David Reich

Question 1

Mitochondrial Eve

Answer 1

c. 170,000 y.a.

The most recent mitochondrial ancestor of all humans alive today.

Question 2

Multiregional Hypothesis

Answer 2

Notion that present day humans living in many parts of Africa and Europe descend substantially from an early dispersal (c. 1.8 million y.a.) of Homo erectus.

This was the leading hypothesis until refuted by genomic data.

Question 3

FOXP2

Answer 3

Mutations of this gene in humans result in the inability to use complex language, especially grammar. One mutation in the FOXP2 promoter occurred ~50,000 y.a. This is believed to have been important in the evolutionary history of Homo sapiens as an advantage over other early humans.

Question 4

Svante Paabo

Answer 4

Leading genetic anthropologist and archaeologist.

First suggested FOXP2’s evolutionary significance and extracted the first Neanderthal genomes.

Question 5

Out-Of-Africa Hypothesis

Answer 5

Notion that modern humans everywhere derive from a relatively recent migration out of Africa and the Near East ~50,000 y.a. Shown to be partially false due to genomic data proving interbreeding between populations of genetically distinct early humans.

Question 6

Denisova Cave

Answer 6

Located in the Atlai Mountains of Southern Siberia. This is where the first Denisovan genome was discovered. Separation between Neanderthals and Siberian Denisovans occurred 470,000-380,000 y.a. , whereas separation between these populations and modern humans occurred ~770,000-550,000 y.a.

Question 7

Australo-Denisovans

Answer 7

Denisovans share the greatest number of genes with New Guineans. However, it is clear that there are vast genetic differences which occurred between the Denisovans found in Siberia and the ancestors of the New Guineans. These differences suggest a population split between Siberian-Denisovans and Australo-Denisovans which took place ~400,000-280,000 y.a.

Question 8

Florensiensis

Answer 8

Small-stature, “hobbit-like” humans of Flores island, Indonesia.

Question 9

Superarchaic Humans

Answer 9

Population which interbred with Denisovans, but not Neanderthals, and accounts for the fact that Neanderthals are more closely related to Sub-Saharan Africans than are Denisovans. This population must have been deeply divergent from all other discovered humans. The first of Reich’s “ghost genomes.”

Question 10

Ancient North Eurasians

Answer 10

Ghost genome of a population which was ancestral to both Northern Europeans and Native Americans. This population and its descendants migrated West into Europe and East across the Bering land bridge into the Americas. More than half of the world’s population derives between 5 and 40% of their genes from this population.

Question 11

The Mal’ta Genome

Answer 11

Discovered in 2013 by Eske Willerslev in Southern Russia.

This genome matched the predicted features of the Ancient North Eurasian ghost genome, and is now accepted as belonging to a true Ancient North Eurasian.

Question 12

Basal Eurasians

Answer 12

Proposed by Iosif Lazaridis as a solution to the enigma that East Asians today are more closely related to ancient European hunter-gatherers than to modern Europeans. With data from the Mal’ta genome, Lazaridis was able to identify a new ghost genome for the Basal Eurasian, the deepest split in the radiation of lineages contributing to non-Africans and harboring no Neanderthal DNA. Iranians and Natufian hunter-gatherers share the highest proportion of Basal European ancestry in the Near East.

Question 13

Reich’s Five Key Events in Ancient Human Migration

Answer 13

1. The Out-Of-Africa migration ~50,000 y.a.
2. Spread of European hunter-gatherers across Europe, ~40,000-35,000 y.a.
3. Gravettian Expansion from Eastern Europe to Western Europe and displacing of Aurignacians, ~30,000-27,000 y.a.
4. Expansion of the Aurignacian-descended Magdalenians from Iberia to central Europe ~20,000-15,000 y.a.
5. The Bolling-Allerod climatic change results in melting of the Alpine glacial wall, allowing a new Near Eastern population to enter Europe and displace the Magdalenians, ~14,000 y.a.

Question 14

Iceman’s Genome

Answer 14

Iceman was found in 1991 in a melting Alpine glacier. Upon genomic analysis, it was found that he was most closely related to the people of Sardinia. He showed little or no Ancient North Eurasian ancestry. This pattern was soon found to be a common motif for genomes in Europe up to ~5,000 y.a. Iceman’s genome dates back to ~5,300 y.a.

Question 15

Yamnaya Culture

Answer 15

Emerged ~5,000 y.a. in the grassland steppes between Europe and China. Its economy was largely based on sheep and cattle herding. This culture was the first to invent the wheel, and soon after came into contact with another group which had domesticated the horse. The combination of these two innovations made the Yamnaya vastly more productive than any contemporary culture.
They made the transition into Europe as the “Corded Ware” culture. Along with goods and ideas, the Yamnaya brought Yersinia pestis (the microbe responsible for black plague) to Europe. The microbe was endemic to the steppes, and so introducing it to the naive European population inadvertently cleared the way for the more resistant Yamnaya to expand West.

