All modern humans descend in the male line from a particular man, nicknamed Genetic Adam, who lived in Africa about 142 thousand years ago (~7,100 generations). This is much older than previously thought. Geneticists discovered this information by mapping mutations on the y chromosomes of modern men.
Before Adam
Archaeological evidence shows modern humans emerged some 200 thousand years ago. Yet, humans exhibit less genetic diversity than expected, far less than our closest primate cousins, the chimpanzees.
The early human population was relatively small. A University of Utah study suggests that 2.1 million years ago the human population was probably about 55.5 thousand people, of whom perhaps 18.5 thousand were ancestors of modern humans. (The Times-Tribune, Mar. 18, 2010).
Genetic Adam
When a yDNA mutation appears in a man, all of his male-line descendants will also carry that marker. If we compile information on a large set of markers, then project them back in time using computer algorithms, we find that the trail of mutations coalesces in a single man who lived some 142 thousand years ago (~7,100 generations) (Cruciani et al. 2011). This date is a little uncertain. The 95% confidence interval is 60 to 142 thousand years ago.
This common ancestor has been dubbed Genetic Adam. He lived in Africa, probably on the plains of east Africa. He might have resembled the Han people who live in south Africa today. The mutation that appeared in Genetic Adam is now carried by every human male on the planet.
The term Genetic Adam is misleading. He was not the first modern human male. His father was undoubtedly fully as human as he was. The mutations in non-functional regions of the y chromosome are “silent” – they don’t do anything. So, none of Genetic Adam’s contemporaries would have thought that there was anything out of the ordinary about him. He was different from his contemporaries only in the sense that his male line descendants have survived down to the present, while those of his contemporaries did not.
There were other men living at the same time, but they did not carry the same mutation and none of the male lines from them survived down to the present.
Genetic Adam is also a misnomer in the sense it does not refer to a fixed individual. As male lines on the edges of the human tree die out, the remaining lines converge on a different man, one who lived more recently.
African Diversity
About 75 thousand years ago (~3,000 generations), one of Genetic Adam’s descendants developed a mutation now called M94. He is the paternal ancestor of the overwhelming majority of people living today. His descendants founded Haplogroups B through T. Only Haplogroup A, which until fairly recently was confined to sub-Saharan Africa, does not carry the M94 mutation. All other modern men are descended in the male line from this man and carry the M94 mutation.
M94 lived on the plains of east Africa. Many of his descendants lived along the coast of northeast Africa.
Near Extinction
Some scientists believe that humans nearly became extinct about 70 thousand years ago (~2,800 generations) when the Toba super-volcano erupted in Indonesia, triggering an environmental catastrophe. According to this theory, the eruption triggered a volcanic winter that lasted 6 to 10 years, and reduced the human population to perhaps 10 thousand, or possibly just 1 thousand, people. (Wikipedia: Toba catastrophe theory).
Eurasian Adam – Out of Africa
About 68.5 thousand years ago (~2,400 generations), one of M94’s descendants developed the M168 mutation. This man is often called Eurasian Adam, because he is the ancestor of everyone outside of Africa (and quite a few people still in Africa). His descendants make up Haplogroups C through T.
M168 might have lived in what is now Ethiopia.
About 45 thousand years ago (~1,800 generations), Haplogroup CT split into an African group (Haplogroup E) and an Asian group (Haplogroup F). Increasing ice in the far north dried up the African climate to the extent that at least two different groups of M168’s descendants left Africa in search of adequate food supplies, or perhaps just seeking new lands.
The first wave of his descendants left Africa close to 60 thousand years ago (~2,400 generations). They followed the southern coastline of Asia eastward. Sea level was as much as 400 feet lower than it is now. They and their descendants ended up in southeast Asia, Australia, southern China, and the Pacific Islands. Some of them joined their distant cousins in North America some 10 thousand years ago (~400 generations).
A second wave of M168’s descendants were forced out by a period of drying. They went north and east out of the Sahara area through Egypt into the Arabian peninsula and the Middle East.
M89 – Founder of Macro-Haplogroup F
M168’s descendant M89 lived about 45 thousand years ago (~1,800 generations), probably in modern-day Iraq. He was the founder of macro-haplogroup F. His descendants include all members of Haplogroups G through R. This means he is the ancestor of virtually everyone in Europe and the Middle East, and of the vast majority of Asians and Native Americans.
