(I) Origin of Present-Day Europeans (and Especially Britons)

choi

, from Harvard Professor Reich's Viewpoints.


(1) Years ago I chanced upon two Nature journals, read them, learned about David Reich for the first time, and read his article in one journal plus, in a later journal, a commentary in a segment called "News Feature":
(a) Ewen Callaway, Divided by DNA: The Uneasy Relationship Between Archaeology and Ancient Genomics; Two fields in the midst of a technological revolution are struggling to reconcile their views of the past. Nature, 555: 573 (Mar 23, 2018’ under the heading "News Feature").
https://www.nature.com/articles/d41586-018-03773-6

Note:
(i) News Feature is contributed by reporters with bachelor's degrees (in biology or science) – not bu researchers doing bench work.
(ii) "Thirty kilometres north of Stonehenge, through the rolling countryside of southwest England, stands a less-famous window into Neolithic Britain. Established around 3600 BC by early farming communities, the West Kennet long barrow is an earthen mound with five chambers, adorned with giant stone slabs. At first, it served as a tomb for some three dozen men, women and children. But people continued to visit for more than 1,000 years, filling the chambers with relics such as pottery and beads that have been interpreted as tributes to ancestors or gods.  The artefacts offer a view of those visitors and their relationship with the wider world. Changes in pottery styles there sometimes echoed distant trends in continental Europe, such as the appearance of bell-shaped beakers * * * "
(A) West Kennet Long Barrow
https://en.wikipedia.org/wiki/West_Kennet_Long_Barrow
(a long barrow near the village of Avebury in central Wiltshire’ table: UNESCO World Heritage Site)
• It is unclear how the site got its name West Kennet. "West Kennet long barrow * * * sits along a ridge overlooking the River Kennet": Digital Digging (Diggitaldigging.com; by Tim Darvill on Jan 12, 2013). Google Maps shows River Kennet runs west to east  straight 1,000 feet north of West Kennet Long Barrow.
• Emphasis here is on the earthen mound, not the boulders surrounding (or inside) it.
• Entrance to West Kennet Long Barrow, Avebury, Wiltshire, England UK, undated (Image ID:AF5D2M).
https://www.alamy.com/stock-phot ... nd-uk-13837291.html
West Kennet Barrow. August 1997
http://www.stone-circles.org.uk/stone/westkennetbarrow.htm
(sketch caption: "Plan of West Kennet Long Barrow (after Darville)")

The "quarry ditches” suggest that boulders were quarried by the Long Barrow.
(B) barrow can be a wheelbarrow or
(n; etymology): "a burial mound"
https://www.lexico.com/definition/barrow


(ii) "Changes in pottery styles there sometimes echoed distant trends in continental Europe, such as the appearance of bell-shaped beakers — a connection that signals the arrival of new ideas and people in Britain. But many archaeologists think these material shifts meshed into a generally stable culture that continued to follow its traditions for centuries.  'The ways in which people are doing things are the same. They're just using different material culture — different pots,' says [archeologist] Neil Carlin at University College Dublin, who studies Ireland and Britain’s transition from the Neolithic into the Copper and Bronze Ages.  But last year, reports started circulating that seemed to challenge this picture of stability. A study1 analysing genome-wide data from 170 ancient Europeans, including 100 associated with Bell Beaker-style artefacts, suggested that the people who had built the barrow and buried their dead there had all but vanished by 2000 BC. The genetic ancestry of Neolithic Britons, according to the study, was almost entirely displaced. Yet somehow the new arrivals carried on with many of the Britons’ traditions. 'That didn't fit for me,' says Carlin, who has been struggling to reconcile his research with the DNA findings.  The Bell Beaker 'bombshell' study appeared in Nature2 in February and included 230 more samples, to make it the largest ancient-genome study on record. But it is just the latest example of the disruptive influence that genetics has had on the study of the human past. Since 2010, when the first ancient-human genome was fully sequenced3, researchers have amassed data on more than 1,300 individuals * * * "
(A) Bell Beaker culture
https://en.wikipedia.org/wiki/Bell_Beaker_culture  
("Arising from around 2800 BC, it lasted in Britain until as late as 1800 BC but in continental Europe only until 2300 BC")

A bell beaker is a kind of beaker (archaeology).
https://en.wikipedia.org/wiki/Beaker_(archaeology)
(B)
• Reference 1 was a mere (online; "Posted May 09, 2017") preprint of Reference 2.
• Reference 2 was Olalde I et al, Nature 555: 190 (2018).
• Reference 3 was
Rasmussen M et al, Ancient Human Genome Sequence of an Extinct Palaeo-Eskimo. Nature 463: 757 (2010).
https://www.nature.com/articles/nature08835.pdf

The first and last author (Eske WILLERSLEV) were affiliated with Natural History Museum of Denmark, University of Denmark and Sino-Danish Genomics Center, BGI-Shenzhen.

