Haplogroup B4'5 originated more than 50,000 years ago, likely in Central Asia. Since then it has spread widely, diversifying through China and southeastern Asia and in the past few thousand years to the remote Pacific Islands. The haplogroup was also carried to the Americas by migrants who crossed a land bridge connecting Siberia to Alaska more than 12,000 years ago. Today haplogroup B4'5 is common in the Amazon River basin of South America and among Native Americans from the southwestern U.S. and northern Mexico.
Haplogroup B4'5 in Asia
Haplogroup B4'5 remains common in Asia today, stretching from Iran to Japan. It is extremely common in parts of China, southeastern Asia and far beyond; the presence of B4'5 at levels of up to 50% among the Maori of New Zealand and native Hawai’ians indicates their shared Southeast Asian heritage.
In Mongolia and southern China there are people bearing haplogroup B4'5 whose mitochondrial DNA bears a distinctive mutation that is also common in the U.S. Southwest – an indication of common descent. The similarity could be coincidence. But it might also indicate that unlike the other haplogroups that spread into North America during the Ice Age, haplogroup B4'5 began its journey not in Siberia but in the heart of Asia, where it remains relatively common.
Recently, archaeologists uncovered the remains of dozens of prehistoric skeletons from present-day Korea. Using the latest technology to extract DNA from the remains, scientists found two individuals - both about 10,000 years old - belonging to Haplogroup B. The fact that Haplogroup B4'5 existed in East Asia so many years ago suggests that some of the earliest Koreans may have migrated from Central Asia.
On mainland Asia, there are two main sub-lineages of Haplogroup B: B4 and B5. Both are more common in Southeast Asia, with lower levels as one travels north across China and into southern Siberia. Haplogroup B4 is found in up to 30% of people from the Guizhou province of southern China, while B5 is found in 18% of people from the neighboring Hainan province.
B4'5 in the Americas
At the peak of the Ice Age, between about 20,000 and 15,000 years ago, massive glaciers covered much of North America and Eurasia. So much water was locked up in the ice sheets that global sea level dropped 300 feet, creating connections between land masses that are isolated by wide straits or passages today. One of those connections was the Bering land bridge, an ice-free but frigid corridor hundreds of miles wide that linked Siberia and Alaska. Mammoths, bison, caribou and other Ice Age mammals roamed back and forth between Siberia and Alaska during this period, as did a few hardy hunter-gatherers who could cope with the region's extreme climate.
As the Ice Age ended, people began moving south from the Arctic into the heart of North America. Within a few thousand years, possibly even faster, the new arrivals had populated the Western Hemisphere down to the tip of South America.
Some of those first Americans had mitochondrial DNA belonging to haplogroup B, which can be found today among a diverse set of populations in western, central and southeastern North America. The haplogroup is found among the Pawnee, Cherokee and Seminole and is strikingly common today among southwestern tribes such as the Pima, Yuma and Washo.
The Anasazi
Haplogroup B4'5 appears to have been a fixture in the Southwest at least since the introduction of agriculture to the region from Mesoamerica 2,500 to 3,500 years ago. In some areas the haplogroup is found in 100% of the Native American population and sometimes multiple populations share the identical forms of the haplogroup; for example, a single variant of haplogroup B4'5 is shared by the Navajo, Zuni, Jemez and Seri groups.
Haplogroup B4'5 reaches levels of 75-90% among the Pueblo groups of New Mexico and Arizona, which are thought to descend from the cliff-dwelling Anasazi who occupied the Southwest from the 8th century AD until their sudden disappearance in the early 12th century.
The Anasazi didn't literally disappear; modern Pueblo people and most scholars believe warfare or environmental catastrophe forced them to abandon their elaborate cliff dwellings for settlements in the Rio Grande valley. Recent studies of DNA extracted from 2,000-year-old remains have supported that view by establishing the presence of haplogroup B4'5 among the Anasazi.
B4'5 in Polynesia
One particular branch of haplogroup B4'5 predominates in yet another region – the remote Polynesian islands of the eastern Pacific Ocean, which were the last place on the planet to be settled by humans. Haplogroup B4a1a1 is virtually universal in Polynesia – but hard to find anywhere else. That pattern, combined with archaeological evidence and oral tradition, suggests that very small numbers of people – in some cases single boatloads – populated the remote islands between about 3,000 and 1,000 years ago.
Geneticists have struggled mightily to figure out where those first Polynesians came from. Early linguistic and archaeological suggestions that they moved swiftly from Taiwan to the South Pacific have fallen from favor in recent years, but are still supported by some genetic researchers. Although B4a1a1 is not found in Taiwan today, its parent haplogroup, B4a1a, appears to have originated there about 13,000 years ago.
B4a1a1 appears to have branched off B4a1a about 9,000 years ago and then spread after leaving Taiwan. Outside of the outer Pacific Islands populated by Polynesians, B4a1a1 has been found in coastal Papua New Guinea and in Indonesia, where the haplogroup is most common on the islands of Ambon and Sulawesi.