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mens (figure 17). This made us wonder if LB1's endocast represented a
miniaturized brain that was inherited from a larger-bodied and larger-
brained Homo erectus ancestor. In other words, was Hobbit's virtual
endocast consistent with the idea that Homo floresiensis was a dwarfed
descendant of Homo erectus ? After all, Homo erectus was living nearby on
the island of Java well before 1 million years ago, when the oldest known
tools were produced on Flores. Perhaps the special features we detected
on LB1's endocast were hand-me-downs from ancestors who had man-
aged to colonize on Flores and then evolve in isolation there.
One way to explore this possibility is to examine the size of the brain
compared with the size of the body. The ratio of brain size to body
size (or relative brain size) scales in highly predictable ways within and
between different species of mammals. Take Homo sapiens, for example.
Smaller-bodied humans have relatively bigger brains than larger-bodied
individuals. A baby, for example, has a relatively large brain (and head)
compared with an adult. This is because, although the absolute sizes
of both the brain and body increase as a child matures, the brain stops
growing first, and RBS therefore decreases until the person's body
reaches adult size. Indeed, an adult would look very strange if his head
were as relatively large as a baby's! The scaling is similar when one
compares contemporary human groups that have very different body
sizes, such as normal-sized people and much smaller human pygmies. In
keeping with the trend for growing individuals, populations of pygmies
have relatively larger brains than populations of normal-sized individu-
als, although the absolute sizes of their brains are somewhat smaller. 23
The same scaling principles work for different contemporary species
that are related to one another. Thus, smaller-bodied monkeys tend
to have a larger RBS than bigger monkeys. This isn't always the case,
however. For example, humans have evolved an extraordinarily large
RBS— so much so that our brains are over three times the size one
would expect for apes with similar body masses.
These scaling principles also break down when one compares spe-
cies of hominins that lived at different times. Despite their smaller bod-
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