SCIENCE science.org 18 FEBRUARY 2022 • VOL 375 ISSUE 6582 727PHOTO: JIM WILSON/
THE NEW YORK TIMES
/ R E D U X
By Anne C. StoneT
he story of humankind’s journey out
of Africa and across the globe is epic
and intricate. In Origin: A Genetic
History of the Americas, anthropo-
logical geneticist Jennifer Raff offers
a sometimes personal account of how
scientists have tried to reconstruct the por-
tion of this story that deals with the first
peopling of the Americas, revealing the suc-
cesses and failures that have accompanied
our efforts to understand this phenomenon
along with some questions that still remain.
Raff ’s book is divided into three parts that
give insight into the complexities of both
science and human history. In the first sec-
tion, she discusses the history of attempts
by European colonists and early scientists
to understand how people came to be in the
Americas and reveals why these often-racist
perspectives have understandably left many
Native Americans hesitant to participate
in scientific research today. Here, she also
clearly summarizes how we know what we
know about early people in the Americas,
reporting some of the relevant archaeo-
logical, linguistic, and morphological find-ings and describing results from some of
the first genetic studies that have brought
new insights to debates over the timing and
number of migrations, as well as the routes
of entry into the Americas.
People first entered the Americas during
the Late Pleistocene via Beringia, a region
that includes part of northeastern Siberia
and Alaska and the (now submerged) land
bridge connecting them. Raff dis-
cusses how they may have moved
farther into North America, ei-
ther by navigating through the
massive Laurentide and Cordil-
leran ice sheets via an “ice-free
corridor” that opened ~14,000
years ago or by traveling around
the ice sheets using watercraft on
a coastal “kelp highway” (as well
as some other fringe ideas).
Raff also outlines the debate
surrounding the “Clovis First”
hypothesis, a once widely ac-
cepted theory positing that the first Ameri-
cans were large-game hunters who arrived
after the glaciers receded. (Spear points
used by the group were first identified near
Clovis, New Mexico.) Clovis First adherents
were highly critical of any archaeological
evidence that supported earlier occupa-
tions and only began to let go of this
theory when indisputable data emerged,including archaeological findings at the
Monte Verde site in Chile, which indicated
that humans were in the Americas at least
1300 years earlier than previously thought.
In the second section of the book, Raff
gives an overview of how ancient DNA
analyses are done and the questions that
they can be used to address. Here, she uses
a clever analogy, comparing the process of
entering the successive chambers of the sa-
cred cave Actun Tunichil Muknal in Belize
to the rituals she performs to maintain ste-
rility while carrying out her research. This
research uses genetics to answer questions
about the initial peopling of the Americas
and the subsequent population history of this
region, with a focus on understanding the
diversity and interactions among Inuit and
Aleut-speaking groups and their ancestors.
In this section, Raff also highlights the
importance of working with, and being
respectful of, descendant communities.
Such efforts are critical to repairing rela-
tionships between those who study ancient
humans and groups with special ties to an-
cient people.
In the book’s final section, Raff de-
scribes what recent ancient DNA research
has brought to scientific debates about the
peopling of the Americas. She explains,
for example, how ancient genomes reveal
links between ancient East Asians and
northern Siberians and modern Indige-
nous Americans. She also summarizes how
recent ancient genome research in the Arc-
tic and the Caribbean has illuminated our
understanding of population expansions,
interactions, and turnovers. In
the Arctic, for example, we now
know that Paleo-Inuit (Dorset)
and later Neo-Inuit (Thule)
populations interacted in some
areas while Paleo-Inuit were re-
placed in others.
Raff does not shy away from
discussing Indigenous critiques
and unease surrounding an-
cient DNA studies, describing
how genome data can be used
or perceived in ways that result
in social, legal, and political con-
sequences for individuals and communi-
ties. DNA testing might result in questions
about tribal membership, for example, or
in challenges to a community’s land claims.
She argues persuasively that ethical paleo-
genomic research should privilege Indig-
enous concerns and be collaborative. j10.1126/science.abn7262Alaska’s Bering Land Bridge National Preserve,
shown here, encompasses a portion of the land bridge
that once connected Asia and North America.The reviewer is at the School of Human Evolution and
Social Change, Institute of Human Origins, Arizona State
University, Tempe, AZ, USA. Email: [email protected]ANTHROPOLOGYAncient DNA sheds light on the peopling of the Americas
Genomes in motion
Origin:
A Genetic History
of the Americas
Jennifer Raff
Twelve, 2022. 368 pp.BOOKS et al.