The Selfish Grandma Gene: The Roles of the X-Chromosome and Paternity Uncertainty in the Evolution of Grandmothering Behavior and Longevity

Figure 3

The threshold for an X-linked mutation causing grandparents (or grandmothers) to favor their granddaughters at the expense of their grandsons to accumulate. These curves represent the thresholds for which such a mutation would increase in frequency. The threshold can be described as the maximum number of times greater the expense of this mutation would be to grandsons, compared to the benefit of the mutation to granddaughters. These values were calculated using the mathematical model from Rice et al. [8, supplement]. We suggest that paternal discrepancy among our species would be approximately 1.3–3.7%. However, this graph shows a range of paternal discrepancy from 0% (all paternity is identified correctly) to 100% (all paternity is identified inaccurately).