Question 16

Bell Beaker Culture

Answer 16

Contemporaneously with the Yamnaya expansion, the Iberian Bell Beaker culture spread to central Europe and exchanged goods and ideas with the Yamnaya. The Bell Beaker culture made the voyage from the Netherlands to the British Isles and largely displaced or eradicated the previous populations there. Those British and Irish skeletons immediately following this period had ~10% native ancestry and ~90% Bell Beaker ancestry. The Bell Beakers also interbreeded with the Yamnaya, and mixed ancestry ranged from 0 to 75% Yamnaya DNA.

Question 17

Indo-European Languages

Answer 17

Many Indo-European languages are now believed to be descendant from Yamnaya. This is particularly evident in shared vocabulary from Yamnaya inventions: wagon, axle, harness, pole, wheel.

Question 18

Aryan Invasion Theory

Answer 18

Theory that a group of Indo-Aryans traveled down from Northwest India and displaced the old Indus civilization with little intermixing. This is a politically loaded theory, and has been seized for ideological purposes by nationalist groups in both Europe and India, including the Nazis.

Question 19

India as a land of collisions

Answer 19

As far as we know, India is the first place where Near Eastern and Chinese crops met, making India’s early agriculture quite versatile.

India was also a mixing pot for languages, housing even today many Indo-European languages as well as the unrelated Dravidian languages and some Austroasiatic languages.

Of course, India is also home to a great mixture of heritages. While most mitochondrial DNA is unique to the subcontinent, Indian heritages largely fall between Europeans and East Asians on a principal component analysis plot, though also showing a clearly distinct ancestry not found outside of India.

Question 20

The Indian Cline

Answer 20

When plotted against one another in a principal component analysis, the populations of India form a gradient of European-related to Andamanese-related heritage which roughly correlates to the North to South distribution of populations stretching from New Delhi in the North to Bangalore in the South. Language also follows this trend, with Indo-European speakers having more European-related heritage, Dravidian speakers having more Andamanese-related heritage, and Austroasiatic speakers seemingly a mixture of Andamanese- and East Asian-related heritage.

Question 21

The Andamanese

Answer 21

North Sentinel Island of the Andaman Islands in the Bay of Bengal is home to one of the remaining largely uncontacted peoples of the world. The Andamanese speak languages so different from any others in Eurasia that they have no traceable connections. They also have little to no European-related heritage, but share a greater degree of heritage with East Asians. They have been identified as the descendants of the Southern Indian population that was a major contributor to Indian ancestry and represents the Southern tip of the Indian Cline.

Question 22

Ancient North Indians

Answer 22

The Northern, Indo-European-speaking, more closely European-related end of the Indian Cline. These ancestors of present-day Indians were a mixture of ancient Iranian farmers and steppe-pastoralists (i.e., the Yamnaya, which explains the relatedness of this population to modern Europeans).

Question 23

Ancient South Indians

Answer 23

The Soutern, Dravidian-speaking, more closely Andamanese-related end of the Indian Cline. These ancestors were a mixture of ancient Iranian farmers and a unique Andamanese-related group with no Yamnaya ancestry.

Question 24

The Indian Caste System

Answer 24

Caste is a distinctive feature of traditional Indian society. There are two levels of the Indian caste: Varna and Jati.

It was once unclear to what extent the caste system’s marital restrictions were followed historically, however it is today known as the caste-system with the deepest history outside of Africa, with some divisions dating back ~2,100 years.

Paraphrasing Reich, though the population of India rivals that of China, India can be more accurately described as being composed of many small populations where as the Han Chinese are truly one large, homogeneous population.

Question 25

Varna

Answer 25

Broadest level of the Indian caste system. Divided into four major ranks: The Brahmans (the priestly group) and the Kshatriyas (the warrior group) are at the top, the Vaishya (the farmers, merchants, and artisans) are in the middle, and the Shudras (the laborers) are at the bottom.

Question 26

Jati

Answer 26

A lower level of the Indian caste system. It is exceptionally more complicated than the Varna, and can be divided into a minimum of 4,600 distinct groups, each with its own status and marital guidelines.

Question 27

Nicholas Dirks

Answer 27

Anthropologist who once made the argument that the British made the caste system in India what it is today as a means of efficient rule during the colonial period.

Genetic evidence has disproven this theory in a large part, as it has revealed with certainty the deep historical roots of the Indian caste system. The extent of the caste system’s history is such that many families who have lived nextdoor in India for generations are more genetically different to one another than are Northern and Southern Europeans. There is also evidence of extensive inbreeding in many of these populations.

