A review of evidence from previous research provides new support for the possibility that the evolution of larger brains in some species is enabled by increased investment of energy by parents in their offspring. Carel van Schaik of the Max Planck Institute for Animal Behavior in Konstanz, Germany, and colleagues present their arguments in a paper published on February 28 in the open access journal PLOS Biology.
Across species, larger relative brain size is associated with cognitive benefits that favor survival. However, larger brains come with higher energy costs. Previous research has examined these costs for adults to deepen our understanding of evolutionary trends in brain size between different species. However, few studies have focused on the energy costs of the developing brain of young organisms.
To help bridge that gap, van Schaik and colleagues addressed an apparent paradox: the larger a species’ brain, the more energy required during development—but large brains aren’t fully functional until they’re complete. growing. This creates a “chicken or egg” or “shoe-strapping” problem: most young offspring of larger-brained species should not be able to meet the energy demands of their own developing, growing brains. the question of how a larger brain size could have evolved.
The researchers hypothesize that parental energy investment in their young increased, and this facilitated the evolution of larger brains.
To examine this possibility, the researchers reviewed evidence from previous studies on the evolution of parental energy investment in young offspring. Warm-blooded species invest energy in their young through actions such as producing eggs, lactating, providing food, carrying or huddling to stay warm. Most cold-blooded species only lay eggs.
Detailed analysis showed that greater energy investment in juveniles did indeed emerge, along with the evolution of a relatively larger brain, and that this additional investment could improve the survival chances of young offspring.
These results support the hypothesis that greater parental energy investment in young offspring facilitated the evolution of larger brains, and that the inability to provide that sustained energy in egg-laying species, in turn, limited the evolution of bigger brains. Future research could build on this study to shed more light on how larger brains evolved.
“The evolution of extended parental provision beyond the egg stage prevented a major evolutionary constraint on brain size, thereby unleashing a massive increase in brain size and cognitive potential among birds and warm-blooded mammals. Almost all of them feed their young after birth or hatch and have much larger brains than their cold-blooded relatives,” says van Schaik.
Increased parental supply and variation in vertebrate brain sizes, PLoS Biology (2023). DOI: 10.1371/journal.pbio.3002016
Available at the Public Library of Science
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