Somewhere between insatiable curiosity and voracious appetitie for the accumulation of wealth lies the motivation for human travel. These two goalposts through which nearly each explorer (and surveyor and merchant and conquistador—traverler, to be perfectly general about it) to roam this planet sailed do not paint the idealized portrait of natural human character, but they nonetheless do accurately depict the aims of those ambitious enough to change the world and therefore merit a place in the halls of history. Even those forgotten travelers, the Irish immigrants fleeing famine in the nineteenth century, for example, traveled in search of riches, or at least wealth greater than they could find at home. Again, through the economics of profit, and quite accidentally, capitalism shows its underappreciated head. Just a curiosity killed the cat, however, the covetous person is always in want. Beyond the Asopistic moral imperatives present in such a saying, lies the hidden and likely unintentional implication that other, less-obvisous consequences result from the oldest and most-American of pursuits.
Discussing the entire history of human transportation within the confines of this brief paper would be, to say the least, a hairy undertaking, so the focus here will resonate on a single individual and the potential unforseen consequences of his and his agents' perfectly intentional actions. In addition, it is far easier, more sensible, and productive, to examine a figure from the relatively distant past. So to begin with, take the case of John Jacob Astor, who died in 1848 as one of America's outstanding foreign merchants ' . Born in Germany, by the time he reached twenty, Astor had already traveled throughout Western Europe and to New York City when he began a trading business. Examine to this point the modes of transportation and distances Astor had traveled: roughly 1334 miles on land and 3670 miles by sea. To do so not only cost an enormous amount, but encouraged the travel of a number of unintended companions: rats, roaches, and pathogens, to ennumerate but a few of the most commonly encountered of parasites. In five short years of his lifespan, Astor traveled more in total distance than any member of the ancient hunter-gatherer cultures would in a lifetime. This travel, the majority of which was completed on ship, was the beginning of a human monoculture.
With advances in travel, particularly in the areas of speed and avalability of transportation, come a number of effects on populational diversity. For one, wealthier people--those that can afford this type of travel--, begin to have a greater genetic advantage over the poor. With travel comes the opportunity to, referring to the act in the Biblical sense, spread one's seed far and wide. Astor, a German, ended up marrying an American of British descent, a union not possible save for the ability to travel in order to first meet each other. Their children, effectively a combination product of British and German genes were that much less genetically diverse than the same number of children born to either Astor or his wife and a member of their own locality. In theory, this could also hold true for British rats stowed away aboard a ship mating with American counterparts. In addition, wealthier families--the same ones able to trvel--could afford to provide for a greater-then-average number of children, thereby further encouraging the incidence of cross-cultural breeding. In the long term, this has two main effects: one, an increase in genetic diversity measured in locality-specific genetic terms and a corresponding decrease of "locality-inbreeding", and two, a decrease in genetic diversity skewed towards the wealthy. Offspring of prosperous families, then, had (and continue to have) an even greater advantage to survive and reproduce for another generation in the age of long-distance transportation than in proir eras. Considering, however, that affluent individuals have always had a significant reproductive advantage, the net effect of commonly available transport was to provide for greater genetic diversity, as per effect one mentioned above.
Mr. Astor, with the help of his wife, founded a fur trading business that made regular ship journeys across the Atlantic and later even the Russians across the Pacific. By the turn of the nineteenth century, Astor's several ships traveled to China and India, as well as throughout North America and to Wester Europe, earning him between $50 and $100 thousand annually. Just to complete this brief biography, it deserves mention that Astor died America's first millionaire, primarily the result of his prescient investment of profits into the rapidly appreciating real estate of Manhattan, New York. There is little doubt that Astor sent his captains and purchasing agents abroad for no purpose other than profit; a retun on the reportedly $800 thousand he had invested in the shipping businesses. Clearly, this international trade Astor and his associates engaged in had little affect on genetic diversity. At least human diversity. What it did manage was the spreading of flora, fauna, and cultural content from continent to continent. Although there can be no conclusive proof that a certain ship brought a certain plant abroud, take the following scenario: the brassica rapa, a small plant grown in Europe for 4000 years (and brought with early settlers to the New World) first began appearing in the Canton region of China around the middle of the nineteenth century. This timing corresponds directly with increased trade between the Americas and the Orient realized primarily by Astor's merchanting business. The brassica rapareproduced so rapidly in the Chinese environment that a variant of the original European plant is now known as "Chinese cabbage" and can now be seen as far north as the Beijing region. It was primarily a pest to Chinese farmers that has been more recently harnessed to provide food for a growing population.. In any case, Trade on such an international scale as was made possible by Mr. Astor, virtually guarantees the introduction of organisms into environments not originally possible, often--although certainly not always--with devastating effects.
As the case of John Jacob Astor and his international merchant shipping industry shows, transportation on a global scale, as motivated by the drive for more and more money, is sure to have a great many effects on genetic and locational diversity of a species. What cannot be assured nor even truly judged is the magnitude and degree to which these introductions affect a given environment, as the examples of the rabbit and cane toad intentionally brought in to Australia so much more clearly show. The best option is to simply not meddle, as ecosystems have a way of sorting themselves out quite effectively. The one problem with this "best option" is obvious: it requires an end to rapid transportation and would stiffle economic development across the world.