                                                              Family: blood is thicker than water
                                                              Me: *angry ice fish noises*

                                                              • Viv Wallace
                                                                Viv Wallace  1 months back

                                                                So theoretically could there be a creature having gold in its blood? Because copper and iron seem to be popular, maybe gold or silver or other metals could do the trick as well?

                                                                • Lünkel
                                                                  Lünkel  5 days back

                                                                  @Viv Wallace I agree

                                                                • Viv Wallace
                                                                  Viv Wallace  5 days back

                                                                  @Lünkel But it is still a very interesting idea to me.

                                                                • Lünkel
                                                                  Lünkel  6 days back

                                                                  Well, gold is basicly the opposite of what you're looking for in a metal in this scenario. Gold is really really bad at reacting with stuff, so binding oxygen to it probably wouldn't work very well. I mean you could probably make it work but I would not expect that to last very long

                                                              • Hello
                                                                Hello  1 months back

                                                                Thousands of years ago our blood was a different colour

                                                                • Jonathan Armstrong
                                                                  Jonathan Armstrong  1 months back

                                                                  Globin Fold, lol.

                                                                  • cosmicVox13
                                                                    cosmicVox13  1 months back

                                                                    What about RH - blood ?

                                                                    • swomp man
                                                                      swomp man  1 months back

                                                                      hey idubbbz cool video!

                                                                      • the sarcastic one
                                                                        the sarcastic one  1 months back

                                                                        Mosquitoes: *ight imma head out now*

                                                                        • SoBeast27
                                                                          SoBeast27  1 months back

                                                                          Wow there's so much knowledge out there.

                                                                          • Samuel Barrow
                                                                            Samuel Barrow  2 months back

                                                                            Gives a whole new meaning to “we all bleed red”

                                                                            • Agey bb
                                                                              Agey bb  2 months back

                                                                              Beautiful video by the way 😣💙♥️💚💛💜

                                                                              • Agey bb
                                                                                Agey bb  2 months back

                                                                                Guys pleeeease make a video about the missing link!!!! My boyfriend and I argued for literally 6 hours straight yesterday about whether or not Australopithecus is certainly the last common ancestor of humans and chimps 😨😨😨

                                                                                • Gordon Freeman
                                                                                  Gordon Freeman  5 days back

                                                                                  There is no "missing link" anymore, that idea died in the early 90's if I'm not mistaken, no idea why it keeps coming up in 2019.

                                                                                • jaymz1999
                                                                                  jaymz1999  1 months back

                                                                                  Agey bb There is no missing link. There is a large chain of changes thought. Ancestor did not go boom one day and became human.

                                                                                • Lord Frieza
                                                                                  Lord Frieza  2 months back

                                                                                  the idea that there must be a specimen that partly resembles an ape but also partly resembles a modern human--is persistent. But the reality is that there is no missing link in our lineage, because that’s not how evolution works.
                                                                                  -description of the video "The Missing Link That Wasn’t" - PBS Eons


                                                                              • Tan C
                                                                                Tan C  2 months back

                                                                                RH Negative blood type Video please, having my first kid and he has RH negative. I want to know more!

                                                                                • Marc Bell
                                                                                  Marc Bell  2 months back

                                                                                  Nobody knows why humans have different blood types. It's weird.

                                                                                  • santiago diez
                                                                                    santiago diez  2 months back

                                                                                    Couldn't say I understood more than 50% of this but still so cool and interesting

                                                                                    • Puppy Puppington
                                                                                      Puppy Puppington  2 months back

                                                                                      Wusuupppp BLUHHHHHDddd

                                                                                      • Abhijit Desai
                                                                                        Abhijit Desai  2 months back

                                                                                        Do specific blood types have any relation with specific allergies?

                                                                                        • Blake Collins
                                                                                          Blake Collins  2 months back

                                                                                          Have you (will you) done one about mitochondria? PLEASE! I'm so curious about how the heck we got something like blue green algae in our bodies.