These are the most frequently used words in this book.
1871
1889
adaptations
adaptive
advantage
against
although
altruism
animals
another
behaviour
between
birds
case
changes
characteristics
choice
coloration
colours
come
costs
darwin
darwinian
darwinism
differences
different
does
effects
even
evidence
evolution
example
explain
explanation
fact
far
female
find
first
forces
forms
found
genes
good
group
however
human
idea
ii
indeed
individual
kind
less
look
males
mate
may
mechanisms
might
must
natural
nature
need
now
offspring
often
organisms
own
part
perhaps
point
pp
preference
principle
problem
question
rather
reason
result
see
seems
seen
selection
selective
sexual
should
social
species
sterility
structure
tail
take
theory
time
two
use
view
wallace
without
work