Frank Sulloway supports this assertion that large birth spacing decreases sibling rivalry in his book, Born to Rebel. Sulloway shows how this happens more successfully in families of large-spaced children. While younger siblings generally have more revolutionary mindsets than their older siblings, this trend was more pronounced in siblings of differing ages. It stands to reason, then as well, that the more resources in a family structure, the less chances there are for conflict between siblings over resources. Perhaps a more preventive form help would be useful on combating rivalry considering our tendency to compete with siblings for resources while protecting them as carriers of half our genes.
Large birth spacing however, has serious consequences for successful gene continuance.
When children are spaced far apart, considerably less gene carrying offspring can be produced. Large birth spacing needs to be able to make up for these costs by having a big effect in making sibling relationships helpful instead of harmful and by putting siblings in a position to create successful niches for themselves as Sulloway describes. Basically, if my hypotheses are refuted, it shows that individual traits are more important than the biological trends in solving the problem of sibling rivalry. I gave this survey to thirty-six students at Miami University. All of the respondents were between the ages of seventeen and twenty-six.