Author | Spencer Wells |
---|---|
Country | United States |
Language | English |
Subject | Human evolutionary genetics |
Publisher | Princeton University Press |
Publication date | 2002 |
ISBN | 0-8129-7146-9 |
OCLC | 53287806 |
599.93/8 22 | |
LC Class | GN281 .W44 2003 |
The Journey of Man: A Genetic Odyssey is a 2002 book by Spencer Wells, an American geneticist and anthropologist, in which he uses techniques and theories of genetics and evolutionary biology to trace the geographical dispersal of early human migrations out of Africa. The book was made into a TV documentary in 2003. [1]
According to the recent single-origin hypothesis, human ancestors originated in Africa, and eventually made their way out to the rest of the world. Analysis of the Y chromosome is one of the methods used in tracing the history of early humans. Thirteen genetic markers on the Y-chromosome differentiate populations of human beings.
It is believed, on the basis of genetic evidence, that all human beings in existence now descend from one single man who lived in Africa about 60,000 years ago. [2] The earliest groups of humans are believed to find their present-day descendants among the San people, a group that is now found in western southern Africa. The San are smaller than the Bantu. They have lighter skins, more tightly curled hair, and they share the epicanthal fold with the people of Central and South East Asia.
Southern and eastern Africa are believed to originally have been populated by people akin to the San. Since that early time much of their range has been taken over by the Bantu. Skeletal remains of these ancestral people are found in Paleolithic sites in Somalia and Ethiopia. There are also peoples in east Africa today who speak substantially different languages that nevertheless share the archaic characteristics of the San language, with its distinctive repertoire of click and pop sounds. These are the only languages in the entire world that use these sounds in speech.
As humans migrated out of Africa, they all carried a genetic marker on the Y chromosome known as M168 (Haplogroup CT (Y-DNA)). [3]
The first wave of migration out of Africa stayed close to the oceans shores, tracing a band along the coastal areas of the Indian Ocean including parts of the Arabian Peninsula, the Middle East, the Indian subcontinent and into South East Asia, down into what is now Indonesia, and eventually reaching Australia. This branch of the human family developed a new marker M130 (Haplogroup C (Y-DNA)).
This first wave appears to have left dark-skinned people along its path, including isolated groups of dark-skinned people in south east Asia such as the aboriginal population of the Andaman Islands (around 400 km off the west coast of Thailand), the Semang of Malaysia, and the Aeta of the Philippines. [4]
The second wave of migration took a more northerly course, splitting somewhere in the area around what is now called Syria to sweep to interior Asia, where it split several more times in Central Asia, north of Afghanistan. The lineages that flowed into Central Asia carry M9 (Haplogroup K (Y-DNA)). Other markers were added after the migration paths went on in several different directions from Central Asia.
From Central Asia, a small group migrated towards the northeast, following reindeer. These were the ancestors of Siberian groups such as the Chukchi people, a few of whom still live a nomadic lifestyle today. An even smaller group, estimated at no more than 20, crossed what is now the Bering Sea approximately 15,000 years ago during the last glacial period, and migrated into North America. They are the ancestors of Native Americans, and 800 years later, they had reached as far as South America.
The African diaspora is believed to have begun some 50,000 years ago, long enough for many changes to have occurred in humans remaining in Africa. The genetic trends reported involve humans who left Africa, and their genetic histories. The diversity found outside of Africa may well have been accentuated since populations migrating to new hunting grounds would rarely have had individuals moving backwards into previously settled regions. But within Africa, isolation would have been geographically aided primarily by the Sahara Desert, leaving people in areas not separated by the desert to travel and migrate relatively freely.
In human genetics, the Y-chromosomal most recent common ancestor is the patrilineal most recent common ancestor (MRCA) from whom all currently living humans are descended. He is the most recent male from whom all living humans are descended through an unbroken line of their male ancestors. The term Y-MRCA reflects the fact that the Y chromosomes of all currently living human males are directly derived from the Y chromosome of this remote ancestor. The analogous concept of the matrilineal most recent common ancestor is known as "Mitochondrial Eve", the most recent woman from whom all living humans are descended matrilineally. As with "Mitochondrial Eve", the title of "Y-chromosomal Adam" is not permanently fixed to a single individual, but can advance over the course of human history as paternal lineages become extinct.
Genetic genealogy is the use of genealogical DNA tests, i.e., DNA profiling and DNA testing, in combination with traditional genealogical methods, to infer genetic relationships between individuals. This application of genetics came to be used by family historians in the 21st century, as DNA tests became affordable. The tests have been promoted by amateur groups, such as surname study groups or regional genealogical groups, as well as research projects such as the Genographic Project.
Spencer Wells is an American geneticist, anthropologist, author and entrepreneur. He co-hosts The Insight podcast with Razib Khan. Wells led The Genographic Project from 2005 to 2015, as an Explorer-in-Residence at the National Geographic Society, and is the founder and executive director of personal genomics nonprofit The Insitome Institute.
A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism mutation. More specifically, a haplogroup is a combination of alleles at different chromosomal regions that are closely linked and that tend to be inherited together. As a haplogroup consists of similar haplotypes, it is usually possible to predict a haplogroup from haplotypes. Haplogroups pertain to a single line of descent. As such, membership of a haplogroup, by any individual, relies on a relatively small proportion of the genetic material possessed by that individual.
Genetics and archaeogenetics of South Asia is the study of the genetics and archaeogenetics of the ethnic groups of South Asia. It aims at uncovering these groups' genetic history. The geographic position of South Asia makes its biodiversity important for the study of the early dispersal of anatomically modern humans across Asia.