introduction: "Presently no genome from an ancient human has been published, the closest being two data sets representing a few megabases (Mb) of DNA from a single Neanderthal. * * * In 2008 we used permafrost-preserved hair from one of the earliest individuals that settled in the New World Arctic (northern Alaska, Canada and Greenland) belonging to the Saqqaq Culture (a component of the Arctic Small Tool tradition; approximately 4,750–2,500 14C years before present (yr BP)) to generate the first complete ancient human mitochondrial DNA (mtDNA) genome. * * *" (footnotes omitted).

material and methods: "The specimen used for genomic sequencing is the largest (approximately 15 X 10 cm) of four human hair tufts excavated directly from culturally deposited permafrozen sediments at Qeqertasussuk[Greenland, Denmark].
(iii) The News Feature" of Nature contains a diagram, where a box stated, "A 4,500-year-old skeleton from a cave in Ethiopia provided the first ancient-human genome sequence from Africa, providing context on movements back from Eueasia. Scientists expect many more examples from Africa this year."

Karen Kaplan, DNA from 4,500-Year-Old Ethiopian Reveals Surprise About Ancestry of Africans. Los Angeles Times, Oct 8, 2015
https://www.latimes.com/science/ ... 20151008-story.html
(reporting Gallego Llorente M et al, Ancient Ethiopian Genome Reveals Extensive Eurasian Admixture in Eastern Africa. Science 350: 820 (Oct 8, 2015)
https://www.science.org/doi/10.1126/science.aad2879
)

For LBK, see Linear Pottery culture
https://en.wikipedia.org/wiki/Linear_Pottery_culture   (is abbreviated as LBK
(from German: Linearbandkeramik); section 1 Name)
But you need not dwell on it. The focus will be on the British Isles, for me at least.

choi

(b) Olalde I (first author) * * * Reich D (last author), The Beaker Phenomenon and the Genomic Transformation of Northwest Europe. Nature 555: 190 (Feb 21, 2018).
https://www.nature.com/articles/nature25738
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973796/

Abstract: "Bell Beaker pottery spread across western and central Europe beginning around 2750 BCE [Before Common Era and Common Era (CE) is the secular counterparts to BC and AD respectively] before disappearing between 2200–1800 BCE. The forces propelling its expansion are a matter of long-standing debate, with support for both cultural diffusion and migration. We present new genome-wide data from 400 Neolithic, Copper Age and Bronze Age Europeans, including 226 Beaker-associated individuals. We detected limited genetic affinity between Iberian and central European Beaker-associated individuals, and thus exclude migration as a significant mechanism of spread between these two regions. However, migration played a key role in the further dissemination of the Beaker Complex, a phenomenon we document most clearly in Britain, where the spread of the Beaker Complex introduced high levels of Steppe-related ancestry and was associated with a replacement of ~90% of Britain’s gene pool within a few hundred years, continuing the east-to-west expansion that had brought Steppe-related ancestry into central and northern Europe 400 years earlier.

introduction: "During the third millennium Before the Common Era (BCE), two new archaeological pottery styles expanded across Europe, replacing many of the more localized styles that preceded them. The ‘Corded Ware Complex’ in north-central and northeastern Europe was associated with people who derived most of their ancestry from populations related to Early Bronze Age Yamnaya pastoralists from the Eurasian steppe (henceforth referred to as Steppe). In western Europe there was the equally expansive 'Bell Beaker Complex' * * * A major debate in archaeology has revolved around the question of whether the spread of the Beaker Complex was mediated by the movement of people, culture, or a combination of both. Genome-wide data have revealed high proportions of Steppe-related ancestry in Beaker Complex-associated individuals from Germany and the Czech Republic, showing that they derived from mixtures of populations from the Steppe and the preceding Neolithic [Anatolian] farmers of Europe. * * *" (footnotes omitted).

Note:
(i) I will explain in another posting, For now, you need to learn only Steppe pastoralists (the two words are interchangeable) are distinct from Iranian farmers (again, (the two words are interchangeable).
(ii) Please read text and view Fig 3 in the section whose heading is Nearly complete turnover of ancestry in Britain/

I did not read references of (1)(a); I had not heard of bell beaker. But to say there was an almost turnover of British residents sound heretical to me, not just nonsensical. I mean, how?  Immigrants or migrants are small in numbers, unable to transport heavy weapons. And where are mass graves?
(iii) This got me to think a lot, including
• who lived in England before Anglo-Saxons arrived?  See Anglo-Saxons
https://en.wikipedia.org/wiki/Anglo-Saxons
(section 2 Early Anglo-Saxon history (410–660) AND section 2.1 Migration (410–560) )
• who were Celts? I live in Boston, which has a NBA team named Celtic.
• Was there no written language in Britain before Anglo-Saxon arrival?  The answer is no. Anglo-Saxons brought Old English (Germanic) with them. I asked around and Americans say they were not taught in schools who were there prior to Anglo-Saxons, whether or when Celts were in England. Nor could I find scientific reports on these topics (until a month ago, see (3)).
(iii) So I was very skeptical about Dr David Reich, whose stories have a lot of holes. Even Dr Reich acknowledged his stories have a lot of holes: His book theorized "ghost populations" to  explain his DNA data. As years pass, some of his ghost populations were confirmed with new DNA data from bones that were not part of previous studies.
(iv) His book will be discussed in Part II.