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 • 1 880

  • Robert Eischen
    Robert Eischen  3 hours back

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

    • ruski muejek
      ruski muejek  1 days back

      Wow so interesting!

      • HonorisCreed
        HonorisCreed  2 days back

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

        • first last
          first last  2 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  2 days back

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

            • M P
              M P  2 days back

              We were squids, THEN we were kids.

              • Gustavo Pomar
                Gustavo Pomar  2 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  2 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  3 days back

                    How can you dislike everything?! XD

                    • Commander Rockwell
                      Commander Rockwell  3 days back

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

                      • Michael Lubin
                        Michael Lubin  3 days back

                        Sequel: How vampires evolved. Many times!

                        • Dalia Capellan
                          Dalia Capellan  4 days back

                          Bloody bastards!

                          • I Scream for Ice Ring
                            I Scream for Ice Ring  5 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  3 days back

                              @Jammie! Cheers to you!

                            • Jammie!
                              Jammie!  3 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  3 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!  3 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  3 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  6 days 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  24 hours 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  1 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  1 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  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  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  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  4 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  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  7 days back

                                                                      @Viv Wallace I agree

                                                                    • Viv Wallace
                                                                      Viv Wallace  7 days 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  1 months back

                                                                        What about RH - blood ?

                                                                        • swomp man
                                                                          swomp man  1 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.

                                                                                      • santiago diez
                                                                                        santiago diez  2 months back

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