Pleasure and pain equally enable a self-satisfaction one might term 'happiness', like the pleasure of consistently demeaning oneself when one finds oneself frustrated by life because demeaning _others_ is pleasurable.
We are comfortable perceiving other species' limitations, even directly perceiving how their behavior or evolution will be their downfall, but we're not particularly good at analyzing ourselves in this way, and its owing to, rather than in spite of, moral constraints, themselves varying from demographic to demographic, so that ultimately the question becomes "_Which kind_ of human should propagate?" For Aristole, only slave-owners could practice virtue, materially and cognitively (though today, epigenitics would tell us there isn't as much of a distinction here as one would wish, or the recent literature indicating IQ drops the _longer_ one is poor as well; Aristotle ultimately had an idea of this as well, but treated of it separately in On the Soul).
We are comfortable perceiving other species' limitations, even directly perceiving how their behavior or evolution will be their downfall, but we're not particularly good at analyzing ourselves in this way, and its owing to, rather than in spite of, moral constraints, themselves varying from demographic to demographic, so that ultimately the question becomes "_Which kind_ of human should propagate?" For Aristole, only slave-owners could practice virtue, materially and cognitively (though today, epigenitics would tell us there isn't as much of a distinction here as one would wish, or the recent literature indicating IQ drops the _longer_ one is poor as well; Aristotle ultimately had an idea of this as well, but treated of it separately in On the Soul).