" . . . Alternatively, it could come down to anatomy, and pig hearts may not be up to the job in a human body. Our hearts have to work much harder to fight gravity than a pig's because we walk on two legs rather than four. . . "
https://www.bbc.com/news/health-60708120

If an animal can proceed quadrupedally
(as our ancestors before ~5 ma could) it
will continue to do so for a whole variety
of reasons -- including this one -- unless
there are compelling circumstances that
bring about the change.

(Failure to identify those 'compelling
circumstances' is the most obvious
defect of the various theories around
here.)

Walking or running bipedally is much
harder on the heart than proceeding
quadrupedally. Assuming that the animal
has a choice, it will get tired much more
quickly in the upright posture.

This is a powerful argument against the
notion that bipedalism evolved to chase
after prey on the savanna. Our basic
design is hopelessly inappropriate for
fast or sustained running.

On Sunday, March 13, 2022 at 11:07:38 AM UTC, Paul Crowley wrote:

> " . . . Alternatively, it could come down to anatomy, and pig hearts may
> not be up to the job in a human body. Our hearts have to work much
> harder to fight gravity than a pig's because we walk on two legs rather
> than four. . . "
> https://www.bbc.com/news/health-60708120

The standard chest shape for terrestrial
animals -- including cercopithecoids -- is
"narrow and deep", whereas in apes it's
"broad and shallow".

See Figure 7 (about half-way through) in:
https://onlinelibrary.wiley.com/doi/10.1111/joa.12454#

Monkeys follow the standard mammalian
pattern, and have their hearts in the
optimum position. The change to the ape
chest form abolished this position, meaning
that the ape heart is badly located and less
efficient than it was among its ancestors.
That loss came about for major reasons,
which yielded great compensating benefits.

What were they?

Op zondag 13 maart 2022 om 12:07:38 UTC+1 schreef Paul Crowley:

> " . . . Alternatively, it could come down to anatomy, and pig hearts may not be up to the job in a human body. Our hearts have to work much harder to fight gravity than a pig's because we walk on two legs rather than four. . . "
> https://www.bbc.com/news/health-60708120

:-DDD

Thanks, Pauli.

Early hominoids perhaps 20 Ma were already orthograde (upright, vertical),
- not for running after antelopes as some incredible imbeciles still believe,
- but simply for wading bipedally & climbing arms overhead in forest swamps & mangroves.

Google "aquarboreal ancestors".

On Sunday 13 March 2022 at 13:09:11 UTC, littor...@gmail.com wrote:

> Early hominoids perhaps 20 Ma were already orthograde (upright,
> vertical),
>
> - but simply for wading bipedally & climbing arms overhead in
> forest swamps & mangroves

Why the fundamental design changes
in anatomy from monkey to ape?
A large baboon would seemingly be
better designed for " . . wading
bipedally & climbing arms overhead
in forest swamps & mangroves . . ".

You're not getting to the heart of
the matter (deliberate pun).

Paul Crowley wrote:

> If an animal can proceed quadrupedally
> (as our ancestors before ~5 ma could)

We find evidence for bipedalism going back 7 to
9 million years.

Chimps split off from our line far more recently than
5 million years ago. Even going by just the y-chromosome
"molecular clock" it's less than 5 million. Factor in other
areas of the genome and you're looking at less than 4
million... like 3.7 million.

I'd give a margin or error of AT LEAST a million years more
recent than that. Molecular dating assumes a constant
rate of change (mutation) when we all know for a fact that
it's not true. Our mtDNA has been under HEAVY selective
pressures. Cold weather, moving north was a big selective
factor, as mtDNA helps us to produce warmth. But mtDNA
also slows down with age, so the longer it lasts the older
we can get. It also seems related to our ability to fight off
cancer.

If you're born in a warm environment, if your mtDNA helps
to keep you warm then it likely would be selected AGAINST.
It won't change. But move a population to a new environment
and such a mutation is selected FOR.

Mutations are the furthest thing from clock like. All the
molecular dating greatly exaggerates age.

Chimps evolved AWAY from upright walking and TO knuckle
walking. It never happened the other way around.

-- --

https://jtem.tumblr.com/post/678757006186889216