Leipzig, Germany. Modern humans have a better sense of smell than the Neanderthals, our ancient cousins, a finding with important implications because olfaction establishes a direct connection between the brain and its environment, with direct influences on human behavior.

Differences in the temporal lobes and olfactory bulbs also suggest a combined use of brain functions related to cognition and olfaction.


In a study published by Nature Communications, led by Markus Bastir and Antonio Rosas, of the Spanish Natural Science Museum (CSIC), high-tech medical imaging techniques were used to access internal structures of fossil human skulls. The researchers used sophisticated 3D methods to quantify the shape of the basal brain as reflected in the morphology of the skeletal cranial base. Their findings reveal that the human temporal lobes, involved in language, memory and social functions as well as the olfactory bulbs are relatively larger in Homo sapiens than in Neanderthals.



Parallel Evolution, Different Brains

The image shows differences in brain shape between an adult Neanderthal (top; red) and an adult homo sapiens (bottom; blue).

Image © Max Planck Institute of Evolutionary Anthropology, courtesy of Phillip Gunz.The increase of brain size is intimately linked to the evolution of humanity. Neanderthals and modern humans are two different human species, but we independently evolved brains of roughly the same size. But the shapes can differ: he structures which receive olfactory input are approximately 12% larger in modern humans than in Neanderthals. This could indicate a difference in the underlying brain organization.

Olfactory information projects to brain regions directly responsible for processing of emotion, motivation, fear, memory, pleasure and also attraction.

Neuroscientists have coined the term higher olfactory functions to describe those brain functions which combine cognition (memory, intuition, perception, judgment) and olfaction. The greater olfactory bulbs and relatively larger temporal lobes in H. sapiens compared to any other human species.

These findings may point towards improved and different olfactory sense possibly related to the evolution of behavioral aspects and social functions. In modern humans the size of the olfactory bulbs is related to the capacity of detection and discrimination of different smells. Olfaction is among the oldest sense in vertebrates. "Also, it is the only one that establishes a direct connection between the brain and its environment", says Markus Bastir, the lead author of the study.

While other senses must pass through different cortical filters, olfaction goes from the environment right into the highest centres of the brain. Moreover, olfaction stops — we always breathe and perceive smells. The neuronal circuitry of olfaction coincides with that of memory and emotion (the limbic system), "which explains the enormous memory retention and vital intensity of olfaction-mediated life events," never sleeps", notes Rosas.

Researchers at the Max Planck Institute of Evolutionary Anthropology, who also contributed to the research, recently showed differences in the patterns of brain development between modern humans and Neanderthals during a critical phase for cognitive development. "In the first year of life the brains of Neanderthals and modern humans develop differently," says Philipp Gunz from Max Planck.

Gunz notes that "Modern humans have smaller faces and smaller noses than their Neanderthal cousins. However, the part of the brain that processes smells, is bigger in modern humans than in Neanderthals". There is a continuous accumulation of evidence that Neanderthals and modern human brains might have worked differently, findings in alignment with their independently evolved large brains. "Our new study offers a glimpse into the functional significance of these developmental differences," adds Jean-Jacques Hublin, who heads the Department of Human Evolution at Max Planck.

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