On Tuesday, February 22, 2022 at 4:31:14 PM UTC-5, Paul Crowley wrote:
> On Saturday, February 19, 2022 at 1:35:16 PM UTC, Pandora wrote:
>
> >> At some point out ancestors stopped being
> >> like other primates (in this respect). I can
> >> see them remaining on an over-crowded
> >> island when it's truly remote. But if they
> >> can see the mainland, or the next island,
> >> there will be a strong incentive get a raft
> >> or flotation aid and head towards it.
> >
> > That's quite different from going in and swimming a few miles.
> > No ape will do that, unless it's a well-trained Homo sapiens.
> Under my scenario, a population of
> chimps became isolated on a large
> island (Zanzibar will do as a model)
> probably as a result of a rise in sea-
> levels -- enough to discourage
> carnivores from crossing. In a few
> thousand years the local carnivores
> would become too inbred and die out.
> The proto-hominins would leave the
> trees, and roam free. They'd get
> used to foraging on coasts, and
> swimming between off-shore islets.
> Their nature would change as they
> evolved into a new form with
> wholly new challenges.
> > > Sure. The robusts went off in some
> > > weird direction.
> >
> > That makes them interesting as a test case for your scenario. They
> > have their origin at about the same time as Homo, but their brains are
> > small (410 cc in KNM-WT 17000), while their jaws and teeth are
> > massive. Quite the opposite of Homo.
> > They couldn't have come from the same island.
> There were several islands. and even
> more as seal-levels went down, with
> the inception of ice-ages.
> > > Hominins are very different from bovids
> > > -- being carnivorous for a start.
> >
> > More likely omnivorous.
> > Besides, we see the same pattern of diversity and niche partitioning
> > in carnivores such as Felidae. Lion, leopard, cheetah, serval,
> > caracal, and a host of other cats are sympatric in Africa today.
> All those carnivores hate each other,
> often fight, and will eat other's young.
> much the same would apply to early
> hominins.
> > > No one (with any sense) would suggest that two
> > > competing hominin species could share
> > > the same habitat.
> >
> > Paranthropus and Homo are distinct enough morphologically to suggest
> > something similar as with felids.
> Felids take much care to hide and
> protect their young which, in any case,
> grow up rapidly. Felids have many
> offspring, so can cope with a high
> death rate in their young. Hominins
> are very different.
> > > Hominins usually swim (in survival
> > > mode or otherwise) with their heads
> > > out of the water (very different from
> > > marine mammals). That drastically
> > > changes the dynamics of heat-loss,
> > > and the physiology that can best
> > > survive the cold.
> >
> > All the more reason the believe that the rest of the body was under
> > selection to make them better swimmers, to stay as short in the water
> > as possible,
> Survival (and most other forms of)
> swimming is with the head out of the
> water. It's going to be slow at the best
> of times. The selective effect of slightly
> more webbing between fingers will be
> minimal, and greatly outweighed by
> the disadvantages during ordinary
> life (e.g. more hand injuries).
> > but hominins do not even have webbed fingers and are
> > still much slower than marine predators such as sharks.
> What's the easiest way to improve
> the swimming speed of something
> like an australopith? (Not racing
> speed -- just survival speed.)
>
> How about larger hands and larger
> feet? And a longer, and more stream-
> lined body?
>
> What do we see with h.sap males?
>
> We don't see any of these cold-swiming-
> adaptations (including large heads and
> brains) with h.naledi -- they were a long
> way from the ocean.
>
> Homo males should also develop
> strong 'breast-stroke' muscles -- for
> moving the arms downwards. These
> will be less developed in austral-
> opiths and h.naledi (other things
> being equal).
> >> Sure. Marine mammals are in cold water
> >> all the time. Hominins were in it only
> >> occasionally, and maybe only rarely --
> >> but enough (may be less than once in a
> >> lifetime) for the cold to exercise selective
> >> effects.
> >
> > Only if they stayed in the water for a prolonged time,
> The waters off East and West Africa
> during ice-ages were much colder.
> However, hope of rescue was probably
> small, and it was up to each swimmer
> to get to shore themselves.
> > long enough to drown for other reasons.
> Drowning often arises from a complex
> of reasons; hypothermia is a major
> factor.
