Changes in the way people move -- changes in the number, routes, and reasons for moving -- are transforming our world in sometimes unexpected ways. PNS commentator Walter Truett Anderson looks at some of these new trends and what they might portend on several fronts. Anderson, author of "Evolution Isn't What It Used To Be" (W.H. Freeman), is a political scientist who writes widely on technology and global governance.

Until recently, the people moving around the world tended to follow certain familiar patterns -- leaving from certain countries and going to certain others. This was the pattern at work in building the United States, the classic "nation of immigrants" -- and it still shapes our image of the world.

But the patterns are changing dramatically, and in ways that are surprising the experts who study such movements -- and transforming politics and culture everywhere.

One piece of this new picture is what researchers Stephen Castles and Mark Miller call the "globalization of migration." Migration is now happening virtually everywhere, within and between all regions of the world -- Europe, the Middle East, Africa, Asia, Latin America. Countries such as Malaysia, which took in hundreds of thousands of workers during the boom years, are now immigrant countries. So are southern European nations such as Greece, Italy and Spain that were for many years zones of emigration. Some countries such as Mexico are both importers and exporters of migrants. Then there is the matter of internal migrants -- China offers an outstanding example -- with millions of people leaving the land to seek their fortunes in the growing cities.

Another aspect of the change is the differentiation of migration. In any particular region where migration is occurring, many kinds of migration are happening all at once -- refugees and workers, temporary and permanent, legal and illegal, highly-skilled professionals and unskilled laborers. The categories often blur, as when people enter a country legally as tourists or guest workers and then become -- legally or illegally -- permanent residents.

Yet another new trend is the feminization of migration. Most migrations used to be dominated by males. Now in many areas, women take the lead, going forth as workers from the Cape Verde Islands to Italy, from the Philippines to the Middle East, from Thailand to Japan.

Migrations bring many changes, both in the countries that people leave and in the countries to which they come. National cultures gain richness and variety but -- inevitably and, for some people, painfully -- old and familiar arts, myths and customs tend to fade away.

Further, immigrant nations -- such as Germany -- commonly develop anti-immigrant political movements. Economic conditions change in many ways -- one of the most significant being the flow of money back to the countries that migrants have left. This has become one of the world's most important forms of foreign aid, and some communities are totally dependent on it.

These changes are so widespread and so rapid that nationality and statehood are becoming fundamentally different from what they were in the recent past. At one time, a person's nationality -- membership in a state, right to protection under its laws, and personal identity -- were defined exclusively in terms of citizenship. Citizenship still counts for a lot -- more in some countries than others -- but it is slowly being shoved aside by new concepts such as "denizenship." This is the word invented by legal scholars to describe the situation in those countries which have ratified human-rights treaties so that access to the legal protections of the state is now based primarily on residence. In some countries, governments now extend to long-term residents not only basic protections -- such as the right to own property, run businesses, speak out on public issues -- but also the right to be employed in the public service, even vote in local elections.

Some observers call this huge surge of human mobility the "transnational revolution." It is not only a matter of economic and political and cultural changes, but a deep shift in how people think of themselves. Obviously people are coming to recognize that they live in the world -- not just in a state or a local community -- and that it is entirely possible for a person from any part of the world to go to any other part.

We have clearly not seen the end to this revolution. The experts say more people will be on the move in the future. And as they do they change the very nature of boundaries, redraw the map of the world in a way that conquerors and diplomats have never been able to do.