The Invisible History of the Human Race (43 page)

women born in the new
:
It is important to keep in mind, though, that these effects, like Nunn’s trust effect and Voigtlander and Voth’s legacy of hate, are probabilistic: There is no guarantee they will have an impact. There is no way to determine which child from which family will do what his grandparents did or think what his grandparents thought.

“careful in dealing with people?”
:
G. Tabellini, “
Culture and Institutions: Economic Development in the Regions of Europe,”
Journal of the European Economic Association
8, no. 4 (2010): 677–716.

as well as poorer economies
:
Another intuitive but actually never-before-measured observation that resulted from Nunn’s analysis was the distinct geographical correlates of trust in Africa today: The closer people live to the coast, the less trusting they are. Why would this be so? Is there a relevant factor in the climate of inland Africa? Do the vagaries of fishing make you more cautious than you might be otherwise? Nunn and his colleagues looked for similar connections between coastlines and distrust in Asia and Europe, but they could find no comparable relationship.

In most parts of the world rugged, mountainous landscapes tend to be less economically successful than flatlands. It’s harder to transport goods through hilly areas. The steeper a slope is, the more erosion is a problem. Watering crops is much more difficult on a slope because it’s harder to control water on a hill than it is on level ground. It can simply require more effort, too, for people merely to live in this kind of landscape, let alone to harvest food or goods from it. Flatter landscapes tend to be cheaper and physically easier to farm and to move about in general. Nunn cited a report from the Food and Agriculture Organization of the United Nations that found that if a slope is greater than two degrees, then it costs more to farm it than it’s worth. If it’s greater than six degrees, it’s not even possible to farm. Yet today in Africa, uniquely in the world, challenging landscapes have better economies. It turns out that the way trust is mapped over the African continent was also shaped by the slave trade. Before 1900, the closer you were to the coast, the more likely it was that you, your parents, and your parents’ parents had been exposed in one way or another to the horror of the trade. The farther people lived from the coast, the less likely it was that they were taken as slaves. N. Nunn and D. Puga, “Ruggedness: The Blessing of Bad Geography in Africa,”
Review of Economics and Statistics
94, no. 1 (2012): 20–36.

Chapter 8: The Small Grains of History

it’s quite close to it
:
S. Leslie, et al., “Fine Scale Genetic Structure of the British Population.” Manuscript submitted for publication, 2014.

“their favorite gene”
:
Quotes from Peter Donnelly in this chapter are from my interviews with him.

“Now we know that”
:
Quotes from Stephen Leslie in this chapter are from my interviews with him.

population genetics and statistics
:
Most geneticists know of Fisher only as a key figure in modern genetics, while most statisticians know of him only as a key figure in statistics.

more than two thousand genomes
:
This was the number after ruling out people who were actually related to one another.

“It was absolutely staggering”
:
Quotes from Sir Walter Bodmer in this chapter are from my interviews with him.

“I had naively expected”
:
Quotes from Mark Robinson in this chapter are from my interviews with him.

produced in Roman times
:
If fourth-century Saxons invaded England today, stomped on all the cell phones, killed the engineers, and shut down the ports, how many generations would it take before stories about a small, flat object that carried people’s voices in it were considered a myth?

Chapter 9: DNA + Culture

“He has some very exciting news”
:
Quotes from Thomas Robinson in this chapter are from my interviews with him.

have had such an effect
:
J. Pongratz, et al., “Coupled Climate—Carbon Simulations Indicate Minor Global Effects of Wars and Epidemics on Atmospheric CO2 between AD 800 and 1850,”
Holocene
21, no. 5 (2011): 843–51.

the ancient Mongolian empire
:
T. Zerjal, et al., “The Genetic Legacy
of the Mongols,”
American Journal of Human Genetics
72, no. 3 (2003):
717–21.

