As I approach our home near Gilgit, it is the walnut tree that triggers the feeling of arrival.

The feeling of approaching home is a subtle and primeval matter. There are many sensory markers that trigger this feeling, yet remain difficult to identify. We hardly notice them in our conscious minds, yet we know them when we experience them. Everyone desires these markers, just as all beings crave a place and a feeling called home.

When we arrive in our recently made home near Gilgit, the primeval feelings all begin as we wind our way past the Karakoram Highway and climb the village lanes lined with boundary walls guarding gardens and homes.

Our first home marker is the sound of gushing water, bubbling and gurgling down the twisted, descending water channel that feeds glacial melt water to each household. When our journey up the village becomes musical with this sound, we know we have left the road and the city behind.

Then we come to a water bridge, a culvert where the sound gushes loudly, and our main visual marker of the feeling of home is apparent. A walnut tree stands to watch over the foaming culvert, its branches spreading wide across the dirt lane in sheltering greenness, extending all around the wheat fields that it adjoins. It is the walnut tree that is our doorkeeper, it is the marker for not just another place we call home, but a time warp.

“Oohh, the walnut tree” chime our girls’ voices in contented anticipation of home as we drive past. And if they are not present, I am sure to echo this chime just for good measure and gladness.

As I have become familiar with walnut trees, I realise this chime of gladness indeed belongs in a time warp. For centuries, travellers must have felt just the same when passing by walnut trees. For walnut trees are actually among humanity’s first forest farms.

Walnuts have been found in the archaeological remains of ancient Babylon, making them at least four-thousand-year-old food items. Juglans regia, or the regal acorn of Jupiter as the Romans called it; this is the Latin botanical name of our old world variety.

Recent research into the origins of the walnut reveals four major genetic pools of the tree, namely the Kyrgyz, the Uzbek, Middle Eastern and East Asian populations. Sampling sites of this research show tantalising zones of walnut distribution mapped from western Anatolia to northeastern China, and lo and behold, of 39 sampled sites, two samples were taken from Pakistan.

The walnuts of Beijing and Xian fall squarely in the East Asian genetic walnut pool. Khotan, Kucha, Kyrgyzstan walnuts are comfortably of native Kyrgyz stock. Bukharan walnuts are naturally of Uzbek genetic stock. Western Iran, Turkey, Georgia and Iraq are logically populated by the Middle Eastern stock.

It is not at all obvious where Pakistani walnuts might belong. My guess was that they might be of Kyrgyz origin since that is the closest genetic pool on the map. Instead, their genetic pool is of Middle Eastern origin.

To find the key to these origins, one must understand the idea of forest farms. We normally understand forests to be stands of trees, often uncultivated by people. Farms on the other hand are devoted to cultivated crops and animals for human consumption. So as the term implies, forest farms, are stands of trees, perhaps uncultivated, but devoted to human consumption.

And that is how the genesis of walnut cultivation happened. Travellers, traders, monks, it is thought carried walnut seeds across millennia along trade and pilgrimage routes. Between Taskent and Samarkand where the northern and central routes of the Northern Silk Road came together, there are convergences of different walnut genetic pools.

Thus, grand trees in small portable balls of walnut seed were carried and planted by travellers quite purposely as long-term crop investments along travel routes. With a life span of some 200 years, walnut trees take about eight years from seed to the first production of nuts. This means that travellers planned long cycles of repeating journeys along ancient trade routes, also allowing for the next generations to benefit from a walnut seed planted along a route as long-term food supplies.

Our Pakistani walnuts of Middle Eastern origins are likely to have travelled along water routes, rather than purely land routes. Down from Georgia and northern Iran, through the Gulf of Hormuz, and then to Gujurat or the Indus Delta, then up north again to Kashmir and Gilgit Baltistan, this is the likely sea, river and land route of our walnuts.

In Gilgit Baltistan, there is a delicious dessert of threaded walnuts dipped in raisin juice and dried in strings called Khelao. I wonder if it is a coincidence that in Georgia there is a traditional sweet called churchkehla of just the same walnut recipe but also including another Middle Eastern native nut, the hazelnut.

Now, as we traverse the long journey from Lahore to Gilgit, and welcome the sight of the walnut tree in our neighbourhood, just so must travellers in history have welcomed the sites of walnut trees they planted decades ago as they return on travel routes they frequented over generations. Every time the walnut offers nourishment, shade and a welcome marker of home and safety.

The writer is a Lahore-based ecologist.