This Ancient Mammal’s Ears Were Built for Chewing

This Ancient Mammal’s Ears Were Built for Chewing


[♪ INTRO] Last week in the journal Nature, researchers
announced that they’ve found a new fossil that might
help us understand one of the most unique features of mammals:
our ears. Also, the little guy is, like, really cute… so there’ that. Called Jeholbaatar kielanae, this animal was
found by paleontologists in Northeast China. It lived in the Cretaceous period, about 120
million years ago, and it likely ate things like bugs and plants. It was pretty small, not much bigger than
a mouse. Though technically it wasn’t a rodent. It’s what’s known as a multituberculate, a different mammal group that was pretty successful until they died out about 34 million years
ago. So that’s neat — it’s always fun to
find new fossil species. But this fossil was also special because its ear bones had been preserved. Besides signature adaptations like producing
milk or having fur, mammals — including humans
— are also have unique, complex middle ear bones. These three little bones, called the malleus,
incus, and stapes, help transfer sound from the eardrum to the
cochlea. Reptiles, in contrast, typically only have
one bone in their ears, the stapes. Thanks to our unique set-up, mammals have
superb hearing, able to detect much higher frequencies than
other land animals. But these bones are also a bit of an evolutionary
mystery. We know two of them, the malleus and incus, evolved from bones in our jaws. But eventually, they moved to our ears, and we don’t fully understand why. Just because they’re helping us hear better
now doesn’t mean that was the original evolutionary
pressure that got them moving. And fossil evidence suggests this actually
happened more than once, independently each time. Researchers have proposed a few ideas for why middle ears evolved. Perhaps they really did improve hearing right
from the get-go. Or maybe the moving bones were a side effect of larger brains reshaping the skull. But the evolution of Jeholbaatar’s ears may actually have had more to do with its
diet. Because Jeholbaatar is so old, scientists
were able to spot one bone seemingly caught in
transition from being part of the jaw to being part of
the ear. Analyzing the shape and placement of the bones, the scientists came to the conclusion that
the shift wasn’t a result of the brain changing the
shape of the skull or other ideas. Instead, by moving up towards the ears, the bone was essentially getting out of the
way of its chewing. This let Jeholbataar move its jaws in a unique, forwards-and-backwards motion. This improved grinding power, and made it
easier for the animal to hear over the sound of its
own noshing. This doesn’t necessarily explain how our own middle ears developed. Jeholbaatar’s group is a cousin to our mammal
group, not an ancestor, and we don’t chew the same
way they did. But it does represent an interesting new hypothesis for how jaw bones can become ears. And it might help explain why multituberculates were so successful for so long. In more modern news, scientists publishing
in the journal Science Translational Medicine have found
that starting HIV treatment within hours of birth may help
HIV-positive newborns. HIV can be passed from an infected parent to their unborn child, and it can be fatal
or cause serious, irreversible damage to the baby’s immune
system. The World Health Organization recommends that doctors start treatments that can control
the infection within just weeks of birth. This new study suggests starting treatment
even earlier, within hours rather than weeks, might be even
better. The researchers, working in Botswana, started
treating a group of ten HIV-positive newborns with
antiviral drugs just hours after they’d been born. They then tracked the children over the course
of two years, taking periodic blood samples and comparing
them to another group of ten babies who received the currently accepted treatment regimen. The blood samples allowed the scientists to
examine traces of the virus within the DNA of the
children’s immune cells. They were able to watch how the infection evolved and changed, as well as how their
bodies were responding to the infection. They found that starting the antiretrovirals
earlier resulted in better immune system responses
and signs of a reduction in something called the viral
reservoir. Typically, when the virus infects a cell,
it hijacks the cell’s machinery and starts producing
new copies of itself. However, some cells go into a resting state
instead, where they don’t produce new copies of the
virus. Those resting cells are effectively hidden from medicines targeting the virus. These cells can lay dormant for years before
turning back on. This hidden cache of the virus makes up the
viral reservoir. By peeking at the traces of viral DNA in immune
cells, the scientists could essentially gauge the
size of the reservoir. They found that shortly before the babies
turned two, the ones that got the earlier treatment had
very low levels when compared to the infants that received
the standard regime. The scientists think follow-up studies might
find even more beneficial effects later on in life. Now, you might think it seems obvious that more medicine earlier is better. But when people’s lives are on the line, scientists have to show that treatments are
effective. This study seems to do that. There are still some barriers, though. The study was pretty small. Starting HIV treatment earlier on a large
scale could represent a huge logistical challenge and require innovations in diagnosis and infrastructure. Remember, we’re talking about catching it
within hours, sometimes in places with very limited resources. But these results show that this change could
have real, dramatic benefits for some of the world’s
most vulnerable populations. And if nothing else, the scientific insights
from this study, about precisely how the newborn immune system responds to the virus, could help optimize
or tailor future treatments. Thanks for watching this episode of SciShow
News, which was brought to you with the help of
our amazing President of Space, Matthew Brant! You too could become President of Space by joining our awesome community of supporters over on patreon.com/scishow. AND before you go, we want to show you these
neat lunar calendars now available over on DFTBA.com! They’ll help you keep track of the phases
of the moon for all of 2020, so you can stay astronomically
informed. You can grab one now. [♪ OUTRO]

