If not for our use of camels, horses, carts, wagons, cars, trains, boats and planes we would eventually no longer be just ONE species!
If we had not created our worldwide transportation systems, which have enabled breeding between all the diverse peoples of the world, then we would have continued to evolve differently in our separate environments and would have become discrete sub-species of humans… to eventually become ‘unable’ to successfully breed with people from other populations.
You may have heard about strong, burly mountaineers passing out in the Himalayas, due to lack of oxygen at these altitudes, whilst small native children, or little old native women carrying pack-horse sized bundles, hurry by. These same mountain-dwellers would pass out if they were taken to sea level. Mere thousands of years have begun to create a sub-species of mountain-dwelling human and only travel and interbreeding with low level dwellers can stop it from happening.
Without Science we would eventually have become the Arab species, the Eskimo species, the Sub-Saharan African species, the Chinese species, etc, etc, etc… ‘Diversity’ in humanity would have a totally different meaning.