 1. The Evolution of Human Personality 11
needed to reach a specific adaptive solution. 
Adaptive problems, like street addresses, are 
specific—  don’t get bitten by that snake, se -
lect a habitat with running water and places 
to hide, avoid eating food that is poisonous, 
select a mate who is fertile, and so on. There 
is no such thing as a “general adaptive prob -
lem” (Symons, 1992). All problems are spe -
cific.
Because adaptive problems are specific, 
their solutions tend to be specific as well. 
Just as general instructions fail to get you to 
the correct location, general solutions fail to 
get you to the right adaptive solution. Con -
sider two adaptive problems—  selecting the 
right foods to eat (a survival problem) and 
selecting the right mates with whom to have 
children (a reproductive problem). What 
counts as a “successful solution” is quite 
different for these two adaptive problems. 
Successful food selection involves identify -
ing objects that have calories, particular 
vitamins and minerals, and do not contain 
toxic substances. Successful mate selection 
involves, among other things, identifying a 
partner who is fertile, a reliable provider, 
and a good parent.
What might be a general solution to these 
selection problems, and how effective would 
it be at solving them? One general solution 
would be “select the first thing that comes 
along.” This would be disastrous, since it 
might lead to eating poisonous plants or 
mating with an infertile person; or alterna -
tively, eating the person and trying to mate 
with the poisonous plant! If anyone ever had 
developed such a general solution to these 
adaptive problems in human evolutionary 
history, he or she failed to become one of 
our ancestors.
In order to solve these selection problems 
in a reasonable way, one needs more specific 
guidance about the qualities of foods and 
qualities of mates that are important. Fruit 
that exhibits cues to being fresh and ripe, for 
example, will signal better nutrients than 
fruit that looks rotten. People who exhibit 
cues to youth and health will be more fertile, 
on average, than people who exhibit cues to 
older age and poorer health. We need specif -
ic selection criteria —qualities that are part 
of our selection mechanisms—  in order to 
solve these selection problems successfully.
The specificity of mechanisms is further 
illustrated by errors in selection. If you make an error in food selection, then you have 
an array of mechanisms that are tailored 
to correcting that error. When you place 
a piece of bad food in your mouth, it may 
taste terrible—  an output of evolved disgust 
mechanisms that motivates you to spit it out. 
You may gag on it if it makes its way past 
your taste buds. And if it makes its way all 
the way down to your stomach, you may 
vomit—  another feature of evolved disgust 
mechanisms designed to get rid of toxic or 
detrimental ingested substances. But if you 
make an error in mate selection, you do not 
spit, gag, or throw up (at least not usually!). 
Rather, that adaptive problem is solved by 
distinct psychological and behavioral out -
puts (e.g., by leaving, selecting someone else, 
or simply telling the person that you don’t 
want to see him or her anymore).
In summary, problem specificity of adap -
tive mechanisms is favored over generality, 
because (1) general solutions fail to guide the 
organism to the correct adaptive solutions; 
(2) general solutions, even if they can some -
times work, lead to too many errors and 
thus are excessively costly to the organism; 
and (3) what constitutes a “successful solu -
tion” fundamentally differs from problem to 
problem (criteria for successful food selec -
tion differ from criteria for successful mate 
selection).
	•Humans possess many evolved psy -
chological mechanisms.  Humans, like most 
organisms, face a large number of adap -
tive problems. The problems of survival 
alone number in the dozens or hundreds— 
problems of thermal regulation (getting too 
cold or too hot), avoiding predators and 
parasites, ingesting life- sustaining foods, 
and so on. Then there are problems of mat -
ing, such as selecting, attracting, and keep -
ing good mates and getting rid of bad mates. 
There are also problems of parenting such 
as breastfeeding, weaning, socializing, de -
ciding on the varying needs of different chil -
dren, and so on. Then there are the problems 
of investing in kin, such as brothers, sisters, 
nephews, and nieces; dealing with social 
conflicts; defending yourself against aggres -
sive groups; grappling with the social hierar -
chy, and dozens more.
	•Because specific problems require spe -
cific solutions, numerous specific problems 
will require numerous specific solutions. 