local_offerevent_note February 27, 2020

account_box Gilbert Heid


local_offer

91 thoughts on “This Ancient Mammal’s Ears Were Built for Chewing”

  • "…to hear over the sound of it's own gnashing." I have a huge problem with that! I frickin' can't hear when I'm eating and have to crank up whatever I'm watching.

  • I'm an ex Jehovah's Witness,, literally, ALL I could hear was "Jahovahtar!" and flinched every time.

    And that, to me, it sounds like some kind of vengeful transformer robot ready to dispense indiscriminate Jesus. Which is equally as unsettling.

    This has been a strange video for me.

  • So basically, treatment for HIV needs to be done to newborns a few weeks from birth…

    One like for one SAO fan that was reminded of Yukki!

  • I thought the title meant that the ears chewed on prey. Like ok evolution, why would you make such a tiny adorable horror machine?

  • This is not a good format for "in this week's science news". The title refers to one thing and I was so confused when you started talking about HIV in newborns… You gotta do 2 videos, or reflect this content through the title of the video, guys.

  • I thought using antivirals on neonates was already known??? I've been working in obgyn for 16 years and we've always given the first dose of azt within 24 hours of birth

  • Did we use to have whiskers? Could those bones be from feeling vibrations in the air with whiskers? Genuinely curious I hope it’s not a stupid question lol

  • Here is something to try, take a metal rack or similar item. Tap it. Tip your ear close to it and tap it. Then rest your chin on it and tap. You hear it loudest through your jaw. So jaw bones becoming ear bones makes perfect sense to me.

  • I have to admit, when you said "the little guy's really cute" I thought at first you were talking about your own ears. (You do have cute ears.) 😉

  • The theory Ive always heard put forward was the chewing aspect. mamalformes and mammals themselves improved the food processing bit at the start of the process with chewing so that dinner was already softened up before it got to the stomach, taking less time and energy off the back end to provide for a more continuous feeding for us, rather than sitting around waiting for our stomachs to clear before going back out on a food search. The reason for that was that as endotherms, we needed to fuel ourselves on a more regular basis in order to maintain that metabolism that allows us to keep a regular body temperature. Chewing and processing our food up front requires more robust jaws, it is said, less smaller bones, so the quadrate and that other small bone…whatever its called, migrated to happily fulfil a happy evolutionary co-incidence and whatnot.

  • De CE crezi ca nu vezi tu bine .
    De CE porti ochelari .
    Pentru CA.
    Domnul Dumnezeu vrea sa-ti arate ca tu nu vezi bine lucrurile .
    Tu gandesti dupa mintea Ta
    Insa caile Domnului sunt neintelese de mintea ta .care este in dungi.
    CE nu recunosti tu este
    Ca tu nu esti nascut din maimutza .
    Ma contrazici ????
    Nu te inbraca in albastru
    Nu ai nimic in comun cu fatza ta .
    Esti un imitator comic
    Faci reclama pe YouTube pentru niste centi amarati .
    Cati bani faci din Ad. Google pe YouTube ?
    Esti o iluzie optica
    Din Harry Pottery
    Voi sunteti vrajitori din Oz

  • Vreti HIV
    O sa aveti dupa credintza si necredintza din inima voastra .
    HIV .este o pedeapsa pentru Desfranare .
    Muzica lui Freddy Mercury
    Si drogurile sunt viatza voastra
    Va apartin
    Voi aveti in inima voastra pe HIV.
    Cu el traiti si cu el Muriti
    Eu al am Pe Domnul Iisus Hristos

  • Voi o sa consumati toate drugurile voastre si tot canabisul si de boala nu veti scapa .
    Pentru ca boala este in voi de mii de ani si o veti primi ca faraon din egipt .
    Mila Domnului este pentru Fii Lui
    Asa ca singura scapare este in Rugaciunea Sfanta .
    Cine nu vs crede in Sfanta Cruce A Lui Hristos , nu va fi scapat de cel rau .
    Lasati hula si mai bine rugati-va pentru iertare de pacate.

