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 • 1 881

  • hagala
    hagala  4 hours back

    no what gives blood the read colour is communism

    • Robert Eischen
      Robert Eischen  2 days back

      I learned word hemoglobin is pretty fun to say. I'm not too bright though. 😅

      • ruski muejek
        ruski muejek  3 days back

        Wow so interesting!

        • HonorisCreed
          HonorisCreed  3 days back

          Thank you for teaching me that I have a slight fear of blood.

          • first last
            first last  4 days 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  4 days back

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

              • M P
                M P  4 days back

                We were squids, THEN we were kids.

                • Gustavo Pomar
                  Gustavo Pomar  4 days 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  4 days 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  4 days back

                      How can you dislike everything?! XD

                      • Commander Rockwell
                        Commander Rockwell  4 days back

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

                        • Michael Lubin
                          Michael Lubin  5 days back

                          Sequel: How vampires evolved. Many times!

                          • Dalia Capellan
                            Dalia Capellan  5 days back

                            Bloody bastards!

                            • I Scream for Ice Ring
                              I Scream for Ice Ring  6 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  4 days back

                                @Jammie! Cheers to you!

                              • Jammie!
                                Jammie!  4 days 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  5 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!  5 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  5 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  1 weeks back

                              Can a human lose their consciousness?

                              • Zane Finlay
                                Zane Finlay  1 weeks back

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

                                • Gender Woman
                                  Gender Woman  1 weeks 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  1 weeks back

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

                                    • Asto Done
                                      Asto Done  2 days back

                                      Gender Woman — In all the cases you mentioned those are metals that came into contact with countless organic materials... So those metals will have catalyzed some reactions & thus produce compounds that give them the distinct “metal” smell.

                                      But if you sterilize and clean a PURE sample of a metal, it has no smell. That’s because again, metals just don’t react with the cells in your nose. Most metals are not volatile enough to make it to your nose, but even if they DO make it (like mercury) then they won’t smell like anything. And because metals are so heavy, they can damage your lungs really badly if you breathe them in.

                                    • Gender Woman
                                      Gender Woman  2 days back

                                      @Asto Done So explain, why some metal things smells in very hot sun? Or when you are in for example a museum, where are many swords and things like that, or some metal vehicles, you can easily smell that specific metal aroma XD Or rusting metal constructions, like bridge. And the blood smells similar.
                                      I understand, that it's smell of reacting metal, but it's still a *metal* .

                                    • Asto Done
                                      Asto Done  2 days back

                                      You can’t smell metal. Metals are very unreactive and the cells responsible for SMELLING them don’t detect anything. However you can breathe metals without realizing it, like mercury, because it has no smell and can’t be seen, it’s very dangerous.

                                      You can only smell a metal when it comes into contact with a human’s skin. Because then some reactions happen which include the metal as a catalyst, and it produces some unique compounds that we associate with the smell of metals.

                                  • Gender Woman
                                    Gender Woman  1 weeks back

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

                                    • JustSay That
                                      JustSay That  2 weeks back

                                      A Mosquito that was hacking internet just found this video!

                                      • Veronica Obiglio
                                        Veronica Obiglio  2 weeks back

                                        Thank you
                                        Very interesting

                                        • Adannaya Elicia
                                          Adannaya Elicia  2 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  3 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  4 weeks back

                                                      I love this channel so much!

                                                      • Luis Vigoreaux
                                                        Luis Vigoreaux  1 months back

                                                        Lol my brain hurts that's amazing tho man

                                                        • David
                                                          David  1 months back

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

                                                          • Alex Tiller
                                                            Alex Tiller  1 months 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  1 weeks 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  1 weeks back

                                                                        @Viv Wallace I agree

                                                                      • Viv Wallace
                                                                        Viv Wallace  1 weeks back

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

                                                                      • Lünkel
                                                                        Lünkel  1 weeks 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  2 months back

                                                                          What about RH - blood ?

                                                                          • swomp man
                                                                            swomp man  2 months back

                                                                            hey idubbbz cool video!

                                                                            • the sarcastic one
                                                                              the sarcastic one  2 months back

                                                                              Mosquitoes: *ight imma head out now*

                                                                              • SoBeast27
                                                                                SoBeast27  2 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  1 weeks 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.