>
> https://www.hofmannlawfirm.com/faqs/how-long-does-it-take-to-get-hypothermia-in-cold-water.cfm
> > And then, the ones that reached the mainland
> > had a failure rate of 99.999%
> This was my estimate of the failure
> rate of refugees, lost on the African
> mainland.
> > there and would leave much less progeny
> > than their island conspecifics who stayed put.
> During ice-ages, sea-levels were (over
> evolutionary timescales) much more
> variable. New islands came into
> existence, and were later drowned.
> Hominins on remote islands were
> more isolated -- and safer for a time.
> But not for long.
>
> Those on islands closer to the main-
> land (or to other islands) would come
> and go from them, and mount
> expeditions to the mainland, lasting
> months or years. They'd learn to cope
> with mainland predators, and their
> populations would be much more
> capable of dealing with the radical
> changes, when they occurred, than
> would isolated populations. They'd
> leave progeny. Isolated populations
> wouldn't.
> >>> Overheating rather than hypothermia seems to have been a problem in
> >>> human evolution.
> >>
> >> One does not rule out the other.
> >
> > When one of two opposing features is no longer needed
> There's nothing 'opposing' here. Early
> hominins sometimes got too hot and
> evolved sweating (for which they needed
> good supplies of water and a range of
> hard-to-get salts of iodine, potassium
> and sodium). Sometimes they were
> exposed to hypothermia, and evolved
> mechanisms to cope with that.
> > than natural
> > selection will reduce it. On land hominins didn't need such a big
> > central heater as is useful in the water. Yet their brains grew ever
> > bigger, culminating in Homo sapiens.
> Bad thinking here. Often one feature
> or requirement will impose strains on
> others, but that's normal.
> >> Brain size took off at about the same time
> >> as ice-ages commenced.
> >
> > Those where mostly a feature of higher latitudes, not the
> > (sub)tropics. Besides, we see the smallest brain sizes in early Homo
> > at the highest latitudes of their range (as low as 546 cc in D4500 at
> > 1.8 mya from Dmanisi, Georgia).
> The effects of Ice-ages were world-wide.
> Water went to the poles. Everywhere
> was drier. Dust everywhere. Continental
> uplands very cold at night. Cold antarctic
> currents travelled much further north
> on both sides of Africa. Plenty of fish in
> them but cold -- brrrr!
> >> Humans are still not fast swimmers, but
> >> catch plenty of fish. It's a question of when
> >> nets came into use.
> >
> > The oldest evidence for such sophisticated techniques is from about
> > 29000 years ago:
> > https://phys.org/news/2018-08-world-oldest-fishing-net-sinkers.html
> Once you have string, nets are very
> easy to make.
> https://www.youtube.com/watch?v=vegEIHaWB8g

Yes, when taught clearly & patiently & safely, yet among thousands of fish-eating fauna, only Hs makes them, and most Hs never do.
No primate but man has ever been observed tying a knot. All great apes weave over-under wicker as part of bowl nest making, none have been observed weaving anything else. Mats & nets of soft fiber are neolithic, baskets of wicker are much older. Some of the basket fish traps used in the Congo river could fit a man inside. The Mbuti Pygmies use nets & spears to hunt, perhaps the inventors.

> > But I also mentioned the numbers from Aramis (5.6% hominidae, 5.5%
> > carnivores), different time different place, which you conveniently
> > snipped.
> Embarrassingly bad. Those numbers
> come from a thorough investigation of
> the Ardi site. It was done to establish,
> as far as possible, the habitat in which
> (hopefully) Ardi lived. The 110 hominin
> fossils are those of Ardi herself (or her
> companions). Much the same number
> of carnivore fossils were also found
> there.
> https://www.researchgate.net/publication/40446786
>
> Locate another 10,000 roughly similar
> fossilferous sites in East Africa and,
> after a thorough investigation, guess
> what you'll find in each?
>
> About the same number (~100) of
> carnivore fossils -- but ZERO hominins.
>
> For every hominin fossil, there are
> ~1,000,000 carnivore fossils.
>
> THAT'S the problem. As every PA field
> person knows -- only too well -- you
> can spend a lifetime in East Africa and
> find NOT ONE hominin fossil.