Chapter 13 (Continued)
- Sex ratio, male: female - we believe it is roughly 50/50, but it isn’t for specific reasons.
- Core reason: females are much better bet for reproductive success than males (humans)
- Females are more likely to breed successfully - sexual selection among our species has made it tougher on men.
- Women have easier time to have sex than men.
- In humans, the sex ratio at birth is males (more of them) - you need more men to get a 50/50 change - not all males will make it
- Not a cultural problem - biological issue - mirrored in other species.
- In process of competition - they are taking each other out.
- Pre-reproduction is high in males for sexual reproduction.
- Possum can actually bias their sex ratios based on their living conditions (Epigenetics) - could just stay at 50/50 but something
takes in the living conditions which are translated to how many female/male she has in each litter.
- If environment is rich in food and resources, then they have 40% increases in sons.
- When possum moms are sick, when environment is love, they have 80% more daughters.
- If there is high predation, they have short life - breed once with many kids, low self-repair and die young.
- If life is good, they live long, have multiple litters, each litter is small, and if they are sick - they self-repair.
- Nematode - 1000 cell, simple organism.
- A single gene controls lifespan.
- Maybe lifespan is a facultative adaption, maybe it is not an immovable wall, and maybe it reads environmental cues.
- Think of lifespan as an adaptation not a number.
Cinderella Factor by Martin Daly
- Infanticide and child abuse - clearly not random occurrences.
- Differential parental solitude is an important adaptation in humans.
- We are not randomly generous with out parenting; we don’t want to start taking in all of our neighbour’s kids.
- Bats - 83% of them nurse from their mom, not another mom - vocalization and smell.
- Lions, monkeys, mice - mom has babies but dad dies - new man comes along to be with mom but kills the babies - why waste my