A large group of M89’s descendants moved up into central Asia above the Caspian Sea. It was very cold there near the edge of the great northern ice pack. Life would have been harsh but food was plentiful. Vast herds of big game thronged the tundra and the grasslands south of the ice pack.
About 40 thousand years ago (~1,600 generations), a new mutation arose in Central Asia, M9, that founded a new Haplogroup K, the ancestor of the Eurasian Haplogroups L through R. His descendants spread over most of Europe, Asia and the Americas. Half of modern Europeans belong to this haplogroup.
Another group of M89’s descendants stayed in or near the Middle East. Some of them might have returned to northeastern Africa. New mutations among them gave rise to the Haplogroups G through J.
(6) About 35 thousand years ago (~1,400 generations), two new groups, R and NO, branched off from K. Haplogroup R moved to western Central Asia. Haplogroup NO moved to eastern Central Asia.
(7) About 30 thousand years ago (~1,200 generations), Haplogroup R split into R1 and R2. Haplogroup R1 moved to the steppe area between the Ural mountains and the Caspian Sea.
(8) About 25 thousand years ago (~1,000 generations), one branch of Haplogroup R1, Haplogroup R1b, reached Iberia and the Atlantic coast. Somewhat later, Haplogroup R1a branched from R1 and became common in the Ukraine.
(9) About 25 thousand years ago (~1,000 generations), the Middle Eastern Haplogroup F sent another branch to Anatolia and further to the Balkans, and a new group emerged, Haplogroup I.
An estimated 80 percent of European men share a common ancestor, who lived as a primitive hunter some 40 thousand years ago (Semino et al., The Genetic Legacy of Paleolithic Homo sapiens sapiens in Extant Europeans: A Y Chromosome Perspective, 2000). He was one of the Paleolithic (Old Stone Age) people who first migrated to Europe, probably from Central Asia and the Middle East, in two waves of migration beginning about 40 thousand years ago. Their numbers were small and they lived by hunting animals and gathering plant food. They used crudely sharpened stones and fire.
About 24 thousand years ago (~960 generations), the last ice age began. The Paleolithic Europeans retreated to three refuge areas: Spain, the Balkans and the Ukraine, where they lived for hundreds of generations.
About 16 thousand years ago (~640 generations), the glaciers melted. The three groups spread out through Europe. The male-line descendants of the group that lived in Spain are now most common in northwest Europe (Haplogroup R1b), those from the Ukraine are primarily in eastern Europe (Haplogroup R1a), and those from the Balkans (Haplogroup I) are most common in central and northern Europe.
Spread of Agriculture
About 10 thousand years ago (~400 generations), the people of the Fertile Crescent developed agriculture. Before that time all humans were hunter-gatherers. With a more stable food supply, populations could expand rapidly. Farmers began moving out of the Middle East, through the islands and along the shores of the Mediterranean, through Turkey into the Balkans and the Caucasus Mountains.
About 8 thousand years ago (~320 generations), during the Neolithic era (New Stone Age), another wave of migration, this time from the Middle East, brought agriculture to Europe. Early theories suggested that the advancing farmers probably displaced or eliminated the hunter-gatherers of Europe. DNA studies have shown that the spread of agriculture involved the movement of some people into Europe who had not been there before, but the spread of farming was primarily through the adoption of the new technology by the existing Europeans.
Many geneticists currently believe that when Haplogroup G, J and Eb1 are found in Europe, it is often (but not always) a marker for the spread of farmers from the Middle East into Europe. About 20 percent of modern European men have y chromosomes that show they descend from this Neolithic migration.
European Cousins
The mutations M201, M52, M170, and 12f2.1 gave rise to Haplogroups G, H, I, and J. Haplogroup G is concentrated near the the Caucasus mountains. Haplogroup H is largely confined to the Indian subcontinent. Haplogroup I spread up through central Europe and into Scandinavia, where it is common today. Haplogroup J is very common in the Middle East, where many Jews, Arabs, and others belong to it. These four haplogroups probably arose between 20 and 30 thousand years ago, but Haplogroup G might be a bit younger.
Read More
- Wikipedia, Genetic Adam
