The semi-arid ape hypothesis

[Primum Sapienti]

From
https://paleoanthropology.org/ojs/index.php/paleo/article/view/1140/1087

The (Semi) Arid Ape: How the Rift Valley
Defined Our Niche

Hypotheses about drivers of human evolution
often address how hominins are ecologically
distinct from closely related apes. These
hypotheses have common ingredients, and many
suggest that the topography and vegetation
of the Eastern African Rift Valley System
(EARS) contributed unique selective pressures
in hominin speciation events. We suggest a
new semi-arid ape hypothesis that centers on
the environment as a force in early hominin
evolution and combines ideas from previous
hypotheses and recent research. Early
hominins (7–3 Ma) likely had species ranges
that extend from mesic forests (found today
on the rift highlands and extend into central
and western Africa) to semi-arid regions,
such as the lower parts (floor) of the EARS.
This range of habitats is their fundamental
niche. Semi-arid regions include the low
elevation regions along the rift floor that
are generally more arid than the regions
surrounding them, in part due to higher
temperatures, higher evaporation, and wind
cycles. The semi-arid ape hypothesis
proposes that drier components of the
hominin range (the realized niche) separated
hominins from non-hominin apes in the
Mio-Pliocene. Chimpanzees today do not
exploit the same type of semi-arid habitats
as reconstructed for Pliocene hominins, nor
are their fossils usually found in the same
regions. We suggest that an early
exploitation of semi-arid habitats, outside
of the central-western African rainforest
belt, resulted in a biogeographic separation
between hominins and other apes. Adaptations
to a broad range of environments and climates
are fundamental for the human ability to
survive in extreme environments today and may
help us survive in more extreme future
environments.

[JTEM]

Post by Primum Sapienti
The (Semi) Arid Ape: How the Rift Valley
Defined Our Niche

It's circular.

The Rift Valley is not only EXACTLY where ancestors
originating in Asia would have wandered inland,
colonizing Africa, but other species are known to
have done exactly that.

Post by Primum Sapienti
Hypotheses about drivers of human evolution
often address how hominins are ecologically
distinct from closely related apes. These
hypotheses have common ingredients, and many
suggest that the topography and vegetation
of the Eastern African Rift Valley System
(EARS) contributed unique selective pressures
in hominin speciation events.

They were following the coast, from Asia, probably
Sundaland, with groups periodically pushing inland
and adapting.

This explains "MultiRegionalism," which has a great
deal of scientific support, but lacked mechanisms
for depositing the different populations everywhere,
and sharing DNA between them.

Aquatic Ape solves both problems.

The followed the coast, exploiting the sea, with
groups sometimes following fresh water sources
(and their food supply) inland. Once there, they
adapted to their new world. The new foods. New
conditions... predators... competition...

They would have occasionally come into contact with
the coastal population again, or some new group
likely pushed inland just as they did, moderating
their evolution... sharing DNA.

The further they got from such entry points, the less
"Human" they become, because the less influx of new
DNA from the waterside population.

This is how our ancestors evolved into Apes.

DEFINITELY happened this way in the case of Chimps.
Probably happened this way in the case of all Apes,
though we're talking pre Homo in their cases...

It fits. It fits all the evidence. It explains other
observations -- like the existence of Chimps. It just
plain works.