HUMAN INTELLIGENCE 263However, it seems to have been the benefi ts of true social cooperation
that we need to keep coming back to. More refi ned cognition, communi-
cation, and epicognition impelled more rapid brain expansion. Th at
started a virtuous evolutionary spiral in cognitive systems. Early hom-
inds were gradually able to release themselves from the confi nes of a
single habitat (to which even our nearest cousins are still tied). With
deeper abstractions of the dynamics of the world, they were better able to
anticipate and change their environments. By thus adapting the world to
themselves, rather than vice versa, they were able to expand into many
less- hospitable environments.
Th e old story, though—or, at least its chronology— has been compli-
cated by more recent fossil fi nds. As with any incursion of species into
new habitats, it turns out that early hominid evolution was not so much
a ladder as like a bush. It consisted of diverse “experiments” with diff er-
ent permutations of features, such as bipedalism, diet, manual dexterity,
and bigger brains.^7 Up to about four or fi ve million years ago, they include
va ri e ties with a braincase similar in volume to today’s chimpanzees
(340–360 cubic centimeters). Other features, such as hands and arms
designed for climbing, are indicative of life in thin forests.
From about 4.5 to 2 million years ago, hominids are represented by a
diverse group of undoubtedly bipedal, socially living creatures with
slightly bigger brains (about 450–500 cubic centimeters). Th ey had hu-
manlike teeth and hands. Th ese have been called Australopithecines
(the most famous being A. afarensis, which existed between 3.9 and 3.0
million years ago). Fossil deposits suggest that they lived in small groups
of twenty to thirty individuals; lake margins or river fl oodplains may have
been their habitat, with the availability of trees for escape from predators,
especially at night. But every now and again another report appears in
Science or Nature of more fossil discoveries suggesting further revisions
to the story.
Th e newer fi nds do not negate the general picture of evolution of co-
operative lifestyle described above; it is only more staggered in time. From
about 2.5 to 1.6 million years ago, remains of a variety of other species ap-
pear in the fossil rec ord in East Africa, including one with more human
features, originally called Homo habilis. (Th e picture is complicated
by the report in 2015 of the discovery of another new species; named
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