A recent paper in Neuron presents the findings of a study examining the age of neurons in human olfactory bulbs. As the ScienceNow article states, your olfactory bulb neurons are the same age as you. In other words, according to the results of this study, we are not generating new neurons to help process smells. This may be an artifact of the study population utilized in this particular experiment, or it could be accurately representing our evolutionary history. Modern day humans do not rely on our sense of smell, and thus we may have simply lost the ability to generate new smell neurons because there was no selective pressure put on that particular trait. It’s an interesting finding nonetheless!