Why smells from childhood mean so much

Few days ago Jonah Lehrer wrote about smell and today an article on New Scientist again talks about the significance of Olfactory bulb.

"Why does the hint of certain smells instantly transport you back to childhood? It may be because the first smell you associate with an object is given privileged status in the brain.
Yaara Yeshurun and colleagues at the Weizmann Institute of Science in Rehovot, Israel, showed volunteers an object such as a chair or pencil that was unlikely to already be associated with a smell at the same time as exposing them to an odour or sound. An hour-and-a-half later, they showed them the same object with a different odour or sound.
One week later, the researchers showed the volunteers the object again and asked them which odour or sound they associated with it, while scanning their brains using functional magnetic resonance imaging.
Volunteers were more likely to mention the first odour – and when they did, their brains showed a characteristic pattern of activity in the hippocampus. This pattern did not appear if volunteers plumped for the second odour, or if they had been exposed to sounds rather than smells.
Yeshurun concludes that the brain reserves a special pattern of activity for memories that represent the first time we have associated a smell with a particular thing – and that such pairings are most likely to be laid down in childhood."

There are three smells I "remember" vividly and comes back to me, haunting me for years. First one is the smell of my great grand mother. She lived with us when I was 7 or 8 years old for just few months and moved with my uncle and later passed away about a year later. She never spoke to anyone, totally incapacitated and I never knew her personally. But her smell comes back "inside me" sometimes (very rare) and I am confident its not from an external  source. Since I inherited her genes, the smell is probably inside me and may be it will come out often as I grow old.

The second smell which I get is the smell of my dad and I do smell like my dad sometimes. Its has a soothing effect on my olfactory bulb and plays a soft lullaby taking me back to the childhood days (I love it!!). My dad lives thousands of miles away but the power of odor dissolves the distance.

The third one is smell of rain and this one is reserved only when I go to India since monsoon rain has its own odor. I cannot begin to explain what all memories that brings with it. Probably the olfactory bulb is the queen of Synesthesia.

What Marcel Proust wrote decades ago was so precise:

"When from a long distant past nothing subsists, after the people are dead, after the things are broken and scattered, taste and smell alone, more fragile but enduring, more unsubstantial, more persistent, more faithful, remain poised a long time, like souls, remembering, waiting, hoping, amid the ruins of all the rest; and bear unflinchingly, in the tiny and almost impalpable drop of their essence, the vast structure of recollection."