Human brains outpace chimp brains in the womb

September 24, 2012, Cell Press
The image shows a 3D ultrasound of a chimp in the womb. Credit: Current Biology, Sakai et al.: “Fetal brain development in chimpanzees versus humans”

Humans' superior brain size in comparison to their chimpanzee cousins traces all the way back to the womb. That's according to a study reported in the September 25 issue of Current Biology that is the first to track and compare brain growth in chimpanzee and human fetuses.

"Nobody knew how early these differences between human and chimp brains emerged," said Satoshi Hirata of Kyoto University.

Hirata and colleagues Tomoko Sakai and Hideko Takeshita now find that human and chimp brains begin to show remarkable differences very early in life. In both , the brain grows increasingly fast in the womb initially. After 22 weeks of gestation, in chimpanzees starts to level off, while that of humans continues to accelerate for another two months or more. (Human gestation time is only slightly longer than that of chimpanzees, 38 weeks versus 33 or 34 weeks.)

This movie shows a pregnant chimpanzee undergoing an ultrasound imaging procedure to explore brain growth in her fetus. Credit: Current Biology, Sakai et al.: “Fetal brain development in chimpanzees versus humans”

The findings are based on 3D ultrasound imaging of two pregnant chimpanzees from approximately 14 to 34 weeks of gestation and comparison of those fetal images to those of human fetuses. While early were suspected, no one had previously measured the volume of chimpanzee brains as they develop in the womb until now.

The findings are part of a larger effort by the research team to explore differences in primate brains. In another Current Biology report published last year, they compared brain development in chimps versus humans via (MRI) scans of three growing chimpanzees from the age of six months to six years (see this article).

Gestational age-related changes in the growth velocity of brain volume in chimpanzee and human fetuses

"Elucidating these differences in the developmental patterns of brain structure between humans and great apes will provide important clues to understand the remarkable enlargement of the modern human brain and humans' sophisticated behavior," Sakai said.

The researchers say they now hope to explore fetal development in particular parts of the brain, including the forebrain, which is critical for decision making, self-awareness, and creativity.

Explore further: Like humans, chimps are born with immature forebrains

More information: Sakai et al.: "Fetal brain development in chimpanzees versus humans" Current Biology, 2012.

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1 / 5 (2) Sep 25, 2012
Everything currently reported, common sense, and everything accurately reported in the past points to the role of nutrient chemicals in brain development both prenatally and postnatally, and to the role of pheromones in brain development postnatally (e.g., in all adaptively evolved species with a CNS). At what point should we expect evolutionary psychologists to take a brief look at the common molecular biology of species that is readily used to detail how the epigenetic effects of nutrient chemicals and pheromones alter the evolution of the brain and behavior?

Kohl, J.V. (2012) Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338.
not rated yet Sep 25, 2012
Science is to ignore "common sense" and look for successful predictions. Maternal hormonal factors are known to be essential for the early fetus.

As for brain and other traits, if other environmental chemicals are important for development they will make themselves heard. Thus far it seems, seeing your lament, not successful. Genetics on the other hand is known to be important and is fruitfully explored.
1 / 5 (2) Sep 25, 2012
Olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans. -- genetically. The epigenetic effects of nutrient chemicals and pheromones on intracellular signaling and stochastic gene expression are predictable in any species because of the common molecular biology of all species. Expressed as common sense: nutrient chemicals (foods) are required for individual survival, and the nutrient chemicals metabolize to species-specific chemicals called pheromones that control reproduction and species survival. This "chemical ecology" is responsible for adaptive eco-evolution via ecological, social, neurogenic, and socio-cognitive niche construction as has been detailed in reports on second-generation sequencing of genomes. Does anyone else wonder why the ENCODE project data does not address epigenetic cause and effect but leads us to think there are random models with explanatory power? What model is that?

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