Question 28

Jose de Acosta

Answer 28

Jesuit priest and naturalist who first proposed that humans first reached an empty America from Asia by crossing an ice bridge in the then-unmapped Arctic. This theory was proposed in 1590.

Question 29

Clovis First Model

Answer 29

Suggests that the Clovis culture was the first south of the North American ice sheets, which melted and opened an ice-free corridor around the time that the Clovis culture appears in the archaeological record.

This theory was later disproven by the discovery of archaeological sites across North and South America which predate the opening of the ice-free corridor by up to ~2,000 years.

Question 30

Coastal Route Hypothesis

Answer 30

The notion that humans entered the Americas thousands of years prior to the ice-free corridor though small ice-free stretches on the northwestern Canadian seaboard with the aid of boats or rafts.

Question 31

First Americans

Answer 31

The ancestors of the vast majority of Native Americans today. This population is thought to have been the first to cross the ice into North America, and subsequently to have expanded dramatically as it moved into a human vacuum. Notably, several populations of Native Americans with little or no First American ancestry exist in the American Arctic.

Question 32

Joseph Greenberg

Answer 32

Linguist who lumped all Native American languages (~1,000 in total) into just three categories, with one category (named Amerind) containing ~90% of all Native American languages. His other families are Eskimo-Aleut, spoken by many indigenous peoples of Siberia, Alaska, northern Canada, and Greenland, and Na-Dene, spoken by a subset of Native Americans living on the Pacific coast of northern North America, in the interior of northern Canada, and in the southwestern United States.

Greenberg hypothesized that these three languages families represented three distinct waves of migration into the Americas.

Though he was heavily criticized for his exceedingly broad Amerind category, genetic evidence has been extremely supportive of Greenberg’s model, with his Amerind language family corresponding strongly to First American ancestry.

Question 33

Population Y

Answer 33

A ghost population identified in trace amounts among Native American populations in the Amazon. This ghost population is present in only up to 6% of the genomes of these peoples, the rest being accounted for by First American ancestry, and is closer related to Australians, New Guineans, and the Andamanese than to Siberians.

The population is named after the word “ypykuera,” meaning “ancestor” in Tupi, the language family of the populations with the largest proportion of this ancestry.

Note that the statistics are based on the assumption that Poplation Y ancestry is not otherwise mixed into what we identify as the First American genome. If this is the case then the true degree of Population Y ancestry in these individuals could be as high as 85%. Ancient DNA from a true, pure Population Y genome is the only way that this mystery in genetic archaeology may be solved.

Question 34

The Na-Dene-Yeniseian Connection

Answer 34

In 2008, linguist Edward Vajda proposed a connection between the Na-Dene languages and the Yeniseian languages, an old language family of central Siberia from which few spoken languages survive today.

Question 35

Paleo-Eskimos

Answer 35

Population which migrated into northern North America after the First Americans and contributed the remaining ancestry to Eskimo-Aleuts and Na-Dene speakers. This migration occurred ~5,000 y.a. and introduced the first archery equipment into the Americas, along with new stone tools.

Question 36

Chukchi

Answer 36

A population of far northeastern Siberia which harbor ~40% First American ancestry and are closer-related to some Native Americans with full First American ancestry than to others.

This indicates that the Chukchi represent back-migration from the Americas to Asia.

Question 37

Southern Route Hypothesis

Answer 37

Notion that East Asia was first populated by migrants that left Africa before fifty thousand years ago and traveled along the Indian Ocean coast, leaving descendants in Australia, New Guinea, the Philippines, Malaysia, and the Andaman Islands. This model was supported by the first ancient DNA evidence, but this initial evidence did not account for ancestry derived from Denosivans, making it misleading.

Question 38

Major Australasian-European Population Splits

Answer 38

-insert image-

By this model, in opposition to the Southern Route Hypothesis, East Asians and indigenous Australasians are descendant from the same Out-of-Africa migration ~50,000 y.a. as ancient European hunter-gatherers and modern Europeans.

Question 39

Yangtze River Ghost Populaton

Answer 39

Detectable as a homogeneous ancestral population in Southeast Asian and Taiwanese genomes, but no longer exists in an unmixed form. This genetic signature overlaps strongly with regions where rice farming expanded from the Yangtze River Basin, where it was invented ~9,000 y.a. This population appears to have spread rice farming as well as Austroasiatic languages, Austronesian languages, and Tai-Kadai languages.

Question 40

Yellow River Ghost Population

Answer 40

Just like the Yangtze River Ghost Population, this population is detectable as a distinct homogeneous ancestor to the Han Chinese. The Yellow River Huaxia tribes developed agriculture contemporaneously with but independent of the Yangtze River population. They spread non-rice agriculture in China and Tibet, and spoke Sino-Tibetan languages.

