Thousands of years before the common era, Bronze Age cities and societies began to crop up around the globe, from the ancient cities of Mesopotamian and the agricultural cultures of pre-dynastic Egypt to the pottery-making civilizations of early China and the settlements and farms of North American cultures.

Around 5000 B.C.E., many cultures were laying down roots, and it would be a few thousand years yet before major trade routes began to join them together. But just because these ancient societies weren't trading doesn't mean their goods weren't connected.

According to a new study, the ancient civilizations of eastern and southwest Asia were split by just two degrees of separation. Nomadic shepherds of central Eurasia, says Discovery News, brought crops from east and west together, growing them at once in camps in Kazakhstan.

One of the grains found in Kazahkstan, bread wheat (Triticum aestivum), was cultivated in the Middle East by 6,000 years ago, but didn’t show up in East Asian archaeological sites until 4,500 years ago. Likewise, another grain found in the shepherd’s camps, domesticated broomcorn millet (Panicum miliaceum), may have originated in what is now China 8,000 years ago, but didn’t appear in southwestern Asia until 4,000 years ago.

Though not part of a deliberate trade route, the nomadic shepherds formed a connection across the rugged terrain of central Eurasia. “The intrepid ancient shepherds of central Asia blazed trails that would expand into the economic highway of the ancient and medieval world. Eventually, the route would carry silks from Han Dynasty China to the Roman Empire and earn the name 'Silk Road,'” says Discovery News.