mtDNA shows how human migrated

Mitochondrial Eve:

Scientists believe that all 7.5 billion people on Earth today are descended from a woman known as Mitochondrial Eve, who lived around 200,000 years ago in eastern Africa.
Mitochondrial Eve’s descendants can be traced using mitochondrial DNA (mtDNA), which is passed down maternally.

Mitochondrial DNA:

MtDNA is inherited only through females, although both men and women possess it. However, a man’s mtDNA is not passed to offspring because it resides in the sperm’s tail, which does not enter the egg during fertilization.
This principle allows scientists to trace human ancestry and migration patterns through mtDNA haplogroups.

Research and Findings:

In 1987, a pivotal study using mtDNA from various populations concluded that all human mtDNA originated from a single population in Africa, dating back to 140,000 to 200,000 years ago.
This research involved data from 145 women and two cell lines, linking modern humans to a common ancestry.

Early Human Migration:

Around 200,000 years ago, humans lived near Lake Victoria, Serengeti Plains, and Mount Kilimanjaro.
Human migrations starting between 150,000 and 100,000 years ago.

Migration Out of Africa:

Approximately 60,000 to 80,000 years ago, mtDNA types L2 and L3 expanded across Africa.
Around 50,000 to 60,000 years ago, L3 type humans moved to Southwest Asia, giving rise to the M and N haplogroups, from which all non-Africans are descended.
A small group left Africa, with only two mtDNA lineages (M and N) surviving.

Global Spread of Haplogroups:

M and N types moved from India to Australia around 50,000 to 40,000 years ago, when lower sea levels during the Ice Age facilitated land travel.
These groups were among the first navigators, possibly constructing rafts to cross seas near Indonesia.
Various mtDNA types emerged as people spread:
- Types I, U, H, and V migrated to Europe.
- Type X moved to Siberia.
- A, B, and F appeared in East Asia.
- C, G, and D also emerged, with Type D advancing to Japan via Korea.
By 33,000 years ago, the Last Glacial Maximum began, with large ice sheets covering Europe and North America, and sea levels (394 feet) lower than today.

People of the Americas:

Around 25,000 years ago, haplogroups A, B, C, and D spread to eastern Siberia and eventually crossed into the Americas via the Bering land bridge during the Ice Age.
Approximately 15,000 years ago, these groups began moving from Alaska to South America as temperatures rose and ice sheets retreated.
An ice-free corridor between the Laurentide and Cordilleran ice sheets allowed further southward migration by 12,600 years ago.

Late Ice Age and Beyond:

The Younger Dryas period (12,900–11,700 years ago) saw a sudden cooling due to a massive freshwater release from Lake Agassiz affecting global climates.
During this time, Type B mtDNA spread to the Philippines, Borneo, Madagascar, and Polynesia, with movements continuing until about 1,000 years ago.

The distribution of various haplogroups today reflects these ancient migrations:
- Africa: L types
- Asia and Australia: N, M, R, and F types
- Europe: U, I, T, H, V types
- Americas and Pacific: A, B, C, D, X, Y, Z types

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