https://neurosciencenews.com/evolution-brain-size-28153/November 29, 2024
The study, published today (Tuesday, 26 November)
in the journal PNAS, overturns long-standing ideas
about human brain evolution. 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 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/epub/10.1073/pnas.2409542121Hominin 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.
Human Brains Evolved Gradually, Not in Sudden Leaps