SCIENCE science.org 3 JUNE 2022 • VOL 376 ISSUE 6597 1043
save both himself and humanity by under-
standing, evading, and stopping a powerful
force. But because the story is set against a
backdrop of technological issues with which
humanity is currently grappling, the book
engages readers in the way the best sci-fi
does: by asking us to reconcile this fictional
world with our own reality.
Despite its apocalyptic premise, Upgrade
manages to end in a way that offers both
hope and perspective. Crouch’s insights ap-
ply not only to his fictional story but also to
how we decide to address the issues that lie
between us and the future the book portrays.
Upgrade: A Novel, Blake Crouch, Ballantine Books,
2022, 352 pp.
The Rise and Reign
of the Mammals
Reviewed by Jerald Pinson^2
There are more than 6000 living species of
mammals inhabiting the planet’s continents
and oceans, and they come in a diversity of
forms. There are runners, diggers, swim-
mers, gliders, fliers, and hulking stompers.
But the mammals living today are a mere
fraction of the beasts that have already come
and gone.
It is hard to know where to start a book
about the origin of mammals, as the lines
that separate them from their relatives be-
come blurrier the farther back you travel in
time. In his new book, The Rise and Reign of
the Mammals, paleontologist Steve Brusatte
covers his bases by rewinding all the way to
the Carboniferous, some 325 million years
ago, when a small band of amphibian-like
organisms with watertight eggs became
geographically separated. This chance oc-
currence was a momentous evolutionary
event, as the descendants of these two
isolated animal groups would ultimately
inherit the Earth. Birds, reptiles, and di-
nosaurs evolved from one group and mam-
mals from the other.
Brusatte takes the reader on a whirlwind
tour of mammal evolution with a breezy nar-
rative that deftly navigates the path between
erudition and oversimplification. He begins
by covering key events in the evolution of
early mammal ancestors. These animals
shirked cold-bloodedness in favor of thermo-
regulation and had wandering jawbones that
transformed into sound-magnifying compo-
nents of early mammalian ears. A soft palate
grew to separate the mouth from the nasal
airways, allowing simultaneous eating and
breathing, and their teeth radiated into com-
plex forms that put just about any type of
food on the menu, from fibrous vegetation to
baby dinosaurs.The second half of the book focuses on
mammals that evolved after the extinction
of the dinosaurs, and it feels like a race to
the finish. Suddenly released from the con-
straints of their erstwhile predators and
competitors, mammals rapidly diversified.
Whereas the largest mammals known to co-
exist with dinosaurs could have fit snugly
in your lap, postdinosaur mammals bal-
looned into a menagerie of leviathan beasts
within just a few million years of the aster-
oid impact.
Much of the living history of land and
ocean environments has been written by
mammals. Brusatte provides an abridged
account of these dramas that is rife with
surprises: walking whales that learned to
swim in the kiddy pool of the Tethys Sea be-
fore roving into the world’s oceans; massive
predatory relatives of modern marsupials
that stalked the jungles of South America;
giant chalicotheres that resembled an im-
probable giraffe-gorilla hybrid; and our
own origin story, spanning back through
the depths of the ice ages.
Brusatte’s deep knowledge of the fossil
record creates a rich tapestry in which each
thread is a mammalian lineage. These inter-
woven threads dip in and out intermittently
and sometimes disappear altogether in the
finality of extinction, but those that remain
always unspool in a bright burst of color to
fill the gap.Corrected 3 June 2022. See full text.