Haplogroup A is a human Y-chromosome DNA haplogroup, which includes all living human Y chromosomes. Bearers of extant sub-clades of haplogroup A are almost exclusively found in Africa, in contrast with haplogroup BT, bearers of which participated in the Out of Africa migration of anatomically modern humans. The known branches of haplogroup A are A00, A0, A1a, and A1b1; these branches are only very distantly related, and are not more closely related to each other than they are to haplogroup BT.
Haplogroup D1 or D-M174 is a subclade of Haplogroup D-CTS3946. This male haplogroup is found primarily in East Asia and the Andaman Islands, though it is also found regularly with low frequency in Central Asia and Mainland Southeast Asia. It's also found as far as Europe and Middle east in lower frequencies.
Haplogroup E-M96 is a human Y-chromosome DNA haplogroup. It is one of the two main branches of the older and ancestral haplogroup DE, the other main branch being haplogroup D. The E-M96 clade is divided into two main subclades: the more common E-P147, and the less common E-M75.
Haplogroup E-V38, also known as E1b1a-V38, is a human Y-chromosome DNA haplogroup. E-V38 is primarily distributed in sub-Saharan Africa. E-V38 has two basal branches, E-M329 and E-M2. E-M329 is a subclade mostly found in East Africa. E-M2 is the predominant subclade in West Africa, Central Africa, Southern Africa, and the region of African Great Lakes; it also occurs at moderate frequencies in some parts of North Africa, West Asia, and Southern Europe.
Haplogroup K or K-M9 is a human Y-chromosome DNA haplogroup. A sublineage of haplogroup IJK, K-M9, and its descendant clades represent a geographically widespread and diverse haplogroup. The lineages have long been found among males on every continent except Antarctica.
Haplogroup Q-M3 (Y-DNA) is a Y-chromosome DNA haplogroup. Haplogroup Q-M3 is a subclade of Haplogroup Q-L54. Haplogroup Q-M3 was previously known as Haplogroup Q3; currently Q-M3 is Q1b1a1a below Q1b-M346.
In human genetics, a human Y-chromosome DNA haplogroup is a haplogroup defined by mutations in the non-recombining portions of DNA from the male-specific Y chromosome. Many people within a haplogroup share similar numbers of short tandem repeats (STRs) and types of mutations called single-nucleotide polymorphisms (SNPs).
Haplogroup DE is a human Y-chromosome DNA haplogroup. It is defined by the single nucleotide polymorphism (SNP) mutations, or UEPs, M1(YAP), M145(P205), M203, P144, P153, P165, P167, P183. DE is unique because it is distributed in several geographically distinct clusters. An immediate subclade, haplogroup D, is mainly found in East Asia, parts of Central Asia, and the Andaman Islands, but also sporadically in West Africa and West Asia. The other immediate subclade, haplogroup E, is common in Africa, and to a lesser extent the Middle East and southern Europe.
In the context of the recent African origin of modern humans, the Southern Dispersal scenario refers to the early migration along the southern coast of Asia, from the Arabian Peninsula via Persia and India to Southeast Asia and Oceania. Alternative names include the "southern coastal route" or "rapid coastal settlement", with later descendants of those migrations eventually colonizing the rest of Eurasia, the remainder of Oceania, and the Americas.
In human population genetics, Y-Chromosome haplogroups define the major lineages of direct paternal (male) lines back to a shared common ancestor in Africa. Men in the same haplogroup share a set of differences, or markers, on their Y-Chromosome, which distinguish them from men in other haplogroups. These UEPs, or markers used to define haplogroups, are SNP mutations. Y-Chromosome Haplogroups all form "family trees" or "phylogenies", with both branches or sub-clades diverging from a common haplogroup ancestor, and also with all haplogroups themselves linked into one family tree which traces back ultimately to the most recent shared male line ancestor of all men alive today, called in popular science Y Chromosome Adam.
In paleoanthropology, the recent African origin of modern humans is the dominant model of the geographic origin and early migration of anatomically modern humans. It follows the early expansions of hominins out of Africa, accomplished by Homo erectus and then Homo neanderthalensis.
The proportions of various human Y-DNA haplogroups vary significantly from one ethnic or language group to another in Africa.
Haplogroup A-L1085, also known as haplogroup A0-T is a human Y-DNA haplogroup. It is part of the paternal lineage of almost all humans alive today. The SNP L1085 has played two roles in population genetics: firstly, most Y-DNA haplogroups have diverged from it and; secondly, it defines the undiverged basal clade A-L1085*.
Haplogroup E-M2, also known as E1b1a1-M2, is a human Y-chromosome DNA haplogroup. E-M2 is primarily distributed within sub-Saharan Africa. More specifically, E-M2 is the predominant subclade in West Africa, Central Africa, Southern Africa, and the region of the African Great Lakes; it also occurs at moderate frequencies in North Africa and Middle East. E-M2 has several subclades, but many of these subhaplogroups are included in either E-L485 or E-U175. E-M2 is especially common among indigenous Africans who speak Niger-Congo languages, and was spread to Southern Africa and East Africa through the Bantu expansion.
The genetic history of Africa is composed of the overall genetic history of African populations in Africa, including the regional genetic histories of North Africa, West Africa, East Africa, Central Africa, and Southern Africa, as well as the recent origin of modern humans in Africa. The Sahara served as a trans-regional passageway and place of dwelling for people in Africa during various humid phases and periods throughout the history of Africa.