Polygynous male primates evolved larger canines than monogamous ones
Evidence
Female jacanas still produce the larger gametes (eggs are bigger than sperm), and it takes them a few weeks to recover between clutches. But this is where female investment stops. Male jacanas spend up to three months tending to eggs and chicks and, as a result, their turnaround time is longer than the females’ (seventy-eight days, on average, compared with twenty-four). At any point in time, roughly half of the males in a population are tied down with existing eggs or chicks, leaving just a few of them free to start new broods, while most of the females are yolked up and ready to go. They could lay eggs immediately if only they had access to a territory-holding, reproductively ready male. In jacanas, there simply are not enough receptive males to go around, and females battle it out for the chance to breed. Sexual selection, rather than selection from predators or prey, drove the evolution of blazing yellow spurs in jacana females. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 160 (
#qualifies, via linked claim)
Sexual selection differs from most forms of natural selection in ways tailor-made for pushing traits to their extreme. For one thing, sexual selection can be a lot stronger than natural selection. Whenever a small subset of males monopolizes access to large numbers of females, the disparity in reproductive success skyrockets. A few victorious males sire dozens or even hundreds of offspring, while the overwhelming majority of males sire none. When payoffs for success are high enough, weapons can evolve to really big sizes. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177 (
#expands, via linked claim)
Categorization
- XREF: connects to: Sexual selection can be far stronger than natural selection and drives weapon extremes — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177; Male parental care can invert the direction of sexual selection and weaponry — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 160; The same three ingredients trigger weapon evolution across wildly divergent animal clades
Related
- Male parental care can invert the direction of sexual selection and weaponry (similarity 0.90)
- In nearly all weaponed species, males carry the weapons, not females. (similarity 0.85)
- Sexual selection can be far stronger than natural selection and drives weapon extremes (similarity 0.82)
- Reproductive success, not survival, drives the largest animal weapons (similarity 0.82)
- Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.81)
- Among jacanas, females are the armed, aggressive sex defending breeding territories. (similarity 0.80)
- Males evolve big weapons to defend resources that females visit (similarity 0.80)
- Jacana females only breed when dominant enough to hold territory. (similarity 0.80)
- Sexual selection stays directionally constant while physical natural selection oscillates (similarity 0.79)
- Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.79)
- Shared clade traits like lengthy female investment predispose entire lineages to weapon arms races (similarity 0.78)
- Sexual selection is uniquely directional because the social environment itself evolves with the weapons (similarity 0.78)
- Identical triggers drive extreme weapon evolution across wildly unrelated clades (similarity 0.78)
- Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.78)
- Social competition environments evolve in tandem with weapons, unlike fluctuating physical environments (similarity 0.78)
Broader Connections
- Male parental care can invert the direction of sexual selection and weaponry
#qualifies(0.85) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 160 - The same three ingredients trigger weapon evolution across wildly divergent animal clades
#expands(0.80) - Sexual selection can be far stronger than natural selection and drives weapon extremes
#expands(0.75) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177