“
Most of the direct descendants”
:
S. Cauchi, “Descendants of Darwin Evolve into Guardians of the Wilderness,”
Age
, November 29, 2009, available at http://www.theage.com.au/national/descendants-of-darwin-evolve-into
-guardians-of-the-wilderness-20091128-jy10.html.

eight hundred or so years
:
When does the copying take place? When men and women copy their chromosomes into sex cells, the sperm and the egg. But they copy only half of their full set into each cell, twenty-three each, so that when sperm and egg get together, they make a full human complement.

“It was a hellish time”
:
Quotes from Donald MacLaren in this chapter are from my interviews with him.

“We beat on FT DNA to give us more”
:
Quotes from Robert McLaren in this chapter are from my interviews with him.

“an old Scottish lineage”
:
Inheritance was not always passed directly down a single line from father to son to grandson to great-grandson. The clan leadership could pass down the male line through brothers and to their sons. But it’s still the same Y chromosome. Two brothers will have the same Y as their father, and they will pass that Y on to their sons.

Johns, originated this way
:
M. A. Jobling, “In the Name of the Father: Surnames and Genetics,”
TRENDS in Genetics
17, no. 6 (2001): 353–57. Much of my data about British surnames, as well as the general principles, comes from interviews with Turi King and Kevin Schurer and from T. E. King and M. A. Jobling, “What’s in a Name? Y Chromosomes, Surnames and the Genetic Genealogy Revolution,”
TRENDS in Genetics
25, no. 8 (2009): 351–60; and T. E. King and M. A. Jobling, “Founders, Drift, and Infidelity: The Relationship Between Y Chromosome Diversity and Patrilineal Surnames,”
Molecular Biology and Evolution
26, no. 5 (2009): 1093–1102.

not the rules of language
:
F. Manni, W. Heeringa, and J. Nerbonne, “To What Extent are Surnames Words? Comparing Geographic Patterns of Surname and Dialect Variation in the Netherlands,”
Literary and Linguistic Computing
21, no. 4 (2006): 507–27.

Y in this population
:
G. R. Bowden, et al., “Excavating Past Population Structures by Surname-Based Sampling: The Genetic Legacy of the Vikings in Northwest England,”
Molecular Biology and Evolution
25, no. 2 (2008): 301–9.

non-Catholic fifth-century warlord
:
My information about the Irish Y, Lord Turlough, and Irish names comes primarily from B. McEvoy and D. Bradley, “Y-Chromosomes and the Extent of Patrilineal Ancestry in Irish Surnames,”
Human Genetics
119, no. 1 (2006): 212–19; and L. T. Moore, et al., “A Y-Chromosome Signature of Hegemony in Gaelic Ireland,”
American Jo
ur
nal of Human Genetics
78, no. 2 (2006): 334–38.

the rule does not apply
:
T. E. King, et al., “Genetic Signatures of Coancestry Within Surnames,”
Current Biology
16, no. 4 (2006): 384–88.

“genealogy, genetics, and
 . . . pure dumb luck”:
Quotes from Glynis McHargue Patterson in this chapter are from my interviews with her.

enough to discredit all documentation
:
Note that the average nonpaternity figure will differ in different eras and within different populations, social classes, or castes.

Chapter 10: Chunks of DNA

“Is this Scott Woodward?”
:
Quotes from Scott Woodward in this chapter are from my interview with him.

just a few years ago
:
Even after development of the Family Tree DNA test that looked at sixty-seven segments on the Y chromosome, many academic studies of the Y chromosome examined only seventeen segments.

not at research facilities
:
A. Congiu, et al., “Online Databases for mtDNA and Y Chromosome Polymorphisms in Human Populations,”
Journal of Anthropological Sciences
90 (2012): 197–212.

“It’s pretty boring”
:
Quotes from Bennett Greenspan in this chapter are from my interviews with him.

“an incredibly strong woman”
:
Quotes from Blaine Bettinger in this chapter are from my interviews with him.

