 1. The Evolution of Human Personality 15
person. Although this may appear to flow 
naturally and effortlessly for some, it ac -
tually entails a complex set of properly se -
quenced and contingent behaviors in order 
to culminate in successful merging of the 
male sperm and female egg. Mating motiva -
tion also entails the intricate tasks of besting 
intrasexual competitors in successful attrac -
tion tactics (Buss, 1988a; Schmitt & Buss, 
1996), perhaps derogation of intrasexual 
competitors to make them seem less desirable 
(Buss & Dedden, 1990), and successful mate 
retention (Buss, 1988b; Buss & Shackelford, 
1997). Mating motivation is a multifaceted 
venture, entailing a host of subtasks, any of 
which can result in a failure. As descendants 
of ancestors who succeeded in all of these 
mating tasks, modern humans have inherited 
the underlying psychological mechanisms re -
sponsible for producing mating motivations 
and behavioral strategies that led to their suc -
cess. Personality theories that fail to include 
mating motivation, broadly conceived, must 
be viewed as woefully inadequate, if they are 
attempting to describe human nature.
Like status striving, however, evolution -
ary analysis provides a powerful rationale 
for predicting sex differences in the nature 
of mating motivation. Due to the asymme -
tries in obligatory parental investment, for 
example, men are predicted to have a greater 
desire than women for a larger number of 
sex partners, and a large body of empirical 
evidence supports this prediction (Buss & 
Schmitt, 1993; Kenrick, Sadalla, Groth, & 
Trost, 1990). Furthermore, a large body of 
cross-  cultural evidence supports the specific 
predictions that men will be more motivat -
ed to seek young and physically attractive 
mates, whereas women will be more moti -
vated to seek mates who offer a willingness 
and ability to accrue and commit resources 
(Buss, 1989a; Kenrick & Keefe, 1992). Per -
sonality theories that include mating moti -
vation, in short, must also include specific 
premises about the ways in which mating 
motivation is known to differ between the 
sexes, corresponding to sex differences in 
the adaptive problems faced over human 
evolutionary history.
Universal  Emotions
Another core feature of human nature pro -
posed by evolutionary psychology involves universal mechanisms of emotion (Buss, 
1989b; Nesse, 1990; Tooby & Cosmides, 
1990b). A large body of cross-  cultural evi -
dence already suggests that certain forms of 
emotional expression are universal (Ekman, 
1973). Evolutionary analysis suggests that 
certain emotions will be universal, designed 
to solve specific adaptive problems. One 
candidate for such a universal emotion is 
jealousy, which we illustrated earlier. Like 
status striving and sexual motivation, evo -
lutionary analysis provides a powerful basis 
for predicting sex differences. These are not 
sex differences in the presence of intensity 
of jealousy, since both sexes have faced the 
adaptive problem of mate retention. And in -
deed, the empirical evidence suggests that 
the sexes do not differ in measures such as 
the frequency and intensity of jealousy expe -
rienced (Buunk & Hupka, 1987).
An evolutionary analysis, however, sug -
gests that the sexes might differ in the events 
that activate jealousy. Specifically, since fer -
tilization occurs internally within women 
and not within men, over evolutionary his -
tory men have faced the adaptive problem 
of “paternity uncertainty.” Since a partner’s 
sexual intercourse with another man would 
have been the primary threat to paternity 
certainty, and hence to successful reproduc -
tion, men’s jealousy mechanisms are hypoth -
esized to be specially keyed to the inputs of 
cue to sexual infidelity by a partner. Ances -
tral women, in contrast, faced a different 
adaptive problem: the loss of a mate’s time, 
energy, effort, attention, investment, and 
commitment, all of which could get rechan -
neled to a rival woman and her children. 
Since a man’s emotional involvement with 
another woman is a leading cue to such re -
direction of commitments, women’s jealou -
sy mechanisms are predicted to be keyed to 
the inputs of cues to emotional involvement 
more than to cues to sexual infidelity per se, 
although the two signals are clearly corre -
lated in nature.
Much empirical evidence supports these 
predicted sex differences (Buss & Haselton, 
2005). In forced-  choice dilemmas, men more 
than women report that they would be expe -
rience greater distress at a partner’s sexual 
infidelity, whereas women more than men 
report that they would experience greater 
distress as a result of a partner’s emotional 
infidelity (Buss et al., 1992). These results 