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Subject: Brains grew faster as humans evolved, study finds
Date: Wed, 27 Nov 2024 23:36:17 -0700
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https://phys.org/news/2024-11-brains-grew-faster-humans-evolved.html

Modern humans, Neanderthals, and other
recent relatives on our human family tree
evolved bigger brains much more rapidly
than earlier species, a new study of
human brain evolution has found.

Scientists from the University of Reading,
the University of Oxford and Durham
University found that brain size increased
gradually within each ancient human
species rather than through sudden leaps
between species. The research, published
November 26 in the Proceedings of the
National Academy of Sciences, overturns
long-standing ideas about human brain
evolution.

The team assembled the largest-ever
dataset of ancient human fossils spanning
7 million years and used advanced
computational and statistical methods to
account for gaps in the fossil record.
These innovative approaches provided the
most comprehensive view yet of how brain
size evolved over time.
....


https://www.pnas.org/doi/10.1073/pnas.2409542121
Hominin brain size increase has emerged
from within-species encephalization

Significance
Our study significantly advances our
comprehension of human brain evolution by
employing a unique approach to dissect
changes in brain size throughout the
complete fossil record of hominins. By
disentangling the dynamics of brain size
change that occur within species from
those occurring across species, we unveil
that increases in brain size primarily
occurred within the lineages comprising a
single species. Such a pattern gives rise
to the overall brain expansion that
scientists herald as a trademark of
modern humanity. Furthermore, we reveal
a trend of accelerating brain size growth
in more recent lineages. This nuanced
understanding deepens our insight into
the evolutionary trajectory of human
cognition and behavior, crucial for
unraveling the complexities of our
species’ unique traits.

Abstract
The fact that rapid brain size increase was
clearly a key aspect of human evolution has
prompted many studies focusing on this
phenomenon, and many suggestions as to the
underlying evolutionary patterns and
processes. No study to date has however
separated out the contributions of change
through time within vs. between hominin
species while simultaneously incorporating
effects of body size. Using a phylogenetic
approach never applied before to
paleoanthropological data, we show that
relative brain size increase across ~7 My
of hominin evolution arose from increases
within individual species which account
for an observed overall increase in
relative brain size. Variation among
species in brain size after accounting
for this effect is associated with body
mass differences but not time. In addition,
our analysis also reveals that the
within-species trend escalated in more
recent lineages, implying an overall
pattern of accelerating relative brain
size increase through time.