https://www.sciencedirect.com/science/article/pii/S0305440325000755
Highlights
* High latitudes habitats impose thermal
demands that resulted in smaller brain
volumes in archaic humans.
* For the same reason, brain volumes
decreased during glacial phases and
increased during interglacials.
* Control over fire allowed at least the
Neanderthals and anatomically modern
humans to mitigate these effects,
enabling larger brains to evolve.
* Since brain size determines key
cognitive capacities, there are likely
to have been significant effects on
archaic human's capacity for culture.
Abstract
High latitude habitats are subject to
thermally-driven energetic constraints
that make their occupation challenging.
This is likely to have had a particularly
significant impact on energy-expensive
tissue like the brain, especially during
periods of lower global temperatures
during the Mid-Pleistocene Ice Ages. I
analyse data on endocranial volumes for
archaic humans (Homo heidelbergensis,
H. neanderthalensis and allies) to show
(1) that cranial volumes were typically
smaller at high latitudes than in the
tropics and (2) that they declined during
cold phases and increased during warm
phases of the Middle Pleistocene Ice Ages.
Within this broad pattern, there is a
significant uplift in cranial volumes
after 400 ka that seems to coincide with
widespread presence of hearths at high
latitudes, suggesting that hominin
populations might have gained at least
partial release from this constraint
through cultural control over fire. While
this might pinpoint the time at which
hominins first began to cook on a regular
basis, fire offers other important
benefits (notably warmth and extending
the length of the working day) that might
have played an equally important role in
buffering populations against thermal
stresses. The larger brain sizes that
this made possible have implications for
social cognitive capacities like
mentalising, that in turn have
implications for language skills,
cultural behaviour and social group size.
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