It is a common belief among scientists that modern man originated in Africa about 200,000 years ago and later spread over the earth via migrations, although some researchers believe modern man originated elsewhere and migrated to Africa. Wikipedia gives a detailed description of human migration. One of the major reasons for migration has been climate change, such as the migration from the central part of the US to the western part of the US. Now, the advent of new climate changes raises the possibility of global migration.
Latter-day Saints believe migrations to the western hemisphere occurred because people were lead by the Lord to the Americas. In addition LDS believe Columbus was led by the Lord to "discover" the American continents and thus open the "door" to permanent settlement of the Americas by European people. Evidence is surfacing that explorers before Columbus came to North and South America before Columbus, but those visits did not lead to permanent settlements. Migrations by Book of Mormon people are discussed in detail in other posts in the Migrations topic.
Following are some of the results obtained by scientists who are researching migrations.
This new research is based on the analysis of male Y-chromosomal genetic markers in about one thousand individuals, representing 50 tribal South American native populations. According to the authors, the extant genetic structure of South America native populations is largely decoupled from the continent-wide linguistic and geographic relationships. This finding demonstrates that the initial human settlement of the Americas was not a single migration process -- regardless of whether it took place through the Bering Strait -- , but rapid peopling, followed by long periods of isolation in small tribal groups.
Scientists have found that Native American populations -- from Canada to the southern tip of Chile -- arose from at least three migrations, with the majority descended entirely from a single group of First American migrants that crossed over through Beringia, a land bridge between Asia and America that existed during the ice ages, more than 15,000 years ago.
"It was only about 20 years ago that people recognized that modern Homo sapiens actually had an African ancestry, and everyone was focused on looking at early Homo sapiens in Europe who appeared around 40,000 years ago," she said. "But we now know that as far as back as around 200,000 years ago, Africa was inhabited by people who were already physically exactly like us today or really close to being the same as us. All of a sudden, it's not Europe in this time period that's really important, it's Africa."
A team of scientists, led by researcher Carles Lalueza-Fox from CSIC (Spanish National Research Council), has recovered part of the genome of two individuals who were alive in the Mesolithic Period, 7000 years ago. The remains were found at La Braña-Arintero site, located at Valdelugueros (León), Spain.
Using a technique called Optically Stimulated Luminescence (OSL) to date one of the sites in Oman, researchers have determined that Nubian MSA toolmakers had entered Arabia by 106,000 years ago, if not earlier. This date is considerably older than geneticists have put forth for the modern human exodus from Africa, who estimate the dispersal of our species occurred between 70,000 and 40,000 years ago. Even more surprising, all of the Nubian MSA sites were found far inland, contrary to the currently accepted theory that envisions early human groups moving along the coast of southern Arabia. "Here we have an example of the disconnect between theoretical models versus real evidence on the ground," says co-author Professor Emeritus Anthony Marks of Southern Methodist University. "The coastal expansion hypothesis looks reasonable on paper, but there is simply no archaeological evidence to back it up.
A consortium of 12 scientists from around the world, including two UF [University of Florida] researchers, gathered last year at the Rockefeller Foundation's Bellagio Center to review 50 years of research related to population resettlement following natural disasters or the installation of infrastructure development projects such as dams and pipelines. The group determined that resettlement efforts in the past have left communities in ruin, and that policy makers need to use lessons from the past to protect people who are forced to relocate because of climate change.