fei75766_ch15_463-494.indd 488  02/24/20 10:48 AM
Part V    Biological/Evolutionary Theories488
sense oftheword (Stamos, 1996). Many critics ofevolutionary theory arequick to
point outthatthecentral tenets ofevolutionary theory areinherently non-falsifiable 
anduntestable because evolution isapastevent anditwould takeatleastthousands 
ofyears toobserve theoutcome ofevolution inanimals. Moreover, theyargue that
evolutionary psychology ismostly afterthefact(post hoc)explanations foranygiven 
phenomenon—in short, evolutionary psychology produces plausible “just-so stories” 
andmany different plausible stories canalways beconstructed toexplain anevolu -
tionary outcome (Gould &Lewontin, 1979; Horgan, 1995).
Yet,other scholars haveargued thisisbothsomewhat inaccurate andalsonot
completely thepoint. Defenders ofevolutionary theory, forinstance, havepointed out
thatdefeating atheory bycontrary facts(falsification) isnottheonlywaythatscience 
proceeds (Ellis &Ketelaar, 2000; Ketelaar &Ellis, 2000). Analternative criterion for
scientific progress iswhether itgenerates novel predictions andexplanations. Bythis
standard, evolutionary theory doesquite well.
Interms ofhowwellevolutionary theory ofpersonality organizes known knowl -
edge,wewould argue thetheory ratesquite highly. Evolutionary theory isverybroad and
long-range initsscope andinthatsense itprovides arange ofexplanations seldom seen
insocial science. Itoffers explanations fortheultimate origins ofnotonlyallbiological 
systems buthuman thought, behavior, andpersonality aswell.
Asaguide for practitioners, however, wegivethetheory relatively lowmarks. 
Evolutionary theory sayslittleabout howweshould raiseourchildren, what we
should teach them andhow, orhowtoconduct therapy totreatmental disorders. The
theory ismore abstract andpurethanconcrete andapplied.
Evolutionary theory ofpersonality rates moderate oninternal consistency. Adap -
tation isaguiding principle andmany ideas stem from thiscoreconcept. Andmost 
scholars agree onhowtodefine adaptation. However, notallagree onwhat isand
isnotanadaptation. Themost glaring example ispersonality. Although Buss, Mac-
Donald, andNettles allagree thatpersonality variability isanadaptation, twoother 
leading theorists, Tooby andCosmides, donot.
Evolutionary theory ofpersonality scores highonthecriterion ofparsimony .
Theideathatyoucanexplain theorigins ofhuman personality withafewkeyconcepts 
ofadaptation, mechanism, andnatural andsexual selection isquite simple.
 Concept of Humanity
It is difficult to say on which side of the optimism-pessimism  debate evolution -
ary theory would fall. It is mostly descriptive and, in that sense, tends to be 
somewhat neutral about describing human nature. Humans are and have been 
capable of incredibly uplifting acts of heroism and bravery and cooperation, 
inspiring works of creativity, and unbelievable and unspeakable acts of vio -
lence and cruelty. Both extremes are part of human nature (Pinker, 2002).
Evolutionary psychology has a complex view on the question of deter -
minism versus free-will . A common assumption of evolutionary theory by Final PDF to printer