  • Nici un doctor nu va poate salva de LA acesata boala .nu este HIV
    Este hula din inima voastra
    Roasa de viermi lui Satana

  • "the brain changing the shape of the skull"
    Anyone else feel a twinge of phrenology?

    "Molly-us" and "multi-too-BEAR-kyou-late"? / dʌz ˈɛn.iˌwən ðɛər noʊ haʊ tu rid ði / IPA / ˈgɪv.ən ɪn ˈdɪk.ʃəˌnɛr.iz /? ==> / ˈmæl i əs / and / ˌmʌl tɪ tʊˈbɜr kjə lɪtˌ /

  • Martillo, yunque, estribo!
    It's called the stapes (stirrup) when it's of genus 1 (from a blood vessel growing through it), and the columella when it's of genus 0. Are the animals which have a stapes the same ones that have three bones in the middle ear?

  • "We don't chew the same way they did" SURE but have you ever been eating a bag of chips and had to put volume on your computer obscenely high just to hear what your watching? Maybe it had to do with that

  • Space. With as many presidents as Space goes through in so short a time, it sounds a very dangerous place to get involved in politics…

  • Damn I thought learning philosophy was impressive from Hank… Then i seen him running another channel… then another. Now this? Hahah Who needs school, Hanks got everything covered

  • Probably not actually related, but this really reminds me of the fact that horses occasionally grow teeth in their ears… then I found out they can grow them the same way almost anywhere. Still wild though!

  • About the lunar phase calendar… what's wrong with september? There are 31 moon phase images distributed over 30 days ….?

  • This is called a sci-show… this video should be called a spec-show, as in speculation… better still a freak-show, as in deviation from your normal show. lol

  • Man, I really don't like the title changes you guys do on your videos.

    I get that it's a bid to keep the clicks rolling, but the original title was more interesting and less clickbait-y, and I was interested in watching before you changed the title.

  • Seriously, this show is very interesting. I wrote any words to laugh but excuse me…I'm old but young in my brain. THANKS FOR ALL OF US.

  • The book Your Inner Fish has a whole chapter dedicated to the possible reason for the jaw bones becoming ear bones. It's an informative and entertaining book in general, in my opinion.

  • Forgive me if im wrong, but the HIV cure for the infants was found out first by the cubans like a couple years ago, i remember reading it on a mexican news page, cant recall the name of it but im sure you guys can find out, you guys seem smart

  • Whatever happened to survival of the fittest now that medicine keeps alive even those most unfit to live?

    Not sure if that's efficient or best ethical use of resources and long term consequences for those people to reproduce knowingly that their offspring will suffer and face many challenges not indicative of a normal life.

    In ancient Sparta those unfit for a normal life would be left to die and the parents would just try again if they themselves were even healthy to begin with. We don't do that anymore and as a result the whole world is becoming weaker, more frail and with tons more problems. Is that ethical? Probably something for societies to reconsider.

    At what point does helping everyone stay alive, becomes worse than letting nature take over?

    Just a philosophical thought. You(whoever reads this) get no right to get mad about these statements. They are all fair questions.

  • This video: the 3 middle ear bones are why we have such great hearing!
    Me, who has tympanosclerosis, booing: sure, maybe for you!
    I'm not really bitter, I just think it's funny that the middle ear bones are supposed to improve our hearing but my body said "screw that" and now I'm HOH

  • Hey, I can wiggle my jaw back and forth, and primates with a mainly vegetarian diet certainly do quite a bit of chewing so it might not be too far fetched that the same thing evolved the same way for the same reason

  • I get the controversy of opening up the idea of abortions based on perceived quality of life, but it should be illegal for for HIV positive people to have biological kids post infection. there r plenty of babies that need to be adopted n it's not like this is a genetic condition, it's not eugenics, it's infection prevention in children. n if they knew they'd have their baby aborted anyway, most people would just avoid getting pregnant n then it's no longer about abortion but simply about contraception. I think it is an act of evil to bring a child u claim to love unconditionally into the world knowing that u have alrdy handed them a looming painful death n the anxiety that comes with spending ur whole life avoid lethal consequences of someone else's actions

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