The mammalian sense of smell is governed by the largest gene family, which encodes the olfactory receptors (ORs). The gain and loss of OR genes is typically correlated with adaptations to various ecological niches.

Australopithecus afarensis, the "beach ape" or water-ape, experienced a loss of functional olfactory receptor (OR) genes^{[1, 2]} in favour of adaptations for foraging shellfish and clams from the seafloor, and this partial loss of sensoriums was a rudimentary adaptation for non-sensory inputs, memes.

The expansion of the brain from Australopithecus to Homo sapien focused selectively on the areas that were co-opted by memes, the memetic cortex.

The eusocial brain and the frontal lobe as a trust organ

With the advent of memes, which are to technology what DNA is to proteins, the executive systems of the brain were co-opted as a trust system for selecting, copying, and mutating memes.

These virtual pheromones allowed the Homo lineage to organise by eusociality, each individual node following a stream of virtual pheromones, amplified through other nodes with similar mediation, similar to how ants follow pheromones, employing millions of individuals into a new type of super-organism, and increasing the number of connections and potential idea-collisions that could form.

References

Loss of Olfactory Receptor Function in Hominin Evolution

Human specific loss of olfactory receptor genes

Notes

• To this end, we have compared the sequences of 50 human OR coding regions, regardless of their functional annotations, to those of their putative orthologs in chimpanzees, gorillas, orangutans, and rhesus macaques. We found that humans have accumulated mutations that disrupt OR coding regions roughly 4-fold faster than any other species sampled. As a consequence, the fraction of OR pseudogenes in humans is almost twice as high as in the non-human primates, suggesting a human-specific process of OR gene disruption, likely due to a reduced chemosensory dependence relative to apes.