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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,
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AND before you go, we want to show you these neat
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