Question 41

The Han Cline

Answer 41

The present day region between the Yellow River in the North and the Yangtze River in the South displays a genomic gradient of Yellow River and Yangtze River Ghost ancestry.

Surrounding areas, such as Tibet, display similar gradients which are admixtures with indigenous hunter-gatherer genomes.

Question 42

Papuan Ancestry in Oceania

Answer 42

Today, all Pacific islanders east of New Guinea have at least 25% Papuan ancestry, up to 90%. However, the earliest inhabitants of these islands, the Lapita pottery culture, had little or no Papuan ancestry. Only later cultures, such as the Vantu culture, displayed Papuan ancestry, reflecting a second migration at least 2,400 years ago. The current model reflects at least 3 distinct waves of migration: The first wave spread East Asian ancestry and the Latpita culture, while the latter two spread two distinct types of Papuan ancestry.

Question 43

Genetic Diversity in Africa

Answer 43

African genome sequences are about a third more diverse than non-African ones due to Out-of-Africa migration bottlenecks. Some pairs of African populations have been isolated for up to four times as long as any pair of populations outside of the continent.

Question 44

The Bantu Expansion

Answer 44

Genomic and linguistic evidence is consistent with the expansion of a proto-Bantu-speaking population South of Cameroon, across Central Africa, and down the Swahili Coast to South Africa, around ~4,000 y.a. It is likely that this expansion was largely due to innovations in agriculture which are known to have originated near Cameroon at this time, and subsequently spread across Africa.

Question 45

The Nilo-Saharan Expansion

Answer 45

Prior to and contemporaneously with the Bantu Expansion to the South, an expansion of Nilo-Saharan speakers spread the language group and cattle-herding techniques to the North as the Sahara desert grew. This expansion originated in the Sahel region, where the Southern border of the Sahara touches the Savannah. It began ~5,000 y.a. and was likely due to the immense success of this culture in braving the Sahara (i.e., the birth of the Saharan Coast trade).

Question 46

Afroasiatic Speakers

Answer 46

Afroasiatic languages contain many languages spoken in Ethiopia, but also a branch of Near Eastern languages including Arabic, Hebrew, and ancient Akkadian. This suggests migration or intermiing between Northeastern Africa and the Middle East, a theory supported by ancient DNA. Genomic evidence points to two waves of North and South migration from the Middle East into Africa, one ~10,000 y.a. and another by Iranian-related farmers ~5,000 y.a. There is as of yet no evidence of South to North migration.

Question 47

Khoe-Kwadi Expansion

Answer 47

These languages arose in Southern Africa and are characterized by click sounds. Based on shared words for herding, it is hypothesized that these languages were brought to South Africa from East Africa by cattle herders ~1,800 y.a. Major genetic contributions by East Africans to this population supports this theory.

Question 48

Tanzanian Herders

Answer 48

Khoe-Kwadi speakers share a disproportionate amount of ancestry with Ethiopians compared to the East African populations they supposedly descend from. This hints at the existence of a ghost population of herders.

Further evidence, including the discovery of a Tanzanian Herder genome in a skeleton of a young girl in Tanzania, demonstrated that this population carried Near Eastern ancestry from mixture with the Afroasiatic speakers in Ethiopia down to Southern Africa, mixing with the East Africans along the way. The discovery of ancient DNA containing 1/3 Tanzanian Herder ancestry and 2/3 San hunter-gatherer ancestry in South Africa strongly supports this theory.

Question 49

The Ari

Answer 49

Most of the present-day population structure of Africa is the result of agriculture-driven expansions in the last few thousand years. However, some highly endogamous populations have survived this period without mixture, shedding light on the previous population structure of Africa.

Many of these populations exist in Ethiopia’s caste, the Ari being the most unchanged population known to the world and having survived without interbreeding significantly for at least the last ~4,500 years. By contrast, the oldest Indian endogamous populations only go back ~2,100 years.

Question 50

East African Forager Ghost Population

Answer 50

Ghost population which once dominated the Swahili Coast, but was largely displaced by the expansion of agriculturalists. This population contributed large amounts of ancestry to the present-day Hadza people of Tanzania, and was more closely related to today’s non-Africans than today’s sub-Saharan Africans. This suggests that this may have been the population which expanded Out-of-Africa ~50,000 y.a. and gave rise to the first populations of Homo sapiens outside of the African continent.

This group gave rise not only to the Hadza, but also to a forager group which once spanned ancient Ethiopia and Lenya, and another which once spanned the Zanzibar Archipelago and Malawi.

Question 51

South African Forager Ghost Population

Answer 51

Ghost population which contained two highly divergent lineages that separated from one another ~20,000 y.a. Modern peoples with South African Forager ancestry are almost entirely restricted to South Africa, contributing most of the ancestry of San hunter-gatherers and forming an important part of the ancestry of nearly all peoples that use languages with clicks.