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.
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