“Little did I know, it’s addicting”
:
Quotes from CeCe Moore in this chapter are from my interviews with her.

networks have changed through time
:
P. Ralph and G. Coop, “The Geography of Recent Genetic Ancestry Across Europe,”
PLoS
Biology
11, no. 5 (2013): e1001555.

second to ninth cousins
:
B. M. Henn, et al., “Cryptic Distant Relatives Are Common in Both Isolated and Cosmopolitan Genetic Samples,”
PLoS ONE
7, no. 4 (2012): e34267.

throughout my genealogical tree
:
If I set up one of my sisters’ genomes and tracked it back up the table next to mine, some of the chunks that my mother passed on to me would overlap considerably with the chunks she passed down to my sister. Yet so random is the distribution of DNA through the generations that, according to Ralph and Coop, we may share no DNA with a number of our fourth cousins. It’s possible, though less likely, that we won’t share any DNA with some third cousins. In fact, technically it’s possible that we have no DNA from one of our grandparents, but, according to Ralph, the chance of that happening is roughly one in ten trillion. See also R. Khan, “Which Grandparent Are You Most Related To?”
Slate
, October 18, 2013, available at http://www
.slate.com/articles/health_and_science/human_genome/2013/10/analyze
_your_child_s_dna_which_grandparents_are_most_genetically_related.html.

“It took us a while”
:
Quotes from Peter Ralph in this chapter are from my interviews with him.

1,000 and 1,500 years ago
:
Ralph’s exercise made me wonder what would happen if I traced my genome back through, say, fifty thousand years. In a nutshell, it would be very disintegrated and widely spread. But what if we started from that point fifty thousand years ago and then asked: What are the odds that all those minuscule bits that are spread all over humanity will come together to form a single genome in fifty thousand years? Calculating that is pretty much impossible. Yet somehow it happened.

This has implications for the genetic databases
:
Even though sharing a common segment with someone doesn’t necessarily mean you have inherited that block from a relatively recent common ancestor, it is often the case that when genetic genealogy companies help customers with shared DNA hook their genealogical trees together, they do find a distant shared cousin from, say, six generations ago. What is the likelihood in this case that the shared block comes not from a shared fourth-great-grandparent but in fact from someone much further back along a different route through the genealogical tree? According to Ralph, the chance of two people sharing a block from a sixth-generation ancestor is close to one, so the chance of the shared block coming from an identified ancestor is pretty high. Yet it is still possible that those two people also share a block that doesn’t come from that ancestor. “If the known ancestor was Charlemagne,” Ralph explained, “the chance that you both inherited blocks from him is pretty small, so the block is probably not from him, especially given the huge number of unknown relatives you share from the time of Charlemagne.”

contributed nothing to you genetically
:
The effect was first pointed out to Patterson by Oxford professor Jotun Hein in 2004. See D. L. Rohde, S. Olson, and J. T. Chang, “Modelling the Recent Common Ancestry of All Living Humans,”
Nature
431, no. 7008 (2004): 562–66.

“Northern Italy had the tradition”
:
Quotes from Guido Tabellini in this chapter are from my interview with him.

Chapter 11: The Politics of DNA

“an intimate and loving relationship”
:
G. Wood, “The Sally Hemings Case,” Barbara Chase-Riboud, reply by Gordon S Wood,
New York Review of Books
, June 12, 1997, available at http://www.nybooks.com/articles/archives/1997/jun/12/the-sally-hemings-case/. Note that in a May 2013
New York Review of Books
article, Wood praised Gordon-Reed’s acute and correct analysis.

match the Hemings Y
:
E. A. Foster, et al., “Jefferson Fathered Slave’s Last Child,”
Nature
396, no. 6707 (1998): 27–28.

deny the Jefferson/Hemings link
:
E. S. Lander and J. J. Ellis, “Founding Father,”
Nature
396, no. 6707 (1998): 13–14.